Chapter 4b: Variations in Genome Structure: Changes in Chromosome Structure

Question 1

chromosomal aberrations

Answer 1

a. deletions
b. duplications
c. inversions
d. Reciprocal Translocation

Question 2

Alterations in the number of genes

Answer 2

deletions and duplications

Question 3

Alterations in the location of genes

Answer 3

inversions and translocations

Question 4

loss of a chromosomal segment; could be homozygous or heterozygous

Answer 4

deletions

Question 5

Genetic Effects of Deletion

Answer 5

• lethal in the homozygous and hemizygous condition
• reduced viability
• modified phenotypic ratio

Question 6

Term for the expression of a normally recessive trait due to the loss of the corresponding dominant allele?

Answer 6

pseudo-dominance

Question 7

syndrome due to a deletion in the short arm of chromosome # 5

Answer 7

Cri du chat syndrome

Question 8

Chromosome 7 loses an end piece
- Turned up nose
- Wide mouth with small chin
- Poor academic skills but well developed verbal and musical skills
- ‘elfin’ facial appearance

Answer 8

Williams syndrome

Question 9

due to a repeated portion in a chromosome due to unequal crossing over or errors in replication

Answer 9

Duplications

Question 10

Genetic effects of duplications

Answer 10

gene redundancy

Question 11

occur when parts of chromosomes become detached, turn through 180 degrees and reinserted in such a way that the genes are in reversed order.

Answer 11

inversions

Question 12

arise from chromosome entanglements and breakages during meiotic prophase; also from recombination between transposable elements

Answer 12

inversions

Question 13

Cause linear rearrangement of genes in a chromosome

Answer 13

inversions

Question 14

In inversion heterozygotes, a __ forms from the pairing of the inverted and non-inverted regions

Answer 14

loop

Question 15

two types of inversions

Answer 15

• pericentric inversion
• paracentric inversion

Question 16

inversion that is situated in a chromosome arm to one side off the centromere

Answer 16

paracentric inversion

Question 17

A child with __, dicentric chromosome 15 arising from a maternal paracentric inversion of chromosome 15q

Answer 17

bisatellited

Question 18

Tobiano color pattern is due to a large __ on Equus caballus chromosome 3 (ECA3), which may alter the expression of the KIT receptor tyrosine kinase.

Answer 18

inversion

Question 19

*Involves interchange of blocks of genes between two
nonhomologous chromosomes

Answer 19

reciprocal translocation

Question 20

• linkage relationships between genes change

Answer 20

reciprocal translocation

Question 21

*Translocation heterozygotes exhibit the characteristic __ during meiotic prophase due to the pairing of homologous chromosome parts

Answer 21

cross-like configuration

Question 22

types of reciprocal translocation

Answer 22

• alternate
• adjacent 1
• adjacent 2

Question 23

type of translocation
- the breaks occur at different points on the chromosomes involved, and the segments are exchanged between non-homologous chromosomes.
- does not directly involve the centromeres of the chromosomes.
- The result is two derivative chromosomes, each carrying a combination of genetic material from the two original chromosomes.
- typically do not lead to significant genetic disorders unless crucial genes are disrupted or gene expression is altered.

Answer 23

alternate translocation

Question 24

• typically involves acrocentric chromosomes
• the long arms of two acrocentric chromosomes break near the centromere, and the long arms fuse, while the short arms are lost.
• results in one large chromosome with the combined genetic material of the two original long arms, and another small chromosome consisting of the fused short arms.

Answer 24

Adjacent 1 Translocation (Robertsonian Translocation)

Question 25

• breaks on both chromosomes adjacent to the centromere, leading to the exchange of terminal segments between the chromosomes.
• involve the centromeres of the chromosomes

Answer 25

Adjacent 2 Translocation

Question 26

In __ a translocation places the c-myc protooncogene in the vicinity of the immunoglobulin heavy chain enhancer. This causes overproduction of c-myc.

Answer 26

Burkitt’s lymphoma

Question 27

a mutated gene that has the potential to cause cancer.

Answer 27

oncogene

Question 28

reciprocal translocation between chromosomes 2 and 22 causes

Answer 28

Alagille Syndrome

Question 29

• Found in leukocytes of patients with chronic myeloid leukemia and other types of leukemia.
• reciprocal translocation in chromosome 9 and 22

Answer 29

Philadelphia chromosome