3. Genes that are located close together on the same chromosome are linked Those genes may be inherited together The total human genome (all of the different genes in humans) is …………

4. How many genes make up the human genome?

6. Sex- Linked Genes- Any gene located on a sex chromosome Most sex-linked genes are located on the X chromosome

7. Sex-Linked genetic disorders mostly affect males b/c they only have one X c’some Many genes on the X c’some do not exist on the Y c’some

8. Common Sex-Linked Genetic Disorders Colorblindness; a defective gene for vision color which is located on the X c’some

9. Hemophilia; two defective genes to control blood clotting located on the X c’some

11. A scientist May Lyon discovered that in human females one X c’some is randomly switched off. Once the X c’some is turned off a dense area in the nucleus is formed. This dense area is called a Bar Body The same process happens in other mammals

13. Nondisjunction- happens when homologous c’somes do not separate. The result: an abnormal amount of chromosomes will be in the gametes Down Syndrome- a disorder that results from an extra copy of chromosome 21