1. Pedigrees and Sex linked Traits
Part 4

2. What is a PEDIGREE A chart used to trace traits throughout a family
Parts of the chart
Circle = females
Squares = males
Half-filled in/Dotted = carrier
Have the gene but do not show signs of it
Filled-in = affected
Have both the gene and symptoms of that trait

3. Pedigrees - A chart used to trace traits through generations of a family -

4. How can a pedigree trace a trait ?
Circle = females
Squares = males
Half-filled in= carrier –
they have the gene but do not show signs of the disorder
Heterozygous – they can pass it on to their offspring
Filled-in = affected
Have both the gene and symptoms of that trait

5. Bellwork: 10/30 Ifc: The following pedigree shows cystic fibrosis
1.Does anyone in generation 3 have cystic fibrosis?
2. Does generation 3 have any carriers?
3. How many female offspring did the first generation have?
How many of the offspring in generation 2 were affected?
4. Describe individual 4 in generation 3 5

6. Sex chromosomes and sex linked disorders

7. How is the sex of offspring determined?
Sex chromosomes – determine the sex of an individual
Y or X
Males = X and Y - XY
Female = X and X- XX

8. Which parent determines the sex of the offspring?XY
male X Y XX
Female X X
It is the male that determines the sex of the offspring.

9. What are Sex-Linked Traits?
Traits controlled by genes located on sex chromosomes (X or Y)
Most are on X chromosome
Traits on the sex chromosomes are passed on differently than traits on the rest of the chromosomes.

10. What are sex linked disorders – a disease or trait on the sex chromosomes
XX - female can be a carrier or have the trait if she has the gene on both
XY male – if it is on the x chromosome, they only need 1 allele to get the disorder.
They show up more in males because they only need one gene to get it and females need both. 10

11. Red-green color blindness
Can not distinguish red from green.
Normal red-green
Red-green colorblind
Some 10 million American men—fully 7 percent of the male population—either cannot distinguish red from green, or see red and green differently from most people. This is the commonest form of color blindness, but it affects only .4 percent of women.
There are three basic variants of color blindness. Red/green color blindness (deuteranopia) is the most common deficiency, affecting 8% of Caucasian males and 0.5% of Caucasian females. The prevalence varies with culture.
Blue color blindness (protanopia) is an inability to distinguish both blue and yellow, which are seen as white or gray. Protanopia is quite rare and has equal prevalence in males and females.

12. What a red-green colorblind person would see
Normal
Red-green colorblind