Color Blindness

Nancy Paguay & Zinani Harriot

2/1/2010

Period. 9/10

Summary of Genetic Disorder• http://www.nlm.nih.gov/medlineplus/ency/imagepages/9962.htm

• This genetic disorder affects the perception of color. There are some cases that may be a very mild difficulty of seeing colors,

while others have a total difficulty with seeing any color.• symptoms: • trouble seeing colors and the brightness of colors in the usual

way• incapable of noticing the different shades of the same or

similar colors• Interesting Facts:• 3 types of color blindness• most common is red-green vision defects. This type occurs

more in men than in women. The other two are blue-yellow and complete absence of color vision.

Are You Color Blind!?!?!?!

What chromosome is your disorder located on?

•May be more than one.•Include a picture

Mode of Inheritance

• How would one acquire the genetic disorder? (Yours may be sex linked, autosomal recessive or autosomal dominant)

• What does sex linked/x-linked, autosomal recessive or autosomal dominant mean? (What does autosomal refer to and what does recessive/dominant refer to? What does “sex linked/x-linked)” refer to?)

• If your disorder is not well understood, explain.• If the disorder has other modes of inheritance,

explain.

Explain what alleles are.

•How many alleles does each person have per gene•Where they come from•How we represent recessive or dominant alleles

-RR, rr, Rr•What is dominance and recessiveness?•Sex linked (x-linked) is represented with XR, or Xr, or Y

Make a punnett square to demonstrate the probability per child depending on the parents

•Make more than one punnett square. Parents determine the ratio of probability of offspring having the genetic disorder. Explain(see below) to the

class how the punnett square works.•Female is on the left and father is represented on the top.

•*** Each punnett square represents the probability PER CHILD. Not all of the children parents may have. ***

• homozygous dominant• heterozygous dominant• homozygous recessive

Use the same punnett square model to…

Explain probability using:•Ratios(must equal 4 because there are 4 possibilities)

•Percentages (must equal 100 because there are 4 possibilities 25% each)

1 : 2 : 11GG : 2Gg : 1gg

25% : 50% : 25%25%GG : 50%Gg : 25%gg

homozygous dominant:heterozygous dominant:homozygous recessive

homozygous dominant:heterozygous dominant:homozygous recessive

Use the same punnett square to use as your model to explain…

• What these letter mean! GG? Gg? gg?

•Phenotype (what you SEE)

GG= GREEN

Gg= GREEN (yellow gene carrier)

gg = yellow

•Genotype (what is in the GENES)GG= Homozygous dominant (GREEN)

Gg= Heterozygous dominant (GREEN)

gg = homozygous recessive (yellow)

If G represents the dominant allele GREEN and g represents the recessive allele yellow, then we can assume that:

Use the same punnett square model to…

Explain Genotype and Phenotype probability using:

• Phenotype -Ratios- 3 GREEN : 1 yellow- Percentages- 75% GREEN : 25% yellow

• Genotype- Ratios- 1GG : 2 Gg : 1 gg - Percentages- 25% GG: 50% Gg : 25%gg

Student PracticePunnett Square Practice

You provide genes for the students: only parents and student fill in the box genotypes and phenotypes

Genotype:Ratio:

Percentage:

Phenotype:Ratio:

Percentage:

- When the students are finished, ask them to share their answers with you. Use the custom animation option to

hide the answers until students have

shared theirs with you.

Lastly, a 3 generation hypothetical Pedigree

Circle = female

Square = male

All White= homozygous recessive gene, person is fine, has 2 copies of the “healthy” gene

All Green= homozygous dominant, person have disorder and 2 copies of the “bad” gene

Half Green/Half White= because this is a dominant disorder (rules of dominance), the person has the disease and only has one copy of the “bad” gene and one copy of the “healthy” gene.

Autosomal Dominant Autosomal Recessive

White= Person is fine. May possibly carry the recessive “bad gene.” Can have one “health” and one “bad” gene of two “healthy genes.”Black= Person is affected. Has 2 “bad” genes.

X-linked

Color gene is “bad” on x chromosome

Color gene is “healthy” on x chromosome

Color gene is “healthy” on x chromosome

One gene is “bad”, one gene is “healthy” on the x chromosome Female is fine.

3 generations, (I: two parents II: 3 children and two spouses III: 4 children, any combo( explain how to READ your punnett square)

Student Practice(you provide generation I, 2, and 3)

Show a pedigree like this, but you fill in the rest using a different sample than the previous page. You choose male and female, who is married to who (you have to add 2 spouses, and who has

children in the Generation III.

I

II

IIIExample:***Ask 3 questions (type them on this page) to make sure the students can analyze a pedigree. (NO yes/no answers) 1. 2. 3.

Example:***Make a key: circle=

square= shaded in= not shaded in= half shaded in=

Father’s Genes