Lecture 5: Sex determination and Linkage

Question 1

Chromosome that determines sex, gene on that chromosome and protein of that gene

Answer 1

Y chromosome
SRY gene
TDF protein

Question 2

Heterogametic

Answer 2

Sex produces 2 different gamete types with 2 different sex chromosomes

Question 3

Monoecious

Answer 3

Both male and female reproductive structures in the same organism

Question 4

Dioecious

Answer 4

Either male or female reproductive structures but not both in one organism

Question 5

Grasshopper XX-XO system

Answer 5

XX female

XO male

Question 6

Bird/reptile ZW-ZZ system

Answer 6

ZW female

ZZ male

Question 7

X chromosome contains

Answer 7

Genetic info for both sexes. At least one copy is required

Question 8

Pseudoautosomal regions

Answer 8

Regions in X and Y chromosomes that are homologous, essential for X-Y pairing during meiosis

Question 9

Haplodiploidy system

Answer 9

Haploid set- male
Diploid set- female
Bees, wasps, ants

Question 10

Turner syndrome genotype

Answer 10

XO

Question 11

Klinefelter syndrome genotype

Answer 11

XXY or XXXY or XXXXY or XXYY

Question 12

Turner syndrome features

Answer 12

XO
Short stature- most common
High arched palate
Retrognathia
Droopy eyes or lazy eye

Question 13

Klinefelter syndrome features

Answer 13

Boys
May be slightly taller
Fatter around the belly
Clumsier
Slower development of motor skills

Question 14

What happens if SRY is transferred to X chromosome

Answer 14

Male phenotype

Question 15

Why is the Y chromosome short

Answer 15

Over time, it has lost DNA due to the lack of crossing over with the X chromosome

Question 16

XYY syndrome

Answer 16

Male has extra Y chromosome, meaning he has 47 total chromosomes
Many have no appreciable characteristics, some may be taller or lack in intelligence

Question 17

Dosage compensation

Answer 17

Inactivation of 1 X chromosome to compensate for different X dosage between the sexes

Question 18

Lyon hypothesis

Answer 18

Suggested that dosage compensation in mammals is by inactivation of all but one X chromosomes in cells with more than one X chromosome.
This is the Barr body

Question 19

Masaicism

Answer 19

A condition in which cells within the same person have a different genetic makeup
e.g. when different X chromosomes are inactivated in neighboring cells

Question 20

Xic’s and X inactivation

Answer 20

X inactivation centers
If two or more are counted, Xist is turned on and its RNA product coats one of the X chromosomes- randomly determined
Additional proteins recognize the inactive X and cause condensation and permanent inactivation
This process is undone during meiosis

Question 21

Common x-linked diseases

Answer 21

Red-green color blindness
Hemophilia A
Hemophilia B
Duchenne/Beckers muscular dystrophy
Glucose-6-phosphate dehydrogenase deficiency

Question 22

Random X inactivation produces

Answer 22

Mosaic

Question 23

X-inactivation unfavorable skewing

Answer 23

X-inactivation may unfavorable inactivate the WT X chromosome and cause female carriers to present phenotype