unit 3: heredity chromosomal inheritance
DESCRIPTION
The Source of Heredity Chromosome Theory Sex determination Genes are found on chromosomes Paired chromosomes segregate during meiosis Chromosomes (not genes) segregate independently Each chromosome contains many genes Sex determination In most animals the male of the species has a Y chromosome. Birds are a notable exception - many species of birds has the XY condition as the femaleTRANSCRIPT
Biology 12
Unit 3: HeredityChromosomal Inheritance
The Source of Heredity• Chromosome Theory
– Genes are found on chromosomes– Paired chromosomes segregate during meiosis– Chromosomes (not genes) segregate independently– Each chromosome contains many genes
• Sex determination– In most animals the male of the species has a Y
chromosome.– Birds are a notable exception - many species of birds
has the XY condition as the female
Unexpected Results for Linked Genes
recombinants
Linkage ,Crossing Over & MappingA
A
B
B C
C
12
5
7
BA + AC BC
12 + 5 7
Therefore, A is not in the middle
AC + CB = AB
5 + 7 = 12
Therefore, C is in the middle!
Sex Linked Inheritance
♂♀ XN Y
XN
XN
♂♀ XN Y
XN
Xn
♂♀ Xn Y
XN
XN
♂♀ Xn Y
XN
Xn
♂♀ XN Y
Xn
Xn
♂♀ Xn Y
Xn
Xn
Pedigree Charts
Parents HeterozygousOffspring recessive
Parents HeterozygousOffspring recessive
Parents HeterozygousOffspring homozygous
dominant
Parents HeterozygousOffspring homozygous
dominant
Inconclusive
Inconclusive
CAN’T BE SEX LINKED RECESSIVE
CAN’T BE SEX LINKED RECESSIVE
CAN’T BE SEX LINKED RECESSIVE
IF SEX LINKED RECESSIVE SUSPECTED
CAN’T BE SEX LINKED RECESSIVE
MOM COULDBE A CARRIER
MOM COULDBE A CARRIER
1. What are everyone’s genotype?
2. What is the probability that III-3 and III-4 will produce another affected offspring?
I
II
III
IV
1 432
3 4
1
2
2
1
1 2