Modern Genetics. Multiple Alleles More than two alleles can be inherited –Example: Blood Types...
-
date post
18-Dec-2015 -
Category
Documents
-
view
220 -
download
1
Transcript of Modern Genetics. Multiple Alleles More than two alleles can be inherited –Example: Blood Types...
Multiple Alleles
• More than two alleles can be inherited– Example: Blood Types– Alleles= IA, IB, i
Blood Type (Phenotype)
Type of Antigen
Possible Genotypes
A A IAIA, IAi
B B IBIB, IBi
AB AB IAIB
O None ii
Multiple Alleles: Cont’d
Blood Type Antigens on RBC Antibodies present
A
Anti-B
B
Anti-A
AB
None
O
Anti-B & Anti A
• Agglutination– Blood coagulates or
clumps together– Antibodies recognize
antigen on surface of blood and attack it
• i.e. B antibodies recognize B antigens
Phenomenon occurs because of genotypes!
Multiple Alleles: Punnett Squares
• Heterozygous A x Heterozygous B
• Genotypes: IAi x IBi
• Type O x AB• Genotypes: ii x IAIB
Chromosomes & Sex Determination
• 23 pairs of chromosomes found in nuclei of a human cell or 46 total chromosomes
• Pairs 1-22: Somatic• Pair #23: Sex-
determining chromosome Karyotype
1. Extract chromosomes from nucleus of a cell
2. Pair up matching chromosomes3. Arrange chromosomes by size
Sex Determination• Female: XX• Male: XY• Baby’s sex
determined by male– Mom X– Dad X or Y
X chromosome
Y chromosome
Sex-Linked Traits
• The X chromosome carries the trait, not the Y
Male Female
Normal
Carrier
Diseased Person
Sex-Linked Traits Examples
• Sex-linked diseases: Color blindness, hemophilia
• Example: Carrier Female & Normal Male
Incomplete Dominance
• Contrasting alleles• 1 allele is partially dominant• Intermediate traits are expressed• Example: Cross Red Flower & White Flower
F1 Generation F2 Generation
Codominance
• Heterozygous with both alleles expressed
• Homozygous red cow mates with homozygous white bull
CRCR x CWCW
CRCW (roan)
Polygenic Traits
• Traits controlled by 2 or more genes– Additive effect
• Example: Height Combination of all body parts put together; determined by many genes on different areas of chromosomes