12.E: Modern Understandings of Inheritance (Exercises)
12.1: Chromosomal Theory and Genetic Linkage
Review Questions
X-linked recessive traits in humans (or in Drosophila ) are observed ________.
- in more males than females
- in more females than males
- in males and females equally
- in different distributions depending on the trait
- Answer
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A
The first suggestion that chromosomes may physically exchange segments came from the microscopic identification of ________.
- synapsis
- sister chromatids
- chiasmata
- alleles
- Answer
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C
Which recombination frequency corresponds to independent assortment and the absence of linkage?
- 0
- 0.25
- 0.50
- 0.75
- Answer
-
C
Which recombination frequency corresponds to perfect linkage and violates the law of independent assortment?
- 0
- 0.25
- 0.50
- 0.75
- Answer
-
A
Free Response
Explain how the Chromosomal Theory of Inheritance helped to advance our understanding of genetics.
- Answer
-
The Chromosomal Theory of Inheritance proposed that genes reside on chromosomes. The understanding that chromosomes are linear arrays of genes explained linkage, and crossing over explained recombination.
12.2: Chromosomal Basis of Inherited Disorders
Review Questions
Which of the following codes describes position 12 on the long arm of chromosome 13?
- 13p12
- 13q12
- 12p13
- 12q13
- Answer
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B
In agriculture, polyploid crops (like coffee, strawberries, or bananas) tend to produce ________.
- more uniformity
- more variety
- larger yields
- smaller yields
- Answer
-
C
Assume a pericentric inversion occurred in one of two homologs prior to meiosis. The other homolog remains normal. During meiosis, what structure—if any—would these homologs assume in order to pair accurately along their lengths?
- V formation
- cruciform
- loop
- pairing would not be possible
- Answer
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C
The genotype XXY corresponds to
- Klinefelter syndrome
- Turner syndrome
- Triplo-X
- Jacob syndrome
- Answer
-
A
Abnormalities in the number of X chromosomes tends to have milder phenotypic effects than the same abnormalities in autosomes because of ________.
- deletions
- nonhomologous recombination
- synapsis
- X inactivation
- Answer
-
D
By definition, a pericentric inversion includes the ________.
- centromere
- chiasma
- telomere
- synapse
- Answer
-
A
Free Response
Using diagrams, illustrate how nondisjunction can result in an aneuploid zygote.
- Answer
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Exact diagram style will vary; diagram should look like Figure 12.2.2 .