Chromosome Structure and Karyotypes

Question 1

What are fragile sites?

Answer 1

Non-staining gaps, occasionally observed in characteristic sites on several chromosomes

Only clinically significant fragile site is on the X chromosome and causes Fragile X syndrome

Question 2

What is fragile X syndrome?

Answer 2

Mutation in FMR1

Causes mental impairment, ADHD, anxiety, Autism, Long facial features, hyperextensible joints

Question 3

What is a centromere?

Answer 3

region of a chromosome to which spindle traction fibers attach during mitosis and meiosis

Question 4

What is a metacentric chromosome?

Answer 4

Chromosome with a centrally placed centromere

Question 5

What is a submetacentric chromosome?

Answer 5

a chromosome with a centromere closer to one end than the other

Question 6

What is an acrocentric chromosome?

Answer 6

A chromosome with a nearly terminal centromere

Question 7

What is satellite DNA?

Answer 7

And fraction of the DNA that differs substantially in base composition (AT or GC rich)

Long series of short tandem repeats clustered around centromeres

Question 8

What is minisatellite DNA?

Answer 8

repeat length of 7-100bp, highly polymorphic e.g. telomeric repeats

Question 9

What is microsatellite DNA?

Answer 9

Tandem single, di-, tri- and tetranucleotide repeat base sequences located throughout the genome

Question 10

What type of microsatellite DNA is associated with disorders?

Answer 10

Trinucleotide repeats in or near genes.

E.g. huntington’s and fragile X syndrome

Question 11

What are SINEs?

Answer 11

Short Interspersed Nucleotide Elements

E.g. Alu repeats

Question 12

What are LINEs?

Answer 12

Long interspersed nucleotide elements

E.g. L1 - 17% of human genomic sequence

Question 13

What is a karyotype?

Answer 13

describes the chromosome constitution in terms of the total number of chromosomes and the sec chromosome constitution

Autosomes are listed from largest to smallest

Question 14

How is the location on a chromosome named?

Answer 14

Chromosome
Arm
Region
Band

Question 15

What is Giemsa (G)-banding?

Answer 15

Stain used to view chromsomes under normal light photo-microscopy

Produces light and dark bands

Question 16

What is Quinacrine (Q)-banding?

Answer 16

Fluorescent dye that binds to AT-rich sequences preferentially

Viewed by fluorescent microscopy

Question 17

What is R (Reverse)-banding?

Answer 17

Stains an opposite banding pattern from the other two.

Question 18

What is C (Centromeric)-banding?

Answer 18

Stain binds to centromeres

Question 19

What is High-Resolution banding?

Answer 19

G or R banding performed at an early stage of mitosis when chromosomes are relatively uncondensed.

Useful in detecting subtle structural abnormalities

Question 20

What is Fluorescent in situ Hybridization? (FISH)

Answer 20

A labeled chromosome-specific DNA segment is hybridized with metaphase then visualized under a fluorescent microscope

Question 21

What is spectral karyotyping?

Answer 21

Uses multiple fluorescent probes specific for sequences on each chromosome to generate a specific color for each chromosome.

Question 22

What is comparative genomic hybridization?

Answer 22

Test and control DNA are labeled with fluorophores, then hybridized to normal metaphase chromosomes. Deletions or additions alter the color ratio.