1. Unit 3: Heredity Chromosomal Inheritance
Biology 12
Unit 3: Heredity
Chromosomal Inheritance

2. 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 female

3. Unexpected Results for Linked Genes

5. recombinants

6. Linkage ,Crossing Over & MappingB C 12 5 7
BA + AC  BC
 7
Therefore, A is not in the middle
AC + CB = AB
5 + 7 = 12
Therefore, C is in the middle!

7. Sex Linked Inheritance

8. ♂ ♀ XN Y ♂ ♀ XN Y Xn ♂ ♀ XN Y Xn ♂ ♀ Xn Y XN ♂ ♀ Xn Y XN ♂ ♀ Xn Y

9. Pedigree Charts

10. Parents Heterozygous
Offspring recessive
Parents Heterozygous
Offspring recessive
Inconclusive
Parents Heterozygous
Offspring homozygous
dominant
Parents Heterozygous
Offspring homozygous
dominant
Inconclusive

11. IF SEX LINKED RECESSIVE SUSPECTED
CAN’T BE SEX
LINKED RECESSIVE
MOM COULD
BE A CARRIER
CAN’T BE SEX
LINKED RECESSIVE
CAN’T BE SEX
LINKED RECESSIVE
CAN’T BE SEX
LINKED RECESSIVE
MOM COULD
BE A CARRIER

12. 1. What are everyone’s genotype?I II
III IV 1 4 3 2
1. What are everyone’s genotype?
2. What is the probability that III-3 and III-4 will produce another affected offspring?