Pedigree Part 2

Traits encoded by autosomes

Autosomal Traits

Types of AUTOSOMAL INHERITANCE PATTERNS

1. Autosomal Dominant Inheritance

2. Autosomal Recessive Inheritance

A single dominant allele on any of the autosomes can lead to expression of a trait

Autosomal Dominant Inheritance

1. Every affected child has an affected parent; no generations skipped

2. Traits occurs about equally in both sexes

3. When an affected person mates with an unaffected person, ~50% of offspring will be affected

Autosomal Dominant Inheritance

two copies of a recessive allele on any of the autosomes can lead to expression of a trait.

Autosomal Recessive Inheritance

1. Traits often skip generations

2. Traits occurs about equally in both sexes

3. Commonly seen in consanguineous matings

4. If both parents are affected all offspring will be affected

5. When an affected person mates with an unaffected person, all offspring will be unaffected

Autosomal Recessive Inheritance

Pronuclei donates the X chromosome

Female Pronuclei

Pronuclei donates either an X or a Y chromosome

Male Pronuclei

• Studied eye color in fruit flies

• Crossed purebred white- eyed females with red-eyed males (R vs r)
• Concluded that gene for white eyes must be located on the X chromosome

Thomas Morgan Hunt

In Sex-Linked traits which is more common? (X Linked or Y Linked)

X-Linked

Traits are expressed in different percentages in males and females. (Y/N)

Yes.

Y-linked traits are expressed only in males. (Y/N)

Yes.

Traits that are from father to son.

Y-Linked Traits

Traits From mother to all children.

Mitochondrial Traits

Expressed in only one gender but genes are present in both genders

Affects only males or females

Secondary sexual characteristics

Sex-limited Traits

What type of traits is associated?

Ex:

Breast development in females

Beard growth in males

Sex-limited Traits

Appears in both genders but is recessive in one gender, dominant in the other

More common in one gender

Sex-influenced Traits

What type of traits is associated?

Ex:

Pattern baldness

Sex-influenced Traits

Females have Two X chromosomes = two copies of genes for all traits carried on the 23rd pair. (Y/N)

Yes.

Males have only One X chromosome = one gene for all traits carried on the 22nd pair. (Y/N)

No.

Males pass the X chromosome to all their daughters, none of the sons

Females pass one of their X chromosomes to all their children

Sex-Linked Recessive Traits

SEX-LINKED INHERITANCE PATTERNS

1. Sex-linked Dominant Inheritance

2. Sex-linked Recessive Inheritance

3. Y-linked Inheritance

A single dominant allele on the X chromosome can lead to a trait/condition

Sex-linked Dominant Inheritance

1. Traits do not skip generations

2. Affected males are from affected mothers

3. Approx. half the children of an affected heterozygous mother are affected.

4. Affected females come from affected mothers/fathers

5. All daughters but none of the sons of an affected father are affected

Sex-linked Dominant Inheritance

A recessive allele on the X chromosome can lead to a trait/condition

Males > Females (8:1)

Affected males transmits the allele to all daughters but none of the sons

Sex-linked Recessive Inheritance

1. Traits may skip generations

2. Most affected individuals are males from affected or carrier mothers

3. Affected males come from mothers who are affected /carriers because they have affected male family members.

4. All sons of affected females should be affected.

5. Affected females come from affected fathers and affected/carrier mothers

6. Approx. half the sons of carrier females should be affected

Sex-linked Recessive Inheritance

Genes carried on the Y-Chromosome

Y-Linked Inheritance

• 59 million base pairs

• Approx. 150 genes

• Identified as sex determining in 1905

The Y Chromosome

Sex Linked disorders are mostly X Linked or Y Linked?

X Linked

Are Sex-Linked disorders more common on male or female?

Male

Examples of Sex-Linked Disorders

• Male pattern baldness

• Red-green color blindness

• Night blindness

• Hemophilia

Example of X-Linked Dominant Disorder

Vitamin-D Resistant Rickets

Examples of X-Linked Recessive Disorders

Hemophilia

Duchenne Muscular Dystrophy