1. INTRODUCTION TO LINKED GENES AND SEX LINKAGE H. Biology/ Ms. Kim

2. Locating Genes on Chromosomes
Are located on chromosomes
Code for protein that determines specific traits.
Figure 15.1

3. Gene Linkage Linked genes
Usually inherited together because located near each other on the SAME chromosome
Genes closer together on the same chromosome are more often inherited together
Each chromosome
Has 100’s or 1000’s of genes
Sex-linked genes exhibit unique patterns of inheritance; genes linked on the X or Y chromosome

4. What is gene linkage?
Thomas Hunt Morgan (1910) noticed that eye color in fruit flies and wing size always seemed to be inherited together in offspring.
This seemed to go against Mendel’s Law of Independent Assortment
Morgan discovered chromosomes are a group of linked genes
Law of Independent Assortment was still true, but chromosomes assort independently, not genes.

5. Gene Linkage
Genes located on the same chromosome will NOT sort independently
They will be inherited together
Gene Linkage:
Tendency of 2 alleles (for different traits) to be inherited together
The closer the genes are, the more likely they are to be inherited together
Probability that two genes will be inherited together is related to the distance between them

6. Mendel’s Principle of Independent Assortment?
Remember: this refers to genes on separate chromosomes
Gene 1
Gene 2

7. What would cause genes on the same chromosome to be inherited separately?
Crossing over!

8. What is gene mapping?
Location of Gene on a chromosome is it’s LOCUS