Inheritance Patterns

Question 1

vertical transmission

Answer 1

phenotype seen in every generation

Question 2

horizontal transmission

Answer 2

phenotype seen in siblings, but not parents

Question 3

autosomal dominant

Answer 3

-affected offspring typically have one heterozygous parent
-vertical transmission
-equal bt male and female
-50% recurrence risk

Question 4

examples of autosomal dominant diseases

Answer 4

-neurofibromatosis type 1
-marfan syndrome
-achondroplasia
-osteogenesis imperfecta
-breast and ovarian cancer
-postaxial polydactyly

Question 5

multiple phenotypic effects of a single allele or pair of alleles

Answer 5

pleiotropy
-ex. marfan syndrome has ocular, skeletal, and cardiovascular effects

Question 6

autosomal recessive

Answer 6

-parents are both heterozygous (carriers)
-horizontal transmission
-either parent can pass to son and daughter
-25% recurrence risk

Question 7

examples of autosomal recessive inheritance

Answer 7

-sickle cell
-cystic fibrosis
-PKU
-tay-sachs
spinal muscle atrophy

Question 8

x linked recessive

Answer 8

-vertical but skips generations
-more males than females affected
-carrier female (half sons affected/unaffected & half daughters carriers/noncarriers)
-affected male ( all daughters carry & all sons unaffected)
-non male to male

Question 9

x linked recessive examples

Answer 9

hemophilia A & B
Duchenne muscular dystrophy
red green colorblind

Question 10

-mutation in genes for clotting factor
-bleeding into soft tissues, muscles, and weight bearing joints

Answer 10

hemophilia

Question 11

x linked dominant

Answer 11

-vertical transmission
-twice as many females affected
-affected females are heterozygous
-affected female (half daughters and sons affected/unaffected)
-affected male (all daughters affected, all sons unaffected)
-no male to male

Question 12

example of x linked dominant

Answer 12

vitamin D-resistant rickets

Question 13

y linked inhertiance

Answer 13

-vertical transmission
-all males
-only father to son

Question 14

mitochondrial inhertiance

Answer 14

-vertical transmission
-equal male and female affected
-only passed from mom

Question 15

reduced penetrance

Answer 15

-individuals with the genotype may not express the phenotype
-offspring still at risk
-example breast and ovarian cancer

Question 16

age dependent penetrance

Answer 16

-symptoms of disease have delayed onset so they may have children before their symptoms show and the offspring are still at risk

Question 17

variable expressivity

Answer 17

-severity of symptoms vary widely
-offspring still at risk
-individuals presentation may be so mild that they may not know they are affected until child is severely affected

Question 18

with a new mutation, do siblings have an increased risk of disease?

Answer 18

no, ex achondroplasia

Question 19

presence of genetically distinct cell lines in the same individual

Answer 19

mosaicism

Question 20

mutation arises from mitotic errors after fertilization and propagates through multiple tissues or organs

Answer 20

somatic mosaicism

Question 21

-two or more siblings affected with no family history
mutation only in egg or sperm cells

Answer 21

germline mosaicism

Question 22

anticipation

Answer 22

-more severe expression and/or earlier age of onset in subsequent generations
-can be caused by expansion of DNA repeats