Question 1

Which of the following best describes the difference between a metacentric and a telocentric chromosome?

Accepted Answer

A metacentric chromosome has the centromere near the middle, while a telocentric chromosome has the centromere at the tip and no p arm.

Question 2

A human cell is observed to have 45 chromosomes, including only one X chromosome and no second sex chromosome. Which syndrome does this karyotype most likely represent?

Accepted Answer

Turner syndrome

Question 3

Which molecular technique is most appropriate for detecting a microdeletion that is too small to be seen by standard chromosome banding?

Accepted Answer

Fluorescent in situ hybridization (FISH)

Question 4

A plant breeder crosses two diploid species (2n=14 and 2n=18) and obtains a sterile hybrid. Chromosome doubling occurs in the hybrid, resulting in a fertile plant. What is the chromosome number of the new fertile allopolyploid?

Accepted Answer

$$2n = 32$$

Question 5

Which of the following is a likely consequence of a paracentric inversion during meiosis if crossing over occurs within the inverted region?

Accepted Answer

Formation of a dicentric chromosome and an acentric fragment

Question 6

A trisomic human zygote is formed when a gamete with $$n+1$$ chromosomes fuses with a normal gamete. What is the resulting chromosome number in the zygote?

Accepted Answer

$$2n+1$$

Question 7

Which of the following best explains why odd-numbered polyploids (e.g., triploids) are often sterile?

Accepted Answer

They cannot form balanced gametes due to unpaired chromosomes during meiosis.

Question 8

A patient is diagnosed with cri-du-chat syndrome. Which chromosomal abnormality is most likely present?

Accepted Answer

Terminal deletion on chromosome 5p

Question 9

Which of the following statements about gene dosage is correct?

Accepted Answer

Aneuploidy alters the dosage of all genes on the affected chromosome, often leading to phenotypic abnormalities.

Question 10

Which chromatin state is associated with actively expressed genes and less condensed DNA?

Accepted Answer

Euchromatin

Question 11

A Drosophila fly has a variegated eye color due to a gene being relocated near centromeric heterochromatin. What genetic phenomenon does this illustrate?

Accepted Answer

Position effect variegation

Question 12

Which of the following best describes the process of trisomy rescue?

Accepted Answer

A trisomic zygote loses one copy of the trisomic chromosome during early mitosis, potentially resulting in uniparental disomy.

Question 13

Which of the following is a direct result of a Robertsonian translocation?

Accepted Answer

The chromosome number drops by two ($$2n-2) $$due to fusion of two nonhomologous chromosomes.

Question 14

Which histone protein is primarily associated with stabilizing the solenoid (30-nm fiber) structure of chromatin?

Accepted Answer

H1

Question 15

A partial duplication heterozygote is best described as an organism that:

Accepted Answer

Has one normal homolog and one homolog with a duplicated segment.

Question 16

Which of the following is a likely outcome of alternate segregation in a reciprocal balanced translocation heterozygote during meiosis?

Accepted Answer

Gametes with a full haploid set of genes and normal viability

Question 17

Which of the following best explains the phenomenon of pseudodominance?

Accepted Answer

A recessive allele is expressed because the dominant allele is deleted on the homologous chromosome.

Question 18

Which of the following statements about chromatin organization is correct?

Accepted Answer

Chromatin loops are anchored to the chromosome scaffold by nonhistone proteins at matrix attachment regions (MARs).

Question 19

A plant with a diploid chromosome number of $$2n=16$$ undergoes autopolyploidization via mitotic nondisjunction. What is the chromosome number of the resulting autotetraploid cell?

Accepted Answer

$$4n=32$$

Question 20

Which of the following is a real-world application of polyploidy in agriculture?

Accepted Answer

Production of seedless watermelons by creating triploid plants

Chromosome Number, Structure, and Abnormalities in Eukaryotes

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