Biochem 2-10 Pedigree Analysis

Front 1

Proband

Back 1

index case. The first family member identified with the trait of interest.

Front 2

What are characteristics of autosomal recessive inheritiance?

Back 2

1.) **Tends to skip generations**
2.) On the average, 1/4 of the offspring of carriers will be affected, 2/3 of the unaffected offspring will be carriers.
3.) Both parents must be carriers.
4.) Common for multiple siblings to be affected (horizontal transmission).

Front 3

What are characteristics of autosomal dominant inheritiance?

Back 3

1.) There are usually several generations of affected offspring (vertical transmission).
2.) All carriers affected.
3.) On the average, ½ of a carrier’s offspring will be affected.
4.) Only one parent need be a carrier.
5.) Homozygotes are usually rare. Most carriers are heterozygotes.
6.) Sporadic cases caused by new mutations may be observable.

Front 4

What are characteristics of sex-linked inheritiance?

Back 4

1.) More males will be affected than females.
2.) Transmission will usually be from affected fathers, through carrier daughters, to affected grandsons.
3.) No father to son transmission.
4.) All daughters of affected fathers will be carriers.
5.) Half the offspring of female carriers will receive the mutated allele. The sons will be affected, the daughters carriers.
6.) Sporadic cases caused by new mutations in hemizygous males may be observable.

Front 5

What are characteristics of multifactorial inheritiance?

Back 5

1.) Distinguishing characteristic of polygenic traits is familial recurrence without any distinctive inheritance pattern.
2.) The more closely related a subject is to an affected relative, the greater the subject’s risk of manifesting the trait.
3.) The occurrence tends to decline in a family from generation to generation.
4.) Risk increases with greater numbers of affected family members.
5.) Risk increases with more sever symptoms in family members.
6.) If occurrence is frequent in a sex, risk increases for family members of that sex.

Front 6

When working pedigree problems, unless there is evidence provided to the contrary, assume the inheritance pattern is________.

Back 6

autosomal recessive

Front 7

Coefficient of Relationship, R

Back 7

the fraction of identical genes shared by two relatives; R=(1/2)^n, where n= number of matings in the inbreeding loop

Front 8

Coefficient of inbreeding, F

Back 8

fraction of homozygous loci resulting from a consanguineous mating; F=R/2

Front 9

monozygotic twins

Back 9

develop from same zygote, R=100%

Front 10

dizygotic twins

Back 10

develop simultaneously from different zygote, R=5%