Module 4 Part 1 Flashcards
define sexual dimorphism
morphological differences between the sexes
how to know sex while looking at karyotype
check the 23rd chromosome
What are Pseudo-Autosomal Regions (PAR) 1 and 2
short, autosomal like homologous regions
- around 30 genes
- one XY or both XX regions pair and cross over during meiosis
what are differential regions
regions of x and y chromosomes which contain genes that are unique to these chromosomes
- sex linked genes and show sex linked patterns
describe y linked patterns of inheritance
the trait is seen only in males
- all male descendants of an affected man will exhibit trait
can females inherit y linked patterns
no, and cannot pass it on either
describe x dosage compensation
one x chromosome is randomly selected for epigenetic silencing
- NO transition from the silenced X chromosome
what does the silenced chromosome form
a condensed, transcriptionally inactive mass in nucleus of female somatic cells
- BARR BODY
exaplain x inactivation on the tortoiiseshell cat
Gene responsible for the fur colour on X chromosome
X^B= orange
X^b= black
male cats= no x inactivation- either orange or black
female cats= one chromosome inactivated
homo= either black or orange
hetero= MOSAIC fur coat
describe normal x-inactivation
- healthy cells have two unaffected/normal copies of the x chromosome, which may carry homo or hetero alleles
-each cell has one x chromosome that is epigenetically silenced - silenced x is chosen randomly
describe disease causing mutation in x-linked gene
- in biologically female
- mutation is heterozygous
x linked recessive= the presence of normal/healthy X in non-silenced cells is sufficient for normal tissue function
x linked dominant= the presence of the normal/healthy X in non-silenced cells is insufficient for normal tissue function
what happens in biological males for x linked diseases
all cells will be affected since only one copy of x chromosomes (more severely affected)
describe hemophilia
blood clotting disorder- recessive x linked
describe red-greem colour blindness
between 7-10% of men and 0.5-1% of women affected- recessive x linked
describe becker’s muscular dystrophy
a milder form of DMD, causing slowly progressive muscle weakness of the legs and pelvis- recessive x linked
describe hypophosphataemia
aka vitamin d resistant rickets- dominant x linked
describe rhett syndrome
a brain disorder that occurs almost exclusively in girls- recessive x linked
lethal in men
what is hemophilia a
deficiency in clotting factor VIII
- 1/5000 births
describe haemophilia b
deficiency in clotting factor IX
- 1/20 000 births
describe x linked dominance in males vs females
more females than males will express the phenotype, but will have milder clinical course than males with the mutation
define gender
describes the characteristics of women and men that are SOCIALLY CONSTRUCTED
what is sex
refers to what is biologically determined
is sry male or female
male
describe sex reversed xx males
often have part of y including the sry gene one on of their x chromosomes
