BIOL0601Provincial Biology: Module 3: Genetics
BIOL0601 Module 3 Assignment 3 (M3A)
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BIOL0601Provincial Biology: Module 3: Genetics
Introduction
BIOL0601 Provincial Biology
Assignment 3
Instructions:
Print Students
Answer questions in the spaces provided on the paper. If you need more space,
append a sheet and make sure that you clearly identify the page with your name,
the assignment title and the question number. Answers to the long answer
questions are to be done on a separate paper. Make sure that you clearly identify
this page with your name, the assignment title and the question number.
Only submit your work to your tutor when all the work in the assignment (questions
and labs) has been completed.
If you are sending your file to your tutor electronically, ensure that it has a file name
that includes the course name, assignment number and your name.
e.g. BIOL0601_A1_Chiu.doc (with your name in place of “Chiu.”)
Topic
Marks
Diagrams
10
Terms and Definitions
9
Matching Questions
9
Short Answer Questions
30
Long Answer Questions
12
Lab 3A
10
Lab 3B
10
Lab 3C
10
Total marks
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BIOL0601Provincial Biology: Module 3: Genetics
Diagrams
1. Each of the micrographs represents a stage of mitosis. Identify the stage, and state why you made
this identification. (10 marks)
The phases flow smoothly from one into the other, and sometimes it is difficult to distinguish at the
boundary between two phases. Each phase however, does have specific features. Use these
features to identify the individual slides, and note those features in the reasons column.
micrograph
stage of mitosis
metaphase
prophase
(early prophase)
anaphase
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reasons
In metaphase (late metaphase) the
chromosomes are lined up along the
equator of the cell and the spindle fibres
are well developed. The chromatids are
about to begin to separate.
This is early in the process. The chromatin
has condensed and the chromosomes are
visible. The centromeres have divided and
are just beginning to move to the poles of
the cell.
The chromatids have separated and the
new nuclei are forming. Cytokinesis is
about to begin.
BIOL0601Provincial Biology: Module 3: Genetics
Prophase
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The chromosomes are visible and the
nuclear membrane is gone. The
centromeres are in position at the poles of
the cell. The cell is organizing itself for the
separation of the sister chromatids.
BIOL0601Provincial Biology: Module 3: Genetics
Terms
1. Place the letter of the definition that matches a term in the left hand column (*) of the chart. (4 marks)
(*)
term
definition
autosome
A
crossing over
B
cytokinesis
C
haploid
D
pedigree
E
meiosis
F
syndrome
G
trisomy
H
Exchange of segments between
non-sister chromatids in the tetrad.
A disorder which is indicated by a group of
symptoms that appear together.
A graphical representation of the
appearance of a certain characteristic
over several generations in a family.
The process whereby the amount of DNA
is halved during the formation of gametes.
Chromosomes other than the sex
chromosomes.
Describes the situation in which there are
three homologous chromosomes instead
of two.
Describes the chromosome number in a
gamete.
The process at the end of mitosis that
produces two new cells.
2. Create a paragraph to show that you understand the relationship between the following terms:
chromosome, gene, allele, dominant, recessive, haploid, diploid, genotype, phenotype, mutation (5
marks)
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BIOL0601Provincial Biology: Module 3: Genetics
Matching
1. This is a family pedigree for the sex linked (X-linked) characteristic, hemophilia.
Squares represent males.
a) Match the description in the following table with the number of the individual or individuals in
the pedigree. Numbers 3 and 22 have been done for you. All individuals in the chart should
be matched when done. (6 marks)
description
homozygous normal female
carrier female
hemophiliac female
normal male
hemophiliac male
unable to say genotype exactly
number on chart
3
22
b) What conditions are necessary for a female to be a hemophiliac? (1 mark)
c) Explain why a male can never be considered
d) a “carrier”. (1 mark)
e) Explain your choice for individual 11 (1 mark)
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BIOL0601Provincial Biology: Module 3: Genetics
Short Answer Questions
1. Compare and contrast oogenesis and spermatogenesis. (4 marks)
2. Outline the stages of the cell cycle and the events that take place in each stage. (4 marks)
3. Two ways in which genetic variation is introduced are:
1. the way the homologous chromosomes pairs line up along the equatorial plate and then
separate in anaphase 1 of meiosis
2. crossing over during metaphase 1 of meiosis
How does each of these contribute to genetic variation? (4 marks)
4. Plants heterozygous for a characteristic which determines petal colour were crossed (AB x AB).
The A allele represents a red phenotype and the B allele represents a white phenotype.
Work out the genotypic and phenotypic numbers if:
1. This is an FI cross. The results will be 1 AA to 2 AB to 1 BB
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BIOL0601Provincial Biology: Module 3: Genetics
2. A and B are incompletely dominant. (2 marks)
3. A and B are co-dominant (2 marks)
5. In summer squash, white fruit color (W) is dominant over yellow fruit color (w) and disk-shaped fruit
(D) is dominant over sphere-shaped fruit (d). If squash with white, disc shaped fruit are crossed,
and both characteristics are heterozygous, what will the phenotypic ratios be? (set up a Punnet
Square to solve this problem) (5 marks)
Hint: The genotype of both parents is WwDd
6. Consider the following situations:
Situation 1: Two genes, A and B are on one chromosome.
Situation 2: Two genes, C and D are on two separate chromosomes.
Both organisms are heterozygous for each gene (Aa, Bb, Cc and Dd). How does this gene
distribution affect the way in which the alleles will be distributed between gametes and passed on to
offspring? ( 3 marks)
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BIOL0601Provincial Biology: Module 3: Genetics
7. Name all the parental genotypic combinations required to produce an individual with blood type A
and genotype IAi (2 marks)
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BIOL0601Provincial Biology: Module 3: Genetics
Long Answer Questions
Answer the following questions on a separate piece of paper. Each of your answers should be two to
three paragraphs long. Use your own wording.
1. Figure 18.4 of your text shows 3 checkpoints in the cell cycle. At each of these checkpoints,
apoptosis will occur if certain conditions exist. What is apoptosis? What is the significance of each
of these checkpoints to the survival of the cell and the survival of the organism? How might these
events relate to cancer? (8 marks)
2. Colour in a type of flower is controlled by 2 genes that together lead to 4 unique colours of petal. The
“A” allele of gene 1 produces the dominant phenotype, blue flowers. The “B” allele of gene 2
produces the dominant phenotype, red flowers. When both alleles occur together (A_B_) the flowers
are yellow. In the absence of either allele “A” or “B”, the flowers are mauve (aabb).
You are given some seeds that were produced by a yellow-flowered plant, and plant them in your
garden. Once the plants have grown and the flowers are blooming, you find every one of the four
colours in your garden. When you count the plants, you find 22 yellow, 19 blue, 21 red and 23 mauve
plants. What can you deduce about the genotypes of the parent plants? What colour (phenotype)
was the other parent plant? Explain your answers completely. (6 marks)
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BIOL0601Provincial Biology: Module 3: Genetics
Lab 3A: Mitosis (Microscope CD)
Introduction
Cells have finite life spans. Some cells live for hours (cells of hair, skin and intestine lining) and some last
longer (red blood cells for 120 days and stem cells for a lifetime!) New cells are produced by a process
called mitosis. In this process a cell produces two daughter cells, “identical” to each other and the original
cell. The cells are identical because they each contain a copy of the DNA from the original cell.
This can be pictured as making an exact copy of a 23 volume encyclopedia (with 2 copie3s of each
volume), with each of the new 23 volume sets containing some of the original and some of the “new”
material. Through a carefully orchestrated series of steps, a single cell makes a copy of its DNA, and then
divides into two, placing one of the DNA copies into each daughter cell. This process of DAN replication
occurs during the M stage of the cell cycle.
Method
The processes that we wish to observe are too small to be seen with the pocket microscope. Pictures have
been taken of cells of the onion root tip and whitefish blastula. These pictures have been included in the
Microscope CD.
1. Examine the video on mitosis on the Microscope CD. Notice that the process is a continuous, smooth
event.
2. Section 18.3 of your text has descriptions and diagrams of each of the phases of mitosis. Examine the
mitosis slides included on the Microscope CD. Find a cell in each of the stages indicated and draw a
diagram of that cell in the space provided in the Results section.
(The slides represent snapshots of a cell in mitosis. You may have to search to find the stages, but they
are all included)
Results
prophase
slide name:
Key observations
power -
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BIOL0601Provincial Biology: Module 3: Genetics
early metaphase
slide name:
Key observations
power late metaphase
slide name:
Key observations
power -
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BIOL0601Provincial Biology: Module 3: Genetics
anaphase
slide name:
Key observations
power -
telophase
slide name:
Key observations
power -
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BIOL0601Provincial Biology: Module 3: Genetics
cytokinesis
slide name:
Key observations
power -
Congratulations, you have now completed Lab 3A
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BIOL0601Provincial Biology: Module 3: Genetics
Lab 3B: Monohybrid Crosses
Please note that you do not need to submit your lab work to your tutor. You do need to
submit the completed tables in the Results section and your answers to the questions in
the Thinking About the Results section.
Introduction
We are all aware that the offspring of parents can display a combination of characteristics from almost
completely maternal to almost completely paternal. Farmers took advantage of this by selectively breeding
plants and animals to produce desired results (more milk from a cow or more fruit on a plant)
In the early nineteenth century, an Austrian monk, Gregor Mendel, whose background was agriculture,
began to approach the selective breeding problem with a view to understanding it and making it more
efficient. He published his work in 1865, but its importance was not recognized until fifty years later. He
was then called the “father of modern genetics”.
We will use a model system to show how genetic characteristics are passed along to the next generation
and how parental characteristics interact to produce the characteristics of the offspring.
Enter the data as you do the lab.
Materials
2 cups (like Styrofoam or paper coffee cups)
10 small objects of the same shape and size but of different colours (like 5 red and 5 green jelly beans –
any two colours will do
Method
In order to study how characteristics were passed along, Mendel did two things:
1. He identified characteristics with two variations (smooth and wrinkled seeds, yellow and green
seeds, tall and short plants)
2. He produced individuals that were pure breeding for each of the characteristics and their varieties.
He then began to cross the pure breeding plants. The pure breeding plants are called the P1 generation
(first parental generation) and the “offspring” were called the F1 generation (first filial generation). He
found that in the F1 generation, one of the variations of the characteristic “disappeared”. In the cross
between tall and short pure breeding plants, all the F1 plants were tall.
He then did something which can be considered brilliant – he crossed F1 plants together. He found that the
variety that had disappeared reappeared and that there was a specific mathematical relationship between
the numbers of tall and the numbers of short plants.
The characteristics are determined by the genes carried by the parents. The varieties of these genes (tall
and short for example) are called alleles. The allele that shows up in the F1 generation is called the
dominant phenotype, and the one that “disappears” is called the recessive phenotype.
Mendel’s experiments could only be explained if each parent had two alleles for each characteristic, and
that these alleles were passed on independently and randomly to the offspring. This was called Mendel’s
Law of Segregation.
The P1 generation
1. Label one of the cups HIS. Label the other cup HERS
2. In order to create the P1 generation, we need homozygous parents. A homozygous individual will have
two identical alleles. Place two “jelly beans” of the same colour in the HIS cup.
3. The second homozygous parent in created by placing two jelly beans of a different colour in the HER cup.
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BIOL0601Provincial Biology: Module 3: Genetics
4. Decide on the dominant phenotype (one of the jelly bean colours). Record this in the Results section.
The F1 generation
5. “Breeding” is accomplished by combining one allele from one parent with one allele from the other parent.
Randomly select (close your eyes) one object from each cup. This is a new F1 individual. Record the
“colour” of the two alleles.
6. Replace the objects in the same cup from which they were taken. Shake the cup and make another
selection. Record the results in. Continue like this until 100 F1 offspring have been “produced”. Count the
total number of each genotype and record it in Table 3.2.1
The F2 generation
7. The F2 generation is produced by crossing F1 individuals. In the F1 individual, there is one of each allele.
Place 1 object of each colour in one cup. Do the same for the other cup. Repeat step 5. After 100 F2
individuals have been produced, record the number of each genotype in Chart 3.2.2
Results
1. Colour of dominant phenotype This is a student choice
2. Table 3.2.1
number of homozygous dominant F1 offspring
none
number of heterozygous F1 offspring
all
number of F1 offspring with 2 recessive alleles
none
3. Table 3.2.2
The numbers for this table should approximate 1:2:1
number of homozygous dominant F2 offspring
number of heterozygous F2 offspring
number of homozygous recessive F2 offspring
Thinking About the Results
1. colour (object) of dominant phenotype
____________________
colour (object) of recessive phenotype
____________________
These are student choices
2. Consider the F1 generation:
a. what is the genotypic ratio?
b. what is the phenotypic ratio?
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BIOL0601Provincial Biology: Module 3: Genetics
3. Consider the F2 generation:
a. what is the genotypic ratio?
b. what is the phenotypic ratio?
4. The Punnet square is a useful tool for analyzing crosses. This is an example Punnet square:
X
x
X
XX
Xx
x
Xx
xx
The X represents the allele for the dominant phenotype and the x represents the allele for the
recessive phenotype. (it is convention that the dominant phenotype is represented by a capital
letter). The top shaded area represents one parent and the side shaded area represents the other
parent. The possible offspring are represented by the central unshaded boxes with each parent
donating one allele to give the genotype of the offspring. The phenotype of the offspring depends
on the relationship between the two alleles.
Use the following blank table to analyze your results for the F2 generation. Define the symbols that you
will use for each allele and fill in the Punnet Square. (the shaded area will contain the alleles donated by
each parent
Define your symbols here:
a) What is the genotypic ratio?
b) What is the phenotypic ratio?
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BIOL0601Provincial Biology: Module 3: Genetics
5. How does your experimental phenotypic ratio (question 3) compare with the expected phenotypic ratio
(question 4b)? How can you explain any differences?
.
6. Assume that the dominant phenotype results in a tall pea plant, and the recessive phenotype results in a
short pea plant. Homozygous dominant pea plants were crossed with homozygous recessive pea plants.
a. What would the F1 generation plants look like?
b. What would the F2 generation plants look like?
c.
If 300 F2 pea plants were produced, how many would expect to be:
tall?
short?
(show your work in solving this problem)
7. In the fruit fly, “wild” eyes are the dominant phenotype. A pair of flies was crossed. This produced 41
offspring with “wild” eyes and 13 offspring with white eyes.
a. What are the genotypes of the parent flies?
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BIOL0601Provincial Biology: Module 3: Genetics
b. What are the phenotypes of the parent flies?
Congratulations, you have now completed Lab 3B.
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BIOL0601Provincial Biology: Module 3: Genetics
Lab 3C: Dihybrid Crosses
Please note that you do not need to submit your lab work to your tutor. You do need to
submit the completed tables in the Results section and your answers to the questions in
the Thinking About the Results section.
Introduction
The monohybrid cross involved one characteristic with two alleles (variations). We will now consider the
situation in which we have two characteristics each with two possible alleles. Mendel called this a dihybrid
cross and from the results he developed his Law of Independent Assortment. The important idea behind
the Law of Independent Assortment is that the two characteristics were passed on independently of each
other. Also remember that Mendel only published his results after he had collected a massive amount of
information on the order of thousands of individuals as statistics become more reliable as the number of
data points increases.
Because there are two characteristics and two variations of each characteristic, there are four possible
combinations in which the alleles may be passed on by one of the parents.
Genotype of F1 individual (heterozygous) in a dihybrid cross
Characteristic 2
Characteristic 1
Allele A
Allele a
Allele B
Allele b
Possible Parental Gametes
Each gamete (egg or sperm) produced by a parent will contain one allele for each characteristic. This
gives rise to four possible combinations of alleles in each gamete. If we use letters rather than symbols,
the result for all possible gamete combinations for one parent is:
AB
Ab
aB
ab
aB
ab
Similarly we have four possible gametes for the other parent:
AB
Ab
AB
Ab
aB
ab
At this point this table should look familiar; it is a Punnet square, only this time it is for a dihybrid cross.
Since there are 4 possible gametes for each parent, there are 16 possible combinations of gametes, or
sixteen possible offspring genotypes. The genotype of each offspring is shown in each of the interior
boxes.
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BIOL0601Provincial Biology: Module 3: Genetics
AB
Ab
aB
ab
AB
AA BB
AA Bb
Aa BB
AaBb
Ab
AA Bb
AA bb
Aa Bb
Aa bb
aB
Aa BB
Aa Bb
aa BB
aa Bb
ab
Aa Bb
Aa bb
aa Bb
aa bb
We can now create a chart of the genotypes
possible filial genotypes
AA BB
Aa BB
aa BB
AA Bb
Aa Bb
aa Bb
AA bb
Aa bb
aa bb
genotypic count from chart
1
2
1
2
4
2
1
2
1
The next step is to look at the phenotypic count. Following the convention that the capital letter represents
the dominant phenotype, we can see that there are 4 distinct phenotypes:
both dominant phenotypes – AABB, AaBB, AABb, and AaBb
one dominant and the other recessive – AAbb and Aabb
one recessive and the other dominant – aaBB and aaBb
both recessive phenotypes – aabb
Now we can look at the phenotypic count. Remember that the dominant phenotype is capable of “hiding”
the recessive phenotype in the heterozygous form.
possible filial (F2) phenotypes
AABB, AaBB, AABb, AaBb
both dominant
AAbb and Aabb
one dominant – the other recessive
aaBB and aaBb
one recessive – the other dominant
aabb
both recessive
phenotypic count
9
3
3
1
This is the typical F2 generation phenotypic ratio: 9:3:3:1 in a Mendelian dihybrid cross.. The F1
generation would be produced by parents (the P1 generation) with the following genotypes: AABB x aabb.
As Mendel discovered, using homozygous parents for the P1 generation produced an F1 generation with
heterozygous offspring (AaBb) all of the same phenotype. They all looked the same because the recessive
phenotype was hidden for both characteristics. When the F1 offspring were crossed, the F2 generation
produced 9/16 offspring showing both dominant phenotypes, 3/16 one dominant and the other recessive,
3/16 one recessive and the other dominant and 1/16 showed both recessive phenotypes.
Given the earlier colour codes (red dominant to green and brown dominant to blue), what would the F2
offspring “look” like?
possible F2 phenotypes
AABB, AaBB, AABb, AaBb
AAbb and Aabb
aaBB and aaBb
aabb
phenotypic count
9
3
3
1
appearance of offspring
red – brown
red – blue
green – brown
green - blue
In this experiment we are going to show how this actually happens. The important thing to see here is that
it is pure random chance and the odds can be worked out for the possible occurrence of each of the
phenotypic combinations.
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BIOL0601Provincial Biology: Module 3: Genetics
Materials
-
2 cups (like Styrofoam or paper coffee cups)
20 small objects of the same shape and size but of different colours (2 objects of 2 different colours
and 2 other objects of different colours representing 2 characteristics with two alleles each)
It is important that the last 2 objects be distinguishable from the first two by touch. For
example, red and green jelly beans for the first 2 objects and brown and blue gummy bears for
the second two objects. (or jelly beans and Smarties)
Method
The F1 generation
1. Select your objects so as to create an individual heterozygous for each of two characteristics. One
characteristic is represented by 2 jelly beans (different colours) and the other by 2 gummy bears
(each of different colours). Place these objects in a cup labelled HIS.
2. Label another cup HERS and place the objects in the cup to represent an individual heterozygous
for the two characteristics. Notice that the genotypes of these two individuals are identical for
these two characteristics, just as would be the F1 individuals in the above example.
3. Since the gamete would contain 1 allele for each characteristic, select 1 jelly bean and 1 gummy
bear from one cup.
4. Do the same for the other cup.
5. These four objects represent one offspring. Record the results (use either colour or letter) When the result
has been recorded, return the objects to their respective cups.
6. Repeat this until you have the results for 100 “offspring”. Count the genotypes and record the numbers of
each genotype in Table 3.3.1
7. Clean up your lab space. If things have been relatively clean, feel free to eat your “experiment”.
Results
Table 3.3.1
genotype
count
Thinking About the Results
1. Write the genotypes of the P1 generation
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BIOL0601Provincial Biology: Module 3: Genetics
2. Colour (and letter) of dominant phenotype for each characteristic:
characteristic 1 ______________
characteristic 2 ______________
3. From your data, fill in the following chart:
number of F2 individuals with 2 dominant phenotypes
number of F2 individuals with 1 dominant and 1 recessive phenotype
number of F2 individuals with 1 recessive and 1 dominant phenotype
number of F2 individuals with 2 recessive phenotypes
4. The expected phenotypic ratio for the F2 generation is 9 : 3 : 3 : 1. How does yours compare to the
expected ratio? How can you explain any differences?
5. In fruit flies normal wings (W) are dominant to stubby wings (w) and hairy abdomen (H) is dominant to
hairless abdomen (h). Heterozygous flies (HhWw) were allowed to breed randomly and produce offspring.
a. Each gamete produced by a parent would contain 2 alleles (one for each trait). Write the 4
possible combinations of alleles that can be produced.
b. Fill in the Punnet Square representing this cross.
c.
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BIOL0601Provincial Biology: Module 3: Genetics
d. If 150 flies were produced, how many individuals of each of the phenotypes would we expect?
(show your work)
Congratulations, you have now completed Lab 3C.
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