Download Name Ch 9 Homework- KEY 1. Cystic fibrosis is a recessive genetic

Name ____________________________
Ch 9 Homework- KEY
1. Cystic fibrosis is a recessive genetic disorder. Ron is homozygous dominant (FF) and Nancy is a carrier
(Ff) of cystic fibrosis. Use a Punnett square to predict the probability that one of their children will have
cysticfibrosis. Include the probabilities for genotype and phenotype of the offspring. Show all work and
box your final answer. (1)
F
f
F
FF
Ff
F
FF
Ff
None of their children will have Cystic fibrosis, however, there is a 50% chance that they
will be a carrier. 50% will be homozygous dominant, without the disease and 50% are heterozygous,
without the disease.
2. Patty is homozygous dominant for freckles (SS), while Charlie is homozygous for no freckles (ss). Draw
a Punnett square predicting the probability if their children will have freckles. Include the probabilities
for genotype and phenotype of the offspring, Show all work and box your final answer. (1)
s
s
S
Ss
Ss
S
Ss
Ss
100% of their children will have freckles. 100% of them will be heterozygous for freckles.
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3. Imagine that Patty and Charlie’s children (from Q 2) were separated at birth, inadvertently met, fell in
love and had children of their own. Draw a Punnett square predicting the probability if their children will
have freckles. Include the probabilities for genotype and phenotype of the offspring, Show all work and
box your final answer. (1)
S
s
S
SS
Ss
s
Ss
ss
There is a 25% chance that their children will be homozygous dominant, a 25% chance that they will be
homozygous recessive and a 50% chance that they will be heterozygous.
There is a 75% chance that they will have freckles and a 25% chance that they will not.
4. In humans colorblindness (b) is an example of a sex-linked recessive trait. In this problem, a male with
colorblindness marries a female who is not colorblind but carries the (b) allele. Using a Punnett square,
determine the genotypic and phenotypic probabilities for their potential offspring. Show all work and
box your final answer. (1)
Xb
X
Xb
XbXb
XbX
Y
XbY
XY
There is a 25% chance of having a homozygous recessive girl, a 25% chance of having a heterozygous
recessive boy, a 25% chance of having a heterozygous recessive girl and a 25% chance of having a
homozygous dominant boy.
There is a 25 % chance that that the couple would have a colorblind girl, a 25% chance that they would
have a color blind boy, 25% chance that they would have a girl that carries the color-blind allele and a
25% chance of have a normal boy.
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5. All the offspring of a cross between a black-eyed fly and an orange-eyed fly have black eyes. This
means that the allele for black eyes is ________ the allele for orange eyes. (1)
A) codominant to
B) recessive to
C) more aggressive than
D) dominant to
E) better than
6. Contrast ‘polyegenic inheritance’ and ‘pleiotropy.’ (1)
Polyegenic inheritance is when a single characteristic in influenced by many genes. Pleiotropy is when a
single gene influences many phenotypic characteristics.
7. Define genotype and phenotype. Also, include an example where you tell me the genotype and
phenotype of an individual (it can be theoretical). (1)
Genotype is the genetic make up of an organism. The phenotype is the outward expression of the traits.
A genotype example is the gene that codes for eye color, EYCL1. The phenotype is blue/green eyes.
8. Explain incomplete dominance and codominance (1).
Incomplete dominance is when the phenotype is intermediate between the phenotype of the parents.
Codominance is when a heterozygous expressed both traits.
9. Sex-linked conditions are more common in men than in women because (1)
A) men acquire two copies of the defective gene during fertilization.
B) men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
C) women simply do not develop the disease regardless of their genetic composition.
D) the sex chromosomes are more active in men than in women.
E) the genes associated with the sex-linked conditions are linked to the Y chromosome, which
determines maleness.
10. What are linked and sex-linked genes (1)
Linked genes are genes located near each other on a chromosome and tend to be inherited together.
Sex-linked genes are linked genes located on the sex chromosomes .
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Ch 10 homework
1. Outline DNA replication. Include the jobs of DNA polymerase and ligase during DNA replication,
and the 4 “phases” (1)
DNA replication: Helicase unwinds the DNA double helix, forming a bubble around the origin of
replication where synthesis starts. DNA polymerase binds to the DNA strands at the origin of replication
and via base pairing, begins to synthesize new daughter strands of DNA. The daughter strand grows in a
5’-3’ direction. Both strands of DNA are synthesizing new daughter strands at the same time. One strand
is able to do this continuously (the leading strand) and the other must be synthesized in short segments
(the lagging strand). DNA ligase then comes in and links the DNA fragments on the lagging strand
forming a continuous strand of DNA.
Phase 1: DNA is unwound via helicase
Phase 2: DNA synthesis starts using DNA polymerase
Phase 3: Ligase connects the lagging strands
Phase 4: Synthesis ends, the enzymes disconnect from the DNA and the two new double helices re-wind.
2. Explain the difference between transcription and translation. (1)
Transcription is the transfer of genetic information from DNA into a RNA molecule.
Translation is the transfer of information on the RNA into a protein.
3.
Which of the following enzymes catalyzes the elongation of a new DNA strand? (.5)
a. helicase
b. primase
c. ligase
d. single-stranded binding protein
e. DNA polymerase
4. What are the complimentary base pairs of DNA and RNA and what type of a bond holds the base
pairs to its compliment ?(1)
DNA A-T, C-G
RNA A-U, C-G
The base pairs are held together via hydrogen bonding
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5. What is the job of the ribosome and the tRNA molecule while using mRNA to make a
polypeptide?(1)
The tRNA serves to fetch free amino acids from the cytoplasm and bring them to the ribosome to be
connected to the growing protein chain.
The ribosome coordinates the functioning of the mRNA and tRNA and make the polypeptides
6.
Where do transcription and translation occur in prokaryotic cells? (.5)
a. on the plasma membrane
b. in the nucleus
c. in the cytoplasm
d. in chromatophores
e. in the cell wall
7. Multiple origins of replication on the DNA molecules of eukaryotic cells serve to (.5)
a. remove errors in DNA replication.
b. create multiple copies of the DNA molecule at the same time.
c. shorten the time necessary for DNA replication.
d. reduce the number of "bubbles" that occur in the DNA molecule during replication.
e. assure the correct orientation of the two strands in the newly growing double helix.
8. Explain the process in which amino acids are added make new polypeptides (1)
The mRNA is fed through the ribosome. A tRNA, carrying an amino acid, binds to the mRNA via anticodon matching at the A-site of the ribosome. The tRNA in the P site transfers the forming polypeptide
to the amino acid that is in the A-site and leaves to retrieve another amino acid. The ribosome moves
down to the next codon. This results in the tRNA that was previously at the A site now residing in the P
site and another tRNA carrying another amino acids fills the A site and the process continues.
9. Explain how DNA mutations lead to evolutionary changes (1)
DNA mutations can change which proteins are made. These changes give evolution something
to select for/against, leading to evolutionary changes.
10. Explain three ways bacteria obtain new genetic material (1)
Transformation- where bacteria uptake foreign DNA from their environment
Transduction- where bacteria acquire new DNA from a phage.
Conjugation- when bacteria physically transfer DNA during “mating”
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11. If one strand of DNA is CGGTAC, the corresponding strand would be (.5)
a. GCCTAG.
b. CGGTAC.
c. GCCAUC.
d. TAACGT.
e. GCCATG.
12. Show how new proteins are made, from DNA to RNA to protein (1)
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