Topic 1 - Mendelian Inheritance

Complete Dominance

Dominant Allele

Incomplete Dominance

None of the two

Codominance

Both

2 affected parents with an unaffected child

DOMINANT

2 unaffected parents with an affected child

RECESSIVE

Autosomal Dominant Disorders

• low survival rate

• rare

Autosomal Recessive Disorders

It comes from a mutation in an allele that is located in one of the 22 pairs of autosomes

It’s homozygous

more common than Autosomal Dominant Disorders

Name some Autosomal Recessive Disorders

1. Albinism

2. Cystic Fibrosis

3. Sickle Cell Disease

4. Thalassemia(α and β)

5. Phenylketonuria

Albinism

• Autosomal Recessive Disorder

• It’s the absence of pigment (hair, skin, eyes)

  (absence of defect of tyrosine which is the enzyme used to produce melanin)

Cystic Fibrosis

Defective or Absent chloride transport channels

Sickle Cell Anemia

Substitution of ana amino acid (from Glutamine to Valine) in the hemoglobin protein in red blood cells

Thalassemia (α and β)

Cannot metabolize the amino acid phenylalanine

Accumulation in the blood and urine

Name Autosomal Dominant Disorders

1. Huntington’s Disease

2. Achondroplasia

Huntington’s Disease

Neurogenerative Disease (disease of the nervous system)

common around the ages of 30-40 years old

Achondroplasia

Dwarfism (rare dominant allele)

Name Dominant Sex Linked Disorders

1. Vitamin D resistant rickets

2. Alport Syndrome

Name Recessive Sex Linked Disorders

1. Hemophilia

2. Color Blindness

3. Duchenne Muscular Dystrophy

Hemophilia

Progressive bleeding is prolonged in the affected individual following an injury

Duchenne Muscular Dystrophy

Weakening of the muscles → loss of coordination

Test for β-thalassemia (carrier identification)

1. prenatal screening

2. premarital screening

3. abortion

we also have CUS and NIPD followed by karyotyping and genetic testing

Mendel’s First Law?

Law of Segregation

Mendel’s Second Law?

Law of Independent Assortment

What is the phenotypic ration of the Law of Independent Assortment?

9:3:3:1

What is the phenotypic ration of the Law of Segregation?

3:1

What is a test cross?

It is the breeding of the unknown genotype individual with a homozygous individual

What does the Law of Independent Assortment say?

Says that each pair of alleles segregates independently of each other pair of alleles during gametes formation

What does the Law of Segregation say?

Says that during gamete formation, the alleles for each gene segregate from each other so that each gamete carried only one allele for each gene

Do ‘Linked Genes’ follow the Law of Independent Assortment?

Yes, they are being inherited together

Do 'Unlinked Genes’ follow the Law of Segregation?

No, because they are inherited independently