In humans there is a dominant allele (A) for the absence of moles; while the recessive allele (a) results in the presence of moles. A couple who are both heterozygous for this locus (Aa) plan to have seven children. a. Expand the binomial (p + q)7.
b. What is the probability that:
(i) The first child that is born will not have moles.
(ii) All of the children will have moles.
(iii) The first two children will have no moles and the last five will have moles.
(iv) Of the 7 children, 4 will have no moles and 3 will have moles
c. Assume this couple now have two children, one with moles and one without moles. What is the probability that the child born without moles is a carrier of the a-allele (ie heterozygous)?


Answer 1


a. (p + q)^7 = p^7q^0+7p^6q+21p^5q^2+35p^4q^3+35p^3q^4+21p^2q^5+7pq^6+p^0q^7

b. i. 0.75

   ii. 0.000061

   iii. 0.012

   iv. 0.17

c. 0.67


a. The expansion of the binomial (p + q)7 would be such that:

(p + q)^7 = p^7q^0+7p^6q+21p^5q^2+35p^4q^3+35p^3q^4+21p^2q^5+7pq^6+p^0q^7

b. Both couples are heterozygous:

             Aa    x    Aa

         AA   Aa   Aa   aa

Since A is dominant over a,

probability of having mole (aa) = 1/4

probability of not having moles = 3/4

Therefore, the probability of the first child not having moles = 3/4 or 0.75

ii. Let the probability of not having mole = p and the probability of having mole = q. From the binomial expansion:

(p + q)^7 = p^7q^0+7p^6q+21p^5q^2+35p^4q^3+35p^3q^4+21p^2q^5+7pq^6+p^0q^7

Probability that all of the children will have moles = p^0q^7

since p = 3/4 and q = 1/4

p^0q^7 = (3/4)^0(1/4)^7 = 0.000061

iii.Probability that the first two children will have no moles and the last five will have moles = 21p^2q5

                       = 21(3/4)^2(1/4)^5

                         = 0.012

iv. Probability that 4 will have no moles and 3 will have moles out of the 7 children = 35p^4q^3

               = 35(3/4)^4(1/4)^3

                      = 0.17

c. Probability that the child born without moles is a carrier of the a-allele  = probability of heterozygous.

From the cross in (b), the genotypes of those born without moles are AA and 2Aa. Therefore, the probability of not having moles and be Aa is:

      = 2/3 or 0.67

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Imagine you discover a yeast mutant that exhibits a general inability to grow and thrive compared to wild-type yeast. You predict that the mutant has a defect in a basic process necessary for survival and therefore examine the cellular levels of 200 common proteins, as well as the levels of tRNAs and rRNAs. You discover that tRNA and rRNA levels are normal, but the levels of all of the proteins you examine are much lower than they are in the wild-type yeast. This suggests that there is a general defect in:



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c. an operon
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A repressor is a protein capable of inhibiting target gene expression by binding to both operator sites and gene silencers. A DNA-binding repressor inhibits the interaction between the RNA polymerase and the DNA promoter sequence, thereby suppressing transcription into RNA. Moreover, the RNA-binding repressor is a protein that binds to the messenger RNA (mRNA) molecule in order to prevent its translation into protein. An inducer can start transcription by interacting with the repressor, thereby separating it from the DNA operator sequence.

1) The sugar found in RNA is called deoxyriboseA) True
B) False

2)The process of translation occurs at the ribosome

B) False

3)Transcription must occur before translation may occur

A) True
B) False



1. False

2. True

3. True


hope this helps you :)

Final answer:

RNA contains ribose, not deoxyribose. Translation occurs at the ribosome. Transcription must occur before translation.


1) The sugar found in RNA is called deoxyribose

B) False

RNA contains the sugar ribose, not deoxyribose. Deoxyribose is the sugar found in DNA.

2) The process of translation occurs at the ribosome

A) True

Translation is the process of synthesizing proteins from mRNA at the ribosome.

3) Transcription must occur before translation may occur

A) True

Transcription is the process of synthesizing mRNA from a DNA template. It occurs before translation can begin.

Learn more about RNA, Translation, Transcription here:


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Using microscopy methods such as fluorescence microscopy and polymerase chain reaction (PCR).


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