Module 4

Question 1

Sexual Dimorphism & What is it determined by?

Answer 1

Morphological differences between the sexes. It is determined by the pair or sex chromosomes.
(XX - female, XY - male)
(differ from autosomes which don’t determine sex)

Question 2

Pseudo-autosomal regions (PAR) 1 and 2

Answer 2

• short, autosomal-like homologous regions
• approx. 30 genes
• one XY or both XX regions pair and cross over during meiosis

Question 3

Inheritance of sex chromosomes

Answer 3

• XX individuals inherit an x-chromosome from each parent
• XY individuals inherit their X chromosome from their mother and Y from their father

Question 4

Y-linked patterns of inheritance

Answer 4

• the trait is seen only in males
• all male descendants of an affected man will exhibit the trait
• females never inherit the trait/can’t pass it on to offspring
• ex. SRY gene

Question 5

X-dosage compensation

Answer 5

One X chromosome is randomly selected for epigenetic silencing
- no transcription from the silenced X chromosome
- silenced chromosome forms a condensed transcriptionally inactive mass in nucleus of female somatic cells

Question 6

The epigenetically silenced chromosome in females is called a…

Answer 6

Barr body

Question 7

Gender reveal party

Answer 7

a celebration where an expectant mother shares/discovers the assumed gender of her baby, based on the baby’s genitalia

Question 8

Gender

Answer 8

used to describe the characteristics of women and men that are socially constructed

Question 9

X-inactivation & inheritance of alleles - NORMAL

Answer 9

• healthy cells have two unaffected/normal copies of the x-chromosome
• they could carry either the homozygous or heterozygous allele for x-linked gene
• each cell has one x-chromosome that is epigenetically silenced
• silenced x is chosen randomly

Question 10

X-inactivation & inheritance of alleles - DISEASED

Answer 10

In females (XX)
if the mutation is heterozygous
- x-linked recessive: presence of normal/healthy non-silenced X is sufficient for normal tissue func.
- x-linked dominant: presence of normal/healthy non silenced X is insufficient for normal tissue func.
if mutation is homozygous: all cells will be affected even with x-inactivation
In males (XY)
- all cells will be affected since only one copy of X-chromosome (more severe affected)

Question 11

X-linked disorders - examples

Answer 11

Recessive disorders
- hemophilia: blood clotting disorder
- red/green colour blindness: affects 7-10% of men & 0.5-1% of women
- Becker’s muscular dystrophy: milder form of Duchenne (causes progressive muscle weakness of the legs/pelvis
Dominant disorders
- hypophoshataemia: aka vitamin-d-resistant rickets
- rett syndrome: brain syndrome that occurs mostly in females (lethal in males)

Question 12

non-binary

Answer 12

people don’t identify as either gender despite their biological sex

Question 13

transgender

Answer 13

identify with the gender opposite to that which has been historically assigned to their biological sex