Chapter 15 - Linkage and Chromosomes

Question 1

Sutton’s Chromosome Theory of Inheritance

Answer 1

states that genes are found at specific locations on chromosomes, and that the behavior of chromosomes during meiosis can explain Mendel’s laws of inheritance

Question 2

Linked gene

Answer 2

group of genes located on the same homologous chromosome

-they are inherited together

Question 3

Unlinked gene

Answer 3

genes located on different chromosomes

-follow the Law of Segregation and Law of Independent Assortment

Question 4

SRY

Answer 4

Sex Determining Region of Y (SRY)

-induces development of testes

Question 5

Sex determination in insects

Answer 5

X-O system
-determined by number of X chromosomes present
females (XX)
males (XO)

Question 6

Sex determination of diploid-haploid system

Answer 6

found in honeybees, ant

• females are diploid (2n)
• fertile female is a queen, infertile females are worker bees
• females are super sisters (related to each other by 75%)
• males are haploid (n)
• unfertilized eggs develop directly into the organism (parthenogenesis)

Question 7

Hemizygous

Answer 7

describes the number of X chromosomes in males

Question 8

autosomal dominant diseases

Answer 8

• polydactyl
• achondroplasia
• hunchback disease
• Huntington disease

Question 9

X-linked gene defects

Answer 9

[ X-recessive disease]
Red-Green colorblindness
Hemophilia
Duchenne Muscular Dystrophy

Question 10

X-chromosome inactivation

Answer 10

addition of methyl group (CH3) to the nucleotide of one random X chromosome

• this activates X-inactive specific transcript (XIST)
• results in the X gene condensing into a Barr body
  e. g. Tortoiseshell cat

Question 11

Recombination frequency

Answer 11

maximum = 50%

Question 12

Linkage map

Answer 12

genetic map deduced from recombinant frequency
-the larger the distance between 2 linked genes, the higher the probability of cross-over, and higher the frequency of genetic recombination

Question 13

Aneuploidy

Answer 13

mutant condition with abnormal number of particular chromosome
Trisomy (2n+1), monosomy (2n-1)

Question 14

Trisomy

Answer 14

2n+1
autosomal
ex) tri 21st = Down syndrome
tri 18th = Edward syndrome

sex-chromosomal
ex) XXY = Klinfelter syndrome
XXX = superwoman
XYY = superman

Question 15

Monosomy

Answer 15

2n-1

autosomal monosomy is lethal

sex-chromosomal monosomy
ex) XO, Turner syndrome