Multiple choice. 2 points each. Pick the best answer for each question. 1. What

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Multiple choice. 2 points each. Pick the best answer for each question. 1. What is the definition of a "gene"? a. Fundamental unit of chemical information b. Functional region of RNA c. Continuous segments along a protein molecule d. A unit of heredity transferred from offspring to parent that holds some characteristic e. a locata ble region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions, and or other functional sequence regions 2. How many origins of replication are found on a human chromosome? a. 0, origins are specific to prokaryotic plasmids b. 1, replication starts in the middle and proceeds bi-directionally c. 2, replication starts at each end, near the telomere d. 3, with random replication origins throughout the chromosome e. Many, depending on the chromosome 3. Which of the following statements about mRNA processing is NOT true in A 7-methylguanosine moiety is added to the 5' region of the mRNA. Splicing removes introns from pre-mRNA using a complex called the Spliceosome. eukaryotes? b. Addition of up to 200 adenine nucleotides occurs at the 3' end of the mRNA Translation begins as the transcript is released from the RNA polymerase. 4. Which statement is true regarding alternative splicing? a. Alternative splicing increases the variety of proteins that can be produced. b. Alternative splicing allows exons from two distinct RNAs to be spliced into a novel protein. c. Alternative splicing removes exons from a pre-mRNA instead of introns. dAlternative splicing allows for increases in genome size relative to organisms that do not complete alternative splicing. Alternative splicing allows for removal of amino acid regions that are unnecessary for protein activity

Explanation / Answer

Option E is correct which states that a gene is a locatable region of the genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions (enhancer, promoter) transcribed regions (coding region) and other functional sequence regions (UTRs). Option E is correct which states that many origins of replication are found in the human chromosomes depending on the chromosome. Infact, in case of eukaryotes multiple origins of replication are found on each linear chromosome. These initiate at different times enabling faster duplication of large amounts of DNA sequences (known as replication timing). Option D is correct, i.e, it is not true. Translation in eukaryotes does not begin as soon as the transcript or pre-mRNA is released from the RNA polymerase. Instead, it undergoes %’ capping and Poly A tailing followed by RNA splicing to remove the introns in order to produce a mature mRNA. This mature mRNA is then transported out of the nucleus to be translated by the ribosomes in the cytoplasm. Option A is correct which states that alternative splicing increases the variety of proteins that can be produced from a single gene. This is brought about by including/excluding different exons from the processed mRNA. Mechanisms include exon skipping, alternate acceptor and donor splice sites, intron retention, and so on. With respect to option B which is also incorrect, it is trans-splicing which enables exons from two different mRNA to be joined to form a novel protein. Alternative splicing therefore allows a cell to produce different proteins (isoforms) from the same gene.

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