Genetic questions

真城

Hi everyone,
Can you explain why the following answers are correct? @@"
Thanks ~

Q1)If each parent can produce 100 genetically distinct gametes, how many genetically distinct offspring can two parents produce?


Correct answer: 10,000




Q2)A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are _____.


correct answer: codominant




Q3)A single genetic locus that controls more than one trait is said to be _____.


correct answer:pleiotropic





Q4)Tom's brother suffers from phenylketonuria (PKU), a recessive disorder. The brothers' parents do not have PKU. What are the chances that Tom, who is normal for this trait, is a carrier of PKU?


correct answer:2/3



thz again^^

fish

原帖由 abc666 於 11/3/2008 06:28 PM 發表

                               
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但應該是Incomplete dominance...
Incomplete dominance是dominant的allele的特徵不是完全表現出來
特徵,如顏色,多是兩個allele的顏色的中間,如某花的allele是紅色和白色,表現型是粉紅色
codominant是兩個allele的特徵同時顯現,如有1個a blood type allele 和b blood type allele的人的血形是ab型而不會是a或b型

an intermediate color that is caused by thepresence of both red and white hairs

Because both colors are present, it is codominant.

A single genetic locus that controls more than one trait is said to be _____.

Pleiotropy : The prefix "Pleio-" means multiple
The property of a gene that has multiple phenotypic effect is called pleiotropy.

Tom's brother suffers from phenylketonuria (PKU), a recessive disorder. The brothers' parents do not have PKU. What are the chances that Tom, who is normal for this trait, is a carrier of PKU?

Conditional Probability:
P(Carrier |  Normal)  <---This means probability/chance as a carrier if you are normal

Let B = dominant allele   
       b =  recessive allele

Since his brother has PKU, which is a recessive disorder, his parents MUST both have genotype Bb
看不到下圖按我

                               
登錄/註冊後可看大圖

Given that Tom is Normal, he should be either one of the three genotype underlined.
If he is a carrier, he would have Bb. Based on the diagram above.
There are 2 Bb within the 3 possibilities. P(Carrier |  Normal)  = 2/3

[ 本帖最後由 fish 於 12/3/2008 04:12 AM 編輯 ]

abc666

1. 100的2次方
試想mother有a和b,father有c和d的gametes
可能的offspring是ac,ad和bc,bd=2的2次方

2.直接的ans...
但應該是Incomplete dominance...
Incomplete dominance是dominant的allele的特徵不是完全表現出來
特徵,如顏色,多是兩個allele的顏色的中間,如某花的allele是紅色和白色,表現型是粉紅色
codominant是兩個allele的特徵同時顯現,如有1個a blood type allele 和b blood type allele的人的血形是ab型而不會是a或b型

3.不懂

4.let normal allele be A,有病的be a
tom BROTHER有病,病的allele是recessive,所是tom的phenotype是aa
one allele comes from father and the other one comes from mother
parents are normal
sothey are heterozygous,Aa

parents              Aa               Aa

gametes      A         a                   A    a
F1                 AA        Aa             Aa               aa

P(carrier)=2/4
但之後的P( carrier  |  already known isnormal)忘了怎計

[ 本帖最後由 abc666 於 11/3/2008 06:37 PM 編輯 ]