Chapter 8_Variation In Chromosome Structure And Number

Question 1

The three most commonly used features of classifying chromosomes are

Answer 1

Location of centromere, size, and banding patterns.

Question 2

The 4 different positions of the centromere

Answer 2

• Metacentric: The centromere is near the middle
• Submetacentric: Slightly off center
• Acrocentric: Significantly off center
• Telocentric: Is at one end

Question 3

Is the chromosome ever exactly in the center?

Answer 3

No, so it has a short arm “p” and a long arm “q”

Question 4

Simple vs. Reciprocal Translocation

Answer 4

• Simple: A single piece of chromosome is attached to another chromosome
• Reciprocal: Two different types of chromosomes exchange pieces, thereby producing two abnormal chromosomes carrying translocations.

Question 5

Terminal Deletion

Answer 5

A normal chromosome has broken into two separate pieces. The piece without the centromere is lost and degraded.

Question 6

Interstitial Deletion

Answer 6

A chromosome has broken in two places to produce three chromosomal fragments. The central fragment is lost, and the two outer pieces reattach to each other.

Question 7

Copy Number Variation (CNV)

Answer 7

A type of structural variation in which a segment of DNA, which is 1000 bp or more in length, exhibits copy number differences among members of the same species.

Question 8

What are the possibilities of CNV?

Answer 8

• Some members of a species may carry a chromosome that is missing a particular gene or part of a gene.
• May involve duplication.

Question 9

Segmental Duplication

Answer 9

The homolog with two copies of gene A

Question 10

Pericentric vs. Paracentric Inversion

Answer 10

• Pericentric: The centromere lies within the inverted region of the chromosome
• Paracentric: The centromere is found outside the inverted region.

Question 11

Position Effect

Answer 11

A chang ein phenotype that occurs when the position of a gene changes from one chromosomal site to a different location.

Question 12

Inversion Heterozygote

Answer 12

An individual carrying one copy of a normal chromosome and one copy of an inverted chromosome.

Question 13

Inversion Loop

Answer 13

For the normal chromosome and inversion chromosome to synapse properly, an inversion loop must form to permit the homologous genes on both chromosomes to align next to each other despite the inverted sequence.

Question 14

Dicentric Chromosome

Answer 14

Contains two centromeres

Question 15

Dicentric Bridge

Answer 15

The region of the chromosome connecting the two centromeres

Question 16

Acentric Fragment

Answer 16

Crossover that produces a piece of chromosome without any centromere. It is lost and degraded in subsequent cell divisions.

Question 17

Telomeres

Answer 17

Specialized repeated sequences of DNA found at the end of normal chromosomes. Telomeres allow cells to identify where a chromosome ends and prevent the attachment of chromosomal DNA to the natural ends of a chromosome.

Question 18

Euploid

Answer 18

Have a chromosome number that is an exact multiple of a chromosome set.

Question 19

Triploid

Answer 19

Contains three sets of chromosomes (3n)

Question 20

Polypoid

Answer 20

Three or more sets of chromosomes

Question 21

Aneuploidy

Answer 21

Alteration in the number of particular chromosomes.

Question 22

Trisomic

Answer 22

(2n + 1)

Question 23

Nondisjunction

Answer 23

The chromosomes do not segregate properly

Question 24

Endopolyploidy

Answer 24

The occurrence of polyploid tissue or cells in organisms that are otherwise diploid

Question 25

Polytene Chromosome

Answer 25

Repeated rounds of chromosomal replication produce a bundle of chromosomes that lie together in a parallel fashion.

Question 26

Meiotic Nondisjunction

Answer 26

Produce haploid cells that have too many or too few chromosomes. If such a cell gives rise to a gamete that fuses with a normal gamete during fertilization, the resulting offspring will have an abnormal chromosome number in all of its cells.

Question 27

Mitotic Nondisjunction

Answer 27

Abnormal disjunction after fertilization in one of the somatic cells. Leads to a patch of tissue.

Question 28

Alloploid

Answer 28

Contains sets of chromosomes from two or more different species.

Question 29

When does nondisjunction occur?

Answer 29

During anaphase of meiosis I or meiosis II (or during anaphase of mitosis)

Question 30

Complete Nondisjunction

Answer 30

A diploid cell and a cell without any chromosomes.

Question 31

Bilateral Gyandromorph

Answer 31

One half of the organism becomes female and one half becomes male

Question 32

Autopolyploid

Answer 32

An individual with one or more extra sets of chromosomes.

Question 33

Alloploidy

Answer 33

A result of interspecies crosses

Question 34

Homeologous

Answer 34

Evolutionarily related chromosomes from two different species.