Question 1

DNA associates very tightly with nucleosomes because

Accepted Answer

Negative charges on the phosphate backbone of DNA are attracted to the positive charges of the lysine and arginine residues of histone proteins, facilitating the tight association between DNA and nucleosomes.

Question 2

The control of the cell cycle involves all of the following EXCEPT

Accepted Answer

Cytokinesis is the process of cytoplasmic division to form two daughter cells, following nuclear division (mitosis or meiosis), rather than a control mechanism of the cell cycle itself. The other options (A, B, C, E) are directly involved in the regulation and checkpoints of the cell cycle.

Question 3

During metaphase,

Accepted Answer

During metaphase, chromosomes are highly condensed and much shorter than they were in interphase, allowing them to be more easily separated and moved to opposite poles of the cell.

Question 4

Horses and donkeys are closely related species that can interbreed. However, the offspring produced are usually sterile and cannot reproduce. What term would best describe the offspring from this mating?

Accepted Answer

Alloploid refers to organisms that have sets of chromosomes from two or more different species, which applies to the offspring of a horse and donkey mating, such as a mule. These offspring are usually sterile due to the differences in their parental chromosomes.

Question 5

When a gamete that is lacking a sex chromosome due to nondisjunction has fused with a gamete carrying an X chromosome, this type of abnormality leads to the ________.

Accepted Answer

The Turner syndrome is characterized by a female having only one X chromosome (45,X) instead of the usual two sex chromosomes. This condition occurs when a gamete lacking a sex chromosome (either an X or Y) fuses with a gamete carrying an X chromosome, resulting in a zygote with a single X chromosome.

Question 6

Chromosomes inside the nucleus do not overlap with each other because

Accepted Answer

Chromosomes occupy distinct, non-overlapping regions within the nucleus known as chromosome territories. This spatial organization is crucial for regulating gene expression and maintaining genomic integrity.

Question 7

A person who inherits an extra X chromosome will have

Accepted Answer

Klinefelter syndrome is characterized by the presence of an extra X chromosome in males, typically resulting in the karyotype 47,XXY. This condition can lead to symptoms such as reduced fertility and physical development issues.

Question 8

Chromosomes are replicated during the ______ phase.

Accepted Answer

Chromosomes are replicated during the S (Synthesis) phase of the cell cycle, where DNA synthesis and replication occur.

Question 9

If two triploid species interbreed, the offspring will be

Accepted Answer

When two triploid species interbreed, their offspring will have six sets of chromosomes, making them allohexaploid.

Question 10

If a cell contains 20 units of DNA during G2, it will have 40 units of DNA during S.

Accepted Answer

During the S phase of the cell cycle, DNA is replicated, so if a cell contains 20 units of DNA during G2, it means it has already doubled its DNA content in the S phase. Therefore, it would have had 10 units before S phase, not 40 units after.

Quiz 15: The Eukaryotic Cell Cycle, Mitosis, and Meiosis