Study Guide for Genetics Common Assessment
To help you on the Genetics Common Assessment, answer the following questions:
1. What are the three stages of the cell cycle? Give a brief explanation of each stage and
be prepared to identify (from an illustration) what is happening in each stage.
Interphase: consists of G1 (cell grows), S (DNA replicates), and G2 (organelles replicate)
Mitosis: division of the nucleus (Prophase, Metaphase, Anaphase, Telophase)
Cytokinesis: division of the cytoplasm and cell membrane/wall
2. What are the stages of meiosis?
Meiosis I: Prophase I, Metaphase I, Anaphase I, and Telophase I
Meiosis 2: Prophase II, Metaphase II, Anaphase II, and Telophase II
Explain the difference in the number of chromosomes produced during the first and
second parts of meiosis. Use the terms “diploid” and “haploid” in your answer.
Meiosis I: starts as a diploid (full set of chromosomes) cell and becomes two haploid
(half the number of chromosomes) cells at the end of this stage.
Meiosis 2: starts as two haploid cells and become four haploid cells at the end
What is the end product of meiosis in both males and females?
Male: sperm (pollen in plants)
Female: eggs (ova)
Mitosis is a process that occurs during ___asexual______ (sexual/asexual)
reproduction while meiosis occurs during ____sexual______ (sexual/asexual)
reproduction.
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3. Draw the structure of a DNA molecule. What are the molecules that make up each
nucleotide and how do the bases fit together with one another?
Make sure the drawing shows alternating phosphates and sugars (deoxyribose) down the sides
with bases (adenine with thymine, guanine with cytosine) serving as the “rungs” Make sure
that they know that DNA is in the shape of a double helix.
4. What happens during semi-conservative (DNA) replication? Why is it called “semiconservative”?
DNA copies itself. It’s called semi-conservative because each new piece of DNA contains
half of the original piece.
5. What happens during transcription and where does it occur in a cell?
The process takes place in the nucleus. A region of DNA (the desired gene) is used to produce
RNA. One of the DNA strands serves as a template to produce the RNA using RNA nucleotides
(uracil taking the place of thymine). When finished, DNA zips back up and RNA can be edited
prior to leaving the nucleus.
6. Explain how a protein is formed through translation? Where does this happen in a cell?
mRNA travels to the ribosome where it attaches. At the same time, transfer RNA is out picking
up specific amino acids. When tRNA comes to the ribosome its three-letter bases (anti-codons)
“look” (A-U, C-G) for the matching mRNA codons and attaches. This puts the amino acids in a
specific order – the basis for a protein.
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7. What role do the golgi apparatus and endoplasmic reticulum play in the production and
secretion of specific proteins by cells?
Golgi apparatus – modifies proteins by adding lipids/carbohydrates to them. Improves their
function
Endoplasmic reticulum – assist in moving proteins around the cell and to the cell membrane
for moving the proteins outside the cell. Rough ER have ribosomes attached to them to
speed up this process.
8. Circle the letter preceding a process that occurs in all living things (you may circle
several choices)
a. Mitosis – not prokaryotes – no nucleus
b. Meiosis – not bacteria
c. Photosynthesis -- not animals
d. DNA Replication
e. Translation
f. Transcription
9. Define the following terms
a. DNA – molecules used to carry genetic information
b. Genes – sections of DNA that code for proteins (and therefore traits)
c. Alleles – variations of genes (like blonde hair, brunette hair, red hair, etc)
d. Chromosomes – structures found within the nucleus of cells that are made of
DNA
Explain how all these terms are related
Chromosomes are made up of DNA, which contains the code for our genes. Changes in the
DNA can create different alleles.
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10. Illustrate and explain a cross between a recessive short and a homozygous tall pea plant
as well as a cross between the offspring of this first generation. Express your answer for
each punnett square in terms of genotype and phenotype
T
T
t
Tt
Tt
t
Tt
Tt
4/4 Tt – Tall
T
t
T
TT
Tt
t
Tt
tt
¼ TT -- Tall
2/4 Tt – Tall (hybrid)
¼ tt -- short
11. Explain how blood type is an example of multiple alleles. Use a punnett square to
illustrate the inheritance of this trait There are three alleles: IA, IB, and i
A Blood = IAIA or IAi
IA
B Blood = IBIB or IBi
IB
IAIB
AB Blood = IAIB
i
IAi
I
¼ AB Blood
IBi
¼ A Blood
ii
¼ B Blood
O Blood = ii
¼ O Blood
12. List and explain the different patterns of gene inheritance (incomplete dominance and
co-dominance) giving examples of each using a punnett square.
Incomplete – blending of alleles (red + white = pink)
Co-dominant – both alleles show up (red + white = red and white)
Incomplete
Co-Dominance
B
B
B
W
BW
BW
4/4 BW == black and
W
BW
BW
white (spotted)
B
W
BW
BW
W
BW
BW
4/4 BW = gray
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13. What is the difference between autosomes and sex chromosomes?
Autosomes are normal chromosomes (you have 22 pairs) and the sex chromosomes (1
pair) determine your gender. They are always shown last on a karyotype.
How do sex chromosomes determine the gender of each child?
XX = female; XY = male The Y chromosome is much smaller than the X chromosome
and students may assume that it carries no traits.
Use punnett squares to show how a recessive sex-linked trait (like colorblindness) can
be passed from a grandfather to his grandson.
B = normal vision
B = colorblind
Colorblind Grandfather
Xb
Y
XB
XBXb
XBY
XB
XBXb
XBY
XB
Y
XB
XBXB
XBY
Xb
XBXb
XbY
Colorblind Grandson
14. Describe what happens during crossing over in meiosis
Homologous chromosomes exchange parts of their DNA. This is good because it helps to create
variety. Occurs during Prophase I of meiosis.
15. List, diagram, and explain the different types of chromosomal mutations.
Deletion – part of chromosome is missing
Duplication – part of a chromosome is doubled
Translocation – crossing over between non-homologous chromosomes
Nondisjunction – missing or extra chromosomes
Polyploidy – an entire extra set of chromosomes (fatal in animals but can provide
benefits to plants)
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16. List the types of gene mutations and their effects.
Point Mutation – one of the DNA bases is switched (see #17 for 3 types)
Frameshift Mutation – an extra base is attached or one base is deleted. Changes all the
remaining amino acids in the protein chain.
17. What’s the difference between silent, missense, and nonsense mutations?
Silent – the change in a DNA base does not affect the amino acid and, thus, the protein
Missense – the change in a DNA base changes the one amino acid, altering the protein
Nonsense – the change in a DNA base codes for a “stop codon”, ending the protein
chain
18. What techniques do plant and animal breeders use to alter the appearances of
domesticated plants and animals?
Selective breeding which consists of:
a.
Inbreeding – trying to promote one good characteristic by breeding closely
related individuals together. Can also bring together two harmful recessive traits.
b.
Hybridization – trying to combine two good characteristics found in separate
individuals by breeding them together
19. How does the process of bacterial transformation (used to create transgenic organisms)
occur and how can it be used to benefit humans?
Use a restriction enzyme to cut open a plasmid (circular piece of DNA in bacteria). Use
the same restriction enzyme to cut out the gene you want to insert. Mix the cut-open plasmid
with the cut-out gene and the “sticky ends” (matching pieces of DNA bases) should cause the
two to combine. This process is being used to insert the human gene for making insulin into
bacteria so that the bacteria now makes human insulin which is needed by diabetics.
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20. What are some of the applications of genetic engineering techniques in the following
fields:
a. Forensics
DNA Profiling/Fingerprinting is used to identify criminals or fathers of children.
Restriction enzymes cut up DNA into different sized pieces and then they are separated by gel
electrophoresis. This works because DNA has a negative charge so it will move towards the
positive side when electricity is run through the gel. The gel separates the fragments – larger
fragments can’t travel as far as the smaller fragments.
b. Agriculture
Genetically modifying foods by inserting new genes can make them more nutritious
or pest/herbicide resistant. The concern is that insects/weeds will evolve to be
pesticide/herbicide resistant or that harmless insects can be killed off, changing the
ecosystem. Another concern is the cost – will only the rich be able to farm?
21. Describe cloning and what are some possible benefits and concerns with this process?
Cloning occurs when the nucleus of one cell is removed and then put into an egg cell
which has had its nucleus removed. A jolt of electricity causes them to fuse. “Dolly” the first
cloned mammal was created this way.
Benefits – can create new organisms which have the characteristics we want. Clone
pets that we love
Concerns – will the new organism behave like the original? It’s not a perfect process so
is it ethical for us to do this, particularly with humans? Are we playing God?
22. Describe what is meant by “genetically modified organisms (GMO’s)” and what are
some possible benefits and concerns with them?
Already answered this in Question 20 part B. Students can list the benefits/concerns
here
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23.
Look at the following pedigree:
a.
How many generations are shown in this pedigree?
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b.
Why are some of these shapes shaded in?
They show the recessive trait (therefore they are homozygous recessive)
c.
Can any of the children in the 2nd generation be homozygous for the dominant
trait? Explain your answer.
No – the mother (circle) in the first generation is homozygous recessive so she
must pass on one recessive allele to the offspring
24.
a.
What process is illustrated above?
Meiosis
b.
How does the chromosome number of the parent cell compare to that of the
daughter cells? Meiosis produces daughter cells with ½ the number of
chromosomes compared to the parent cell
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25.
a.
How many chromosomes would be found in pea plant pollen?
7 (contains half the diploid amount)
26.
a.
The above diagram represents the results of DNA profiling. In Lane A is the DNA of a
woman, while in Lane B is the DNA of her child. Which lane contains the father’s DNA?
How can you tell?
F – DNA that didn’t match up with mom’s had to come from the father
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27.
a.
What type of inheritance is illustrated in the drawing shown above?
Incomplete Dominance – the hybrids are pink.
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