Complex patterns of inheritance Chapter 13

1
Complex patterns of inheritanceChapter 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 oclock 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 individuals 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 GroupingExample 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 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-A Anti - B O A, B, AB, O
16
(No Transcript)
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)