Genetics Finals study guide

1. In a cross between a dihybrid (AaBb) and a double-recessive (aabb), which result would indicate that the two genes are linked?

a. more parental type than recombinant offspring

b. more recombinant than parental type offspring

c. equal proportions of all offspring types

a. more parental type than recombinant offspring

2. What form of bacterial gene exchange involves a viral intermediate?
a. transformation
b. conjugation
c. transduction

c. transduction

3. Some Drosophila can survive with only one copy of chromosome 4, and homologous pairs of all other chromosomes. What type of chromosome abnormality does this represent?

a. aneuploidy

b. polyploidy

c. inversion

a. aneuploidy

5. True or False: Horizontal gene exchange occurs from parents to offspring.

False

7. Chromosomal abnormalities that affect gene dosage are ______ to alter phenotype.

a. more likely

b. less likely

a. more likely

11. What type of bonds hold the two strands of DNA together?

a. covalent

b. ionic

c. hydrogen

c. hydrogen

12. In our DNA isolation procedure, the role of the detergent in our initial buffer was to:

a. break open the lipid cell membrane

b. remove the carbohydrate cell wall

c. precipitate the DNA into solid form

a. break open the lipid cell membrane

13. You want to grow bacteria that are thi- his- strpᴿ. What kind of media should you use to ensure survival of bacteria of this specific genotype?

a. media containing thi, his, and strp

b. media containing his and strp

c. media containing only minimal salts and carbon source

d. media containing his and strp

e. media containing thi and strp

d. media containing his and strp

14. Which one of the following statements is true of polyploidy?

a. it results in an abnormal number of only one chromosome

b. it is always lethal

c. it occurs only in animals

d. it can produce fruits that are larger and/or seedless

d. it can produce fruits that are larger and/or seedless

15. You have a fly with only one copy of the chromosome that carries the WT allele of the bristle trait (b+/–). If this fly is crossed to a homozygous bent-bristle fly (b/b), what offspring phenotype ratio will you observe?

a. all WT flies, none monosomic

b. all bent-bristled flies, none monosomic

c. 1:1 WT: bent bristled, none monosomic

d. 1/2 WT : 1/2 bent bristled and monosomic

e. all monosomic bent-bristled

d. 1/2 WT : 1/2 bent bristled and monosomic

16. Translocations can be caused by which of the following? (Select all that apply)

a. chromosome breakage and re-joining

b. homologous recombination at repetitive DNA elements

c. nondisjunction

d. cross-species fertilization

a. chromosome breakage and re-joining

b. homologous recombination at repetitive DNA elements

17. You want to determine whether the Arabidopsis genes apetala (whose mutation causes petal-less flowers) and glabrous (whose mutation causes shiny, hairless leaves) are linked. You cross a plant heterozygous for both traits (Aa Gg) to a plant that is homozygous recessive for both traits. What kind of cross is this?
a. test cross
b. reciprocal cross
c. complementation cross
d. dihybrid cross

a. test cross

18. In the U-tube experiment, 2 auxotrophic strains were grown in a chamber that allowed their media to mix, but prevented the cells of either strain from coming into contact with each other. This prevented the formation of colonies that could grow on minimal media. This result provided evidence for which type of bacterial gene exchange?

a. transformation

b. conjugation

c. transduction

d. vertical gene transfer

b. conjugation

19. While many chromosome structure changes can be harmful, others offer potential benefits. In one type of chromosome structure change, extra copies of genes can protect against harmful effects of mutations, and may result in beneficial new gene functions. This is most likely associated with:

a. deletion

b. duplication

c. inversion

d. translocation

b. duplication

20. Which two nucleotides are purines?

a. adenine and guanine

b. adenine and thymine

c. cytosine and guanine

d. cytosine and thymine

a. adenine and guanine

22. A bacteriophage that can remain dormant in the bacterial host chromosome is known as a/an:

a. lytic phage

b. prophage

b. prophage

23. Current policy argues that human gene editing (via CRISPR or other techniques) should be prohibited because of concern for unintended harmful consequences to current and future generations. What type of ethical argument does this most reflect?

a. utilitarianism

b. deontology

c. virtue ethics

d. distributive justice

a. utilitarianism

You cross a purple-flowered plant to a white-flowered plant and find that all the offspring have purple flowers. Which of the following can you conclude from this result?

a. the purple-flowered parent was heterozygous

b. purple is dominant to white

c. the white-flowered parent was heterozygous

d. there is not enough data to determine either the genotypes of the inheritance pattern

b. purple is dominant to white

During which phase of the cell cycle are sister chromatids produced?

a. G1

b. S-phase

c. G2

d. end of mitosis

b. S-phase

You cross a female fly with singed bristles to a WT male fly. The offspring include 496 WT females and 498 singed-bristle males. Does this trait show evidence of sex linkage?

a. No. We see a 1:1 ratio, as would be predicted.

b. Yes, this pattern suggests a Y-linked trait because it is only present in the male offspring.

c. Yes, this pattern suggests an X-linked trait because males would show the phenotype of the X-chromosome inherited from their female parent.

d. Not enough evidence to determine

c. Yes, this pattern suggests an X-linked trait because males would show the phenotype of the X-chromosome inherited from their female parent.

You cross a star-eyed fly to a WT-eyed fly and observe equal proportions of WT and star-eyed offspring. What can you conclude about this cross?

a. star eyes are dominant to WT

b. both parents were homozygous for their respective traits

c. one parent was heterozygous and the other was homozygous

d. there are two different genes required for the star-eye phenotype

c. one parent was heterozygous and the other was homozygous

A pea plant is heterozygous for the pod color gene. What proportion of its gametes will carry the dominant allele of the trait?

a. none

b. ¼

c. ½

d. ¾

e. all

c. ½

In foxes, two alleles of a single gene, P and p, may result in lethality (PP), platinum coat (Pp), or silver coat (pp). What offspring phenotype ratio would you expect if both parents have a platinum coat?

a. All platinum

b. 1:1 platinum: silver

c. 2:1 platinum: silver

d. 3:1 platinum: silver

c. 2:1 platinum: silver

You want to determine the inheritance pattern of a novel trait in chickens (in which the female is the heterogametic sex). You have found that the trait is more common in females than in males, but is present in both. Which of the following explanations are consistent with the data?

a. the trait is X-linked

b. the trait is Z-linked

c. the trait is W-linked

d. the trait is autosomal

b. the trait is Z-linked

In setting up Punnett squares, we always begin with gametes showing only a single allele for each gene of interest. This is a reflection of which of Mendel's Laws?

a. independent assortment

b. equal segregation

c. recessive vs dominant

b. equal segregation

Which ethical framework focuses on specific actions in order to determine whether something was right or wrong?

a. utilitarianism

b. deontology

c. virtue ethics

d. distributive justice

b. deontology

You have two purple flowers and want to determine whether their phenotypes are due to mutations in two different genes, or different alleles of the same gene. You cross them to each other and obtain all WT flowers in the F1. What can you conclude?

a. the flowers have different alleles of the same gene that results in purple flowers

b. the flowers have mutations in different genes that both result in purple flowers

c. purple flower trait is dominant to WT flower color

d. both parents were heterozygous for the purple trait

b. the flowers have mutations in different genes that both result in purple flowers

You are holding a 200-1000 ul pipette, and the 3-digit reading shows 090. How many microliters does this represent?

a. 9.0 ul

b. 90.0 ul

c. 900.0 ul

c. 900.0 ul

Which DNA replication enzyme is responsible for relieving the over-winding created by helicase?

a. DNA polymerase

b. Sliding clamp

c. Topoisomerase/ DNA gyrase

d. Primase

c. Topoisomerase/ DNA gyrase

Which DNA replication enzyme is also required for PCR?

a. DNA polymerase

b. Sliding clamp

c. Topoisomerase/ DNA gyrase

d. Primase

d. Primase

Which of the following statements about DNA replication is FALSE?

a. DNA template is read in the 3' to 5' direction

b. The replication process is conservative

c. DNA replication is bi-directional

d. New DNA is synthesized in the 5' to 3' direction

b. The replication process is conservative

The simplest level of DNA packaging involves

a. Solenoid coils

b. Chromatin fibers

c. Nucleosomes

c. Nucleosomes

Zhang and colleagues (Science, 2025) recently used a novel tagging strategy combined with specialized microscopy to view the cellular location of ribosomal subunits. They were able to image the 40S and 60S subunits. Based on the ribosome subunit sizes, what type of cell would they have been working with?

a. prokaryote

b. eukaryote

b. eukaryote

Excess exposure to UV irradiation can lead to somatic mutations in skin cells, thus increasing the risk for skin cancer. Could such mutations be passed down to any future offspring of an individual who experienced these mutations?

a. Yes - all mutations are heritable in eukaryotes

b. No - only mutations in germline cells are heritable in eukaryotes

b. No - only mutations in germline cells are heritable in eukaryotes.

10b. Which type of mutation is UV exposure most likely to cause?

a. Depurination

b. Thymine dimer

c. Alkylation

d. Tautomeric shift

b. Thymine dimer

10c. Does this represent a spontaneous or induced mutation?

a. Spontaneous

b. Induced

b. Induced

10d. What type of repair mechanism would be best suited to repairing this type of mutation?

a. Nucleotide excision repair

b. Non-homologous end-joining

c. Mismatch repair

a. Nucleotide excision repair

Viral genomes can be made of which of the following?

a. Double-stranded DNA

b. Single-stranded DNA

c. Double-stranded RNA

d. Single-stranded RNA

e. Any of the above

e. Any of the above

In eukaryotes, more DNA packaging correlates with (more/less) access for transcription. (Circle correct answer).

less

The secondary structure of a protein represents

a. the order of amino acids

b. local folding such as alpha-helices and beta-sheets

c. the overall 3-D shape

d. multiple polypeptides forming a single functional unit.

b. local folding such as alpha-helices and beta-sheets

Several SNPs (single nucleotide polymorphisms) have been identified that may contribute to risk for a blood disease. An individual's genotype for such an allele can be determined by a combination of PCR and restriction enzyme cutting, followed by running a gel to view the resulting DNA products. An individual with the C allele produces a band of 300 bp, and an individual with the G allele produces bands of 100 and 200 bp, what would you see on a gel for someone who is heterozygous at this DNA location?

a. 1 band (300 bp)

b. 2 bands (100 and 200 bp)

c. 3 bands (300, 200, and 100 bp)

d. 1 band (600 bp)

c. 3 bands (300, 200, and 100 bp)