Have some questions

by **bleet** on Sun Feb 05, 2006 7:02 pm

sorry if this is posted int he wrong area but my class is human biology so i just came here

I have these questions and some I dont understand completely and others I want to know if I have them right.

#1. Freckle sare an autosomal dominant trait.
Elizabeth has freckles but her husband Benny does not have freckles. You also are good friends with Elizabeth's parents, Elizabeth's mother has freckles but Elizabeth father's does not have freckles. You can answer all her questions which are listed below.

1. What are the genotypes of the Parents?
my answer: Elizabeth=Ff and her husband =ff
2. What are the genotypes of the grandparents?
my answer: I didnt understand this question because I dont know any way of figuring this out from the information I was given.. need help on this 1.
3. What is the probability the child has freckles?
my answer: 50%
4. What is the probability the child does not have freckles?
my answer: 50%
5. Provide the Punnet Square to support your answers.
my answer: I used a punnet square Ff by ff to get these answers

#2. A tropical plant found in Africa has the dominant traits of black bark and blue flowers, the recessive traits are expressed as smooth bark and white flowers. If two heterozygous plants were crossed what would be expected probabilities for all the possible offspring for these two traits. Please include your Punnett Square.

my answer: I'm not sure what it means exactly by "crossed" so I'm not sure how to do this question someone please explain.

#3. There is a disorder that causes short stature commonly known as "Dwarfism" and genetically referred to as "Achondroplasia". Dwarfism is an autosomal dominant trait. If a mother has Dwarfism and the father has normal height, Answer the following Questions:
1.What are the genotypes of the parents?
my answer: like number 2 in question #1 im not sure how i would determine the genotypes if it doesnt say heterozygous or homozygous.. explain please

2. Include a Punnet Square to show what all the probabilities of having a child with Achondroplasia.
my answer: can really answer without understanding question 1.

#4. If both parents have the disease of colored-blindness (X lined recessive) what:
1. is the probability that they have a son that is color blind?
my answer: 100%
2. is the probability that they have a daughter that is color blind?
my answer: 100%

For these answers I used A Punnet Square XcXc by XcY and I came up with this.. is this correct?
#5. A person with type A blood has a child with person, who is type B. Using a Punnet Suares indicate all the possible outcomes and probabilities for their children's blood type.
my answer: this 1 I didnt understand much because the different Blood types.. A,B,AB,O so this 1 I would need help with also

Please help

and sorry for the long post

these are review questions for the final which helped me understand alot but also some i still dont understand

by **Poison** on Sun Feb 05, 2006 10:43 pm

I like the people who tries first and then ask.

OK, so;
#1: you can have 2 possibilities for grandma and 1 for grandpa. (make sure that you are not given an info like: Elizabeth has a sister/brother that does not have freckles. If so, the grandma's genotype will be determined exactly.)
#2:cross: You obtain the offsprings. For an easier explanation, you make a punnet square and you"cross" the traits. It is the thing you already do.

#3: You can figure out the father's. And the mother can be either homozygote or heterozygote. I think that's why it says "probabilities".
Means you will have 2 punnet squares. You will cross homozygote and heterozygote mother with the father one by one.
#4: Right
#5: A is dominant over O. B is dominant over O. A and B are co-dominant. So a person with blood group A can be either AO or AA. Same for B. If you cross A and B you will have the blood group AB. I think you can do the rest.

Ask if something is not clear.

PS: It is more genetics than human bio. I hope you don't mind me moving it.

by **bleet** on Mon Feb 06, 2006 2:59 am

thanks for replying

. I understand the questions alot more now but just wanted to make sure I got most (hopefully all) correct

I went over the questions again and I came up with these.
#1 I'll have to ask my teacher about this once since it has 2 possible answers

thanks

#2 i came up with 75% Black bark and 25% smooth bark

#3 question 1: Mother-XdX and Father-XY
#3 question 2: 1 son and 1 daughter have Dwarfism and 1 son and 1 daughter do not.
#5 AB is the only possibility for the child? so since the question is asking about the phenotypes, the genotypes AA,AO and BB,BO dont matter if its talking about the blood type do they?
Thanks again for the help

really appreciate it.

by **Poison** on Mon Feb 06, 2006 6:40 pm

For #3: It says "autosomal" . Don't be mistaken. If you use X or Y for a question like that, you will probably get 0.

And you have 2 possibilities for the mother. You skipped that. It does not say the mother is homozygote or heterozygote. Go through that again.

Give your possibilities as %. That's what teachers like. Don't saysomething like " son and 1 daughter have Dwarfism and 1 son and 1 daughter do not. " kind of thing. We are talking about "probabilities". I mean, if you say like that, the teacher will say: "so, is it guaranteed to have that exactly". Teachers like those kind of arguements.

#5: They do. Think about that again. Cross the letters one by one. you will cross: AAxBB and AOxBB and AAxBO and AOxBO and obtain possibilities. Even if the question is asking about phenotypes, do the crossing. You may have children with: A or B or AB groups. Do that and see. (It does not say "heterozygote" or "homozygote" for the parents.)