Individual | Genotype |
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Purple Tomatoes
Have you seen the purple ketchup that young kids think is cool? Eeeeew! But what if you could grow a purple tomato?—you could make a fortune! After combing through 100s of tomato fields, you find a single tomato plant that produces purple tomatoes. You carefully cross it with an ordinary, red tomato plant and find that half of the offspring are purple and half are red. Thinking you’ll be able to find a pure-breeding purple tomato, you cross pairs of purple offspring. No matter how many crosses you make, though, you find that the offspring of purple x purple always come out mostly purple, but with a smaller number of red and a similar number that have an odd blue-ish color.
a. Give a genetic explanation for how purple color is produced.
b. Diagram the purple x red cross and the purple x purple cross to show that the results match those you expect based on your hypothesis. Be sure to define your symbols clearly.
A pedigree for Gaucher disease, a human genetic disorder resulting in anemia and problems with liver and spleen function, is shown below.
a. Gaucher disease is caused by a recessive allele. Give specific evidence from the pedigree that supports this conclusion.
b. If we assumed that the Gaucher allele is extremely rare in the population, could it actually be a dominant allele? Explain why or why not, using specific evidence from the pedigree.
c. What is the genotype of each of the following individuals: (i) II-4 Aa (ii) II-5 Aa (iii) I-2 Aa or AA
In cats, the gene for calico (multicolored) cats is codominant and sex-linked. Females that receive a B and an R gene have black and orange splotches on white coats. Males can only be black or orange, but never calico.
Here’s what a calico female’s genotype would look like.
a. What percentage of the kittens will be black and male? _________
b. What percentage of the kittens will be calico and male? _________
c. What percentage of the kittens will be calico and female? _________
2. Show the cross of a female black cat, with a male orange cat.
a. What percentage of the kittens will be calico and female? _____
b. What color will all the male cats be? _____
#4 Class Set - Do not write on!!
Draw your own Pedigree - Case study #1:
Albinism is a condition in which there is a mutation in one of several possible genes, each of which helps to code for the protein melanin. This gene is normally active in cells called melanocytes which are found in the skin and eyes. Melanin is the protein that gives your skin color. Albinism involves a significant reduction or absence of the production of melanin, giving affected individuals a lack of normal coloration to their skin/eyes.
Two normally-pigmented parents have 3 children. The first child (a girl) and their second child (a boy) have normal pigmentation. Their third child (a girl) has albinism. That girl marries a normally pigmented male and they have four children. The first three (two girls and a boy) have normal pigmentation. Their fourth child (a girl) has albinism like her mother.
Instructions:
1. Draw a pedigree showing all the individuals described in the problem. (Shade in affected individuals)
2. Label the genotypes of as many individuals in the pedigree as possible.
3. What is the mode of inheritance of albinism?
Genetic Counseling and Karyotypes
A couple expecting a baby have a routine screening for genetic abnormalities in their developing baby. While meeting with the genetic counselor after the meeting, the counselor shows them the karyotype of their child. (See the karyotype to the right)
How will the genetic counselor answer these questions for the parents?
What are the modes of inheritance for the shaded traits?
A)
B)
C)
Pregnancy and Blood Incompatibilities
Red blood cells have different proteins on their surface to help the body recognize them and let them do their job. One of the proteins that red blood cells have on them is called the Rh factor. Only some people have the Rh factor on their red blood cells: red blood cells don’t actually need it to function. People are either Rh+ (they have the Rh factor on their blood cells) or Rh-, they don’t have the factor on their blood cells. The Rh+ allele is dominant to the Rh- allele.
Another protein on the surface of red blood cells is the A/B/O protein. This determines your blood type. The A and B alleles are codominant, while the O allele is recessive. A person can have type A, B, AB, or O blood.
During labor, if an Rh- mother has a baby who is Rh+, her immune system may attack the baby’s red blood cells. Additionally, if a type O mother has a type A, B, or AB baby, her immune system may attack the baby’s red blood cells. Both of these issues can be treated if doctors know ahead of time.