Genetics I

Question 1

codominance

Answer 1

both alleles contribute to phenotype

ABO blood group

Question 2

variable expressivity

Answer 2

phenotype varies with same genotype

Question 3

incomplete penetrance

Answer 3

not all individuals with mutant genotype show phenotype

Question 4

pleiotrophy

Answer 4

one gene contributes multiple phenotypes

Question 5

anticipation

Answer 5

increased severity and earlier onset disease over multi generations

Question 6

loss of heterozygosity

Answer 6

two hit hypothesis

inherited mutation - tumor suppressor gene

complementary allele must be mutated as well

Question 7

dominant negative mutation

Answer 7

heterozygote produces nonfunctional altered protein also prevents normal gene product from functioning

Question 8

linkage disequilibrium

Answer 8

tendency certain alleles at 2 loci to occur together

more or less often than by chance alone

Question 9

mosaicism

Answer 9

distinct cell line same individual

Question 10

mccune albright syndrome

Answer 10

mutation GPCR

unilateral cafe-au-lait spots, polyostotic fibrous dysplasia, precocious puberty

survivable if patient has mosaicism

Question 11

locus heterogeneity

Answer 11

mutation at different loci - similar phenotype

Question 12

allelic heterogeneity

Answer 12

different mutation same loci - similar phenotype

Question 13

heteroplasmy

Answer 13

variable expression of mitochondria inherited disease

both normal and mutated mito DNA present

Question 14

uniparental disomy

Answer 14

2 copies chromosome 1 parent
no copies from other parent

individual is euploid - normal # chromosomes

heterodisomy - meiosis I error
isodisomy - meosis II error

Question 15

hardy weinberg

Answer 15

p2 + 2pq + q2 = 1
p + q = 1

frequency X-linked recessive - males = q / female = q2

Question 16

assumption hardy weinbery

Answer 16

no mutation
natural selection no occurring
random mating
no migration

Question 17

prader willi and angelman syndrome

Answer 17

deletions chromosome 15

Question 18

prader willi syndrome

Answer 18

maternal imprinting - inactivated
chromosome 15

gene mom normally silent
paternal gene deleted

hyperphagia, obesity, intellect disability, hypogonadism

Question 19

angelman syndrome

Answer 19

paternal imprinting - inactivated
chromosome 15

gene dad normal silent
maternal gene deleted

inappropriate laughter, seizure, ataxia, intellect disability

Question 20

imprinting

Answer 20

one allele inactivated - methylation

Question 21

autosomal dominant

Answer 21

most generations
male and female affected

often structural gene defect

Question 22

autosomal recessive

Answer 22

seen 1 generation only

often enzyme deficiency

Question 23

X-linked recessive

Answer 23

son heterozygote mom - 50% chance affected

no male to male transmission

skips generations

Question 24

X-linked dominant

Answer 24

father transmit to all daughter

mother transmit to 50% of daughter and sons

Question 25

mitochondrial inheritance

Answer 25

transmitted only through mother

ex/ mito myopathy - ragged red fibers

Question 26

auto dominant polycystic kidney disease

Answer 26

massive enlargement kidneys

mutation PKD1 - chromosome 16 - MC
or mutation PKD2 - chromosome 4

Question 27

familial adenomatous polyposis

Answer 27

autosomal dominant

mutation chromosome 5q = APC gene

colon covered adenomatous polyps

Question 28

familal hypercholesterolemia

Answer 28

autosomal dominant

defective LDL receptor

tendon xanthoma - achilles

Question 29

hereditary hemorrhagic telangiectasia

Answer 29

autosomal dominant

disorder blood vessels

telangiectasia, recurrent epistaxis, skin discolorations
-arteriovenous malformation

Question 30

osler weber rendu syndrome

Answer 30

hereditary hemorrhagic telangiectasia

Question 31

hereditary spherocytosis

Answer 31

autosomal dominant

mutation spectrin or ankyrin RBCs

hemolytic anemia

increased MCHC and RDW

tx - splenectomy

Question 32

tx hereditary spherocytosis

Answer 32

splenectomy

Question 33

huntington disease

Answer 33

autosomal dominant

depression, dementia, chorea movement

trinucleotide CAG repeat - chromosome 4

anticipation

Question 34

li-fraumeni syndrome

Answer 34

autosomal dominant
abnormal TP53

multi malignancy early age

SBLA cancer syndrome
-sarcoma, breast, leukemia, adrenal gland

Question 35

marfan syndrome

Answer 35

autosomal dominant
chromosome 15 - mutation fibrin - scaffold for elastin

hypermobile joint, tall and skinny, subluxation of lens, aortic dissection

Question 36

MEN

Answer 36

autosomal dominant

multiple endocrine neoplasias
-1, 2A, 2B

Question 37

MEN1

Answer 37

MEN1 gene

Question 38

MEN2

Answer 38

RET gene

Question 39

NF1

Answer 39

von-recklinghausen disease
autosomal dominant

cafe au lait spots - cutaneous neurofibroma - optic glioma, pheochromocytoma, lisch nodule (iris hamartoma)

chromosome 17

Question 40

NF2

Answer 40

autosomal dominant
chromosome 22

bilateral acoustic neuroma, juvenile cataract, meningioma, ependymoma

Question 41

tuberous sclerosis

Answer 41

autosomal dominant

numerous benign hamartomas

Question 42

von hippel lindau disease

Answer 42

autosomal dominant

deletion VHL - tumor suppressor
chromosome 3

develop numerous tumors