Lecture Notes

Question 1

HDAC (Histone deacetylases)

Answer 1

deacetylation of chromatin (condensed inactive)

Question 2

HAT (Histone acetyl transferases)

Answer 2

acetylation of chromatin (open active)

Question 3

Bromodomain

Answer 3

proteins bind acetylated, phosphorylated residues

Question 4

Chromodomain

Answer 4

proteins bind methylated residues

Question 5

Compound heterozygote

Answer 5

genotype with 2 different mutant alleles at one locus

Question 6

Polymorphism

Answer 6

alternative genotypes present in a population

Question 7

Penetrance

Answer 7

the proportion of individuals manifesting disease

Question 8

Expressivity

Answer 8

the extent to which a mutation exhibits a phenotype

Question 9

Genetic heterogeneity

Answer 9

can result from different mutations at 1 locus (allelic), or from mutations at different loci (locus).

Question 10

Phenotypic heterogeneity

Answer 10

occurs when the same mutation manifests itself differently among individuals

Question 11

Degree of Relationship (n)

Answer 11

corresponds to the number of uninterrupted line segments connecting two blood relatives in a pedigree chart.
The proportion of alleles two related individuals have in common = (½)n

Question 12

Coefficient of inbreeding (F)

Answer 12

is the proportion of loci at which a person is homozygous by descent =½ coefficient of relationship

Question 13

Pleiotropy

Answer 13

the production by a single gene of two or more apparently unrelated effects.

Question 14

Allelic Heterogeneity

Answer 14

is the phenomenon in which different mutations at the same locus cause a similar phenotype. These allelic variations can arise as a result of natural selection processes, as a result of exogenous mutagens, genetic drift, or genetic migration.

Question 15

Locus Heterogeneity

Answer 15

is a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci. For example, retinitis pigmentosa has autosomal dominant, autosomal recessive, and X-linked origins. However, only one mutant locus is needed for the phenotype to manifest.

Question 16

X-linked Dominant

Answer 16

Affected fathers always transmit the disease to their daughters but never their sons; affected mothers have a 50% chance of transmitting the disease to all their children

Question 17

X-linked Recessive

Answer 17

Affected fathers will have daughters who are carriers; they have 50% chance of passing on to their children of which females will be carriers and males will present the disease

Question 18

Mosaicism

Answer 18

Mutation occurring during cell proliferation leads to a proportion of the cells carrying the mutation; if the mutation occurs in germ cells the mutation can be passed on to offspring

Question 19

X inactivation

Answer 19

Female carriers will present disease to some degree due to random inactivation of paternal or maternal X chromosome in different cells (ex Duchenne’s muscle dystrophy)

Question 20

Anticipation

Answer 20

severity increases in subsequent generations

Question 21

Factors defining inheritance of mitochondrial DNA

Answer 21

1. heteroplasmic- more than one type of mitochondrial DNA may be present in cells from a single individual (threshold for phenotypic expression)
2. inherited maternally
3. random segregation

Question 22

complications to the basic pedigree patterns that may impact diagnosis and/or counseling

Answer 22

New mutations, genomic imprinting, reduced penetrance, variable expressivity, phenotypic variability, delayed onset, small family size

Question 23

phenotypic variability

Answer 23

disorders that affect multiple organs can produce different symptoms in related family members (pleiotropy) due to effects of environment or other genes

Question 24

acrocentric chromosomes

Answer 24

13, 14, 15, 21, 22

Question 25

genetic flow

Answer 25

described as the process by which genes diffuse into a foreign population over time

Question 26

assumptions of Hardy Weinberg

Answer 26

Large population (not influenced by chance fluctuations) Random mating (no preference based on phenotype similarities) No mutation (no conversion of P allele to Q allele) No selection (all genotypes are equally capable of mating and producing offspring)

Question 27

genetic drift

Answer 27

involves chance changes with the environment favoring a genetically defined subpopulation

Question 28

founders effect

Answer 28

occurs when a small subpopulation with a different allele distribution breaks away from the general population

Question 29

reduced

Answer 29

occurs in conditions that affect the ability of diseased individuals to have offspring