Lecture 11 - Chromosome Variation I

Question 1

What are the different chromosome morphologies based off of centromere location?

L11 S33

Answer 1

Metacentric:
-centrally located

Submetacentric:
-located slightly off center

Acrocentric:
-located near the end but still has notable short arms

Telocentric:
-located so close to the end no short arms are notable

Question 2

What are the different types of banding and what is responsible for banding?

L11 S36

Answer 2

G banding:

• Giemsa stain
• most common method

Q banding:
-quinacrine stain

C banding:
-centromere heterochromatin

R banding:
-regions rich in cytosine-guanine base pair

Question 3

What do the terms aneuploidy and polyploidy mean?

L11 S42

Answer 3

Aneuploidy:
-loss or gain of chromosomes

Polyploidy:
-more than two complete sets of paired chromosomes are present

Question 4

What types of chromosomal rearrangements are there?
What are the negative consequences of each?

L11 S45

Answer 4

Duplication:

• segment of chromosome is duplicated
• formation of a fragile loop during prophase I
• increased doseage

Deletion:

• segment of chromosome is duplicated
• formation of a fragile loop during prophase I
• decreased doseage

Inversion:

• segment of chromosome is flipped
• formation of a fragile inversion loop during prophase I
• potential loss of DNA, including centromere

Translocation:
-segment of chromosome is exchange with another segment from a nonhomologous chromosome

Question 5

Differentiate paracentric inversion and pericentric inversion.

L11 S56

Answer 5

Paracentric:

• confined to one arm of a chromosome (does not involve centromere)
• produces a dicentric chromosome and an acentric chromosome (this DNA will be lost during replication)

Pericentric:

• involves both arms of a chromosome (involves centromere)
• produces chromosomes with duplicate/missing genes (likely nonviable)

Question 6

A dicentric chromosome is produced when crossing over takes place in an individual heterozygous for which type of chromosome rearrangement?

L11 S62-63

A. Duplication
B. Deletion
C. Paracentric inversion
D. Pericentric inversion

Answer 6

C. Paracentric inversion

Question 7

What is a Robertsonian translocation?

L11 S65

Answer 7

Translocation between the long arm and short arms of two nonhomologus acrocentric chromosomes. This results in one large, metacentric chromosome consisting of both long arms and a short chromosome consisting of both short arms (typically lost)

Question 8

What is the outcome of a Robertsonian translocation?

L11 S71-72

A. Two acrocentric chromosomes
B. One metacentric chromosomes and one chromosome with two very short arms
C. One metacentric and one acrocentric chromosome
D. Two metacentric chromosomes

Answer 8

B. One metacentric chromosomes and one chromosome with two very short arms