Question 1

Which of the following best describes the alternation of generations in plants?

Accepted Answer

A diploid multicellular form alternates with a haploid multicellular form during the life cycle.

Question 2

In mosses, which structure is the dominant, visible form and what is its ploidy?

Accepted Answer

The gametophyte, which is haploid ($$n)$$

Question 3

During spermatogenesis in animals, how many functional sperm cells are produced from one diploid precursor cell?

Accepted Answer

Four functional sperm cells

Question 4

Which of the following statements about oogenesis is correct?

Accepted Answer

Only one of the four cells produced during meiosis becomes a functional egg; the others become polar bodies.

Question 5

What is the chromosomal composition of a zygote immediately after fertilization in animals?

Accepted Answer

Diploid ($$2n$$), with one set of chromosomes from each parent

Question 6

A karyotype reveals three copies of chromosome 21 in a newborn. Which condition does this indicate?

Accepted Answer

Down syndrome (Trisomy 21)

Question 7

Which event during meiosis can lead to aneuploidy such as monosomy or trisomy?

Accepted Answer

Nondisjunction, where chromosomes fail to separate properly

Question 8

If nondisjunction occurs during meiosis I in oogenesis, what is the expected outcome after fertilization?

Accepted Answer

All resulting zygotes will be either monosomic or trisomic for the affected chromosome.

Question 9

Which of the following is a viable autosomal trisomy in humans?

Accepted Answer

Trisomy 21 (Down syndrome)

Question 10

A patient has a karyotype showing 45 chromosomes with only one X chromosome and no Y chromosome. Which syndrome is this?

Accepted Answer

Turner syndrome

Question 11

Which of the following best explains why aneuploidy of sex chromosomes is less likely to be fatal than autosomal aneuploidy?

Accepted Answer

Sex chromosomes affect fewer essential body systems than autosomes.

Question 12

A person with the karyotype XXY is most likely to have which syndrome, and what is a common feature?

Accepted Answer

Klinefelter syndrome; may not be diagnosed until after puberty due to subtle symptoms

Question 13

Which gene is responsible for male development, and what happens if it is deleted from the Y chromosome?

Accepted Answer

The SRY gene; deletion leads to female characteristics even if a Y chromosome is present

Question 14

Which chromosomal structural change involves a segment of one chromosome moving to a non-homologous chromosome?

Accepted Answer

Translocation

Question 15

A child is diagnosed with Williams syndrome, which is caused by a deletion at the end of chromosome 7. What protein is missing, and what is a typical physical feature?

Accepted Answer

Elastin; elfin facial features

Question 16

Which of the following is an example of a translocation syndrome that results in a congenital heart defect due to a translocation between chromosomes 2 and 20?

Accepted Answer

Alagille syndrome

Question 17

The Philadelphia chromosome, associated with chronic myeloid leukemia, is the result of which chromosomal event?

Accepted Answer

A translocation between chromosomes 9 and 22

Question 18

Which of the following best describes the difference between deletion and duplication chromosomal mutations?

Accepted Answer

Deletion removes a segment of a chromosome; duplication repeats a segment within the same chromosome.

Question 19

A fertilized egg divides by mitosis to form a multicellular organism. What is true about the chromosome number in the resulting somatic cells?

Accepted Answer

Each somatic cell has the same chromosome number as the original zygote ($$2n).$$

Question 20

Which of the following scenarios is most likely to result in a viable human birth?

Accepted Answer

A zygote with trisomy 21

Chromosomal Basis of Inheritance and Disorders: Life Cycles, Meiosis, and Chromosome Abnormalities

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