Mastering Biology Chapter 17

Life as we know it depends on the genetic code: a set of codons, each made up of three bases in a DNA sequence and corresponding mRNA sequence, that specifies which of the 20 amino acids will be added to the protein during translation. Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that there are only 2 bases (A and T) in the Martian DNA, and there are only 17 amino acids found in Martian proteins. Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms? 2 bases 3 bases 4 bases 5 bases 6 bases The answer cannot be determined from the information provided.

5 Bases

Based on the genetic code chart above, which of the following would be the result of this single base-pair substitution? a silent mutation (no change in the amino acid sequence of the protein) a missense mutation causing a single amino acid change in the protein a frameshift mutation causing a single amino acid change in the protein a nonsense mutation resulting in early termination of translation a frameshift mutation causing extensive change in the amino acid sequence of the protein

A nonsense mutation resulting in early termination of translation

After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? A translation stop codon is added at the 3' end of the pre-mRNA. Coding sequences called exons are spliced out by ribosomes. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.

A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA

What is the function of RNA polymerase? It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule. It relies on other enzymes to unwind the double helix. It unwinds the double helix and adds nucleotides to a growing strand of RNA. It adds nucleotides to the 5' end of the growing mRNA molecule. All of the above.

It unwinds the double helix and adds nucleotides to a growing strand of RNA

Protein targeting pathways: PFK and Insulin Choose between: a) Golgi -> ER-> outside of Cell b) ER-> Cytoplasm c) Cytoplasm only d) Cytoplasm -> ER -> outside of cell e) ER -> Golgi -> Cytoplasm f) ER -> Golgi -> outside of cell g) Cytoplasm -> Golgi -> Outside of cell h) Nucleus -> Cytoplasm

PFK: Cytoplasm only Insulin: ER -> Golgi -> outside of cell

During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand? the location along the chromosome where the double-stranded DNA unwinds the base sequence of the gene's promoter which of the two strands of DNA carries the RNA primer the location of specific proteins (transcription factors) that bind to the DNA

The base sequence of the gene's promoter