Top Banner
C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment
9

C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Jan 14, 2016

Download

Documents

Dwain Patrick
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

C-13 Part IINon-Mendelian inheritance

Most phenotypes reflect the influences of several to many genes

and by the environment

Page 2: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Continuous variation• When multiple genes act

together to produce a physical (phenotypic) character, a gradation or range of differences occur.

• Examples: height, weight in humans

• Referred to as polygenic traits

Page 3: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Pleiotropic effects

• Occurs when an allele has >1 effect on phenotype

• Examples are:– Sickle cell anemia

– Cystic fibrosis

Page 4: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Incomplete dominance

• Situation where 2 alleles “blend” to form hybridized phenotype

• Examples:– Flower color in 4

o’clocks and snapdragons

Page 5: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Environmental effects

• Allele expression may be affected by environmental conditions

• Examples:– Coat color in arctic foxes

– Coat color in Himalayan rabbits and Siamese cats

• ch allele affected by temp >33 C tyrosinase enzyme inactivates + reduces melanin pigment production

Page 6: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Epistasis – genes acting “in concert”

• Situation whereby 1 gene pair affects the expression of a 2nd gene pair

• Examples:– Anthocyanin (purple)

pigment in corn

– Animal coat colors

Page 7: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Epistasis (cont’d)• Horse coloration involves 2

or more gene pairings..• EE or Ee is for black• ee is for red (sorrel)• PLUS other genes can add to

base colors• (Bay is AA, EE – black with

agouti gene; Buckskin is AA, EE, CcrC – bay with cremello gene, Dun is AA, EE, Dd – bay with dun gene; Palomino is ee, CcrC – sorrel with cremello gene)

Page 8: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Mutation of genes causes genetic disorders

• Most gene disorders are RARE – nonadaptive

• Most are recessively inherited:– Tay Sachs disease Sickle cell anemia

• Some disorders are inherited in a dominant fashion:– Huntington’s disease

Page 9: C-13 Part II Non-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment.

Multiple alleles and Blood Groups

• ABO Blood groups– IAIA and Iai = type A

– IBIB and IBi = Type B

– IAIB and IBIA = Type AB

– ii = Type O

• Rh blood factor• Rh +

• Rh-