Genetics Exam 2

Question 1

1. A mutation in DNA that does not change the amino acid sequence of the resulting protein is
   a. impossible
   b. a missense mutation
   c. a nonsense mutation
   d. a silent mutation

Answer 1

d. a silent mutation

Question 2

2. A woman suffers from, and successfully recovers from skin cancer. The woman and her husband are trying to decide if they should have children. What is the likelihood their first child will have a higher than average likelihood of skin cancer?
   a. 50%
   b. 20%
   c. 12.5%
   d. 0%

Answer 2

d. 0% (Somatic mutation not heritable)

Question 3

3. A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). What is the total number of chromosomes present in rat
   gametes?
   a. 21
   b. 42
   c. 84
   d. 126
   e. 168

Answer 3

a. 21

Question 4

4. Which of the following is the correct order of the phases in mitosis?
   a. Metaphase, Prophase, Interphase, Anaphase, Telophase
   b. Prophase, Metaphase, Anaphase, Telophase, Interphase
   c. Prophase, Metaphase, Interphase, Telophase, Anaphase
   d. Telophase, Anaphase, Prophase, Metaphase, Interphase

Answer 4

b. Prophase, Metaphase, Anaphase, Telophase, Interphase

Question 5

5. Which phase of the mitotic cell cycle has two identical copies of the genome in the cell for the entire phase?
   a. I
   b. S
   c. G2
   d. M

Answer 5

c. G2 (DNA has replicated, but mitosis hasn’t started)

Question 6

6. When do homologous chromosomes separate in meiosis?
   a. During prophase
   b. At anaphase I
   c. At anaphase II
   d. they don’t have to separate because they never pair up!

Answer 6

b. At anaphase I

Question 7

7. What is a tetrad?
   a. The four haploid products of meiosis
   b. Two pairs of sister chromatids
   c. The four kinetochores of paired homologous chromosomes
   d. The four nuclei that fuse during meiosis

Answer 7

b. Two pairs of sister chromatids (one from each homolog)

Question 8

8. Expanding nucleotide repeats such as CAGCAGCAGCAGCAG are often the result of_______.
   a. excess amounts of cytosine, adenine, and guanine in the cell.
   b. a slippage of the DNA template during replication.
   c. the movement of a transposon.
   d. reversion mutations.

Answer 8

b. a slippage of the DNA template during replication

Question 9

9. Base analogs are mutagenic because of which characteristic?
   a. They produce changes in DNA polymerase that cause it to malfunction.
   b. They distort the structure of DNA.
   c. They are similar in structure to the normal bases, but base pair differently.
   d. They chemically modify the normal bases.

Answer 9

c. They are similar in structure to the normal bases, but base pair differently

Question 10

10. Homologous chromosomes and sister chromatids differ in that
    a. homologous chromosomes arise from DNA replication and sister chromatids belong to siblings
    b Homologous chromosomes are the copies from each parent and sister chromatids belong to siblings.
    c. Homologous chromosomes are the copies from each parent and sister chromatids are the product of DNA replication of each
    homolog.
    d. Homologous chromosomes are the product of DNA replication of each homolog and sister chromatids are the copies from each
    parent.

Answer 10

c. Homologous chromosomes are the copies from each parent and sister chromatids are the product of DNA replication of each homolog

Question 11

11. Which statement is most correct?
    a. During interphase sister chromatids are present on different alleles
    b. During interphase different genes are present at the same locus on sister chromatids
    c. During interphase homologs are present on different alleles
    d. During interphase different alleles are present at the same locus on different homologs

Answer 11

d. During interphase different alleles are present at the same locus on different homologs

Question 12

12. Trisomy 21 is caused by ____________ during either meiosis I or meiosis II.
    a. crossing over
    b. nondisjunction
    c. chiasmata
    d. disjunction

Answer 12

b. nondisjunction

Question 13

13. In a germline cell there are two pairs of chromosomes (2N=4). F and f represent two different alleles (versions or variants) of one
    gene, and Q and q represent two different alleles of another gene. On one pair of chromosomes are the F & f alleles, and on the other
    pair of chromosomes are the Q and q alleles. If this cell divides normally to produce sperm, what are the possible sperm genotypes?
    A) F, f, Q, q
    B) Ff, Ff, Qq, Qq
    C) FQ, fq, Fq, fQ
    D) Ff, Qq, FQ, fq, Fq, fQ

Answer 13

C) FQ, fq, Fq, fQ (independent assortment)

Question 14

14. A mutation in DNA that changes a single amino acid of the resulting protein is
    a. impossible
    b. a missense mutation
    c. a nonsense mutation
    d. highly improbable

Answer 14

b. a missense mutation

Question 15

15. Suppose there are two genes on two different chromosomes, one gene called G and the other called D. An individual has the genotype
    Gg,Dd. Which of the following drawings correctly shows cells in this individual after DNA replication but before cell division of the first
    meiosis? Assume no recombination/crossing-over occurs between the homologs. Circle one.

Answer 15

a) Two chromosome pairs, each with two sister chromatids. Alleles are G/g and D/d – this is correct.15.

Question 16

16. Post-translational modifications of proteins that bind to DNA in eukaryotic cells including phosphorylation, methylation, and
    acetylation are known as_____________.
    a. mutagens
    b. the histone code
    c. enhancers
    d. insulators

Answer 16

b. the histone code

Question 17

17. When do sister chromatids separate in meiosis?
    a. At anaphase I
    b. At anaphase II
    c. During prophase
    d. During cytokinesis

Answer 17

b. At anaphase II

Question 18

18. When do homologous chromatids separate in meiosis
    a. At anaphase I
    b. At anaphase II
    c. During prophase
    d. During cytokinesis

Answer 18

a. At anaphase I

Question 19

19. In eukaryotic cells the nuclear envelope separates the processes of transcription and translation. This allows eukaryotic cells to
    perform __________ before translation that enhances the number of different proteins that can be made from a specific gene.
    a. alternative splicing
    b. polyadenylation
    c. RNA capping
    d. all of the above

Answer 19

a. alternative splicing

Question 20

20. You perform a CHIP (Chromatin Immunoprecipitation) assay to determine
    a. if there are chloroplast genes in a sample
    b. which DNA sequence a known transcription factor binds to in a genome.
    c. which transcription factor a fragment a known DNA fragment binds to in a cell.
    d. to see if gene regulatory networks are similar between two organisms.

Answer 20

b. which DNA sequence a known transcription factor binds to in a genome

Question 21

21. Ploidy refers to the number of sets of chromosomes found in an organism. Most multicellular organisms are _____.
    a. haploid
    b. tetraploid
    c diploid
    d. polyploid

Answer 21

c. diploid

Question 22

22. siRNAs act ____________________.
    a. to connect tRNAs and mRNAs in the ribosome
    b. to remove introns.
    c. to silence genes by turning over tRNA
    d. to silence genes by turning over mRNA

Answer 22

d. to silence genes by turning over mRNA

Question 23

23. When considering the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA
    polymerase(s) binds. What is a consensus sequence?
    a. GAGA
    b. GCATGCAT
    c. the most probable set of nucleotides at a functional position.
    d. any trinucleotide repeat

Answer 23

c. the most probable set of nucleotides at a functional position

Question 24

24. The amount of a specific protein that accumulates in the cell can be regulated by___________________
    a. the amount of transcription.
    b. the amount of translation.
    c. the amount of protein turnover or proteolysis.
    d. the rate of mRNA degradation
    e. all of the above

Answer 24

e. all of the above

Question 24

25. The MLH1 gene is located on chromosome 3 in humans and four different alleles have been identified. The maximum number of alleles a single normal individual can have is: a. 1 b. 2 c. 3 d. 4

Answer 24

b. 2 (One from each parent)

Question 25

26. Chromatin structure plays a role in eukaryotic but not bacterial gene regulation. In general condensed chromatin represses gene expression; Chromatin structure must therefore be altered before transcription can take place. Chromatin structure is altered by________ a. chromatin- remodeling complexes. b. modification of histone proteins. c. changes to DNA methylation. d. all of the above.

Answer 25

d. all of the above

Question 26

27. Humans have 23 pairs of chromosomes. If a human had 47 chromosomes that would be the result of______. a. Polyploidy b. Aneuploidy c. Triploidy d. Diploidy

Answer 26

b. Aneuploidy

Question 27

28. ___________ means that all cells in an organism contain the same genetic information, or genome, and the ability to create a complete organism. a. Mitosis b. Meiosis c. Genomic equivalence c. aneuploidy

Answer 27

c. Genomic equivalence

Question 28

29. Which of the following is most likely a loss of function mutation? a. silent b. missense c. nonsense d. transversion e. transposition

Answer 28

c. nonsense (Usually creates a premature stop codon)

Question 29

30. Which of the following leads to gametes receiving incorrect numbers of chromosomes? a. apoptosis b. synapsis c. heterozygosity d. nondisjunction

Answer 29

d. nondisjunction

Question 30

31. Describe in detail how one DNA repair mechanism works including the type of mutation does it repair. (10 pts.)

Answer 30

drawing Nucleotide Excision Repair (NER): NER repairs bulky lesions such as thymine dimers (caused by UV light). Steps: Damage recognized by protein complex. DNA is unwound around the lesion. Endonuclease cuts strand on both sides of damage. Damaged segment is removed. DNA polymerase fills in gap using complementary strand. DNA ligase seals the nick. Type of Mutation Repaired: Pyrimidine dimers and bulky chemical adducts.