Download DNA Function - Grayslake Central High School

Advanced
Genetics
Codominance


Both alleles are detectable in a specimen
Gene:
Cattle coat color
Alleles
CR = red
CW = White
Genotypes
CRCR
= red coat
CWCW
= white coat
CRCW
= roan coat
Incomplete Dominance
W
W
C C
R
R
CC

R
W
CC
Heterozygous phenotype is intermediate
Multiple Alleles


More than two alleles exist for a gene
Human blood type
Multiple Alleles
Blood Type
Genotype
Antibodies
Practice Problem
A child with blood type A needs a blood transfusion.
Her mother is blood type B, and her father is type AB.
What is the probability that her brother (if we don’t
have time to test his blood) could donate a compatible
supply of blood to her?
Sex-Linkage (X-Linkage)

A
M
M
b
B
n
N
Somatic cells have 2 alleles per gene for…



A
Genes on autosomes
Genes on the x-chromosome in females
Somatic cells in males have only one allele per x-linked gene.
Sex-Linkage (X-Linkage)

Colorblindness is caused by a recessive x-linked allele.
What are the possible genotypes?
 What phenotypes correspond to these genotypes?
 What are the expected offspring from a cross between a
carrier female and a colorblind male?

Practice Problems

Hemophilia is caused by a recessive x-linked allele.



What would have to be true for a woman to inherit hemophilia?
What do you know about the father of a hemophiliac male?
In Drosophila melanogaster, a gene on the X chromosome enables
gastrulation, the infolding of the embryo that forms the digestive tract.
Only one functional allele is necessary for successful gastrulation, but
the recessive phenotype flies fail to develop.


What is the predicted ratio of females to males surviving to maturity from a
cross between a carrier female and a normal male?
What would have to be true for a female to express the disorder?
Blood Typing, Part 2

Rh Factor
Rh+


Rh-
A type AB- mother and a type B+ father really
want to have a type A+ child. How likely are
they to do it on the first shot?
The man’s mother is O-.
Pedigrees

Determining nature of inheritance using family histories
Practice Pedigree
Tribrachiosis
Dibrachiosis