Unit 4
Meiosis, Inheritance and Variation of Traits
NGSS Standards
LS3-1: Ask questions to clarify relationships about the role of DNA and chromosomes in coding the
instructions for characteristic traits passed from parent to offspring.
LS3-2: Make and defend a claim based on evidence that inheritable genetic variations may results
from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication,
and/or (3) mutations caused by environmental factors.
LS3-3: Apply concepts of statistics and probability to explain the variation and distribution expressed
traits in a population.
Name _______________________________________________________________
Teacher ________________________________________ Period _______________
Essential Questions and Learning Targets
EQ 1: What causes genetic variation in sex cells?
A. I can explain and model the process of crossing over.
B. I can explain and model the process of independent assortment.
EQ2: How does the environment influence your phenotype?
A. I can identify factors contributing to epigenetics.
B. I can define epigenetics.
C. I can differentiate between the impact of mutations in mitosis and meiosis.
EQ 3: How can we predict the distribution of alleles in a population?
A. I can use a Punnett Square to determine the genotypes and phenotypes of the
parental generations.
B. I can use a Punnett Square to determine the probability of the genotypes and
phenotypes of offspring.
C. I can differentiate between genotype and phenotype.
EQ4: How are sex cells created?
A. I can explain the difference between haploid and diploid.
B. I can compare and contrast meiosis I and meiosis II.
C. I can explain the role of homologous chromosomes in meiosis.
D. I can compare and contrast mitosis and meiosis.
EQ5: How does fertilization create unique individuals?
A. I can define fertilization.
B. I can explain how fertilization contributes to variation.
Introduction to Meiosis and Fertilization
EQ 4-D: I can compare and contrast mitosis and meiosis.
EQ 5-A: I can define fertilization.
From BBC: GCSE Bitesize – Mitosis and Meiosis
Website: https://www.youtube.com/watch?v=oB50VEgTXlA
1. What is the overall purpose of Mitosis?
2. What is the difference between the outcomes of Asexual and Sexual reproduction?
3. Why is Meiosis needed?
4. Human egg and sperm each contain ______ chromosomes. These combine to make a total of
________ chromosomes in the offspring.
5. Why are genetically unique egg and sperm beneficial?
Fertilization video: Nucleus Medical Media
Website: https://www.youtube.com/watch?v=_5OvgQW6FG4
6. What is fertilization?
7. Why could it be said that you are truly 1 in a million?
Introduction to Homologous Chromosomes Activity
EQ 4-C: I can explain the role of homologous chromosomes in meiosis.
EQ 3-C: I can differentiate between genotype and phenotype.
Create a summary list of important details and terms from each of the following cards. You should record any
information that you feel might be helpful in understanding these concepts. Really try and summarize the
important information from the reading.
Page 1 - What are Homologous chromosomes?
1. Define homologous chromosomes.
Basic Sketch
2. What is similar about homologous chromosomes?
3. What is different about homologous chromosomes?
4. What is an allele?
Page 2 - What makes two alleles heterozygous or homozygous?
5. Provide examples of heterozygous alleles using upper/lower case letters. ______________________
6. What makes them heterozygous?
7. Provide examples of homozygous alleles using upper/lower case letters. ______________________
8. What makes them homozygous?
9. At the DNA level, what ultimately are different about the 2 different alleles?
10. What is the difference between a Genotype and a Phenotype?
Page 3 - What are NON-homologous chromosomes?
11. Explain the characteristics of non-homologous chromosomes and
draw a sketch of them to the right.
Basic Sketch
Page 4 - Application of Terms:
Follow the directions in the 4 bullet points located underneath the image and complete them below:
12. Fictional Allele Key for one chromosome pair:
Analysis questions:
1. Where would the original homolog from each homologous pair have come from?
2. What could be some genes that have many alleles in the human population and have lots of
variation?
Homologous Chromosomes Practice
EQ 4-C: I can explain the role of homologous chromosomes in meiosis.
Directions: The image below shows the nucleus of a cell found in a horse. Inside of the nucleus are
three pairs of homologous chromosomes labeled 1 through 6. Two of the chromosomes are uncoiled
in a chromatin state and four are coiled and wrapped tightly in a chromosome. For Part 1, use your
knowledge of homologous chromosomes, identify which ones are homologous and support your
claim with evidence. Helpful hint…an uncoiled chromosome could match up with a coiled one! In
Part 2 analyze a claim and answer some analysis questions.
Part 1
Claim 1: ______________________________________
Evidence:
Claim 2: _______________________________________
Evidence:
Part 2
1. Explain why the claim below is incorrect (refute the claim).
Claim: “Chromosomes 3 and 4 are homologous because each is uncoiled and appear to
be the same length.”
Explanation:
2. Why do you think that sometimes chromosomes are coiled up and sometimes they are uncoiled?
3. When do you think you would want each of those?
Directions: Below are three images of chromosomes labeled 1, 2, and 3 and each contain six genes
(In reality, most chromosomes contain hundreds to thousands of genes). Chromosome 1 is
labeled with the traits that are controlled by these 6 genes. Chromosome 2 is the sister chromatid of
chromosome 1. Chromosome 3 is homologous to Chromosome 1 and 2 with half the genes
heterozygous and half homozygous. With this information, fill in the rest of Chromosome 2 and 3.
1- Sister
Chromatid
Trait
Brown eyes
High math
ability
High risk heart
disease
Fair skin tone
Low
resting pulse
Blonde
Hair
Gene
2- Sister
Chromatid
Trait
Brown eyes
Gene
3- Homologous
Chromosome
Trait
Blue eyes
Gene
Analysis Questions:
1. If you were asked to analyze two chromosomes to determine if they were homologous, what
would you look for?
2. If you were asked to analyze two chromosomes to determine if they were NON – homologous,
what would you look for?
3. If you were asked to analyze two chromosomes to determine if they were sister chromatids,
what would you look for?
4. Could homologous chromosomes ever be totally identical? Explain why or why not.
Shapes & Forms of DNA throughout Mitosis & Meiosis
EQ 4-A: I can explain the difference between haploid and diploid.
EQ 1-A: Ican explain and model the process of crossing over.
EQ 5-B: I can explain how fertilization contributes to variation.
Chromatin:
Chromosome:
Identical sister chromatids:
Crossing over:
Tetrad:
Homologous
Chromosomes:
Gene for eye color
(Brown)
Gene for skin tone
(Fair skin)
Diabetes Gene
Gene for enzyme that allows
for normal kidney function
Gene that cannot break down
lactose
Gene for eye color
(Hazel)
Gene for skin tone
(Olive)
Normal non-Diabetes Gene
Gene for enzyme that allows
for normal kidney function
Gene that breaks down the sugar lactose
Diploid Cell:
Haploid Cell:
Fertilization:
Analysis Questions Shapes/Forms of DNA and Chromosomes
1. Describe how chromatin structure of DNA is different than the chromosome structure of DNA.
2. Propose a reason why DNA might need to be in a chromatin state and why it might need to be in a
chromosome state.
3. Describe the difference between an individual chromosome versus two chromatids.
4. Look at the homologous chromosomes. Describe some ways in which homologous chromosomes are
similar. Then describe ways in which they are different.
Similar
Different
5. Describe what makes up a tetrad. Why is it called a tetrad?
6. Why is crossing over a necessary part of Meiosis and making egg and sperm cells?
7. Analyze the diploid and haploid cell. Describe how they are different.
8. What exactly happens in fertilization? Use the words haploid and diploid in your answer.
Man’s mother
Man’s father
You are about to study the process of
meiosis and trace the journey of
chromosomes as they are divided into the
sperm cells of the man to the right. As an
FYI, women also do meiosis to make egg
cells. By analyzing this example of
meiosis, you should learn HOW meiosis
creates genetically unique gametes (egg
cells and sperm cells).
The two older individuals are the man’s
father and mother from which he inherited
his chromosomes. This man inherited his
dark grey chromosomes from his father
and his light grey chromosomes from his
mother.
Man
1
This cell to the right is located in the man’s
testes and is about to go through the
process of meiosis. Notice how the
homologous chromosomes are randomly
floating around inside the nucleus of this
cell.
2
1. What are homologous chromosomes?
3
2. There are 3 homologous pairs, use the
numbers on the chromosomes to list
the homologous chromosomes.
Lets follow this cell as it begins the
process of dividing into four unique sperm
cells.
4
6
Cell A
5
The cell shown below has begun the process of meiosis by copying its DNA so that each
chromosome is attached to an identical sister chromatid. Notice how each chromosome went
from being a lone structure to being attached to its clone. DNA polymerase must copy each
chromosome so that two identical sets of chromosomes can be made. The cell needs to
duplicate its DNA so there is enough DNA to be divided into four different sperm cells. This also
occurs in women as they produce egg cells.
3. Label the centromere and sister chromatids.
4. What phase does DNA replication occur in?
Cell B
During this critical point in meiosis, the homologous chromosomes randomly line up in the center of
the cell. Notice how the homologous pairs are side by side. For the homologous pair of
chromosomes located at the top of the cell, the one the man inherited from his dad lined up on the
right and the one he inherited from his mom is on the left. The second homologous pair however,
lined up differently with his dad’s on the left and his mom’s on the right. This process of random
lining up of homologous chromosomes helps ensure that all this man’s sperm cells carry a unique
combination of his alleles. During different rounds of meiosis, these chromosomes will arrange in a
different pattern each time. This process is known as Independent Assortment and without it this
man would run the risk of producing identical sperm cells. Independent assortment is one reason
why all organisms have one-of-a-kind combination of traits. Independent assortment mixes the
mom/dad chromosomes.
5. Define Independent Assortment.
6. Why would identical sperm (or egg) cells be bad in the long run?
Cell C
The image to the left shows a cross over between this man’s first
pair of homologous chromosomes. Notice that the parts that
crossed over carried the alleles for e and B/b. Cross-overs only
occur between homologous chromosomes. A cross over between
two NON-homologous chromosomes would be abnormal and
produce sperm or egg carrying abnormal combinations of genes.
Cross-over events occur between homologous chromosomes to
mix-up the combinations of alleles on chromosomes. By shuffling
the combination of alleles on chromosomes, meiosis can ensure
that no two sperm cells belonging to this man will be identical.
Here’s how this cross over event occurred: The lower part of the
chromosome this man inherited from his father (dark grey) broke off
from the top portion. This lower portion was carrying the recessive e
instruction and the recessive b instruction. The same corresponding
part broke off from the chromosome he inherited from his mom (light
grey). That portion was carrying the recessive e allele and the
dominant B allele. Each segment exchanged places and reattached
on the opposite homologous chromosome. Cross over can occur in
multiple locations along two homologous chromosomes and can
often involve the two outer chromosomes exchanging their alleles as
well.
7. Define recessive.
In order to understand how cross over events shuffle genetic
information, compare the two homologous chromosomes before and
after the cross over. Notice that the chromosome this man inherited
from his mother carried the dominant G, recessive h, recessive e,
and dominant B. After the exchange of DNA between the two
homologous chromosomes, the chromosome then carried the
Dominant G, recessive h, recessive e, and recessive b.
This model showing the “mixing-up” of genetic information between
chromosomes is not fully accurate. In real life, chromosomes carry
approximately 500 – 1000 genes allowing for dozens of cross-over
events to occur along the length of two homologous chromosomes.
This “shuffling” of DNA creates a prodigious amount of different
genetic combinations for a single organism ensuring that all
offspring will carry a unique combination of genetic instructions and
traits.
8. How does crossing over increase genetic diversity?
In the image bellow the homologous chromosomes are line up down the equator or center of the cell.
9. Is this image before or after crossing over? How do you know?
10. How is this line up different than how the chromosomes line up in mitosis?
11. Are the sister chromatids identical? Why or why not?
Cell D
This stage of meiosis shows the once single cell splitting into two separate cells each cell carrying
half the number of chromosomes as compared to the original cell. The dashed lines represent a
structure called the spindle fibers that attach to the centromere (center portion of each chromosome)
pulling it towards the new cell. Notice that only the homologous pairs of chromosomes are being
pulled apart and dragged into separate cells. The sister chromatids (now no longer identical clones
due to crossing over) remain attached. The end result of this stage will be two cells carrying only
NON-homologous chromosomes.
12. What is being separated in this image?
13. How is this different than mitosis?
Cell E
Two fully separated, haploid cells that each carry half the original number of chromosomes as the
parent cell. Notice that each chromosome is no longer in the same cell as its homologous partner.
Each cell only contains NON-identical sister chromatids and is considered at this point a haploid cell.
14. How are the images below similar to mitosis?
15. What is haploid?
16. What is the haploid number in humans?
17. Label a chromosome.
18. Using evidence from this image, explain how you know that the cell is haploid.
Cells F
19. What is being separated in this image?
Cells G
Cells H
A comparison of all the sperm cells produced by this man will show that all the sperm cells have a
one-of-a-kind combination of alleles despite the fact that all came from the same individual. Also
notice that the haploid sperm cells carry half the instructions of the original pre-sperm cell. These
sperm cells are ready to fertilize a haploid egg cell. However, the more likely outcome for most
sperm and egg cells is death, as most gametes never fertilize to produce offspring. Consider the
average number of sperm (billions) and egg (millions) produced compared to the average number of
offspring produced (humans 2-3, lions 8-10, sharks 4-5, other species) in one’s lifetime.
20. What is the end result of meiosis?
Meiosis Notes
EQ 4-B: I can compare and contrast meiosis I and meiosis II.
EQ 4-D: I can compare and contrast mitosis and meiosis.
Why Do We Look So Different?
Definition of Meiosis
Divided Into 2 Divisions
Meiosis ___ & Meiosis ___
Each division is divided into 4 stages:
-
Chromosomes In Meiosis
Homologous Chromosomes –
Interphase
-Same as Mitosis:
Crossing Over
Meiosis I
Description
Prophase I
Metaphase I
Anaphase I
Telophase I
Cytokinesis
Illustration
Meiosis II
Description
Prophase II
Metaphase II
Anaphase II
Telophase II & Cytokinesis
Independent Assortment
Sperm Cell Formation
Illustration
Egg Cell Formation
Non-Disjunction
Example:
- Down Syndrome
- Large fold in palm
- Bent ears
- Close set eyes
Diploid Cells and Haploid Cells
EQ 4-A: I can explain the different between haploid and diploid.
Number of
Number of
Number of
Diploid Haploid Chromosomes
Species
Chromosomes Chromosomes
Number Number
in Stomach
in Egg Cell
in sperm Cell
Cell
Dolphin
44
Polar
Bear
Horse
Giraffe
Number of
Chromosomes
in starting cell
of meiosis
after DNA
replication
37
32
62
1. Fill out the entire chart above using the data given in each row.
2. The cell below is found inside a woman’s ovary and is going through meiosis. List are all the possible
genetic combinations she can produce given the information below?
3. Below are four images of different cells. Label each cell as a haploid cell or a diploid cell and
use evidence to support your claim.
Nerve Cell/Neuron
Claim:
Evidence:
Sperm Cell
Claim:
Evidence:
4. The image below shows a tetrad with each chromosome label with a number it. Draw and image of
this tetrad during and after cross over of meiosis. You decide which part crosses over.
Before
During
5. Using the tetrad image above, indicate when the above tetrad forms during meiosis.
6. Using the number, which ones are sister chromatids?
7. Using the numbers, which ones are homologous?
8. During what part of meiosis do the homologous chromosomes separate into their own cell?
9. During what part of meiosis do the sister chromatids separate into their own cell?
After
10. Draw a pair of homologous chromosomes with the following:
1. Half of the genes should be heterozygous.
2. Some genes should be homozygous dominant
3. Some genes should be homozygous recessive.
4. Include an allele key
11. Draw a diploid cell with a diploid number of 6. (Show the chromosomes inside).
12. Draw a haploid cell that was made from the diploid cell you just drew in question 11.
Cowboy Meiosis Activity…..Yee Haw!
Independent
Assortment
Heads= Dad on left
Tails= Dad on right
Meiosis I
Crossing over
Heads= crossing over
occurs
Tails= crossing over
does not occur
Independent
Assortment
Heads= switch
chromosomes
Tails= do not
switch
chromosomes
Meiosis
II
1
2
3
4
Name: __________________________________ Period: ________
Cowboy Meiosis Lab Report
EQ 1-A: I can explain and model the process of crossing over.
EQ 1-B: I can explain and model the process of independent assortment.
Place a checkmark next to the traits present in your 4 sperm cells.
Phenotype/Trait
Fast Twitch
Slow Twitch
Low Risk Cancer
High Risk Cancer
Gluten Tolerant
Gluten Intolerant
Lactose Tolerant
Lactose Intolerant
Normal Sight
Near-Sighted
High Risk Cholesterol
Low Risk cholesterol
Fast DNA polymerase
Normal DNA polymerase
Weak Tooth Enamel
Strong Tooth Enamel
Attached Earlobes
Unattached Earlobes
Normal Red Blood Cells
Sickle Shaped RBCs
Normal Skin Tone
Albinism
Sperm 1
Sperm 2
Sperm 3
Sperm 4
Compare your Sperm #1 to some other group’s Sperm #1. Are they similar or different? Why do you
think that is?
Examine your results from the lab and think about what you did to answer the following questions:
1. What is independent assortment and how does it lead to genetic variation?
2. Explain how independent assortment was modeled in this lab.
3. What is crossing over and how does it lead to genetic variation?
4. Explain how crossing over was modeled in this lab?
5. Is it possible for two sperm cells to have exactly the same DNA/traits? Explain
Name ___________________________________Period _______
Genetics Webquest
EQ 3-C: I can differentiate between genotype and phenotype.
EQ 3-A: I can use a Punnett square to determine the probability of the genotypes and phenotypes of offspring.
EQ 3-B: I can use a Punnett square to determine the genotypes and phenotypes of the parental generations.
Link 1: http://www.glencoe.com/sites/common_assets/science/virtual_labs/E09/E09.html
Read through the paragraphs under “How are traits passed from parent to offspring?” in order to answer
the following questions.
1. What is a trait?
2. Define genotype:
3. Each “letter” of a gene represents one form of the trait, also known as an _________________.
4. How are dominant alleles represented? Recessive alleles?
5. Define phenotype:
6. Read through the directions and perform your genetic crosses for each of your creature’s traits.
Fill in the following punnett squares and list the possible phenotypes for each cross.
Link 2: http://pbskids.org/dragonflytv/games/game_dogbreeding.html
Click “Why” at the bottom of the webpage.
7. Breeders want to breed puppies with the most desirable traits. How is this accomplished?
8. What are genes?
9. Explain what happens if a puppy gets the allele for black hair from one parent and the allele for brown
hair from the other parent.
Click “How to Play” and read through the directions.
Click on “Level One” and begin playing by choosing a male and female border collie in order to breed a
puppy that has black fur.
10. If black fur is the dominant trait, use the letter B or b to identify the genotypes of your parent collies.
Genotype of father: _______________
Genotype of mother: _______________
How many trials did it take for you to breed a puppy with black fur? __________
Complete the following punnett square illustrating the possible offspring outcomes if you have two parents
that are both HETEROZYGOUS for black hair. Remember, black hair is dominant (B) and brown hair is
recessive (b).
11. Possible Genotypes and Probabilities in %s: _____________
_____________
12. Possible Phenotypes and Probabilities in %s: _________________
____________
_________________
Link 3: http://www2.edc.org/weblabs/Punnett/punnettsquares.html
Read the text and follow the directions on each page.
13. Why do scientists use punnett squares?
14. Two chickens mate, both are heterozygous for brown fur (Bb). A ratio is a comparison between multiple
values. For example, 1:1 or 1:2:1. What is the ratio of possible genotypes resulting from this cross?
Ratio: __________________
15. What does each number in the ratio signify?
16. Remembering that B is the dominant allele for brown feather color and b is recessive, how often (what
percentage of the time?) would we expect to see brown chicks in the cross above?
Perform the cross of the two lemmings on the next page by filling in the punnett square.
17. Suppose the gene of the lemmings you just crossed is the gene that causes albino offspring. Albinism is a
condition in which the normal pigment of the skin, fur, and even eyes is absent. This is a recessive trait. Based
on your punnett square, what is the probability of producing lemmings that are “carriers” for albinism?
____________ %
18. Based on your punnett square, what is the probability of producing an albino lemming? _________ %
19. What were the genotypes of the lemmings you chose in order to produce a higher percentage of albino
offspring?
_______________ x _______________
Read the text on the following slide.
20. What is a dihybrid cross?
21. What are the genotypes of the parents who produce at least one long-tailed, albino lemming?
___________________ X ___________________
Name_________________________________Hr____
The Snowman Family
EQ 1-A: I can explain and model the process of crossing over.
EQ 1-B: I can explain and model the process of independent assortment.
EQ 3-A: I can use a punnett square to determine the probability of the genotypes and phenotypes of offspring.
EQ 3-C: I can differentiate between genotype and phenotype.
EQ 4-B: I can compare and contrast meiosis I and meiosis II.
Frosty and his wife, Frostina, are expecting some new snow babies! They are excited to see what types
of traits the new snow children will inherit. Complete the following information and then use that to
draw a picture of each of their new adorable snow babies!
Frosty's (Dad) Chromosomes
Frostina's (Mom) Chromosomes
Before Meiosis begins, the DNA replicates in Interphase.
1. Model DNA Replication in each parent's chromosomes by drawing in the identical sister chromatid of
the Homologous pairs. You will end up with 2 tetrads for each parent.
Frosty:
Frostina:
In Prophase I, crossing over may occur in the tetrad of each parents homologous chromosomes. 2. With
your partners, choose 2 genes to cross over for Frosty and choose the other two genes to cross over for
Frostina. Only cross over the inside sister chromatids.
Draw the new tetrads below after crossing over:
3. Label the tetrads below after you showed crossing over. The tetrads are shown lining up on the
equatorial plane during Metaphase I. 4. Now model how the homologous chromosomes separate during
Anaphase and Telophase I of Meiosis.
Frosty
Frostina
Now the chromosomes are shown lining up on equatorial plane for Metaphase II of Meiosis. 5. Next the
chromatids would separate. 6. Draw what the 4 gametes would like once Anaphase and Telophase II of
Meiosis are complete.
Frosty's gametes (sperm cells)
Frostina's gametes (egg cells)
7. Now illustrate the process of fertilization by randomly selecting one of Frosty's sperm and pairing it
with one of Frostina's egg cells. 8. Then determine what alleles (letters) would be found in the snow baby
that resulted from those two gametes. 9. Finally use the chart below to determine what traits the snow
babies would have. Remember the dominant allele (capital letter) would show in heterozygous.
Alleles (letters)
Alleles (letters)
Alleles (letters)
Alleles (letters)
Type of Nose
Number of Buttons Scarf pattern
Type of hat
A= Carrot
B= 3
D= rainbow stripes
E= top hat
a= Coal
b= 4
d= rainbow polka dots
e= cowboy hat
Fertilization: Combination of the egg and sperm
Sperm # ______
+
Egg # _______
+
Sperm # ______
+
Egg # _______
+
Sperm # ______
+
Egg # _______
+
Sperm # ______
+
Egg # _______
Snow Baby #1
Resulting alleles
(letter pairs)
Snow Baby #1
Genetic traits
_______ ______
_______ _______
_______ ______
_______ _______
Snow Baby #2
Resulting alleles
(letter pairs)
Snow Baby #2
Genetic traits
_______ ______
_______ _______
_______ ______
_______ _______
Snow Baby #3
Resulting alleles
(letter pairs)
Snow Baby #3
Genetic traits
_______ ______
_______ _______
_______ ______
_______ _______
Snow Baby #4
Resulting alleles
(letter pairs)
Snow Baby #4
Genetic traits
_______ ______
_______ _______
______ ______
_______ _______
The Snowman Family!!
Draw Frosty and his wife Frostina and their 4 snow babies on the bottom with all of their genetic traits.
Make sure to number the snow babies.
Analysis Questions:
1. What is independent assortment and how does it lead to genetic variation?
2. Explain how independent assortment was modeled in this activity.
3. What is crossing over and how does it lead to genetic variation?
4. Explain how crossing over was modeled in this activity?
5. Is it possible for two sperm cells to have exactly the same DNA/traits? Explain
6. How different were your various snow babies? Why did they end up relatively similar?
7. What would you expect to happen when the snow babies have snow babies of their own someday?
What types of traits would they probably have or not have?
8. What are some events that could influence what types of traits end up in the different sperm or
eggs?
Karyotypes
Arrangement of homologous pairs of chromosomes is called a karyotype. In metaphase chromosomes are
easiest to observe, count and photograph. Chromosomes are then cut out and matched with their
homologous pairs. Recall that homologous chromosomes look similar because they carry versions of the
same genes and one chromosome comes from the mother and the other from the father. Humans have 46
chromosomes (23 homologous pairs) in every single one of their body cells. The first 22 pairs are called
autosomes, and the 23rd pair are called sex chromosomes because they are the ones that determine the
individual’s sex. Female chromosomes are XX and a male is XY. The Y chromosomes does not match the X
but this is normal.
1. Does this karyotype show the chromosomes for a boy with
trisomy 21?
__ yes
__ no
If not, draw the necessary change in the karyotype to show
trisomy 21.
2. When a cell has three copies of a chromosome, the extra copies of the genes on this chromosome result
in extra copies of the proteins coded for by these genes, and this causes abnormal cell function. If an
embryo has an extra copy of chromosome 21 (trisomy 21), the embryo may die or a baby may be born
with Down syndrome, which includes mental retardation, a broad flat face, a big tongue, short height, and
often heart defects.
Explain how Down syndrome can be due to a chromosomal mutation but is not inherited.
For Karyotype Practice go to:
http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html
Introduction:
1. What causes a dark band on the chromosome? ______________________________
2. What is a centromere? _______________________________________________
Part 1: Patient Histories:
Click on Patient Histories. You will be completing a karyotype for Patient A, B & C
Patient A (Click on the link to “Complete Patient A’s Karyotype”)
*Match the chromosome to its homolog by clicking on it. After all the matches are complete you’ll
analyze your patient. (Scroll down to view your completed karyotype).
3. What is patient A’s history? (summarize) ______________________________________________
4. a. How many total chromosomes are in your karyotype? – count them _________
The last set of chromosomes are the sex chromosomes, if you have two large
chromosomes, your patient is XX (female), one large and one small indicates and XY
(male).
4b. What sex chromosomes does your patient have? ___________
4 c. Which chromosome set has an extra chromosome? _______
5. What diagnosis would you give this patient (what disease)? ______________
Patient B - click on the link to go to Patient B and repeat the above process.
6. What is Patient B’s history (summarize) _______________________________________________
7. a. How many total chromosomes are in your karyotype – count them _________
b. What sex chromosomes does your patient have? ________
c. Which chromosome set has an extra chromosome? _______
8. What is the diagnosis? __________________________________
Patient C - click on the link to go to Patient C and repeat the above process.
9. What is patient C’s history (summarize)? _________________________________________
10. a. How many total chromosomes are in your karyotype – count them _________
b. What sex chromosomes does your patient have ? ________
c. Which chromosome set has an extra chromosome? _______
11. What is the diagnosis? ________________________________
12. Explain why these disorders are so difficult to cure?
Mutation Jigsaw Assignment
EQ 2-C I can differentiate between the impact of mutations in mitosis and meiosis.
Goal: Students should gain an understanding of the effects of mutations. The students should be able
to understand how errors in DNA can affect the physical traits of individual organisms. They should
also be able to see how mutations affect species differently. They should also be able to see how some
mutations has positive or negative effects that may not be associated directly to the trait directly
affected by the gene.
Students should be placed in 8 groups.
Groups should go to the following website:
http://learn.genetics.utah.edu/content/variation/outcomes/
Directions: Each group is assigned a different mutation from the sight.
Shar Pei dogs
Double-muscled cattle
Extra-toed cats
Curly hair
Mendel’s wrinkled peas
Red hair
Song Learning Birds
1) Each group should look at their mutation and summarize the following items for their mutation:
Trait, Protein, DNA, Example in other species, Variation, disease or both. These sections are on the
website for each mutation. If your group has time you should expand your knowledge with more
research.
2) Your group will present to the class explaining each of the above sections for your topic. You can
simply go through the website on the projector in front of the class.
Notes:
Trait:
Protein:
DNA:
Example in other species:
Variation/disease or both:
Thinking Question:
1) What are some of the differences in the mutagens that cause these changes in the various
examples?
2) How does this activity show that a trait can be both positive and negative?
3) How do humans benefit from these mutations through selective breeding in animals?
I can differentiate the impact of mutations in mitosis and meiosis.
Name: _________________________________________________ Period: _______
Modeling Mutations
In the world of genes- is change good or bad?
EQ 2-C I can differentiate between the impact of mutations in mitosis and meiosis.
A mutation is a change in the genetic material of the cell that can occur on several levels in different
places within chromosomes. It is more common than you may think. During cell replication, a mistake
occurs every 100,000 nucleotides. That’s about 120,000 typos each time one of our cells divides.
Fortunately, the cell is able to repair most of these changes. Thanks to mutations, we all have some new
variations that were not present in our parents. Mutations are caused by “mutagens” which may be
chemicals, viruses, or environmental agents like X-rays from the sun.
This activity will explore the different places in which mutations occur that may cause populations to
change over time. But do all mutations cause problems or are some beneficial or even silent or just cause
variation?
On your lab table you will build a section of DNA from each of 4 cells: an egg cell, a sperm cell, a skin cell,
and a stomach cell. Thee original nucleotides of the genes are represented by yellow beads. A mutagen
has altered one nucleotide and this is represented by a red bead. Blue beads signify nucleotides in
between genes. Compare all the models at your table to answer the questions.
Procedure:
1. Thread the beads (nucleotides) on the pipe cleaner according to the chart. Yellow beans represent the
original nucleotides in each gene. Blue beads are nucleotides in between the genes. Red beads represent
different nucleotides put in place due to a mutagen.
2. For analysis, place your model by the corresponding sign and answer the questions below.
Model Bead Chart
POSTION: 1
Egg Cell
Y
Sperm
Cell
Stomach
Cell
Skin Cell
2
3
4
5
6
7
8
9
10
11 12
13
14
15 16
17
18
19
20
Y
Y
Y
Y
Y
R
Y
Y
Y
Y
B
B
B
B
B
B
B
B
Y
Y
Y
Y
Y
Y
Y
Y
B
B
B
B
R
B
B
Y
B
Y
Y
Y
Y
Y
Y
Y
Y
B
B
R
B
B
Y
Y
Y
Y
Y
Y
Y
B
B
B
B
Y
Y
Y
Y
B
B
B
B
Y
Y
Y
Y
Y
R
Y
Y
Y
B
B
B
Analysis questions:
1. Which cell(s) carry a mutation within a gene? ___________________________________________
2. Which cell(s) carry a mutation between genes? _________________________________________
3. Which cell(s) have a mutation that will appear in the next generation?
______________________________________________________________________________________
4. What mutations will affect only body cells?
_____________________________________________________________________________________
5. Can the mutation that occurs in the stomach cell possibly be helpful to digestion?
Why or why not?
______________________________________________________________________________________
______________________________________________________________________________________
6. The mutation in the skin cell is caused by UV rays. Could cancer result from this mutation? If you
answered yes, what specifically would this mutation cause to happen? If you answered no, why would the
skin be protected from this mutation?
______________________________________________________________________________________
________________________________________________________________________________________
____________________________________________________________________________________
7. If the mutation that occurs in the skin cell confers protection to UV rays by some means, what would
you expect to happen to the occurrence of this mutated gene in future generations?
Explain your reasoning.
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
8. What is the main idea that you have learned from this lab?
_____________________________________________________________________________________
________________________________________________________________________________________
____________________________________________________________________________________
Name______________________________Hr_____
What is Epigenetics?
EQ 2-A: I can identify factors contributing to epigenetics.
EQ 2-B: I can define epigenetics.
Genome
Epigenome
All of your hereditary information
Tells the genome what to do
Actual genes you inherit from
your parents.
Controls whether genes are
turned on or off
(Expressed or not expressed)
Can’t be changed. Stays the
same your entire life.
Like the hardware for your
Vs.
May change during your life. Not
permanent.
Epigenome really controls what genes are turned on or off in cells. (Epigenomic tags)
2 methods to control gene expression:
1. Methyl groups- made from carbon and hydrogen
Bind to genes and say do or do not express this gene.
Like a on/off switch
2. Histones- proteins that DNA winds itself around
Can change how tightly or loosely DNA is wound around them.
Like a control knob
If loosely wound…DNA/gene will express more
If tightly wound….DNA/gene will express less
Every cell has a distinct methyl and histone pattern which gives the cell its marching orders!
What are some factors that can change your Epigenome?
 What you eat
 What you drink
 Smoking
 Stress
 Environmental factors
 Toxins or Chemicals
They are now realizing that changes in your epigenome can also affect your offspring and even their
offspring too! Some epigenomic tags get stuck and are passed down to offspring.
Nova Science Now Video: Epigenetics (13 minutes)
Watch the video clip and answer the questions below.
1. Why is studying identical twins helpful in epigenetics?
2. What does the mice experiment show about epigenetics?
3. What happens as identical twins age?
4. Why is studying the epigenome helpful for cancer research?
5. The video makes the claim “Your genome your inherit, your epigenome you have a responsibility for.”
Explain what that claim means.
6. Explain how watching this video clip makes you feel. What questions do you still have?
EPIGENETICS NOTES – Gene Expression
Name: __________________________________________
EQ 2-A: I can identify factors contributing to epigenetics.
EQ 2-B: I can define epigenetics.
Watch the clip and answer the following questions. https://youtu.be/T9JQj7WfGbA
1. How is a clone identical and/or different than you after 50 years?
2. What is a Genome?
3. What is Epigenetics?
4. Explain how epigenetics affects identical twins.
5. Explain the significance of Methyl Groups in epigenetics.
6. Explain the significance of histones in epigenetics.
7. In the clip he relates genetics to your computer. Fill in the blank with the analogy he uses.
“The genome, the DNA, is the ___________________________ while the epigenome is more like the
_______________________________”In simpler terms: “The _________________________ does the work and
the ______________________ tells the genome what to do.
8. What stays the same and what changes in your genome over the course your life?
9. Explain 2 ways that your epigenetics can change over your life?
10. Describe how epigenetics is inherited from generation to generation.
11. Describe the epigenetics study in Sweden.
12. Explain how the decisions you make today affect the genome of future generations.
Meiosis Review
Define the following words:
-
Homologous:
-
Haploid:
-
Diploid:
-
Crossing Over:
-
Law of Independent Assortment:
Describe what happens during each of the phases below:
-
Interphase:
-
Prophase I:
-
Metaphase I:
-
Anaphase I:
-
Telophase I:
-
Prophase II:
-
Metaphase II:
-
Anaphase II:
-
Telophase II:
-
Cytokenesis II:
In the space below, draw what is happening based on the description provided.
Interphase: Each chromosome
makes a copy of itself
Prophase I: Homologous
chromosomes cross-over at
the A/a gene and the E/e
gene.
End of Cytokenesis I:
Two new cells are
made, having
different
chromosomes
compared to the
original cell.
End of Cytokenesis
II: Each cell
contains half the
amount of
chromosomes
compared to the
original cell and all
4 cells are
genetically unique.
_______ 1. In humans, body cells have ____ total chromosomes and sex cells have ____ total
chromosomes.
a. 46, 46
b. 23, 46
c. 23, 23
d. 46, 23
_______ 2. What are homologous chromosomes? Choose all that apply.
a. Chromosomes of the same size.
c. A pair of chromosomes with different genes.
b. Chromosomes of the same shape.
d. A pair of chromosomes, one from each parent.
_______ 3. At the end of meiosis, how many cells are created?
a. 1
b. 2
c. 3
d. 4
_______ 4. What kind of sex cells do males and females make?
a. Males make eggs, females make sperm c. Males and females both make egg cells
b. Males make sperm, females make eggs d. Males and females both make sperm cells
5. Explain why crossing over is so important for sex cells.
6. What is the difference between diploid and haploid cells?
Write the stage each cell is in below. Do not forget to write I or II.
7. _________________________
8. ___________________________
9. ___________________________
Write the name of the stage that matches the description below. Do not forget to write I or II.
10. __________________________ Homologous chromosomes move towards opposite sides of the cell.
11. __________________________ Four new daughter cells form.
12. What type of cell undergoes meiosis?
13. Define homologous chromosomes?
14. For each of the following state if the cell is haploid or diploid.
Sperm cell =
Liver cell =
Egg cell =
Stomach cell =
15. If the diploid number in a liver cell is 52, how many chromosomes are there in the egg of this
organism? _________
16. During meiosis, the chromosome number:
a) is doubled
b) is reduced
c) remains the same
d) becomes diploid
17. Cells starting mitosis & meiosis begin with a (haploid or diploid) set of chromosomes.
18. How many times do cells divide during meiosis? _______
19. What are the stages of meiosis called?
Meiosis I: _________________, _____________________, _________________, ____________________/cytokinesis
Meiosis II: _________________, _____________________, _________________, ____________________/cytokinesis
20. Draw a tetrad: What phase do you first see this in?
21. Which of the following best describe the term “crossing over”?
a.) An exchange of information between two homologous chromosomes
b.) A molecular interaction between two sister chromatids
c.) A molecular interaction between two non-sister chromatids
d.) A separation of two sister chromatids
22. Crossing-over can be found in the stage of
a.) Prophase I
b) Prophase II
c) Anaphase I
d) Anaphase II
23. Which letter in figure #2 represents meiosis? Why?
24. Which letter in figure #2 represents mitosis? Why?
Figure 2
25. Is DNA copied before Meiosis II? _______
26. How many cells form at the end of Meiosis II and how many chromosomes do they contain?
_____________, _____________
27. A sperm cell is a (gamete, zygote), and is (haploid, diploid).
28. When a sperm cell and an ovum/egg merge, they undergo the process of fertilization, and give rise
to a (gamete, zygote), which is (haploid, diploid).
29. What is the ultimate goal/purpose of mitosis? What term do we use to describe the new cells?
30. What is the difference between chromosomes, chromatids, and homologous chromosomes? You
may draw a picture as your answer.
31. How are DNA and chromosomes related?
32. What is the difference between a haploid, diploid, and zygote?
Haploid:
Diploid:
Zygote:
33. How does Meiosis differ from Mitosis?
34. What does Meiosis create? Haploids or Diploid? Somatic cells or gametes?
35. What is a gamete? How do we represent the chromosome number: 2n or n?
36. What is crossing over? When does it happen? Draw a picture.