Patterns of Inheritance

Question 1

locus

Answer 1

segment of DNA at a specific location

Question 2

alleles

Answer 2

alternative variants of a gene

Question 3

wild-type

Answer 3

single prevailing allele present in the majority of individuals (depends on population)

Question 4

variants

Answer 4

mutants; gene other than WT

Question 5

polymorphisms

Answer 5

variant alleles; may affect disease susceptibility

Question 6

mutations

Answer 6

new genetic changes in a family or disease–cause mutant alleles

Question 7

“non-gene” regions

Answer 7

non-protein coding RNAs lie in intergenic regions (within introns) –miRNA/lincRNA

Question 8

genotype

Answer 8

entire set of alleles in a genotype or set of alleles at a specific locus

Question 9

phenotype

Answer 9

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

Question 10

homozygous

Answer 10

individuals 2 alleles are FUNCTIONALLY identical at a specific locus

Question 11

heterozygous

Answer 11

2 alleles are FUNCTIONALLY different

Question 12

hemizygous

Answer 12

only 1 allele of a gene (men = X chromosome)

Question 13

compound heterozygous

Answer 13

2 heterogoenous recessive alleles at a particular locus that cause genetic disease in a heterozygous state

Question 14

pedigree

Answer 14

graphical representation of the family tree

Question 15

kindred

Answer 15

extended family depicted in pedigree

Question 16

proband

Answer 16

1st affected person brought to clinical attention (can be multiple)–analyze all other family members in relation to the proband

Question 17

consultand

Answer 17

person who brings the phenotype to clinical attention (can be affected or unaffected individual)

Question 18

first degree relatives

Answer 18

parents, siblings, offspring of proband

Question 19

second degree relatives

Answer 19

grandparents, grandchildren, nieces, nephews, half-sibs

Question 20

third degree relatives

Answer 20

first cousins

Question 21

relative degree assignments

Answer 21

first, second, third, etc based on NUMBER OF STEPS in the pedigree between the two relatives

Question 22

consanguineous

Answer 22

couples sharing 1+ ancestor in common; closely related (2nd cousins or closer)

Question 23

fitness

Answer 23

genetics term; refers to the measure of the impact of a condition/genotype on reproduction–defined by number of offspring who survive to reproductive age compared to a control group

Question 24

vertical transmission

Answer 24

transmission of a disease from one generation down to the next; implies family history of disease; excludes sporadic cases

Question 25

mosaicism

Answer 25

X-linked disorders; females randomly inactivate 1 X-chromosomes in each cell; phenotypic expression only in a subset of cells

Question 26

pure dominant

Answer 26

both homozygotes and heterozygotes show identical severity of phenotype

Question 27

semidominance

Answer 27

disease is more severe in homozygotes than heterozygotes--incomplete dominance--more common

Question 28

codominant

Answer 28

2 different allels are expressed together (ABO)

Question 29

penetrance

Answer 29

probability that a mutant gene will have any phenotypic expression

Question 30

reduced penetrance

Answer 30

When the percent of individuals with a mutant genotype demonstrating some disease phenotype is less than 100%

Question 31

expressivity

Answer 31

severity of expression of the phenotype in individuals with the same disease-causing genotype

Question 32

variable expressivity

Answer 32

when severity of a disease differs in people who have the same genotype

Question 33

congenital disease

Answer 33

phenotype recognized at birth

Question 34

late-adult onset

Answer 34

common way that severe autosomal dominant disease can continue to be passed on; don't show up until after individual has reproduced (Huntington's)

Question 35

allelic heterogenity

Answer 35

different alleles caused by different mutations of the SAME GENE result in varying disease phenotype; depending on severity of mutation, you get a range of different phenotypes

Question 36

locus heterogeneity

Answer 36

disease phenotype is caused by mutations in distinctly DIFFERENT GENES

Question 37

CFTR

Answer 37

allelic heterogeneity

Question 38

phenotypic heterogeneity

Answer 38

different mutations in SAME GENE cause completely DIFFERENT DISEASES

Question 39

RET gene mutation

Answer 39

phenotypic heterogeneity; causes dominantly inherited Hirschsprung and endocrine cancers

Question 40

autosomal recessive inheritance

Answer 40

occurs in mutant homozygotes or compound heterozygotes; no normal alleles

Question 41

sex influenced autosomal recessive inheritance

Answer 41

NOT X-linked recessive; both sexes develop the disease, one sex just has a higher frequency (increased penetrance)

Question 42

inbreeding

Answer 42

similar to consanguinity, but at the population level; describes individuals from a small pop. tending to choose their mates from within the same population (cultural, geographic, or religious influence)-->share gene alleles from ancestors (increasing homo. recessive disorders)

Question 43

likelihood of new mutations in autosomal dominant disorders rises dramatically with ____ of the parents

Answer 43

age

Question 44

Sex-limited phenotypes in autosomal dominant disorders

Answer 44

Different from X/Y-linked--can be mapped to an autosome and has direct father-son transmission; trait is seen ONLY in one sex; male-limited precocious puberty

Question 45

Precocious puberty

Answer 45

male-limited sex-limited autosomal dominant disorder

Question 46

Hemophilia A

Answer 46

X-linked disorder

Question 47

Purpose of X-inactivation

Answer 47

dosage compensation for expression of X-linked genes

Question 48

How do you determine if X-linked disorder is recessive or dominant?

Answer 48

Phenotype of heterozygous females; if consistently expressed in carriers = dominant

Question 49

Manifesting heterozygotes

Answer 49

X-linked recessive female carriers show some abnormalties in phenotype (severity depends on what the target tissue is)

Question 50

If an affected males' daughters are all affected, but his sons are not, what is the inheritance pattern?

Answer 50

X-linked dominant inheritance (females have to have X from father--has to be mutant; males get normal Y)

Question 51

Only females exhibit disease; sons that exist are normal phenotype:

Answer 51

X-linked dominance with male lethality (living males received WT X from mother)

Question 52

Mutational Mosaicism

Answer 52

can occur from early development when clone of cells develops from a single mutation; these cells go on to form a tissue or part of tissue that is abnormal

Question 53

Mitochondrial Disorders

Answer 53

only inherited from mother; both male and female offspring have equal presentation of disease