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1

Linked genes:
A)are located near each other on the same chromosome.
B)violate the law of independent assortment.
C)segregate together during meiosis.
D)All of the above.
E)None of the above.
2

You cross a truebreeding normal corn plant with a true breeding plant with variegated seed coat and colorless endosperm. You suspect the genes are linked, so you cross one of the resulting normal offspring to a true breeding variegated, colorless plant. What are your expected results if the genes are completely linked?
A)1 normal: 1 variegated: 1 colorless: 1 variegated and colorless
B)9 normal: 3 variegated: 3 colorless: 1 variegated and colorless
C)3 normal: 1 variegated and colorless
D)3 variegated and colorless: 1 normal
3

For the cross in the previous question, you get the following results. Calculate a chi square value using an expectation of independent assortment and determine if the genes are likely to be linked or not. Normal 350; variegated 63; colorless 57; variegated and colorless 330.
A)The chi square value is greater than the critical value; these genes are likely to be linked.
B)The chi square value is greater than the critical value; these genes are unlikely to be linked.
C)The chi square value is less than the critical value; these genes are likely to be linked.
D)The chi square value cannot help us predict linkage.
4

From the results in the previous question, calculate a map distance between these two genes.
A)0.15 map units
B)0.85 map units
C)1.5 map units
D)15 map units
5

How did Morgan demonstrate crossing over?
A)A fly that received only y+w+m+ and ywm chromosomes from her parents was able to transmit different combinations of alleles to her offspring.
B)A fly with a gray body and red eyes (wild type) was able to produce offspring with gray bodies and white eyes.
C)True breeding yellow, white, miniature flies always had yellow, white, miniature offspring.
D)None of these examples demonstrate crossing over.
6

What was unique about the chromosomes studied by Creighton and McClintock?
A)They carried different alleles for two linked genes.
B)They were unable to cross over.
C)These chromosomes were unable to synapse during meiosis I.
D)Physical structures of the chromosomes allowed them to be distinguished from each other.
7

Which of the following would be a reasonable way to demonstrate that twin spots are caused by mitotic recombination?
A)Collect a large number of flies with twin spots and verify that in all cases, both halves of the twin spot are the same size.
B)Collect a large number of petunias with twin spots and verify that they are able to pass this phenotype to their progeny.
C)Design cytologically distinct chromosomes that must recombine to cause the twin spot; analyze chromosomes from the spots with a microscope.
D)Try to clone new individuals from the cells in the twin spots and analyze their phenotype.
8

You begin to study a novel plant species and discover that this diploid plant has 16 chromosomes. How many linkage groups would you expect to find?
A)16
B)8
C)4
D)It is impossible to tell from the information provided.
9

You calculate map distances between genes A, B, and C based on all pairwise dihybrid crosses. When you perform the trihybrid cross to verify your results, you discover that, despite analysis of a very large number of progeny, you have only about half as many double crossover progeny as you expect. Which explanation is the most reasonable?
A)Your dihybrid cross data are an underestimate of the distance between the more widely separated genes.
B)You are seeing an example of interference.
C)You are seeing an example of random sampling error.
D)None of these.
10

Consult Fig 5.8. In a dihybrid cross involving Bar eye and little fly genes, what frequency of recombinant progeny do you expect?
A)2.1
B)11.1
C)57.0
D)68.1
11

Consult Fig 5.8. What percentage of double crossover progeny would you expect in a trihybrid cross involving aristaless, dumpy, and black? (Assume no interference.)
A)0.05%
B)5%
C)13%
D)48.5%
12

You set up the following dihybrid mapping cross in fruit flies.
P e+e+ roro cq cq x ee ro+ro+ cq+cq+. After backcrossing F1 males to ee roro cq cq females, you get the following results: gray body, rough eyes, claret eyes 576; ebony body, smooth, red eyes 564. How can you explain this result?
A)The genes are not linked.
B)Crossing over does not occur in male Drosophila.
C)These genes are X linked.
D)A and B only.
E)None of the above.
13

What is a convenient way to identify gene order in a trihybrid mapping cross?
A)Look for double crossover progeny and identify the gene that was flipped relative to parentals.
B)Look for the largest class of single crossovers and the two genes are the ones on the ends.
C)Look for the smallest class of single crossovers to identify the genes which are closest together.
D)A and B only.
E)All of the above.
14

Why is tetrad analysis useful for studying genetics?
A)Cells within a tetrad are haploid so genotype is directly reflected in the phenotype.
B)Cells within a tetrad reflect the events of meiosis.
C)Analysis of simple systems can elucidate general rules that apply more broadly.
D)All of the above.
E)None of the above.
15

Tetrad analysis automatically includes the centromere as an additional point in mapping crosses, because
A)crossovers that are not between a gene and the centromere do not affect the relationship of that gene to the chromosome during division.
B)crossovers that are between a gene and the centromere cannot be identified in this system.
C)when studying crossovers between genes, the position of the centromere is irrelevant.
D)All of the above.
E)None of the above.
16

Formation of the following pattern in an ordered octad is due to what event during meiosis? Pattern: AAaaaaaAA
A)No crossing over and normal segregation in meiosis I.
B)Crossing over and normal segregation during meiosis I.
C)Crossing over and segregation during meiosis II.
D)No crossing over and segregation during meiosis II.
17

In an unordered tetrad with the parental ditype:
A)all spores have the same genotype.
B)all spores have the genotype of one of the parental strains.
C)all four spores have different genotypes.
D)all spores are diploiD. In a parental ditype, the spores are of both parental types in a 2:2 ratio.
E)Correct!
F)This would be a tetratype.
G)The diploid zygote divides by meiosis to generate haploid spores.
18

You set up a mapping cross involving two genes in Aspergillus and determine the following percentages of tetrad types: parental ditype 51%, nonparental ditype 49%. What can you say about your genes?
A)They are closely linked.
B)They are unlinked.
C)They are lethal.
D)They are not expressed in the phenotype.
19

You set up a mapping cross involving your favorite gene (YFG) in Neurospora and determine the following octad types: 4:4 arrangement 83; 2:4:2 arrangement 7; 2:2:2:2 arrangement 10. What is the distance between your gene and the centromere?
A)7 cm
B)10 cm
C)17 cm
D)83 cm
20

You set up a mapping cross involving two genes of interest in Saccharomyces and determine the following tetrad types: 8 nonparental ditype; 37 tetratype; 80 parental ditype. Calculate the most accurate map distance between these two genes.
A)18.7mu
B)32.3mu
C)64.6mu
D)None of these is accurate.
21

Every chromosome in a diploid cell comprises a linkage group.
A)True
B)False
22

Crossing over involves the physical exchange of DNA between chromatids.
A)True
B)False
23

If two genes are linked, a double heterozygote will only be able to produce two possible types of gametes.
A)True
B)False
24

Crossing over only occurs within a bivalent.
A)True
B)False
25

Parental phenotypes in the offspring are the most common in a mapping cross.
A)True
B)False
26

Morgan was able to demonstrate linkage of genes to chromosomes because he studied X linked genes.
A)True
B)False
27

Chi square analysis can help distinguish between two competing hypotheses.
A)True
B)False
28

Creighton and McClintock's important discovery was that they were able to demonstrate linkage between a translocation and a neighboring gene.
A)True
B)False
29

Twin spots are only possible in doubly heterozygous individuals.
A)True
B)False
30

In linkage mapping, one map unit is equal to one % crossover frequency.
A)True
B)False
31

Trihybrid mapping crosses are more accurate than dihybrid mapping crosses.
A)True
B)False
32

You can predict the number of double crossovers in a region accurately if you have a detailed genetic map.
A)True
B)False
33

Unordered tetrad analysis allows determination of the specific events of meiosis I and II.
A)True
B)False
34

Unordered tetrad analysis is useful for determining recombination frequencies.
A)True
B)False
35

Double crossovers can occur between multiple chromatids.
A)True
B)False







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