Inheritance Patterns through

Pedigrees

MMHS ScienceMr. Chitraroff

Main Inheritance TypesMain Inheritance Types

1. Autosomal Recessive2. Autosomal Dominant3. X-Linked (Sex-Linked) Recessive4. X-Linked (Sex-Linked) Dominant

Autosomal = Inherited on the body chromosomes #1-44.Sex-Linked = Inherited on the Sex Chromosomes #45 & 46. (XX or Xy)

Pedigree SymbolsPedigree Symbols

Autosomal Dominant Traits1. Almost all individuals will be heterozygous. (Hh)

2. Every affected individual has an affected biological parent. There is no skipping of generations.

3. Males and females have an equally likely chance of inheriting the mutant allele and being affected. The recurrence risk of each child of an affected parent is 1/2.

4. Normal siblings of affected individuals do not transmit the trait to their offspring.

5. There are never carriers (half-shaded symbols).

Autosomal DominantAutosomal Dominant

Autosomal Dominant DisordersDisease Symptoms

Huntington’s Disease

Symptoms may include involuntary movements and loss of motor control. In addition, personality changes may occur, with loss of memory and decreased mental capacity.

Achondroplasia (dwarfism)Achondroplastic dwarfs have short stature, with an average adult height of 131 cm (4’3”)

PolydactlyDisorder of more than 5 fingers or toes per appendage.

Jason Acuna

aka “Weeman”

a legal dwarf

Polydactly

Autosomal Dominant

Autosomal Dominant

Autosomal Recessive

1. Traits will often skip a generation.2. Parents may not have the trait, but can pass it

on to offspring. (e.g. Het)3. Males and Females are equally affected.4. Both parents can be carriers. (half-shade)

Autosomal Recessive

Examples: Examples: *Cystic fibrosis

*Tay-Sach’s disease

Males and females are equally likely to be Males and females are equally likely to be affected.affected.

TThe recurrence risk to the unborn sibling he recurrence risk to the unborn sibling of an affected individual is 1/4.of an affected individual is 1/4.

The trait is characteristically found in The trait is characteristically found in siblings, not parents of affected or the siblings, not parents of affected or the offspring of affected.offspring of affected.

Parents of affected children may be Parents of affected children may be related. The rarer the trait in the general related. The rarer the trait in the general population, the more likely a population, the more likely a consanguineous mating is involved.consanguineous mating is involved.

Albinism InheritanceWhich Type of Inheritance is this?

Albinism…revealed

Circled symbols show Heterozygous Individual (Aa)What’s gross about this pedigree?

Jamaican Albino “Yellow Mon”

Sex-Linked Traits

1. Passed on from the (X) Sex Chromosome.2. Fathers pass trait on to daughters.3. Mother’s pass trait on to daughters or sons.4. Usually skips a generation.5. Males more likely affected than females.6. Female carriers possible, not males.

Sex Linked RecessiveSex Linked Recessive

Examples:

–Color-blindnessColor-blindness

–Duchenne Muscular DystrophyDuchenne Muscular Dystrophy

The disease is never passed from father to son.

Males are much more likely to be affected than females.

•All affected males in a family are related through their mothers.

Trait or disease is typically passed from an affected grandfather, through his carrier daughters, to half of his grandsons.

Sex-Linked Recessive Disorders• Hemophilia-blood doesn’t clot

• Colorblindness—Can’t see certain colors.

• Duchenne Muscular DystrophyDuchenne Muscular Dystrophy——degenerative degenerative breakdown of muscles.breakdown of muscles.

• Anosmia – Inability to smell.