Genetics In Medicine

Front 1

allelic heterogeneity

Back 1

genetic heterogeneity because of different mutations at the same locus

Front 2

locus heterogeneity

Back 2

genetic heterogeneity because of different mutations at different loci

Front 3

retinitis pigmentosa
Ehlers-Danlos syndrome

Back 3

photoreceptor degeneration
collagen defect

examples of diseases that may have autosomal dominant or recessive or x-linked

Front 4

cystic fibrosis due to mutation in CFTR

Back 4

most common autosomal recessive disease in whites

Front 5

consanguinity

Back 5

parents are related and could have inherited the mutant allele from a single common ancestor

Front 6

genetic isolate

Back 6

small group in which frequency of rare recessive gene is different from general population
result of geographic, religious, linguistic barriers

Front 7

hemochromatosis

Back 7

example of autosomal recessive disorder that is sex influenced

enhanced absorption of iron, but affects females less because they eat less iron and discard more in menstruation

Front 8

5 characteristics of autosomal recessive inheritance

Back 8

1. if appears in > 1 members of family, it is typically seen in sibship, not parents, offspring, or other relatives

2. males and females equally affected (for most diseases)

3. parents of affected child are asymptomatic carriers

4. parents may be consanguineous, especially likely if gene mutation is rare

5. recurrence risk for each sib of proband is 1/4

Front 9

every affected person in pedigree has an affected parent as far back as the occurrence of original mutation
this is example of

Back 9

autosomal dominant and
x-linked dominant

Front 10

autosomal dominant transmission distinguished from x-linked dominant by

Back 10

male-to-male transmission

Front 11

fitness

Back 11

probability of transmitting one's genes to next generation as compared to avg. probability of population

measured by number of offspring of affected people who survive to reproductive age

fitness = 0, never reproduce, so due to new mutations

Front 12

penetrance

Back 12

probability that a gene will have any phenotypic expression at all

or the percentage of people with a particular genotype who are actually affected, at least to some degree

Front 13

expressivity

variable expressivity

Back 13

severity of expression of phenotype

severity of disease differs in people who have the same genotype

Front 14

pleiotropy

Back 14

single abnormal gene or gene pair produces diverse phenotypic effects, ex: which organ systems are involved and which signs and symptoms occur

Front 15

neurofibromatosis NF1

Back 15

example of disease that shows differences in expression

age-dependent penetrance - not all newborns show symptoms

variable expressivity: varies from only spots on skin to tumors

Front 16

male-limited precocious puberty

Back 16

example of sex-limited autosomal dominant inheritance

boys go through puberty at early age
nonpenetrant in heterozygous females

Front 17

difficulty in distinguishing
1. sex-limited autosomal inheritance
from 2. x-linked heritage when ________

Back 17

males do not reproduce because then one can't establish male-male transmission

use gene mapping to determine chromosome and consequent recurrence risk

Front 18

in x-linked
males can have ____ phenotypes
females can have ___ phenotypes

Back 18

males have 2
- affected
- unaffected

females have 3
- homozygous unaffected
- heterozygous
- homozygous affected

Front 19

5 characteristics of autosomal dominant inheritance

Back 19

1. phenotype usually appears in every generation except
- new mutation
- nonpenetrance or subtle expression

2. any child of affected parent has 50% risk of inheritance

3. phenotypically normal parents don't transmit phenotype to children
- except in nonpenetrance

4. males and females equally likely to transmit phenotype to children of either sex

5. isolated cases usually due to new mutation
the less fitness - the greater proportion due to new mutations