Lec 5 princp gen inheritance

Question 1

Lyonization

Answer 1

x-inactivation. which X inactivated is random (one x can handle all duties) calico cat

Question 2

Mosaicism

Answer 2

which cells from a patient have different genotypes (and karyotypes) problems in early cell division

Question 3

Ex of mosaicism

Answer 3

Down syndrome (some 46XX some 47XX+21)

Klinefelter (some 46XY some 47XXY)

Turner Syndrome (some 46XX, some 45XO)

Question 4

Meiosis rounds summary

Answer 4

round one is homolougs seperated (randomly align)

second round separates the chromatids (they have been cross overed)

Question 5

Meiotic errors

Answer 5

Euploid- normal

polyploid- presence of complete set of extra chromosomes (plants)

Aneuploidy- missing or additional individual chromosomes

Question 6

Examples of non disjunction

Answer 6

Turner syndrome

klinefelter syndrome

downs syndrome

patau syndrome

edwards syndrome

Question 7

Turner Syndrome

Answer 7

45 XO

female

short

ovarian hypofunction to failure

puberty problems

infertile

webbed neck

normal intell

Question 8

Klinefelter syndrome

Answer 8

47 XXY

some with no/limited symptoms

some cog/soc/behav difficulties

hypogonadism

tall

infertility

can be mosaic

more X chrom can increase symptoms

Question 9

Downs syndrome

Answer 9

47XX+21

most common

icreased risk older age

can be due to translocation

Question 10

Patau syndrome

Answer 10

47XX+13

severe developmental abnormal

most death within 1 week

Question 11

Edwards syndrome

Answer 11

47XX+18

abnormal develop

perinatal death within 1 year

Question 12

genomic imprinting

Answer 12

gene silencing (methylated)

one of the alleles is transcriptionally inactive no mRNA produced

30 genes paternally imprinted

70 genes maternally imprinted

other allele will be expressed

Question 13

genomic imprinting and germ cells

Answer 13

remain throughout lifespan

in germ cells imprints reset at each generation

so erased and reset during meiosis

Question 14

Prader-Willi syndrome

Answer 14

chrom 15

Imprinting on chrom 15

deletion of the paternal PWS gene thats active and AS thats inactive

short stature, hypotonia, small hands/feet

obesity, intellectual disability

Question 15

Angelman syndromes

Answer 15

Imprinting on chom 15 has PWS and AS close oppo activity on each copy

maternal copy deletion active AS gene and inactive PWS

severe intellectual disability, seizures

ataxic gait

Question 16

uniparental disomy

Answer 16

two chromosomes are inherited from the same parent they will have parent-specific imprinting

Question 17

pleiotropy

Answer 17

individuals with same genotype have multiple phenotypes

Question 18

proband (propositus)

Answer 18

first diagnosed person in pedigree

Question 19

Autosomal Dominant inheritance

Answer 19

unaffected individuals do not transmit trait

expected in every generation

recurrent risk 50%

Ex. postaxial polydactyly

Question 20

autosomal recessive

Answer 20

recurrent risk for heterozygote parents is 25%

affected mate with normal have normal children

higher occurrence with inbreeding

Question 21

x-linked recessive

Answer 21

hemizygous males

unaffected male dont transmit trait

female transmit 50% of time

all daughters of affected males are heterozygous

Question 22

X-linked dominant

Answer 22

rare

males transmit to all females

females half and half to offspring

Question 23

reduced penetrance

Answer 23

frequency a gene manifests itself is called penetrance

some cases 100% with genotype present phenotype

other cases penetrance is less than 100%

ex. retinoblastoma (90%)

Question 24

variable expressivity

Answer 24

range of phenotypes that vary between individuals with a specific genotype

ex. neurofibromatosis

Question 25

locus heterogeneity

Answer 25

single disorder, trait , or pattern caused by mutations in genes at different chromosomal loci

osteogenesis and imperfecta

Question 26

genotype frequency vs allele frequency

Answer 26

Question 27

hardy weinberg

Answer 27

find population frequencies P² (AA)

2pq(Aa)

q² (aa)

Question 28

consanguinity and recessive diseases

Answer 28

more likely to produce offspring affected by rare autosomal recessive disorders

mortality rates increase among offspring

Question 29

mitochondrial DNA more or less mutations

Answer 29

MOre mutations due to close to reactive oxygen species

Question 30

Leber’s hereditary optic neuropathy (LHON)

Answer 30

degen of ret ganglion cells

acute of subacute loss of central vision

part of mitochondria disorders (usually need a threshold of affected mito in order to be expressed)

Question 31

Mitochondrial encephalomyopathy, lactic acidosis, and stoke-like episodes (MELAS

Answer 31

high energy tissues

stroke and dementia

lactic acidosis

threshold of mitochondria need to be affected to be symptomatic

Question 32

Multifactorial inheritance

Answer 32

mixuture of polygenic (combined effects multi genes)

and multifactorial (enviro factors variations in trait)

follow both tend to follow bell-shaped distribution

Question 33

liability distribution

Answer 33

diseases that dont follow bell curve

Question 34

threshold of liability

Answer 34

this must be crossed before the disease is expressed

for ex if 5 threshold is 5 genes and only 2 mutated then still normal function