Module 5

Question 1

Cytogeneticists use 3 main features to identify and classify chromosomes:

Answer 1

location of centromere, relative sizes, and banding patterns (all observed in karyotype)

Question 2

G-Banding

Answer 2

Using giemsa stain to identify homologous regions of chromosomes (some regions bind strongly to the stain, others do not)

Question 3

Chromosomal Deletion

Answer 3

Loss of a chromosomal segment, can be terminal (end of chromosome is lost) or interstitial (middle component is lost, two outer pieces reattach), can be detrimental

Question 4

Repetitive Sequences

Answer 4

Chromosomal duplication causing misalignment between homologous chromosomes, resulting in nonallelic homologous recombination, can have detrimental physical effects

Question 5

Chromosomal Duplication

Answer 5

Repetition of a chromosomal segment, often not very harmful phenotypically

Question 6

Chromosomal Inversion

Answer 6

A change in the direction of part of the genetic material along a single chromosome, can be either pericentric (including centromere) or paracentric (peripheral)

Question 7

Chromosomal Translocation

Answer 7

A segment of a chromosome attaches to a different one, can be simple (one piece moves) or reciprocal (two chromosome exchange pieces)

Question 8

Banding pattern is useful because:

Answer 8

distinguishes individual chromosomes, detects changes in chromosome structure, and reveals evolutionary relationships among chromosomes of similar species

Question 9

Gene Family

Answer 9

Two or more genes with similar function in a single species derived from the same duplicated ancestral gene (paralogs, ex. globin gene family)

Question 10

Copy Number Variation (CNV)

Answer 10

A segment of DNA varying in copy number among members of the same species, associated with disease in humans

Question 11

Break Point Effect

Answer 11

An inversion occurring within a vital gene, separating it into two nonfunctional parts

Question 12

Position Effect

Answer 12

An inversion where a gene is repositioned in a way that alters its expression

Question 13

Inversion Loop

Answer 13

Must form for normal and inverted chromosomes to synapse properly

Question 14

Reciprocal translocations arise from two different mechanisms:

Answer 14

chromosomal breakage/DNA repair and abnormal crossovers (between nonhomologous chromosomes), not many consequences with balancing translocations but unbalanced translocations are associated with phenotypic abnormalities

Question 15

Euploidy

Answer 15

Variation in the number of complete chromosome sets (ex. diploid = 2n, triploid = 3n, tetraploid = 4n), polyploidy often lethal in animals but some variation does occur (ex. bees)

Question 16

Aneuploidy

Answer 16

Variation in the number of particular chromosomes within a set (ex. monosomy = 1, trisomy = 3), detrimental due to extreme difference in gene expression

Question 17

Endopolyploidy

Answer 17

Diploid animals produce tissues that are polyploid such as liver cells, potentially to enhance gene products

Question 18

Polytene Chromosomes

Answer 18

Occur in salivary glands of Drosophila and other insects, undergo repeated replication (512 chromosomes)

Question 19

Benefits for plants to be polyploidy:

Answer 19

Larger in size, more agriculturally robust, odd number of chromosomes makes them sterile (ex. seedless fruit)