Complex patterns of inheritance Chapter 13

Pedigrees Tracking Family History http://www.alicesfamilytree.com/images/alice_family_tree.jpg

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

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 http://www.uchsc.edu/gs/gs/genc/images/meeting.gif

Key parts of a pedigree

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.

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

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

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

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

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

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

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.

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

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 http://nobelprize.org/medicine/educational/landsteiner/index.html

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

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.

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