Deck 6: Genetic Linkage and Mapping in Eukaryotes

Question 1

You have calculated the interference value for a given mapping experiment to be 30%. What does this mean?

A)30% more double crossovers occurred than expected
B)30% fewer double crossovers occurred than expected
C)70% more double crossovers occurred than expected
D)70% fewer double crossovers occurred than expected

Answer 1

B

Question 2

Which of the following statistical tests is used to determine if two genes are linked or assorting independently?

A)Sum rule
B)Binomial expansion
C)Product rule
D)Chi-square test

Answer 2

D

Question 3

The process of recombination may rarely occur during mitosis.

Answer 3

True

Question 4

In a chi-square test to determine if two genes are linked or assorting independently, what is the default (null) hypothesis that is tested?

A)The genes are linked to one another
B)The genes are assorting independently
C)The genes are located on the sex chromosomes
D)No crossing over occurs
E)The distance between the genes is very small

Question 5

Twin spotting provides evidence of what genetic event?

A)Meiotic recombination
B)Mitotic recombination
C)Linkage
D)Mutation
E)Biological evolution

Question 6

A genetic linkage map indicates that precise distance between two genes of interest.

Question 7

Crossing over is more likely to occur between genes that are ______ on a chromosome.

A)Close together
B)Far apart

Question 8

The middle gene of a three gene mapping experiment can be determined by examining the genotypes of which of the following?

A)Offspring that resemble the parents
B)Offspring that exhibit a single crossover event
C)Offspring that exhibit double crossover events
D)None of the answers are correct

Question 9

Which of the following defines the principle of linkage?

A)Two or more genes that are physically connected on a chromosome
B)Genes that are transmitted to the next generation as a group
C)The process by which genetic information is exchanged between homologous chromosomes
D)All of the answers are correct
E)Both two or more genes that are physically connected on a chromosome and genes that are transmitted to the next generation as a group

Question 10

In a mapping experiment with three linked genes, which phenotype should occur most often in the F₂ offspring?

A)Parental phenotypes
B)Phenotypes of individuals with single crossover events
C)Phenotypes of individuals with double crossover events
D)All of the phenotypes should occur equally in the F₂ generation

Question 11

While mapping two genes in Drosophila, you observe 30 recombinants among 200 total offspring. What is the distance between these genes?

A) 30 map units
B) 6.67 map units
C) 200 map units
D) 15 map units

Question 12

An organism that contains patches of tissue that vary for a specific characteristic such as a pigment, can be an example of which of the following?

A) Linkage
B) Meiotic recombination
C) Mitotic recombination
D) Translocations
E) None of the answers are correct

Question 13

A map distance of 23.6 between two genes indicates which of the following?

A)The genes are 23.6 millimeters apart
B)There are 23.6 other genes between the two genes of interest
C)23.6% of the offspring exhibit recombination between the two genes
D)23.6% of the offspring do not survive

Question 14

In a given mapping experiment, you expect that incidence of double crossovers is 3.5%, but you only observe 2.5%. This can be explained by ________________.

A) Interference
B) Linkage
C) Coincidence
D) Segregation

Question 15

Experimental evidence that crossing over occurs between the X chromosomes of female Drosophila was provided by __________.

A)Morgan
B)Punnett
C)Darwin
D)Bateson

Question 16

Assume that genes C and D are located on the same chromosome. On one chromosome, alleles C and D are found, while the homologue contains alleles c and d. Which of the following would be evidence of a recombination event?

A)Alleles C and D together on one chromosome
B)Alleles c and d together on one chromosome
C)Alleles C and d together on one chromosome
D)Alleles c and D together on one chromosome
E)Both alleles C and d together on one chromosome and alleles c and D together on one chromosome

Question 17

The visual proof that chromosomes exchange pieces of information during crossing over was provided by __________.

A)Bateson and Punnett
B)Morgan and Bridges
C)Creighton and McClintock
D)Watson and Crick

Question 18

Which of the following are highly desirable characteristics of an organism that make it relatively easy to construct a genetic linkage map?

A) Short generation times
B) Produces large numbers of offspring
C) Easily crossed
D) All of the answers are correct

Question 19

The first observational evidence that genes may be inherited together rather than by simple Mendelian inheritance was provided by __________.

A)Mendel
B)Morgan and Bridges
C)Bateson and Punnett
D)Boveri and Sutton
E)None of the answers are correct

Question 20

A testcross is always performed between the individual that is heterozygous for the genes to be mapped and an individual who is ____________.

A)Heterozygous for the genes
B)Homozygous dominant for the genes
C)Homozygous recessive for the genes
D)Lacking the genes
E)None of the answers are correct

Question 21

In ascomycete fungi, the arrangement of the spores in the ascus that directly reflects the order in which they were produced during meiosis is called an ______.

A)Unordered tetrad
B)Unordered octad
C)Ordered tetrad
D)Ordered pentad

Question 22

In humans, there are _______ autosomal linkage groups, plus an X and Y chromosome linkage group.

A) 23
B) 46
C) 22
D) 92

Question 23

Map distances above 50 are considered unreliable due to the occurrence of double-crossovers between the genes.

Question 24

Creighton and McClintock worked with _______ and their model system to show that homologous chromosomes physically exchange genetic information during crossing over.

A) fruit flies
B) peas
C) corn
D) tobacco

Question 25

Another name for a chromosome is a _______, since it contains genes that are often inherited together.

A) linkage group
B) crossing over group
C) genetic recombinant
D) bivalent

Question 26

In certain algae and in most ascomycete fungi, the nuclei in the cells present in the majority of their life cycle are in the _____ condition.

A)Diploid
B)Haploid
C)Triploid
D)Tetraploid

Question 27

In fungal gene mapping, the abbreviation NPD stands for new parental ditype.

Question 28

Which of the following is not one of the principles of linkage that Morgan obtained from his experiments?

A) Genes that are on the same chromosome may be inherited together.
B) Crossing over exchanges pieces of chromosomes and creates new allele combinations.
C) The likelihood of crossing over occurring between two genes is dependent on the distance of the genes from one another.
D) Genes that are on the same chromosome are always transmitted together as a unit.

Question 29

The rearrangement of alleles by the process of crossing over is called genetic linkage.

Question 30

Map distance is the number of recombinant offspring divided by the total number of nonrecombinant offspring.

Question 31

A fungal reproductive structure that contains all of the products of a single meiotic division is called the ascus.

Question 32

The end result of meiosis in fungi is a tetrad of spores.

Question 33

Two genes that are located on the same chromosome are said to be _______.

A)physically linked
B)recombinant
C)parental-like
D)nonparental-like

Question 34

An ascus that contains two parental spores and two nonparental spores is called a tetratype.

Question 35

In fungi like Neurospora crassa, the diploid structures are called spores.

Question 36

A map unit or centimorgan is equal to a 10% recombination frequency.

Question 37

The locus is the physical place of a gene on a chromosome.

Question 38

A negative interference value indicates that the first crossover event enhanced the occurrence of additional crossover events in the region.

Question 39

Following crossing-over, chromosomes with genetic combinations that resemble the parents' chromosomes are called nonrecombinant.

Question 40

Which of the following procedures may be used to map genes in a fungi with an unordered tetrad ascus?

A)Testcross
B)Monohybrid cross
C)Dihybrid cross
D)Chi-square analysis
E)Analysis of interference

Question 41

The locus B on the X chromosome of a malaria-carrying mosquito shows a 49% recombination rate with respect to the locus M. Since a recombination rate of 50% is essentially indistinguishable from independent assortment, you might be tempted to look for a locus that falls between B and M. Before you decide to do all that work, you run a chi square test to determine the P value of your experiment. Which of the following P values would be most likely to tell you that you should accept the conclusion that locus B and locus M are, indeed, 49mu apart and that another locus is not necessary?

A) P = 0.45
B) P = 0.07
C) P = 0.05
D) P = 0.0007

Question 42

The diploid garden pea plant has 14 chromosomes. The haploid fungus Neurospora crassa has 7 chromosomes. Neither organism has separate male and female individuals. Therefore, the number of linkage groups in these two organisms is:

A) Garden pea has 14 linkage groups, and Neurospora has 7.
B) Garden pea has 7 linkage groups, and Neurospora has 7.
C) Garden pea has 8 linkage groups, and Neurospora has 8.
D) Gardent pea has 15 linkage groups, and Neurospora has 8.

Question 43

The genotype hsp+ HSP- is something that you could easily expect to find in the fungus Neurospora crassa.

Question 44

The number of linkage groups in a species that does not have sex chromosomes is:

A)1n
B)1n + 1
C)2n
D)2n + 2

Question 45

In a mapping cross, you determine that the recombination frequency between:
Loci Q and P is 12%
Loci Q and L is 15%.
If locus Q is in between loci P and L, then the recombination frequency between P and L should be approximately:

A)3%
B)27%
C)50%
D)75%

Question 46

You notice that in most biology and genetics textbooks, the authors show that Gregor Mendel used flower color as one of his pairs of traits. The purple flower phenotype is dominant to the white flower phenotype. However, if you go back to Mendel's experiments, you see that he actually studied seed coat color. The purple seed coat phenotype was dominant to the white seed coat phenotype. Mendel did note that plants with purple seed coats had purple flowers and plants with white seed coats had white flowers.
Is the gene for seed coat color pleiotropic because it also affects flower color, or are the seed coat color gene and the flower color gene very closely linked? To find out the answer to this question, you assume that the genes for flower color and seed coat color are different genes, and your null hypothesis is that they assort independently. You designate the flower color gene wf and the seed coat color gene sw. Plants that are WF__, SW___ have purple flowers and purple seed coats. Plants that are wf wf, ws ws have white flowers and white seed coats.
You do the testcross WF wf, SW sw X wf wf, sw sw and collect 15,206 offspring. What result would tell you that the wf and sw loci are probably the same, pleiotropic locus?

A)One of the offspring had white flowers and purple seed coats.
B)About half of the offspring had purple flowers and purple seed coats, and all the rest had white flowers and white seed coats.
C)All of the offspring had purple flowers and purple seed coats.
D)None of the offspring had white flowers and white seed coats.

Question 47

The number of linkage groups in an organism with sex chromosomes equals:

A)1n
B)2n +1
C)1n + 1
D)2n + 2

Question 48

The percentage of recombination associated with independent assortment should approximate 50%.

Question 49

Mitotic recombination occurs between homologous chromosomes. In which of the following would you not expect to encounter mitotic recombination?

A)The fungus, Aspergillus nidulans
B)Tobacco plants
C)Homo sapiens
D)Drosophila melanogaster

Question 50

If you want to determine how the alleles of different loci interact in their various combinations, it is best to have a system where you do not have to worry about dominance and recessiveness. Which of the following would represent a system where you do not have to worry about dominance and recessiveness?

A)Homo sapiens
B)Garden peas
C)Drosophila melanogaster
D)Chlamydomonas reinhardtii