Genetics

Question 1

If sibling has disease, chance of another sibling being a carrier is 2/3 is only true for which mode of inheritance?

Answer 1

Autosomal recessive

Question 2

In an autosomal dominant disease, what explains the disease frequency remaining the same?

Answer 2

Replaced by de novo mutations

Question 3

If you don’t have a family history, what is the chance mom of an affected is a carrier in an X-linked disease?

Answer 3

2/3 chance mom is a carrier

Question 4

If deletion is greater than 100 bp and known what test do you use to confirm diagnosis?

Answer 4

FISH

Question 5

What test do you use for a series of known point mutations?

Answer 5

ASO

Question 6

What test would you use for a CAG repeat expansion in SCA?

Answer 6

PCR and electrophoresis

Question 7

What test would you use for a full mutation in fragile X?

Answer 7

Southern blot

Question 8

What test would you perform if the gene location is know. But there is no time to identify mutation?

Answer 8

CA repeat, or RFLP/southern blot assuming information from linkage

Question 9

Known mutation and les than 100 kb?

Answer 9

Southern blot

Question 10

Severe hemophilia A is a result of?

Answer 10

Intrachromosomal rearrangement of F8 gene

Question 11

What happens to restriction sites in rearrangements and what test would you use to identify it, as in severe hemophilia A?

Answer 11

Changes the length of DNA between restriction sites, use southern blot

Question 12

Generally all mutations in same gene result in same phenotype describes what?

Answer 12

Haploinsufficiency

Question 13

Different mutations in same gene may result in different phenotypes, as seen in FGFR

Answer 13

Gain of function

Question 14

Different mutations in same gene yield a milder phenotype, as seen in collagens

Answer 14

Dominant-negative

Question 15

Mutations that reduce or abolish function are known as?

Answer 15

Recessive disorders (autosomal or x-linked)

Question 16

Premature termination codons do not result in what?

Answer 16

Truncated polypeptides

Question 17

To observe GOF or Dom-neg effect, mutant proteinmp must be?

Answer 17

Synthesized

Question 18

If you see same severity of phenotype from Missense and null mutations in the same gene then Missense mutation must result in?

Answer 18

Loss of function

Question 19

PKU shows what type of heterogeneity?

Answer 19

Allelic

Question 20

Most common CAH repeats are a result of what?

Answer 20

Recombination between misaligned 30kb repeats

Question 21

When sequence of one gene is copied onto another we call that?

Answer 21

Gene conversion

Question 22

X inactivation is?

Answer 22

Random

Question 23

How can x-inactivation appear non-random?

Answer 23

As in girl with DMD, cells with mutation are unstable and die

Question 24

Transcriptionally active chromatin is predominantly ____________ and has high levels of?

Answer 24

Unmethylated, acetylated histone tails

Question 25

Prader-Willi syndrome is?

Answer 25

Paternal expression and maternal imprint of SNRPN region

Question 26

Angelman syndrome is?

Answer 26

Maternal expression and paternal imprint in UBE3A region

Question 27

Make carriers of fragile x premutation may develop?

Answer 27

Tremor/ataxia

Question 28

Myotonic dystrophy is an example of?

Answer 28

Anticipation (with maternal expansion bias)

Question 29

What are the polyglutamine diseases and what expansion is associated with them?

Answer 29

Huntington and SCA, exonic CAG expansion through paternal transmission

Question 30

Alpha thalassemia is a result Of?

Answer 30

Deletion of alpha globin genes

Question 31

Beta thalassemia results from?

Answer 31

Null mutation in beta globin

Question 32

Sickle cell is a result of?

Answer 32

Missense mutation (A to T) in beta globin gene

Question 33

For any gene expressed in multiple cell types, an enhancer mutation will only cause a phenotype in the cell type in which?

Answer 33

The enhancer was supposed to work

Question 34

Multifactorial disorders are seen?

Answer 34

In small families, multiple disease genes/pt, low penetrance, unaffected individuals can also carry susceptible alleles

Question 35

Poor metabolizers of codeine get?

Answer 35

No benefit from the drug

Question 36

25-30% of prescription drugs are metabolized by?

Answer 36

Cytochrome P450s

Question 37

FIRST screenings check for?

Answer 37

hCG, and PAP-A

Question 38

Second trimester screening checks for?

Answer 38

AFP, hCG, UE3, inhibition A

Question 39

What is the hardy Weinberg equation?

Answer 39

P^2 + 2pq + q^2 = 1