Answers to Quiz#4:

Questions 1-4.  One of the two strands of a DNA molecule has the following sequence at a gene
        TACGGGCCGAAC

1.  What is the sequence of nucleotides on the other strand of DNA?
    ATGCCCGGCTTG

2.  What is the sequence of codons on the mRNA (using the original strand of DNA--TACGGGCCGAAC)?
    AUGCCCGGCUUG
    codon #1 = AUG
    codon #2 = CCC
    codon #3 = GGC
    codon #4 = UUG

3.  What is the anticodon sequence on the tRNAs?
    UAC (corresponds to codon #1)
    GGG (corresponds to codon #2)
    CCG (corresponds to codon #3)
    AAC (corresponds to codon #4)

4.  What is the sequence of amino acids? Remember to use the codon sequence on the mRNA NOT the anticodons on tRNA!
        methionine--proline--glycine--leucine

5.  Suppose that the original DNA strand has a mutation so that the sequence becomes
        TACGGGCCGAAG
What effect will the mutation have on the protein, if any?  Explain.

The mutation in the last codon will change the amino acid that goes into the protein at that point. Rather than leucine (coded for by codon #4 UUG), this protein will have phenylalanine in that position (coded for by mutated codon #4 UUC).  Therefore, that protein will be different since it no longer has the same sequence of amino acids (the primary structure).  A different primary structure will potentially change the three dimensional structure of the protein (secondary, tertiary, and quartenary structures) such that the protein may no longer function like the protein produced from the original strand.
However, had the mutation occurred in the third "letter" (nucleotide) of the second or third codon (CCC or GGC) then there would have been no effect on the protein because the third nucleotide ("letter") in these codons is redundant (could put A, C, G, or U in the third position and you would get the same amino acid).  For example, had CCC been changed to CCA, CCG, or CCU, you will still get proline.
This redundancy has led many scientists to hypothesize that the earliest cells probably only had a two "letter" (nucleotide) genetic code (i.e. the codons were only two nucleotides long rather than 3).  If you look at the genetic code, many amino acids are not affected by which nucleotide is in the third position in the codon.  The few amino acids that are affected may have evolved after the genetic code became a 3 "letter" code rather than a 2 "letter" code.

6.  Albinism is a recessive trait that results in a lack of pigmentation in the skin.  Suppose a man and woman who both have normal skin pigmentation want to know the probability of producing an albino child.  The man's brother was albino (i.e. his parents with normal skin pigmentation produced an albino child), but the woman's family has no history of albinism.  What is the probability (chance) that this couple will have an albino child?

First, set up the alleles.  I will use A = "normal" pigmentation and a=albino.  Next, decide on the possible genotypes of the parents.  Since the woman's family has never produced any albino individuals, she is most likely homozygous dominant for this trait.  However, you do not know that for sure because she could carry the recessive allele as a heterozygote.  The man may be heterozygous since both of his parents were also heterozygous (he had a 50% chance of being heterozygous and a 25% chance of being homozygous dominant), or he could be homozygous dominant.  To answer this question you need to set up all possible crosses between these two people who both have the dominant phenotype:
If the woman AA x man Aa--possibility of producing an aa child = 0/4 or 0%
If the woman Aa x man AA--possibility of producing an aa child = 0/4 or 0%
If the woman AA x man AA--possibility of producing an aa child = 0/4 or 0%
If the woman Aa x man Aa--possibility of producing an aa child = 1/4 or 25%
Therefore, if either the man or the woman are homozygous dominant then the possibility of producing an albino child is 0.  However, if both of them are heterozygous, they have a 25% chance of producing an albino child.
Technically if you add of all of their probabilities they only have a 1 in 16 chance of producing an albino offspring without knowledge of their genotype as AA or Aa, but I would be satisfied with your answer if you set it up like I outlined above.