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UIowa Human Biology, Exam 2 questions with complete solutions rated A+
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UIowa Human Biology, Exam 2What is transcription? - correct answer ✔✔Transcription is the process by which a gene region of DNA is
read 3'-->5' by RNA polymerase II while it synthesizes an mRNA transcript 5'-->3'.
What are the reasons to have an RNA intermediate? - correct answer ✔✔-To keep the DNA protected in
the nucleus.
-So you can make many transcripts of 1 gene to amply expression
-RNA is transient (it degrades), so you can change which genes are made into proteins
Describe the first processes of transcription: - correct answer ✔✔Initiation: 4 things need to occur in
order to initiate transcription:
1. Open chromatin arrangement
2. Gene-specific transcription factors bind DNA in activating orientation: activators bound & repressor
removed
3. General transcription factors bind DNA & make a beacon
4. RNA polymerase locates beacon & binds DNA
Describe the second process of transcription: - correct answer ✔✔Elongation: RNA polymerase unwinds
DNA, reads DNA, & synthesizes mRNA. mRNA sequence is determined by complementary base pairing
between the template DNA strand and corresponding RNA bases.
Describe the third process of transcription: - correct answer ✔✔Termination: Termination sequence in
DNA causes RNA polymerase to detach from DNA, mRNA then detaches from RNA polymerase.
What is translation? - correct answer ✔✔rRNA (ribosome) and tRNA build a protein by reading the
genetic code of the mRNA strand in the cytoplasm. Codons in the mRNA represent amino acids.
Describe what is meant by each of the 6 properties of the genetic code: - correct answer ✔✔1.Triplet -
codons are in sets of 3 RNA base pairs.
, 2. Non-overlapping - mRNA bases are read only once in sets of 3. So, 9 mRNA bases consist of 3 codons
and code for 3 amino acids.
3. Degenerate - multiple different codons can be translated to the same amino acid.
4. Unambiguous - each codon is always translated into 1 amino acid
5. Punctuated- The same start codon AUG is at the beginning of EVERY transcript in EVERY live organism.
Similarly, 3 stop codons are at the end of EVERY transcript in EVERY live organism.
6. Universal - the same codons translate to the same amino acids in EVERY live organism.
6. What are the 3 types of RNAs we talked about today, and what are their roles in the central dogma? -
correct answer ✔✔mRNA - a copy of a DNA protein coding region that is used to make proteins by tRNA
and rRNA
tRNA - reads mRNA by matching anticodon region in tRNA to codons of mRNA. tRNAs are 'charged' with
amino acids, and drop off the corresponding amino acid according to the codon in the mRNA transcript.
rRNA - ribosome - facilitates the reading and binding of tRNA to mRNA. Catalyzes the bond between the
protein being made and the amino acids brought over by the tRNA.
7. Describe what occurs during the first part of translation: - correct answer ✔✔Initiation - tRNA binds to
the start codon (AUG) on the mRNA and this triggers the assembly of the rRNA on the mRNA transcript.
Describe what occurring during the second part of translation: - correct answer ✔✔Elongation - The E, P,
and A sites on the ribosome guide the tRNAs as they read the mRNA. There are 3 mRNA base pairs in
each of the 3 sites representing 1 codon in each site. The rRNA catalyzes the bonds between amino acids
before the tRNAs leave through the E site.
Describe was occurs during the third part of translation: - correct answer ✔✔Termination - When a stop
codon is reached. No tRNA comes to bind to it, and the rRNA disassemble and releases the protein.
What role do histones play in gene expression? - correct answer ✔✔They hold information to
decondense DNA into an open arrangement when a gene needs to be expressed
DNA is read in this direction by RNA polymerase - correct answer ✔✔3' --> 5'
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