1. The Chromosomal Basis of Inheritance
Marie Černá

2. Thomas Hunt Morgan 1910s - 20s

3. Morgan’s experiments fruit fly: Drosophila melanogaster
prolific breeders (100s of offspring / 2 weeks)
4 pairs of chromosomes (8, XY; 8, XX)

5. Morgan’s laws linked genes on the same chromosome
are located linearly in the gene loci
tend to be inherited together

6. Genetic recombination
Independent assortment of chromosomes (unlinked genes)
- 50% frequency
crossing over (linked genes)
- the greater the distance between two genes,
the more points there are between them
where crossing over can occur
1 centimorgan = 1% recombination frequency

7. Genetic maps linkage map - based on recombination frequencies
cytological map
- based on stained bands of chromosomes
that can be seen in the microscope
genetic map
- based on DNA nucleotide sequences

8. Sex determination in mammals (humans), some insects (fruit flies)
in some insects
(grasshoppers, crickets, roaches)
in birds, some fishes,
some insects (butterflies, moths)
in bees and ants

9. Literature Biology, eighth edition, Campbell, Reece
Unit three: Genetics
Chapter 15:
The Chromosomal Basis of Inheritance
Pages