University of Iowa Human Biology Exam 2 with precise detailed answers

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University of Iowa Human Biology Exam 2 with precise || || || || || || || || ||




detailed answers ||




What is transcription?
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Transcription is the process by which a gene region of DNA is read 3'-->5' by RNA
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polymerase II while it synthesizes an mRNA transcript 5'-->3'.
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What are the reasons to have an RNA intermediate?
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-To keep the DNA protected in the nucleus.
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-So you can make many transcripts of 1 gene to amply expression
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-RNA is transient (it degrades), so you can change which genes are made into proteins
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Describe the first processes of transcription:
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Initiation: 4 things need to occur in order to initiate transcription:
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1. Open chromatin arrangement
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2. Gene-specific transcription factors bind DNA in activating orientation: activators bound
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& repressor removed
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3. General transcription factors bind DNA & make a beacon
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4. RNA polymerase locates beacon & binds DNA
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Describe the second process of transcription: || || || || ||




Elongation: RNA polymerase unwinds DNA, reads DNA, & synthesizes mRNA. mRNA
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sequence is determined by complementary base pairing between the template DNA strand
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and corresponding RNA bases.
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Describe the third process of transcription: || || || || ||




Termination: Termination sequence in DNA causes RNA polymerase to detach from DNA,
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mRNA then detaches from RNA polymerase.
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What is translation? || ||




rRNA (ribosome) and tRNA build a protein by reading the genetic code of the mRNA strand
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in the cytoplasm. Codons in the mRNA represent amino acids.
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Describe what is meant by each of the 6 properties of the genetic code:
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1.Triplet - codons are in sets of 3 RNA base pairs.
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2. Non-overlapping - mRNA bases are read only once in sets of 3. So, 9 mRNA bases consist
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of 3 codons and code for 3 amino acids.
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3. Degenerate - multiple different codons can be translated to the same amino acid.
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4. Unambiguous - each codon is always translated into 1 amino acid
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5. Punctuated- The same start codon AUG is at the beginning of EVERY transcript in
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EVERY live organism. Similarly, 3 stop codons are at the end of EVERY transcript in
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EVERY live organism. || ||




6. Universal - the same codons translate to the same amino acids in EVERY live organism.
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6. What are the 3 types of RNAs we talked about today, and what are their roles in the
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central dogma? ||




mRNA - a copy of a DNA protein coding region that is used to make proteins by tRNA and
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rRNA



tRNA - reads mRNA by matching anticodon region in tRNA to codons of mRNA. tRNAs are
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'charged' with amino acids, and drop off the corresponding amino acid according to the
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codon in the mRNA transcript.
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rRNA - ribosome - facilitates the reading and binding of tRNA to mRNA. Catalyzes the
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bond between the protein being made and the amino acids brought over by the tRNA.
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7. Describe what occurs during the first part of translation:
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Initiation - tRNA binds to the start codon (AUG) on the mRNA and this triggers the
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assembly of the rRNA on the mRNA transcript. || || || || || || ||




Describe what occurring during the second part of translation:
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Elongation - The E, P, and A sites on the ribosome guide the tRNAs as they read the mRNA.
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There are 3 mRNA base pairs in each of the 3 sites representing 1 codon in each site. The
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rRNA catalyzes the bonds between amino acids before the tRNAs leave through the E site.
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