Question 1

Which of the following can be found in normal carrier individuals?&#10;A) Paracentric inversions&#10;B) Translocations&#10;C) Pericentric inversions&#10;D) Deletions&#10;E) All of the above

Accepted Answer

All of the options listed (Paracentric inversions, Translocations, Pericentric inversions, and Deletions) can be present in normal carrier individuals without causing any phenotypic effect. These chromosomal rearrangements can be balanced, meaning no genetic material is gained or lost, allowing the carrier to be phenotypically normal.

Question 2

Which of the following refers to the central constriction of a chromosome?&#10;A) Telomere&#10;B) Centromere&#10;C) Centriole&#10;D) Chromatid&#10;E) Central repeat

Accepted Answer

The central constriction of a chromosome is called the centromere. It is the point where the two chromatids of a duplicated chromosome are held together, and it plays a crucial role in the separation of chromosomes during cell division.

Question 3

Why are phytohemagglutinin and then colchicine added to blood samples before chromosome analysis is done?&#10;A) To lyse the red blood cells&#10;B) To enhance the chromosomal banding patterns&#10;C) To stimulate the cells to divide and arrest at metaphase&#10;D) So that chromosomes will align nicely on mitotic spindles&#10;E) So that homologous chromosomes will be paired at the equatorial plane of the cell

Accepted Answer

Phytohemagglutinin and colchicine are used to stimulate cells to divide and arrest at metaphase, which is the stage of the cell cycle where chromosomes are most condensed and visible. This allows for easier analysis of the chromosomes.

Answer: B
 Colchicine can enhance the chromosomal banding patterns, making it easier to identify specific regions of the chromosomes.

Question 4

Which form of chromosomal DNA stains darkly and is largely composed of unexpressed,repetitive DNA?&#10;A) Euchromatin&#10;B) 5' UTRs&#10;C) Heterochromatin&#10;D) Nucleosomes&#10;E) Introns

Accepted Answer

Heterochromatin stains darkly and is largely composed of unexpressed, repetitive DNA. Euchromatin is lightly staining and contains expressed genes. 5' UTRs and introns are not forms of chromosomal DNA, while nucleosomes are the basic units of DNA packaging and are found in both heterochromatin and euchromatin.

Question 5

The significance of a Robertsonian translocation is which of the following?&#10;A) The loss of the sequences in the p arms of the involved chromosomes&#10;B) Inability of the involved chromosomes to recombine&#10;C) The risk of an unbalanced chromosome complement in gametes&#10;D) Loss of chromosomal material in somatic cells during mitosis&#10;E) Robertsonian translocations are generally benign

Accepted Answer

The significance of a Robertsonian translocation is the risk of an unbalanced chromosome complement in gametes. This is because the translocation involves the fusion of two acrocentric chromosomes at their centromeres, leading to the loss of the short arms of the chromosomes and the possibility of unequal segregation of the fused chromosomes during gamete formation. This can result in gametes with a missing or extra chromosome, which can lead to chromosomal disorders in offspring.

Question 6

What is the value of chromosome banding?&#10;A) The chromosomes can be visualized&#10;B) All chromosomes stain similarly&#10;C) Each chromosome has a characteristic banding pattern&#10;D) Genes are stained&#10;E) Specific DNA sequences can be visualized

Accepted Answer

Chromosome banding allows each chromosome to have a characteristic pattern of light and dark bands, which can aid in identifying specific chromosomes and abnormalities.

Question 7

Due to differences in male and female meiosis,advanced paternal age effect is more likely to be associated with what type of mutation?&#10;A) Chromosome abnormalities&#10;B) Translocations&#10;C) De novo dominant mutations&#10;D) Aneuploidies&#10;E) Fragile sites

Accepted Answer

Advanced paternal age effect is more likely to be associated with de novo dominant mutations, as older sperm are more prone to accumulate mutations during meiosis. This type of mutation occurs in the DNA sequence of a single gene and can cause diseases such as Marfan syndrome or achondroplasia. Chromosome abnormalities, translocations, aneuploidies, and fragile sites are also associated with advanced paternal age, but de novo dominant mutations are the most likely type of mutation to occur.

Deck 3: Chromosomes and Cell Division