Question 1

Experimental evidence that crossing over occurs between the X chromosomes of female Drosophila was provided by ________.
A) Morgan
B) Punnett
C) Darwin
D) Bateson

Accepted Answer

Morgan was the scientist who provided experimental evidence that crossing over occurs between the X chromosomes of female Drosophila.

Question 2

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.

Accepted Answer

The default (null) hypothesis in a chi-square test for linkage is that the genes are assorting independently. This means that the genes are located on different chromosomes or are far enough apart on the same chromosome that crossing over events during meiosis are unlikely to occur. The goal of the test is to determine if there is evidence to reject this null hypothesis and conclude that the genes are linked, meaning they are located close enough on the same chromosome that they tend to be inherited together more often than expected by chance.

Question 3

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

Accepted Answer

The lower observed incidence of double crossovers than expected can be explained by interference, meaning that the occurrence of one crossover affects the likelihood of another crossover occurring nearby. This can result in fewer double crossovers than expected. Linkage and segregation would not explain the discrepancy, and coincidence is not a relevant concept in this context.

Question 4

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.

Accepted Answer

The principle of linkage refers to the fact that two or more genes that are physically connected on a chromosome are often transmitted together as a group during meiosis. Therefore, choice E, which includes both the idea of physical connection and transmission as a group, is the best choice. The other choices (genes that are transmitted as a group, genetic information exchange between homologous chromosomes) do not fully capture the principle of linkage.

Question 5

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

Accepted Answer

A testcross is performed between an individual heterozygous for the genes and an individual homozygous recessive for the genes. This helps to determine the genetic makeup of the heterozygous individual and to map the location of the genes on a chromosome.

Question 6

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

Accepted Answer

Short generation times, producing large numbers of offspring, and being easily crossed are all desirable characteristics for constructing a genetic linkage map. The more quickly an organism goes through generations, the more opportunities there are for recombination and the creation of new genetic combinations. Producing large numbers of offspring increases the chances of finding rare genetic recombination events. Easily crossed organisms simplify the process of creating genetic crosses and allow for the creation of large mapping populations.

Question 7

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.

Accepted Answer

Interference is a measure of the degree to which one crossover event inhibits another nearby crossover event. A 30% interference value means that there were 30% fewer double crossovers than expected based on the assumption of independent assortment.

Question 8

Crossing over is more likely to occur between genes that are ________ on a chromosome.
A) Close together
B) Far apart

Accepted Answer

The answer of Crossing over is more likely to occur...

Question 9

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

Accepted Answer

Mitotic recombination can result in patches of genetically distinct tissue in an organism. This occurs when there is a spontaneous genetic change during mitotic division, resulting in a different genotype in one of the daughter cells. This can lead to variations in pigmentation or other visible characteristics in different patches of tissue. Linkage and meiotic recombination occur during meiosis and involve the shuffling and segregation of genetic material, but do not typically result in patches of tissue with distinct characteristics. Translocations involve the exchange of segments between non-homologous chromosomes and are not likely to result in patches of tissue variability.

Question 10

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.

Accepted Answer

Recombination events result in the exchange of genetic material between homologous chromosomes, leading to new combinations of alleles. In this case, alleles C and d together on one chromosome and alleles c and D together on the other chromosome indicate that recombination has occurred, mixing the original configurations (C and D together; c and d together).

Question 11

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.

Accepted Answer

Double crossover events can provide information about the order of genes and the relative distances between them. The middle gene can be determined by identifying the two crossover events and using the information to deduce the order and distance between the three genes. Offspring that resemble the parents or exhibit single crossover events do not provide enough information to determine the middle gene.

Question 12

The process of recombination may rarely occur during mitosis.

Accepted Answer

Recombination, although much less common during mitosis than in meiosis, can occur through mechanisms such as mitotic crossover, contributing to genetic diversity and DNA repair.

Question 13

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

Accepted Answer

The answer of While mapping two genes in Drosophila, you...

Question 14

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.

Accepted Answer

Map distance represents the frequency of recombination between two genes. A map distance of 23.6 indicates that 23.6% of the offspring exhibit recombination between the two genes. Option A is incorrect as the unit of measure is not given. Option B is incorrect as map distance does not indicate the number of intermediate genes. Option D is irrelevant as it does not relate to the concept of map distance.

Question 15

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

Accepted Answer

Bateson and Punnett provided the first observational evidence of genes being inherited together, which led to the discovery of genetic linkage, challenging the idea of independent assortment in Mendelian inheritance.

Question 16

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

Accepted Answer

The Chi-square test is used to determine if there is a significant difference between observed and expected values. In genetics, it is commonly used to determine if two genes are linked or assorting independently. The null hypothesis is that the genes are assorting independently, and if the calculated chi-square value is greater than the critical value, the null hypothesis is rejected, indicating that the genes are linked.

Question 17

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.

Accepted Answer

Since the three genes are linked, the parental genotypes are expected to be the most common in the F2 offspring, followed by individuals with single crossover events and then individuals with double crossover events. Because there are more possible ways for the linked genes to stay together during meiosis than to become separated, the parental genotypes are the most likely to be inherited by the F2 generation.

Question 18

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

Accepted Answer

A genetic linkage map indicates the relative positions of genes on a chromosome based on the frequency of recombination between them, not the precise physical distance.

Question 19

Twin spotting provides evidence of what genetic event?
A) Meiotic recombination
B) Mitotic recombination
C) Linkage
D) Mutation
E) Biological evolution

Accepted Answer

Twin spotting occurs due to mitotic recombination, a process where chromosomes exchange segments during mitosis, leading to genetically distinct daughter cells. This can result in visible patches of different phenotypes in organisms, providing evidence of the event.

Question 20

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

Accepted Answer

Creighton and McClintock provided the visual proof of chromosome exchange during crossing over through their experiments with corn. They observed the physical exchange of chromosomal segments during meiosis, which provided concrete evidence for the concept of genetic recombination. The other choices were important geneticists, but they did not provide direct visual proof of crossing over.

Quiz 6: Genetic Linkage and Mapping in Eukaryotes

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

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

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 ________.

Which of the following defines the principle of linkage?

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

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

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

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

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?

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?

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

The process of recombination may rarely occur during mitosis.

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

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

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

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

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

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

Twin spotting provides evidence of what genetic event?

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