Human genetic inheritance patterns

Human Genetics

I. 5 Human Patterns of Inheritance:

a. Complete Dominance (Basic Mendelian Genetics)

b. Incomplete Dominancec. Co-dominanced. Sex-Linkede. Polygenic

a. Complete Dominance

• Traits inherited are either DOMINANT or RECESSIVE

• Ex. BB, Bb, bb

b. Incomplete Dominance

• Traits inherited show a new phenotype that is a BLENDING or MIXING of parental alleles–HETEROZYGOUS results in a blending

of two alleles–Use 2 different CAPITAL letters to

represent (neither allele is dominant or recessive)

Incomplete Dominance cont.Ex: 4 o’clock flowers, snapdragons, Tay Sach’s Disease

Incomplete Dominance cont.Ex: 4 o’clock flowers, snapdragons, Tay Sach’s Disease

Incomplete Dominance cont.Ex: 4 o’clock flowers, snapdragons, Tay Sach’s Disease

c. Co-dominance

• Trait inherited shows a new phenotype that EXPRESSES BOTH parental alleles

–HETEROZYGOUS condition results in the expression of both alleles

– Use 2 different capital letters to represent

Co-dominance continuedEx: Roan Horse

X

Co-dominance continuedEx: Roan Horse, Dalmatian

d. Sex Linked Traits• Traits are controlled by genes on

the X or Y chromosomes

a. _X linked traits can be passed on to males and females

b. _Y linked traits can only be passed to males

X-Linked Traits

1. Affect the X chromosome

2. _FEMALES tend to be CARRIERS and pass on the trait to their sons - XtY

3. Females can be affected but BOTH X chromosomes must have the gene for the trait - XtXt

Examples:

Hypertrichosis – Human Werewolf Syndrome:

Congenital generalized hypertrichosis (CGH) Rare, X-linked dominant trait

Found in a single multigenerational Mexican family

Colorblindness Self Test:

NUMBERS: 5 | 8 | 9 | 5 | 3 | 5 | 9 | 10 |

Hemophilia

Male Pattern Baldness

Genotypes of Male Pattern Baldness

e. Polygenic Traits

• Traits are controlled by MULTIPLE gene pairs

1.Genes may be on same or different chromosomes

2.Expressed trait varies greatly

Ex. Hair color, eye and skin colors, height, weight

II. How to study patterns of inheritance in families

Two Methods:1. _KARYOTYPE: Photograph of an individual’s

chromosomes arranged in homologous pairs and can be viewed underneath a microscope

a. Used to identify problems with chromosomes

• _ABNORMAL NUMBERS• _DAMAGED OR BROKEN• _TO DETECT GENETIC DISEASES

Typical Karyotype: Normal Individual

Pattern of Inheritance:Normal Chromosome Pattern

Abnormality:None

Notation:46, XY, Male

2. _PEDIGREE CHART: Diagram to show genetic traits and used to map genetic traits through generations

a. Shows SEX, PHENOTYPES, and GENOTYPES of family members

b. Can predict patterns of inheritance

c. Uses symbols