1. Complex patterns of inheritance Chapter 13

2. Pedigrees Tracking Family History

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

4. Pedigrees 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

5. Key parts of a pedigree

6. Pedigrees
Pedigree 1: An idealized pedigree of a family with hypercholesterolemia, an
autosomal dominant disease where the heterozygote has a
reduced number of functional low density lipoprotein receptors.

7. Phenotype and allele interaction
Incomplete dominance – dominant & recessive traits are blended
Example: Four o’clock flower color – red, white, pink
Remember: Vegetable juice

8. Phenotype and allele interaction
Codominance – dominant & recessive traits both show up completely and individually
Example: Blood types A & B, Horse coat color
Remember: Salad & cows

9. Phenotype and allele interaction
Multiple alleles - More than 2 alleles control the phenotype
Example: blood types A, B, O, eye color

10. Phenotype and Gene interaction
Polygenic traits – more than one gene controls phenotype
Examples: skin (4 genes), fingerprints

11. Phenotype and Gene interaction
Epistasis = one gene can interfere with the expression of another
Examples: mouse fur color (5 genes) – one gene overshadows the others
Albanism – no pigment

12. Environmental Interaction with Genotype
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

13. Fingerprints
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.

14. ABO Blood Grouping Example of Multiple-allele traits
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

15. Blood Group System Blood Type Antibodies Receives From Donates To A
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 O H
Anti-A
Anti - B

16. Blood Type of Parents
Possible Genotypes of Parents
Possible Blood Types Among 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
Ai and ii
B and B
Bi and Bi
B and O
B and AB
Bi and AB
Bi and ii
AB and AB
AB and O
AB and ii
O and O
ii and ii O

17. Karyotype
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.

18. analysis involves comparing chromosomes
length
the placement of centromeres
the location and sizes of G-bands (stains)