1.2 X -linked

Question 1

x vs y chromosomes

Answer 1

x chromosomes has many important genes in addition to gender determinants but Y-chormosomes are mostly just for gender

Question 2

x linked diseases

Answer 2

mostly seen in males, female carriers normally don_t present, 50% chance for male to get disease from heterozygous mother

Question 3

y chromosome

Answer 3

mostly strictly involved in determination of male gender by inducing testicular development. If testicular development is disrupted in early development, female phenotype is born

Question 4

x linked disorders are

Answer 4

always expressed in males

Question 5

x linked dominant

Answer 5

rare–expressed in females, half of cells affected (inactivation of one x chromosome in every cell); storage diseases G6PD deficiency

Question 6

x linked recessive

Answer 6

more common–duchenne muscular dystrophy hemophelia

Question 7

y-linked

Answer 7

no recorded y-linked diseases – affected male does not transmit to sons but all daughters are carriers; female carrier transmits diseases to 50% of sons and transmitts a carrier state to 50% of daughters

Question 8

female may suffer partial disease bc of

Answer 8

mosaicism for x-chromosome –>lyon hypothesis meaning random inactivation —sometimes there is a preferential activation and you can have some expression of disease but that’s not common

Question 9

G6PD def

Answer 9

makes red cells prone to lyse under oxidant conditions, females will lyse half the cells, males will lyse all the cells, so you’ll see the disease in both but to different extents – remember this is an AD disease

Question 10

x-linked father transmistion

Answer 10

does not transmit to sons, but transmits to all daughters

Question 11

x-linked mother transmition

Answer 11

50% of sons get the disease and 50% of daughters get the carrier state

Question 12

x-linked dominant fater tramission (rare)

Answer 12

all daughters, none of sons

Question 13

x-linked dominant mother transmission

Answer 13

50% of sons and daughters

Question 14

x-linked dominant disorders

Answer 14

hemophilia, chornic granulomatous disease, Duchenne M.D., fragile x

Question 15

Hemophillia A

Answer 15

factor 8 deficiency - most common inherited serious bleeding disorder - numerous mutations - most severe cases have large DNA inversion and no factor 8 is produced

Question 16

Hemophillia A severe, moderate, slight

Answer 16

1% 2-5% 6-50%

Question 17

Clinical course of hemophilillia A

Answer 17

from profound bleeding to minor symptoms, easy bruising and bleeding into areas prone to trauma (joints), hemarthrosis may be crippling, bleeding time and PT normal, PTT elevated, Treatment: factor 8 injections, comlications with anti 8 antiboides and AIDS

Question 18

bleeding time

Answer 18

the time it takes to stop bleeding after a standardized cut. It is a measure of platelet fn

Question 19

prothrombin time looks at

Answer 19

extrinsic pathway – 7–>10

Question 20

partial prothromboplastin time (PTT) looks at

Answer 20

intrinsic pathway – 12-11-9-10

Question 21

Hemophillia B

Answer 21

christmas factor 9 deficiency – clinically same as A

Question 22

Ehlers-Danlos syndrome

Answer 22

complex disease affecting collagen synthesis – heterogenic disease w/ over 10 variants –all 3 modes of inheritance are seen – organs rich in collagen, skin, joints, and ligaments most frequently involved

Question 23

Ehlers Danlos syndrom clinical features

Answer 23

since collagen lacks normal tensile strength, skin stretches and joints are hypermobile to gortesque proportions – contortionists – leads to serious complications including rupture of bowels and aorta

Question 24

collagen synthesis

Answer 24

alpha chain synthesis, hydroxylation, glycosylation, alpha chain arrangement, triple helix formation, clipping of N and C terminal peptides, crosslinking

Question 25

Ehlers Danlos syndrome type 6

Answer 25

recessive loss of lysyl hydrolase affecting hydroxylation, collagen types I and III, rupture of cornea and retinal detachment

Question 26

Ehlers Danlos syndrome type 4

Answer 26

dominant negative defect in alpha chain, collagen type III, rupture of vessels and intestines

Question 27

Ehlers Danlos syndrome type 7

Answer 27

dominant negative change in alpha chain that resists peptide cleavage, Type I collagen –> alpha chain synthesis and clipping of N and C terminal peptides are affected

Question 28

Ehlers Danlos syndrome type 9

Answer 28

defect in copper binding protein that reduces activity of lysyl oxidase. On x-chromosome so x-linked –>affects crosslinking