Tracking Family History

A chart that shows multiple family generations and relationships to track the inheritance of genetic traits.

Can be used to determine genotypes of family members.

Can be used to help predict probability of future generations expressing certain traits.

Important tool for genetic counselors

Incomplete dominance – dominant & recessive traits are blended Example: Four o’clock

flower color – red, white, pink

Remember: Vegetable juice

Codominance – dominant & recessive traits both show up completely and individually Example: Blood types A &

B, Horse coat color Remember: Salad & cows

Multiple alleles - More than 2 alleles control the phenotype Example: blood types A, B, O, eye color

Polygenic traits – more than one gene controls phenotype Examples: skin (4

genes), fingerprints

Epistasis = one gene can interfere with the expression of another Examples: mouse

fur color (5 genes) – one gene overshadows the others

Albanism – no pigment

The environment can influence gene expression Affects phenotype

Examples: Sun exposure – affect s skin &

hair color Temperature – sea turtles

produce more females in warm years and more males in cold years

Identical twins – nutrition, healthcare & physical activity influence appearance

An individual’s fingerprints are controlled by polygenic inheritance, but also by the fetal environment. The ridge pattern of a fingerprint can be altered during weeks 6 – 13 of fetal development as the fetus touches the wall of the amniotic sac with its fingertips.

Identical twins who have identical genes have different fingerprints.

There are three alleles to blood Ai (antigen for A) Bi (antigen for B) Oi (antigen that

can be changed called H)

Ai produces the antigen A found on the RBC and co dominate

Bi, antigen B, co dominate

Oi, recessive changing antigen

Blood Type

Antigen

Antibodies Receives From

Donates To

A A, H Anti-B A, O A, AB

B B, H Anti – A B, O B, AB

AB A, B, H

none A, B, AB, O

AB

O H Anti-AAnti - B

O A, B, AB, O

Blood Typeof Parents

Possible Genotypesof Parents

Possible Blood TypesAmong Children

A and A Ai and Ai A and O

A and B Ai and Bi A, B, AB, O

A and AB Ai and AB A, B, and AB

A and O Ai and ii A and O

B and B Bi and Bi B and O

B and AB Bi and AB A, B, and AB

B and O Bi and ii B and O

AB and AB AB and AB A, B, and AB

AB and O AB and ii A and B

O and O ii and ii O

During mitosis, the 23 pairs of human chromosomes condense and are visible with a light microscope.

A karyotype analysis usually involves blocking cells in mitosis and staining the condensed chromosomes with Giemsa dye, “G”.

The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a dark band.

These bands are not a single gene but represent hundreds of genes.

analysis involves comparing chromosomes length the placement of

centromeres the location and

sizes of G-bands (stains)