Sex related inheritance patterns

Question 1

what is sex linked

Answer 1

-gene on sex chromosomes
-due to unequal sizes of chromosomes
-heterogamic sex has fewer genes
(XY male mammal or ZW female bird)

Question 2

X inactivation

Answer 2

-female mammals have X-inactivation
-called lyonization
-one X chromosome is inactivated (condenced X in nucleus called barbody)
-dosage compensation
-X^sX^s=100% activation in female embryo
-X^sX^s=50% activity in female fetus/adult
X^sY=50% activity in male

Question 3

is there Z inactivation in males birds

Answer 3

there no evidance

Question 4

calico in cats

Answer 4

-females:
-X^ob/X^ob=black
-X^O/X^O=orange
-X^O/X^ob=calico

-males:
X^O/Y=orange
X^ob/Y=black
X^OX^obY+calico

-orange patch: X with orange allele (X^O) active, X with black allele (X^O) compacted into barr body
-black patch: X with orange allele (X^O) compacted into barr body, X with black allele (X^O) active

Question 5

X linked diseases examples

Answer 5

-muscular dystrophy in dogs
-factor VIII hemophilia in horses and dogs

Question 6

why might you not breed an X linked disease affected male

Answer 6

means no affected females

Question 7

Z linked traits

Answer 7

-used in commercial chicken sexing
-roosters must have the recessive genotype
-down colour=silver(M) or gold (F) in chicks
-primary feather growth (male-s female-L)

Question 8

sex linked dominant- streaked hairless in Holstein

Answer 8

female:
Xh/Xh=normal
XH/Xh=hairless patches
XH/XH=impossible

male:
Xh/Y=normal
XH/Y=die as fetus

Question 9

what is the name for Y-linked

Answer 9

holandric

Question 10

holandric

Answer 10

-Y linkes
-transmitted only through males
-gene for primary sex charicteristics (Sry)
-penis+scrotum

Question 11

hormonal milieu altering phenotype examples

Answer 11

-comb and wattle size in poultry
-mahogany colour of ayrshire cattle
-scurs

Question 12

mahognany colour of cattle

Answer 12

-MM cows/steers=dark bulls=dark
-Mm cows/steers=pale bulls=dark
-mm cows/steers=pale bulls=pale

Question 13

scurs in cattle

Answer 13

-sex influenced
-begin growth at 4 months of age
-not attached to the skull
-gene on chromosome 19, but not identified yet
-bulls only need one copy to grow, females need two
Sc/Sc cows= scurred bulls=scurred
Sc/sc cows=smooth bulls=scurred
sc/sc=smooth

Question 14

epistasis

Answer 14

-gene-gene interactions
-genotype at one locus is able to mask the phenotype cause by the genotype at another locus
-classic example=albinism
(masks hair colour, eye colour, hoof colour, all of which are controlled by different genes

Question 15

epistatic interactions between polled gene and scur gene

Answer 15

-PP polled and any scur genes=polled
-Pp =Sc/Sc cows= scurred bulls=scurred
Sc/sc cows=smooth bulls=scurred
sc/sc=smooth
pp horned and any scur genes= horned

Question 16

implications of scurs

Answer 16

-all scurred cattle are P/p never P/P
-all scurred females are Sc/Sc-cull

Question 17

sex limited traits

Answer 17

-cryptorchidism (mini breeds) or antlers (except caribou/reindeer)
-only males have the phenotype
-both males and females have the alleles

Question 18

pleiotrophy

Answer 18

-exception related to mendelian inhert
-disorder where multiple organ systems are affected
-ie. polled intersex goats