Question 1

Which of the following best describes a submetacentric chromosome?

Accepted Answer

The centromere is located between the center and the tip, resulting in a short p arm and a long q arm.

Question 2

A karyotype is most useful for which of the following purposes?

Accepted Answer

Identifying abnormalities in chromosome number or structure in an individual.

Question 3

Which of the following statements about aneuploidy in humans is correct?

Accepted Answer

Only trisomies of chromosomes 13, 18, and 21 are seen in newborn infants.

Question 4

Which of the following best explains the increased risk of Down syndrome with maternal age?

Accepted Answer

Prolonged arrest of oocytes in prophase I leads to degradation of cohesin proteins, increasing nondisjunction risk.

Question 5

A patient is found to have Turner syndrome. Which genetic mechanism most likely explains their phenotype?

Accepted Answer

Monosomy of the X chromosome resulting in haploinsufficiency of the SHOX gene.

Question 6

Which of the following is a characteristic of polyploidy?

Accepted Answer

The presence of three or more complete sets of chromosomes in the nucleus.

Question 7

A chromosome breakage that results in a fragment lacking a centromere is most likely to cause which of the following outcomes during cell division?

Accepted Answer

The acentric fragment will be lost because it cannot attach to the spindle apparatus.

Question 8

Which of the following best describes the outcome of an unequal crossover event between homologous chromosomes?

Accepted Answer

One homolog will have a partial duplication and the other a partial deletion.

Question 9

Which type of chromosome inversion includes the centromere within the inverted region?

Accepted Answer

Pericentric inversion

Question 10

During meiosis in a paracentric inversion heterozygote, crossing over within the inversion loop can result in which of the following?

Accepted Answer

A dicentric chromosome and an acentric fragment, both of which are genetically unbalanced.

Question 11

Which of the following is true regarding Robertsonian translocations?

Accepted Answer

They involve the fusion of two nonhomologous chromosomes, often resulting in the loss of genetic material.

Question 12

Which of the following statements about chromatin organization is correct?

Accepted Answer

Chromatin must be compacted to fit into the nucleus and to regulate gene expression.

Question 13

Which of the following best describes the nucleosome core particle?

Accepted Answer

An octamer of histone proteins (two each of H2A, H2B, H3, and H4) wrapped by DNA.

Question 14

Which of the following equations correctly represents the chromosome number in a trisomic human cell?

Accepted Answer

$$2n + 1$$

Question 15

A scientist uses fluorescent in situ hybridization (FISH) to detect a specific gene on a chromosome. Which of the following best explains how FISH works?

Accepted Answer

A fluorescently labeled molecular probe binds to a complementary DNA sequence on the chromosome, allowing visualization under a fluorescence microscope.

Question 16

Which of the following statements about histone proteins is correct?

Accepted Answer

Histone proteins are among the most evolutionarily conserved proteins, indicating a critical function in chromatin structure.

Question 17

During DNA replication, how are nucleosomes reassembled on the newly synthesized DNA?

Accepted Answer

Most nucleosomes are assembled from a mixture of old and new histone components.

Question 18

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is less condensed and contains actively expressed genes, while heterochromatin is tightly condensed and contains fewer expressed genes.

Question 19

A cell is found to have three sets of chromosomes, each set from a different species. This is an example of:

Accepted Answer

Allopolyploidy

Question 20

Which of the following best explains why chromatin remodeling is necessary for transcription?

Accepted Answer

Nucleosomes must be repositioned or temporarily removed to allow RNA polymerase access to the DNA template.

Eukaryotic Chromosome Abnormalities and Molecular Organization: Study Notes

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