Lecture 11

Question 1

Metacentric

Answer 1

Centromere is located in the middle of the chromosome

Question 2

Submetacentric

Answer 2

Centromere is located NEAR the middle of the chromosome, but it favors one side or the other (not directly in the middle)

Question 3

Acrocentric

Answer 3

Centromere is located near the end of the chromosome

Question 4

Telocentric

Answer 4

Centromere is located at the end of the chromosome

Question 5

What is the NOR?

Answer 5

Nucleolar Organizer Region; region around which the nucleolus forms; can be detected by silver staining and is a useful landmark for chromosome identification; contains tandem repeats of genes encoding ribosomal RNA

Question 6

Steps in Karyotyping

Answer 6

1. Chromosomes prepared from actively dividing cells
2. Halted in metaphase (with Colchicine)
3. Chromosomes arranged according to size

Question 7

G Banding

Answer 7

Bands with giemsa stain; heterochromatin stains intensely, euchromatin stains lightly; 400-600 bands can be identified in metaphase chromosomes

Question 8

Q Banding

Answer 8

Bands with quinacrine stain; florescent stain for A/T rich regions

Question 9

C Banding

Answer 9

Reveals centromeric heterochromatin; constitutive heterochromatin around the centromere is intensely stained

Question 10

R Banding

Answer 10

Regions rich in cytosine-guanine base pairs; uses reverse giemsa staining; treatment with high temperature, low pH, or acridine orange

Question 11

T Banding

Answer 11

Telomeric banding after heat denaturation

Question 12

Aneuploidy

Answer 12

Loss or gain of chromosomes

Question 13

Polyploidy

Answer 13

Cells or organisms containing more than two complete paired (homologous) sets of chromosomes

Question 14

Deletions

Answer 14

Loss of a chromosomal segment; large deletions are easily detected; during pairing, normal chromosome loops out

Question 15

Effects of Deletions

Answer 15

Imbalances in gene product, expression of a normally recessive gene (pseudodominance), and haploinsufficiency

Question 16

Paracentric Inversion

Answer 16

Inversion in which the breakpoints are confined to one arm of a chromosome; inverted segment does not span the centromere

Question 17

Pericentric Inversion

Answer 17

Inversion in which the breakpoints occur on both arms of a chromosome; inverted segment spans the centromere

Question 18

Inversions in Meiosis in Homozygous vs Heterozygous Individuals

Answer 18

Homozygous - no problems arise during meiosis
Heterozygous - homologous sequences align only if the 2 chromosomes form an inversion loop; individuals with para- or peri- centric inversions often have nonfunctional gametes due to loss of large amounts of genetic material during meiosis

Question 19

Reciprocal Translocation

Answer 19

Exchange of material between homologous chromosomes

Question 20

Nonreciprocal Translocation

Answer 20

Transfer of genes from one chromosome to another nonhomologous chromosome

Question 21

Robertsonian Translocation

Answer 21

Rare chromosomal rearrangement that, in humans, generally occur in the 5 acrocentric chromosome pairs 13, 14, 15, 21, and 22; other robertsonian translocations can occur, but do not lead to a viable fetus; frequency is about 1:1000 newborns