Chapter 7: Patterns of Single-Gene Inheritance

Question 1

Location on a chromosome for a segment of DNA or a gene

Answer 1

Locus

Question 2

-alternate variants of a gene

Answer 2

Alleles

Question 3

-permanent change in the nucleotide sequence or arrangement of DNA

Answer 3

Mutation

Question 4

-group of alleles at two or more closely linked loci on a chromosome

Answer 4

Haplotype

Question 5

-exhibited when a locus has at least 2 relatively common alleles (frequencies greater than 0.01) in the population

Answer 5

Polymorphism

Question 6

genetic constitution of an individual, either overall or at a specific locus

Answer 6

Genotype

Question 7

-observable expression of a genotype as a morphological, clinical, cellular, or biochemical trait

Answer 7

Phenotype

Question 8

-expression of a single abnormal gene produces multiple diverse phenotypic effects  the connection is often not obvious or understood

Answer 8

Pleiotropic

Question 9

-determined by the alleles at a single locus

Answer 9

Single-gene disorder

Question 10

-when a pair of alleles at a locus are identical

Answer 10

Homozygous

Question 11

-when two alleles are different at a particular locus

Answer 11

Heterozygous

Question 12

-person with two different mutant alleles at a locus

Answer 12

Compound heterozygote

Question 13

-genes and gene loci present in only one copy in an individual  e.g. most genes on the sex chromosomes for males

Answer 13

Hemizygous

Question 14

-graphic representation of the family tree using standard symbols

Answer 14

Pedigree

Question 15

-the extended family depicted in a pedigree

Answer 15

Kindred

Question 16

(synonyms: propositus or index case)-first person in a pedigree to be identified clinically as having the disease in question

Answer 16

Proband

Question 17

-first cousins

Answer 17

Third degree relatives

Question 18

-grandparents and grandchildren, uncles and aunts, nephews and nieces, and half-sibs

Answer 18

Second degree relatives

Question 19

-parents, sibs, and offspring of the proband

Answer 19

First degree relatives

Question 20

-brothers and sisters, a family of sibs forms a sibship

Answer 20

Sibs

Question 21

-person who brings the family to attention by consulting a geneticist

Answer 21

Consultand

Question 22

-describes mating between descendants of a common ancestor

Answer 22

Consanguineous

Question 23

-if there is only one affected member in a family

Answer 23

Isolated Case

Question 24

-occurrence of a disease in a family with no apparent genetic transmission pattern (often the result of a new mutation)

Answer 24

Sporadic case

Question 25

-measure of the impact of a condition on reproduction-refers to the probability (between 0.0 and 1.0) that a gene will be passed on to the next generation

Answer 25

Fitness

Question 26

Who is mostly affected with X-linked recessive inheritance?

Answer 26

Males

Question 27

What are most Recessive disorders due to?

Answer 27

loss of function mutations

Question 28

the frequency or probability of expression of an allele, failure to express a phenotype at less than 100% is reduced

Answer 28

Penetrance

Question 29

production of the same or similar phenotyes by different genotypes at the same or at a different loci

Answer 29

genetic heterogeneity

Question 30

different mutations within the same gene (at the same locus)

Answer 30

allelic heterogeneity

Question 31

the production of identical or similar phenoytypes by mutations at two or more different genes

Answer 31

locus heterogeneity

Question 32

Expressed when only one chromosome of a pair carries the mutant allele and the other chromosome has the wild-type allele

Answer 32

dominant

Question 33

Expressed only when both chromosomes of a pair carry mutant alleles at a locus

Answer 33

recessive

Question 34

genoytype in which two different mutant alleles of the same gene are present

Answer 34

compound heterozygote

Question 35

Answer 35

Male Female Sex Unspecified of children of sex indicated Affected Non penetrant carrier may manifest disease Obligate carrier, will not manifest disease

Question 36

Answer 36

Proband Deceased Individual Stillbirth Adopted into family Adopted out of family Arrow indicates consultand seeking counseling Spontaneous Abortion

Question 37

Answer 37

Marriare or union Divorced Consanguinuity Monozygotic twins Dizygotic twins twins of unknown zygosity

Question 38

Answer 38

Pedigree w/ generations & individuals numbered Miscarraiage No offspring Multiple Unions Pregnancy with information on dates if available Termination of pregnancy

Question 39

the degree of phenotypic expression of a gene or genotype

Answer 39

Expressivity

Question 40

When the severity of the disease differs in people who have the same gene alteration, even within the same family

Answer 40

Variable Expressivity

Question 41

absence of expressivity

Answer 41

nonpenetrance

Question 42

- occurs only in homozygotes or compound heterozygotes -\> 2 mutant alleles - one normal gene is able to compensate for the mutant gene - must have inherited a mutant allele from each parent

Answer 42

autosomal recessive

Question 43

- expressed when only one chromosome of a pair carries the mutant allele and the other chromosome has the wild-type allele - make up more than half of mendellian disorders - incidence is very high

Answer 43

Autosomal Dominance

Question 44

-typically expressed phenotypically in all males who inherit it, but only in females who are homozygous (herterozygous females are usually unaffected)

Answer 44

X-linked recessive mutations

Question 45

-NO male to male transmission; all of the daughters are affected

Answer 45

X-linked dominant

Question 46

- mimics autosomal inheritance - mutation can cross-over from the X to the Y during male gametogenesis

Answer 46

Psuedoautosomal Inheritance

Question 47

- caused by a mutatoin that occured after conception and the patient has normal parents - Ex: segmental neurofibromatosis

Answer 47

somatic mosaicism

Question 48

parent is phenotypically normal and tests negative for being a carrier, but has more than one child with a highly penetrant AD or X-linked disorder -Ex: OI, Hemopilila A and B, DMD

Answer 48

Germline mosaicism

Question 49

- characterized by an expansion within the affected gene of a segment of DNA with repeating units of 3 or more nucleotides - disease results when the number of repeats underoges expansion leading to abnormal gene expression and/or function - results in more than a dozen morsly neurological disorders; polygultamine disorders

Answer 49

Unstable Repeat Expansions

Question 50

earlier onset of disease in later generations

Answer 50

anticipation

Question 51

-multiple copies of mtDNA replicate during cell division and sort randomly among newly synthesized mitochondria which are distributed randomly between 2 daughter cells

Answer 51

Replicative segregation

Question 52

where a daughter cell receives mitochondria that contain only a pure population of either normal or mutant mtDNA

Answer 52

homoplasmy

Question 53

daughter cell receives a mixture of mitochondria, some with and some without the mutation

Answer 53

heteroplasmy