Exam 2 Review

Question 1

_____ represent the evolutionary relationships among groups of organisms

a. Species concepts
b. Nodes
c. Phylogenetic trees
d. Alignments
e. Synonymous rates of substitution

Answer 1

c. Phylogenetic trees

Question 2

The following testcross produces the progeny shown: Aa Bb x aa bb -> 10 Aa Bb, 40 Aa bb, 40 aa Bb, 10 aa bb

What is the percent recombination between the A and B loci?

a. 40%
b. 20%
c. 80%
d. 10%
e. 50%

Answer 2

b. 20%

Question 3

In a given population, the “A” allele is at a frequency of 0.8, and the “a” allele is at a frequency of 0.2. Assuming Hardy-Weinberg equilibrium, what should the frequency of A/A homozygotes be in the population?

a. 0.064
b. 0.8
c. 0.16
d. 0.32
e. 0.64

Answer 3

e. 0.64

Question 4

Inbreeding changes allele frequencies, but a genetic drift affects mainly genotypic frequencies

a. True
b. False

Answer 4

b. False

Question 5

Which of the following statements about genetic exchange in bacteria is NOT true?

a. Interrupted conjugation results in the production of Hfr strains

b. Plasmids do not have to integrate into the host cell of chromosome in order to be replicated

c. Antibiotic resistance can be transferred from one bacterial cell to another by conjugation

d. In conjugation there has to be a physical connection between the donor cell and the recipient cell

e. The order of gene transfer is not the same for different Hfr strains

Answer 5

a. Interrupted conjugation results in the production of Hfr strains

Question 6

In humans, spontaneous abortion (miscarriage) is relatively common, occurring in 15-20% of cases where women know they are pregnant. What is thought to be the most common cause of these pregnancy losses?

a. Translocations
b. Nucleotide repeat expansions
c. Mitotic errors
d. Errors in chromosome number
e. Blood type incompatibility

Answer 6

d. Errors in chromosome number

Question 7

Assume that an individual of A/a B/b genotype is involved in a testcross and four classes of testcross progeny are found in equal frequencies. Which of the following statements is TRUE?

a. The genes A and B are on the same chromosome and are closely linked

b. The A and a genes are on different chromosomes, as are the B and b genes

c. The genes A and B could be located on different chromosomes or on the same chromosome and very far apart

d. The genes A and B are probably between 10 and 20 map units apart on the same chromosome

Answer 7

c. The genes A and B could be located on different chromosomes or on the same chromosome and very far apart

Question 8

Double-stranded, circular, extra-chromosomal DNA elements such as F factors and R are known as:

a. R-determinants
b. Capsids
c. Plasmids
d. Plaques
e. Partial diploids

Answer 8

c. Plasmids

Question 9

HIV is an example of a retrovirus. What is a way in which retroviruses differ from other types of viruses?

a. They attach to a specific receptor on the host cell

b. They are easily transmitted across different species

c. They contain single-stranded RNA inside the capsid

d. They use reverse transcriptase to make DNA from RNA

Answer 9

d. They use reverse transcriptase to make DNA from RNA

Question 10

Non-disjunction occurs most often in _____, and if often due to a failure of proper chromosome pairing and proper crossing over.

a. Mitosis
b. Meiosis I
c. Meiosis II
d. Both a and c
e. Fertilization

Answer 10

b. Meiosis I

Question 11

Human cells that have an extra copy of chromosome 18 are

a. Triploid
b. Trisomic
c. Tetrasomic
d. Euploid
e. Polyploid

Answer 11

b. Trisomic

Question 12

In growing fruit for agricultural purposes, why might growing a triploid strain be desirable?

a. It would have a shorter generation time
b. It would be easier to hybridize with other species
c. It would be a more appealing color
d. It would be sterile and therefore seedless
e. It would be smaller, and easier to grow more plants/trees in a small space

Answer 12

d. It would be sterile and therefore seedless

Question 13

Linked genes are

a. on different chromosomes
b. dominant
c. recessive lethal
d. on the same chromosome
e. allelic

Answer 13

d. on the same chromosome

Question 14

10% recombination between linked genes correspond to

a. 25 map units
b. 50 map units
c. 1 map unit
d. 100 map units
e. 10 map units

Answer 14

e. 10 map units

Question 15

Interference occurs when

a. two genes are far apart on a genetic map
b. two genes are assorting independently
c. one crossover inhibits another
d. the number of recombinant progeny classes in the testcross of a heterozygote exceeds the number of parental progeny
e. a crossover causes the termination of the meiosis event in which the crossover is occurring

Answer 15

c. one crossover inhibits another

Question 16

A three-point testcross is often used to

a. isolate mutations affecting a particular trait
b. determine if chromosome mutations are present
c. determine whether mutations occur at the same or different loci
d. efficiently map genes
e. do a complementation test

Answer 16

d. efficiently map genes

Question 17

Regarding the linkage of genes on a chromosome and recombination, what does “interference” refer to?

a. The reduction in the actual number of double recombinant progeny, relative to the expected number, based on map distance

b. The role of independent assortment at meiosis

c. The lack of recombination observed in male Drosophila

d. Errors in mitosis leading to mutations

e. Incorrect pairing of homologous chromosomes

Answer 17

a. The reduction in the actual number of double recombinant progeny, relative to the expected number, based on map distance

Question 18

Polyploids have _____

a. Less than two sets of chromosomes
b. two sets of chromosomes
c. more than two sets of chromosomes
d. two sets of chromosomes and an extra chromosome 21

Answer 18

c. more than two sets of chromosomes

Question 19

A physical map often measure _____, whereas a genetic map measures _____

a. map units between genes; centiMorgans

b. centiMorgans; base pairs

c. distances in base pairs along the chromosome; centiMorgans

d. distances between chromosomes; distances between genes

e. map units between genes; physical distances along the chromosome

Answer 19

c. distances in base pairs along the chromosome; centiMorgans

Question 20

_____ is the product of sampling errors and chance events that may result in changes in allelic frequencies

a. Inbreeding
b. Mutation
c. directional selection
d. genetic drift
e. evolution

Answer 20

d. genetic drift

Question 21

What is the likely fate of a chromosome that does not have a centromere?

a. It will be lost, resulting in aneuploidy

b. It will be duplicated, resulting in aneuploidy

c. it and its homologous chromosomes will be duplicated, resulting in polyploidy

d. it will not be able to separate from its sister chromatid, resulting in nondisjunction

e. it and its homologous chromosome will be lost, resulting in polyploidy

Answer 21

a. It will be lost, resulting in aneuploidy

Question 22

What type of bacterial gene transfer involves a virus?

a. Transpositon
b. transduction
c. conjugation
d. transformation

Answer 22

b. transduction

Question 23

Which of the following mutations is NOT an example if chromosome rearrangement?

a. A single gene on a chromosome is inverted

b. A set of three genes on a chromosome is duplicated

c. A section of chromosome is deleted

d. A single chromosome is deleted

Answer 23

d. A single chromosome is deleted

Question 24

Select the definition of aneuploidy

a. the addition or loss of less than a full set of chromosomes or chromosome pairs

b. a complete chromosome set or an exact multiple of the haploid chromosome set

c. a chromosomal complement with at least three complete sets of homologous chromosomes

d. the number of chromosome sets that make up a complete genome

Answer 24

a. the addition or loss of less than a full set of chromosomes or chromosome pairs

Question 25

A minimal medium is used to support the growth of _____ bacteria a. prototrophic b. auxotrophic c. heterotrophic d. prokaryotic e. metatrophic

Answer 25

a. prototrophic

Question 26

After performing a testcross with a dihybrid (crossing an individual who is heterozygous at two genes with an individual who has homozygous recessive alleles at both genes), you examine the progeny ratios. You find that the frequency of recombinant-type allele combinations is much less than 50%. What is the most likely hypothesis to explain these results? a. The two genes are unlinked and exhibit independent assortment b. Epistasis c. There is linkage to the X-chromosome d. There must be some type of experimental error, as it should be impossible to get more parental type progeny than recombinant type progeny e. the two genes are linked

Answer 26

e. the two genes are linked

Question 27

A karyotype might NOT be useful in which of the following circumstances? a. A banana farmer wants to know whether the crops being grown are triploid or tetraploid b. A mother gives birth to a child with a syndrome that may be caused by a deletion on the long arm of chromosome 18 c. A karyotype can be informative in all of these situations d. A reciprocal translocation between chromosome causes a specific form of leukemia 9 and 22 e. A genetic disease runs in a family and is cause by a single nucleotide substitution in a gene

Answer 27

e. A genetic disease runs in a family and is cause by a single nucleotide substitution in a gene

Question 28

An F plasmid in E. coli will replicate itself via _____ in conjugation. a. semi-conservative replication b. liberal replication c. transcription d. fast replication e. rolling circle replication

Answer 28

e. rolling circle replication

Question 29

Antibiotic resistance in a population of bacteria is spread rapidly because the gene conferring antibiotic resistance is usually a. A bacterial homologue or prion proteins b. A rDNA bacterial gene c. Secreted outside the bacterial cell d. A chromosomal bacterial gene e. A bacterial plasmid gene

Answer 29

e. A bacterial plasmid gene

Question 30

XO individuals are best described as a. trisomic b. monosomic, with the second sex chromosome completely missing c. normal hemizygous males, with the Y allele known as "O" present d. Normal females whose cells don't undergo X inactivation e. Transcribed individually and then ligated

Answer 30

b. monosomic, with the second sex chromosome completely missing

Question 31

Which of the following best describes a prophage? a. A phage whose genome has been integrated into the bacterial genome b. A phage that is wild-type c. A phage with DNA packaged inside a protein coat, before infecting a bacterium d. A phage containing bacterial genes e. A phage that is recombinant between two different genotypes

Answer 31

a. A phage whose genome has been integrated into the bacterial genome

Question 32

True or false? Linked genes appear in a 9:3:3:1 ratio in a dihybrid cross a. true b. false

Answer 32

b. false

Question 33

Choose the type of virus that best describes the novel coronavirus (SARS-CoV-2) that causes COVID-19 a. Phage virus b. DNA virus c. Retrovirus d. Lysogenic virus e. RNA virus

Answer 33

e. RNA virus

Question 34

Most strains of cultivated bananas were created by crossing plants within and between two diploid species: Musa acuminate (genome AA) and Musa balbisiana (genome BB). Some bananas have genome AAB, which is an example of what kind of polyploidy? a. autotatraploid b. autotriploid c. allotriploid d. allotetraploid e.. allodiploid

Answer 34

c. allotriploid

Question 35

The fitness of the wolf population on Isle Royale had decreased for many years, particularly in the 90's and 00's. What is thought to be the main factor driving this fitness decline? a. migration of new wolves from the mainland b. parasites c. disassortative mating d. new mutations e. inbreeding depression

Answer 35

e. inbreeding depression

Question 36

If the assumption of the Hardy-Weinberg law are met, the genotype frequencies in a population will stabilize after _____ generation(s) of random mating a. p2 b. an unknown number of c. one d. zero e. several

Answer 36

c. one

Question 37

_____ refers to the situation where the heterozygote has a lower fitness than both homozygotes (W11 > W12 < W22) a. heterozygote superiority b. underdominance c. hardy-weinberg equilibrium d. overdominance e. genetic rescue

Answer 37

b. underdominance

Question 38

A given population has allele frequencies of p = 0.1 and q = 0.9. Assuming Hardy-Weinberg equilibrium, what should the frequency of heterozygotes be in this population? a. 0.1 b. 0.9 c. 0.81 d. 0.09 e. 0.18

Answer 38

e. 0.18

Question 39

In lysogeny, which of the following occur? a. A copy of the phage genome integrates in the host chromosome as a prophage b. Recombination between phage genomes c. The lac operon is active d. The bacteriophage makes many copies of itself and lyses the cell e. Binding of the sigma factor

Answer 39

a. A copy of the phage genome integrates in the host chromosome as a prophage