Genetics

Question 1

Do all mutations alter proteins?

Answer 1

No

Question 2

Do all mutations affect phenotype?

Answer 2

No

Question 3

Are loss of function mutations usually dominant or recessive?

Answer 3

recessive

Question 4

What is haploinsufficiency?

Answer 4

reduced activity from lof mutation is not sufficient, causing the phenotype to be dominant

Question 5

What is a gain of function mutation? Is it usually dominant or recessive?

Answer 5

dominant; novel action is gained from mutation EX: Huntington’s disease increases protein aggregation and causes cell toxicity

Question 6

What is a dominant negative mutation?

Answer 6

abnormal function interferes with normal allele EX: collagen mutation in osteogenesis imperfecta

Question 7

What is a transition mutation?

Answer 7

AT –> GC

Question 8

What is a transversion mutation?

Answer 8

CG –> GC

Question 9

What is a missence mutation?

Answer 9

changes AA to one with dissimilar biochemical properties

Question 10

What is a nonsense mutation?

Answer 10

early stop codon

Question 11

What is a neutral mutation?

Answer 11

changes AA to one with similar biochemical properties

Question 12

What is a silent mutation?

Answer 12

bp change which does not change AA

Question 13

What is a frameshift mutation?

Answer 13

changes rule of 3 and alters entire protein sequence

Question 14

What is the difference between genetic heterogeneity and pleitropy?

Answer 14

genetic heterogeneity: many alleles can give rise to same phenotype
pleitropy: single allele can give rise to several phenotypes

Question 15

What is the classic example of allelic heterogeneity?

Answer 15

Cystic Fibrosis

Question 16

What is locus heterogeneity?

Answer 16

phenotype caused by mutations in genes at different chromosomal loci

Question 17

What is the classic example of locus heterogeneity?

Answer 17

retinitis pigmentosa

Question 18

Mutations in what typically leads to diseases of the connective tissues?

Answer 18

collagen or elastin

Question 19

What is the clinical presentation of Ehlers-Danlos Syndrome (EDS)?

Answer 19

class of 10 disorders with joint flexibility problems; loose joints, stretchy skin

Question 20

What is the clinical presentation of Epidermolysis Bullosa (EB)?

Answer 20

skin blisters and tearing

Question 21

What is the clinical presentation of Marfan Syndrome?

Answer 21

long, tall, and fragile (fibrilin (elastin) mutation)

Question 22

What is the clinical presentation of Osteogenesis Imperfecta?

Answer 22

brittle bone disease; blue sclera

Question 23

What is the role of the FBN1 gene in Marfan Syndrome?

Answer 23

part of cell signaling pathway which increases TGF-beta signaling; weakend heart valves, lungs, aorta

Question 24

What are the implications for lack of lysine in the diet versus lack of tryptophan in regards to collagen formation?

Answer 24

tryptophan never integrates into collagen so it is less deleterious to not have it in one’s diet

Question 25

What is a sarcoma?

Answer 25

malignant tumor of mesenchymal origin

Question 26

What is a carcinoma?

Answer 26

malignant tumor of epithelial origin

Question 27

What are the two stages of acquiring cancer?

Answer 27

1) activatino of an oncogene

2) destruction of tumor suppressor gene

Question 28

What is the most common virally-induced cancer?

Answer 28

HPV leads to cervical cancer

Question 29

Most cells of the body are in which phase of the cell cycle?

Answer 29

G1 phase

Question 30

Where is the cycle check in the cell cycle?

Answer 30

G1 to S phase
G2 to Mitosis
oncogenes destroy these “stop signs”

Question 31

When is DNA doubled in the cell cycle?

Answer 31

S phase

Question 32

What turn on and off the cell cycle?

Answer 32

cyclin-dependent kinase (cdk)

Question 33

What is the most important tumor suppressor gene?

Answer 33

p53

Question 34

What is retinoblastoma?

Answer 34

Ch13, RB1 gene
Can be inherited + acquired 2nd mutation
or both acquired

Question 35

What is the “two-hit hypothesis”?

Answer 35

tumor suppressor genes cause cancer when both copies of the allele are mutated

Question 36

Which cancer mutation would be more probable to inherit, proto-oncogene or tumor suppressor gene?

Answer 36

tumor suppressor gene

Question 37

How does the Philadelphia chromosome cause cancer?

Answer 37

constitutively activate a proto-oncogene with a promoter from another onco-gene through translocation