Transcript Inheritance Patterns through Pedigrees

Inheritance Patterns
through
Pedigrees
MMHS Science
Mr. Chitraroff
Main Inheritance Types
Autosomal = Inherited on the body chromosomes #1-44.
Sex-Linked = Inherited on the Sex Chromosomes #45 & 46. (XX or Xy)
1.
2.
3.
4.
Autosomal Recessive
Autosomal Dominant
X-Linked (Sex-Linked) Recessive
X-Linked (Sex-Linked) Dominant
Pedigree Symbols
Autosomal Dominant Traits
1.
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 Dominant
Autosomal Dominant Disorders
Disease
Symptoms
Symptoms may include
involuntary movements and loss
of motor control. In addition,
Huntington’s Disease
personality changes may occur,
with loss of memory and
decreased mental capacity.
Achondroplastic dwarfs have
Achondroplasia (dwarfism) short stature, with an average
adult height of 131 cm (4’3”)
Polydactly
Disorder 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
Males and females are equally likely to be
affected.
The recurrence risk to the unborn sibling
of an affected individual is 1/4.
The trait is characteristically found in
siblings, not parents of affected or the
offspring of affected.
Parents of affected children may be
related. The rarer the trait in the general
population, the more likely a
consanguineous mating is involved.
Examples:
*Cystic fibrosis
*Tay-Sach’s disease
Albinism Inheritance
Which 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.
2.
3.
4.
5.
6.
Passed on from the (X) Sex Chromosome.
Fathers pass trait on to daughters.
Mother’s pass trait on to daughters or sons.
Usually skips a generation.
Males more likely affected than females.
Female carriers possible, not males.
Sex Linked Recessive
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.
Examples:
–Color-blindness
Trait or disease is typically passed
from an affected grandfather,
through his carrier daughters, to half
of his grandsons.
–Duchenne Muscular Dystrophy
Sex-Linked Recessive Disorders
• Hemophilia-blood doesn’t clot
• Colorblindness—Can’t see certain colors.
• Duchenne Muscular Dystrophy—degenerative
breakdown of muscles.
• Anosmia – Inability to smell.