BIOL 2153 Chapter : HW 7
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5). The table shows five different mutations of a small section of a gene.
Use the base-pairing rules to complete the second column. For each mutation, write the sequence for any mRNA codons that will be changed as a result of the mutation in bold. Write any codons that wonât be changed in regular font.
Using the genetic code chart from question #3, identify any stop codons in the mRNA molecules â write these codons in red
For each mutation, write any amino acids that will be changed in the last column in bold font. Use red XXXs to indicate any amino acids that will be missing as a result of stop codons and use use regular font indicate any amino acids that will not be changed.
| DNA (Template Strand) | mRNA codon | Polypeptide |
| Original DNA = GCAAGTACCTGA | CGU UCA UGG ACU | arg â ser â trp â thr |
| Mutation = GCCAGTACCTGA (nucleotide change underlined) | ____ ____ ____ ____ | ___ ___ ___ ___ |
| Mutation = GCACGTACCTGA (nucleotide change underlined) | ____ ____ ____ ____ | ___ ___ ___ ___ |
| Mutation = GCAAGTACTTGA (nucleotide change underlined) | ____ ____ ____ ____ | ___ ___ ___ ___ |
| Mutation = GAAGTACCTGA (first C deleted) | ____ ____ ____ ____ | ___ ___ ___ ___ |
| Mutation = GCAAGTACTGA (second C deleted) | ____ ____ ____ ____ | ___ ___ ___ ___ |
Question 4
Using the terms provided, complete the statements below. Some terms may apply more than once, while others may not apply at all. (15 points)
| Guanine histone Double helix Adenine conservative cytosine | Okazaki fragments Thymine introns Leading strand RNA polymerase 5-prime to 3-prime | Uracil chromatin DNA ligase Semi-conservative promoter | Lagging strand DNA polymerase nucleosomes Electron transport chain enhancer |
Watson and Crick determined that DNA exists in the form of a _______________, where two antiparallel chains of nucleotides wind around each other. The nitrogenous bases project to the interior where they hydrogen bond in specific pairs, ___________ with __________ and _____________ with ____________.Meselson and Stahl demonstrated that DNA is replicated by the _______________ model in which the parent molecule unwinds and each strand serves as a template for synthesis of a new strand. Synthesis of DNA is carried out by _________________, which builds the new strands in the ___________ direction. While the ______________ grows continuously; the _______________ is built in short sections called _________________, which will eventually be joined together by __________________. Eukaryotic __________________ is composed of DNA and _____________ proteins that bind together forming ________________________, the basic units of DNA packaging.
Question 5
In the table below, predict (yes or no) whether or not the E. coli lac operon will be transcriptionally active in the presence or absence of glucose or lactose as indicated and respond to questions "a" and "b."
| Lactose | Glucose | Lac expression? |
| No | Yes | |
| Yes | Yes | |
| Yes | No |
Explain each of your answers in terms of the molecular mechanisms that are known to underlie the regulation of the lac operon. Which mechanism is considered to be negative control and which is considered to be positive control? Explain.
Question 6
Use the genetic code table in your textbook to aid you in answering the questions below. (15 points)
a.) Use the genetic code table to deduce the amino acid sequence of a protein encoded by the mRNA shown here:
5âAUGAUUGGAGGUUUGAUCGGGCAAUAGGGGUUUCAGUAAAUG3â
b.) Explain how the above sequence in "a" illustrates that redundancy of the genetic code.
c.) Explain what would happen if a mutational event caused the underlined "G" to be changed to a "U"? What is the name for this kind of mutation?
