Question 1

In a testcross between a dihybrid plant (YyRr) and a homozygous recessive plant (yyrr), what percentage of the offspring are expected to display recombinant phenotypes, assuming the genes are unlinked?

Accepted Answer

50%

Question 2

Which chromosomal alteration is most likely to result in a child with severe intellectual disability and a distinctive catlike cry?

Accepted Answer

Deletion of chromosome 5

Question 3

A diploid organism has a normal chromosome number of $$2n = 46. $$After nondisjunction during meiosis, a zygote is found to have $$2n + 1$$ chromosomes. What is this condition called?

Accepted Answer

Trisomy

Question 4

Which of the following best explains why plants tolerate polyploidy better than animals?

Accepted Answer

Polyploidy often results in more normal appearance in plants

Question 5

During meiosis, homologous chromatids may break and rejoin at incorrect places, resulting in one chromatid losing more genes than it receives. What is the outcome of this event?

Accepted Answer

One chromatid has a deletion and the other has a duplication

Question 6

Which chromosomal alteration moves a segment from one chromosome to a nonhomologous chromosome?

Accepted Answer

Translocation

Question 7

A child is born with three copies of chromosome 21. What is the name of this condition, and what is the chromosomal formula?

Accepted Answer

Down syndrome, $$2n + 1$$

Question 8

Which of the following is a result of nondisjunction during meiosis?

Accepted Answer

Some gametes have $$n + 1$$ chromosomes and some have $$n - 1$$ chromosomes

Question 9

Which syndrome is caused by the presence of an extra X chromosome in a male (XXY)?

Accepted Answer

Klinefelter syndrome

Question 10

Which chromosomal alteration reverses the orientation of a segment within a chromosome?

Accepted Answer

Inversion

Question 11

A patient is diagnosed with chronic myelogenous leukemia (CML). Which chromosomal event is responsible for this condition?

Accepted Answer

Reciprocal translocation between chromosomes 9 and 22

Question 12

If a diploid embryo is homozygous for a large deletion, what is the likely outcome?

Accepted Answer

The embryo will be missing many essential genes and is usually lethal

Question 13

Which of the following best describes the physical basis for genetic recombination of unlinked genes?

Accepted Answer

Random orientation of homologous chromosomes during metaphase I

Question 14

Which of the following is NOT a type of chromosomal alteration?

Accepted Answer

Mutation

Question 15

Which condition is the only known viable monosomy in humans?

Accepted Answer

Turner syndrome (XO female)

Question 16

Which of the following increases genetic variation in a population and is essential for natural selection?

Accepted Answer

All of the above

Question 17

A plant with three complete sets of chromosomes is described as:

Accepted Answer

Triploid ($$3n)$$

Question 18

Which of the following offspring from a dihybrid testcross (YyRr × yyrr) is considered a recombinant type?

Accepted Answer

yyRr

Question 19

Which chromosomal alteration repeats a segment, potentially leading to gene dosage effects?

Accepted Answer

Duplication

Question 20

Which of the following statements about aneuploidy is correct?

Accepted Answer

Aneuploidy can result in syndromes with characteristic symptoms

Chromosomal Basis of Inheritance and Genetic Disorders Part 2

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