Gene linkage

1. 11-5. Gene Linkage and Mapping
• Gene linkage
– Thomas Hunt Morgan
– Genes on the same
chromosome are linked
and usually inherited
into the same gametes
– It is the chromosome
that assort
independently, not
individual genes

2. • Linkage and crossing over
– linked genes may also seperate into different gametes
– Because of crossing over
– The farther apart two genes are on the same
chromosome, the greater the chance of crossing over
between them.
Why?

3. A B C D
Crossing over will disrupt linkage between A
and B more often than C and D

4. • Gene map
– The relative locations of each known gene on one
chromosome
Exact location on chromosomes
Chromosome 2

5. • Sex-linked
• Genes on the sex chromosome
(usually on x, called x-linked)
• Eg: Color blindness gene, Hemophilia
gene
• Pedigree: a chart that shows genetic
relationship in families
male female
mating
offspring in order
sex not known
Have disorder