Genetics Ch 4

Front 1

what laws were derived from mendel's experiments

Back 1

unit inheritance, segregation, independent assortment

Front 2

what is the law of unit inheritance

Back 2

parental phenotypes do not blend in offspring

Front 3

what is the law of segregation

Back 3

two members of a pair of genes segregate and pass to different gametes

Front 4

what is the law of indep. assort

Back 4

random recombination of maternal and paternal chromosomes in gametes.

Front 5

what is medelian inheritance

Back 5

Also known as single gene inheritance
Describes a trait that is attributable to a single gene

Front 6

what are the 4 patterns of medelian inheritance

Back 6

autosomal recessive/dominant; x linked recessive/dominant

Front 7

what is dominant

Back 7

gene expressed when 1 copy is present

Front 8

what is recessive

Back 8

gene expressed when 2 copies present

Front 9

in male w/ x linked dominance how many copies of a gene are needed to procude the disease

Back 9

1

Front 10

most disorders caused by enzyme defects are what

Back 10

recessive

Front 11

disorders caused by non-enzymatic or structural proteins are usually what

Back 11

dominant

Front 12

risk assessment is an important part of what type of studies

Back 12

medical genetics

Front 13

true or false: Because probabilities are proportions they lie between zero and one inclusive

Back 13

true

Front 14

what are the fundamental concepts of probabilty

Back 14

multiplication rule/ addition rule

Front 15

what is the multiplication rule

Back 15

if two trials are independent, the probability of obtaining a given outcome in both trials is the product of the probabilities of each outcome

Front 16

what is the addition rule

Back 16

probability of either one outcome or another is the sum of the respective probabilities

Front 17

what is genotype frequency

Back 17

The proportion of individuals in a population that carry a specific genotype. (A genotype is an individual’s allelic constitution at a locus.)

Front 18

what is gene frequency

Back 18

In a population, the proportion of chromosomes that contain a specific allele.

Front 19

who created the hardy weinberg principle

Back 19

Godfrey Harold Hardy (1877-1947) a Cambridge mathematician
Wilhelm Weinberg (1862-1937) a German physician

Front 20

what is the purpose of the hardy weinberg principle

Back 20

Working independently, they used algebra to explain how gene frequencies can be used to predict genotypic frequencies in populations

Front 21

what is the hardy weinberg equilibrium

Back 21

Hardy explained how mathematically inept biologists had deduced from Mendel’s work that dominant traits would increase in populations, while recessive traits would become rarer. This seems logical, but is untrue. H &W disproved the assumption that dominant traits increase while recessive traits decrease using the language of algebra

Front 22

what does the hardy weinberg equilibrium state

Back 22

gene frequencies remain constant from one generation to the next.

Front 23

when does the hardy weinberg equilibrium happen

Back 23

when mating is random and the population is large, with no migration, genetic drift, mutation, or natural selection

Front 24

what does p represent

Back 24

the frequency of all dominant alleles for a gene

Front 25

what does q represent

Back 25

the frequency of all recessive alleles

Front 26

p + q =

Back 26

1

Front 27

what is the hardy weinberg equation

Back 27

the genotype frequencies for a gene with two alleles are expressed by the binomial expansion: p² + 2pq + q² = 1

Front 28

what is the pattern of inheritance of autosomal dominant disorders

Back 28

vertical transmission, generation to generation

Front 29

what is the pattern of male vs female inheritance of autosomal dom. disorders

Back 29

equal

Front 30

true or false- father to son transmission is not seen in autosomal dom. disorders

Back 30

false, is seen

Front 31

true or false: The recurrence risk for an autosomal dominant disorder is 50%. Because of independence, this risk remains constant no matter how many affected or unaffected children are born.

Back 31

true

Front 32

what are the characteristics of autosomal recessive disorders

Back 32

rarely present in the parents, collateral relatives or ancestors, but may appear in siblings

Front 33

what is the pattern of male vs females in autosomal recessive disorders

Back 33

equal

Front 34

consanquinity is commonly seen in what type of pedigrees

Back 34

AR

Front 35

what type of disorders cluster in ethnic groups with relative geographic or religious isolation and increased consanguinity

Back 35

AR

Front 36

what is the pattern of penetrance and phenotypical variability in AR

Back 36

Penetrance is usually complete and there is little phenotypic variability

Front 37

most AR are what type of abnormalities

Back 37

enzymatic

Front 38

what is the recurrence risk for AR disorders

Back 38

25%; Quasidominant inheritance, with a recurrence risk of 50%, is seen when an affected homozygote mates with a heterozygote

Front 39

what is quasidominant inheritance

Back 39

Occurs when a carrier of a recessive disease gene mates with an individual who is homozygous for the disease

Front 40

what is the pattern of carrier state of quasidominant inheritatance

Back 40

half the children will be affected and half will be heterozygous carriers. This pattern mimics that of an autosomal dominant trait.

Front 41

new mutations are a common cause of what

Back 41

appearance of a genetic disease in a person with no previous family history of the disorder.

Front 42

what is the pattern of recurrence risk in siblings of new mutations

Back 42

very low, but the recurrence risk for the person's offspring may be substantially increased

Front 43

what does germline mosaicism commonly cause

Back 43

two or more offspring may present with an autosomal dominant or X-linked disease when there is no family history of the disease.

Front 44

what is germline mosaicism

Back 44

During embryonic development of one of the parents, a mutation occurred that affected the germ line but not the somatic cells

Front 45

what is penetrance

Back 45

The probability of expressing a phenotype given that an individual has inherited a predisposing genotype

Front 46

what is seen in reduced penetrance

Back 46

an individual who has the genotype for a disease may not exhibit the disease phenotype at all, even though they can transmit the disease gene to the next generation

Front 47

what % of the obligate carriers of a retinoblastoma-causing mutation (i.e., those who have an affected parent and affected children and therefore must themselves carry the mutation) do not have the disease

Back 47

10%; The penetrance of the disease-causing genotype is then said to be 90%.

Front 48

Penetrance rates are usually estimated by what

Back 48

examining a large number of families and determining what percentage of the obligate carriers (or obligate homozygotes, in the case of recessive disorders) develop the disease phenotype

Front 49

what is age dependent penetration

Back 49

delay in the age of onset of a genetic disease is known as age dependent penetrance

Front 50

what is an example of age dependent penetration

Back 50

huntingtons

Front 51

true or false: Penetrance and expression are distinct entities. Penetrance is an all-or-none phenomenon: One either has the disease phenotype or does not. Variable expression refers to the degree of severity of the disease phenotype

Back 51

true

Front 52

what can cause variable expression of a genetic disease

Back 52

environmental effects, modifier loci, or allelic hetergeneity

Front 53

what is locus heterogeneity

Back 53

Quite commonly, a single disease phenotype is caused by mutations at different loci in different families

Front 54

what is allelic heterogeneity

Back 54

different mutations are seen within the same disease locus

Front 55

what is an example of locus heterogeneity

Back 55

adult polycystic kidney dz

Front 56

what is adult polycystic kidney disease

Back 56

autosomal dominant disorder in which a progressive accumulation of renal cysts is seen

Front 57

what is the ratio of adult polycystic kidney dz

Back 57

1/1000 ppl of european descent

Front 58

what dz accounts for 8% to 10% of end-stage renal disease in North America

Back 58

adult polycystic kidney disease

Front 59

what is ACKD cause by

Back 59

mutations in genes on either chromosome 16 (PKD1) or chromosome 4 (PKD2).