CPPS403 - Chromosomes - 4

Question 1

What are the three types of chromosomal abnormalities?

Answer 1

1. Polyploidy
2. Aneuploidy
3. Chromosomal rearrangements

Polyploidy involves one or more entire extra sets of chromosomes, aneuploidy involves an abnormal number of one chromosome, and chromosomal rearrangements involve structural changes in chromosomes.

Question 2

How can chromosomal abnormalities arise?

Answer 2

1. Errors in cell division
2. Non-disjunction during meiosis
3. Fertilization defects

Non-disjunction can lead to aneuploidy, while fertilization defects can lead to polyploidy.

Question 3

What is polyploidy?

Answer 3

One or more entire extra sets of chromosomes

Examples include triploidy (69 chromosomes) and tetraploidy (92 chromosomes). Most polyploid human embryos spontaneously miscarry.

Question 4

What is aneuploidy?

Answer 4

Abnormal number of one chromosome

Examples include trisomy (an extra chromosome) and monosomy (a single copy).

Question 5

What is trisomy 21 and what is it associated with?

Answer 5

Down Syndrome; associated with advanced maternal age

Trisomy 21 involves two maternal and one paternal chromosome 21.

Question 6

What are examples of additional aneuploidy disorders?

Answer 6

1. Patau syndrome (trisomy 13)
2. Edwards syndrome (trisomy 18)

These disorders result from specific trisomies that lead to various clinical features.

Question 7

What are the two types of structural chromosomal variations?

Answer 7

1. Unbalanced rearrangements
2. Balanced rearrangements

Unbalanced rearrangements differ in DNA content, while balanced rearrangements have the same DNA sequences but in different positions.

Question 8

What is the Philadelphia Chromosome?

Answer 8

Translocation abnormality in chronic myeloid leukemia (9,22)

It involves the fusion of the ABL gene on chromosome 9 and the BCR gene on chromosome 22, producing a tyrosine kinase that is always active.

Question 9

What is a Robertsonian translocation?

Answer 9

Occurs between acrocentric chromosomes; results in one derivative chromosome

It involves the fusion of the long arms of two chromosomes and the loss of the short arms, which are lost without consequence.

Question 10

What is G-Banding/Giemsa Staining used for?

Answer 10

A cytogenetics technique to produce a karyotype by staining condensed chromosomes

It helps visualize large chromosomal anomalies and identify each chromosome by its distinct banding pattern.

Question 11

What is Fluorescence In Situ Hybridization (FISH)?

Answer 11

Technique used to identify specific chromosomes or detect microdeletion syndromes

FISH can identify duplications or deletions in the genome that may not be visible by karyotype.

Question 12

What is Comparative Genomic Hybridization?

Answer 12

Technique that determines genome-wide copy number alterations

Originally started to detect 5-10kbp deletions or additions, now with high-resolution genomic arrays.

Question 13

Fill in the blank: The short arm of a chromosome is referred to as the _______.

Answer 13

p arm

Chromosomes are divided into p arms (short) and q arms (long).

Question 14

True or False: Polyploidy is compatible with life in humans.

Answer 14

False

Most polyploid human embryos spontaneously miscarry.

Question 15

What is the role of telomeres?

Answer 15

Protect chromosome ends from deterioration

Telomeres are regions of highly repetitive DNA that remain compact throughout the cell cycle.

Question 16

What is a karyotype?

Answer 16

A visual representation of an individual’s chromosomes

It displays the number and structure of chromosomes in a cell.