Genetic disorders III

Question 1

definition: anticipation

Answer 1

disease appearing sooner in the son than it did in the father

Question 2

definition: intermediate alleles

Answer 2

genes with repeat sizes that are larger than normal, but still small enough to not cause clinical problems

Question 3

fragile X has what type of inheritance?

Answer 3

XLD (reduced penetrance)

Question 4

fragile X has what TRE? what gene? what chromosome?

Answer 4

1. CGG 2. FMR1 3. X

Question 5

what is the normal range of CGG repeats? affected range?

Answer 5

1. 6-40 2. over 200

Question 6

definition: intermediate range (fragile x)

Answer 6

range of repeats that is normally stable, but 10-30% may change in repeat size when transmitted from a female

Question 7

when does expansion from pre- to full mutation occur in fragile x mutation?

Answer 7

via female meiosis

Question 8

what are the clinical features of fragile x?

Answer 8

long face, large ears, prominent jaw, macroorchidism

Question 9

what is the inheritance pattern for HD?

Answer 9

autosomal dominant

Question 10

what is the TRE for HD?

Answer 10

CAG

Question 11

what is the normal range of TREs for HD? affected range?

Answer 11

1. less than 262. more than 36

Question 12

what does the gene responsible for HD encode? what is its function?

Answer 12

1. huntingtin 2. protein expressed by neurons and glia of CNS

Question 13

edward syndrome consists of which additional chromosome?

Answer 13

18

Question 14

what are the clinical features of edward syndrome?

Answer 14

rocker bottom feet, small jaw, prominent occiput, cardiac defects

Question 15

patau syndrome consists of which additional chromosome?

Answer 15

13

Question 16

what are the clinical features of patau syndrome?

Answer 16

midline deformities, PDA, situs inversus

Question 17

what is the ploidy of turner syndrome?

Answer 17

45, X

Question 18

how does turner syndrome occur?

Answer 18

most often results when an egg containing 23 chromosomes is fertilized by a sperm containing only 22 chromosomes, lacking a sex chromosomes

Question 19

what are the clinical features of turner syndrome?

Answer 19

cystic hygroma, lymph blockage (webbed neck, puffy hands / feet), low set and rotated ears, VSD, coarctation of aorta, short 4th metacarpal

Question 20

what percentage of conceptions with a 45, X karyotype end in miscarriage?

Answer 20

99%

Question 21

what is the ploidy of klinefelter syndrome?

Answer 21

47, XXY

Question 22

definition: imprinting

Answer 22

methylation of a given gene

Question 23

what is the cause of prader willi syndrome?

Answer 23

imprinting of paternal PWS genes

Question 24

what is the cause of angelman syndrome?

Answer 24

imprinting of maternal AS gene