Multiple Alleles and Genetic Disorders

Human blood types

3 possible alleles for presence or absence of antigens on the surface of red blood cells.

1. IA : Co-dominant, A antigen

2. IB : Co-dominant, B antigen

3. ii : Recessive, no antigen

Blood cell compatibility

Blood group AB : Both A + B antigens (No antibodies for those antigens). Can receive blood from any group. Cannot donate blood to A, B, or O, only AB. Universal Recipient

Blood group A : A antigens (Plasma contains antibodies against B antigens). Can receive blood from A or O. Can donate to A or AB

Blood group B : B antigens (Plasma contains antibodies against A antigens). Can receive blood from B or O. Can donate to B or AB

Blood group O : No antigens (Plasma contains antibodies for A and B antigens). Can only receive blood from O. Can donate blood to anyone. Universal Donor.

Environmental Influences

Factors such as temperature determine whether a gene is turned on or off

Genetic Disorders

• A disease of disorder that is caused by a genetic mutation

Causes :

1. Germline mutation (Changes in DNA sequence)

2. Chromosomal mutation (Caused by a non-disjunction event in meiosis)

Gene mutations

• Can be caused by mutagens (Environmental factors that change DNA : UV light, radiation)

• Mutations in body cells can lead to cancer'

• Mutations in sex cells can be passed on to an offspring

Types of mutations

Good : Allows offspring to survive better and reproduce in it’s environment

Bad : Harmful to organisms and offspring

Benign : Doesn’t affect offspring survival and reproductive abilities

Patterns of Inheritance

1. Autosomal Dominant : Dominant gene on a non-sex chromosome

2. Autosomal Recessive : Recessive gene on a non-sex chromosome

3. Sex-Linked Recessive : Recessive gene on the X-chromosome

4. Codominant : Codominant gene on a non-sex chromosome

Chromosomal Mutations

Caused by non-disjunction (Homologous chromosomes or chromatids stick together instead of separating during meiosis)

Non-Disjunction

Results in 2 kinds of gametes, 1 has an extra chromosomes, 1 lacks a chromosome

Genetic Disorder :

1. XXX Female - Infertile, Taller, puberty is delayed, 47 chromosomes

2. XXY Klinefelter’s male - Infertile, 47 chromosomes, don’t produce proper testosterone

3. XO Turner’s Female - Infertile, short stature, 45 chromosomes

Autosomal Non-Disjunction

1. Autosomal Monosomics : Cannot survive

2. Trisomy Extra #13, 15, or 18 : Severe defects, only live 3 months

3. Trisomy Extra #21 : Usually survive to adulthood, skeletal defects, intellectual disabilities (Down Syndrome)