MCB4304 Study Guide Exam 1 Questions & Answers 2024/2025
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MCB4304 Study Guide Exam 1 Questions & Answers 2024/2025
In addition to the "Central Dogma" what are some recent relevant emerging topics? Which one do you think is most interesting and why? - ANSWERSSome recent emerging topics are epigenetics, genetic engineering of chromosomes. CRISPR.
Di...
MCB4304 Study Guide Exam 1
Questions & Answers 2024/2025
In addition to the "Central Dogma" what are some recent relevant emerging topics? Which one do you
think is most interesting and why? - ANSWERSSome recent emerging topics are epigenetics, genetic
engineering of chromosomes. CRISPR.
Differentiate nucleotide from nucleoside. - ANSWERSnucleotide: sugar, base, and phosphate group.
nucleoside: only pentose sugar and nitrogenous base
Why is the DNA/RNA orientation 5' -> 3'? - ANSWERSnucleotides can only add to the 3' end at the free
hydroxyl group. It is arranged this way due to polarity and the negatively charged phosphates must point
up in relation to the rest of the strand in the internal part of the DNA helix.
Okazaki fragment - ANSWERSa short segment of DNA transcribed on the lagging strand of the DNA.
Why are Okazaki fragments synthesized in small fragments? - ANSWERSbecause the 5'-3' direction of
synthesis in the lagging strand opposes the overall direction that transcription is occurring in the
molecule as it is complementary and flipped in orientation, so it must be made in small fragments then
bound together with the rest of that molecule while it waits for more DNA fragments to open up.
Where are the DNA, RNA, and protein located in a eukaryotic cell? - ANSWERSDNA: nucleus
RNA: nucleus and cytoplasm (used as RNA pols, and template mRNA)
proteins: nucleus for synthesis then transported out of the cells.
What is an allele? - ANSWERSa set of codons (gene) that code for a certain trait. there is often a
dominant and a recessive allele and they create certain traits in an individual.
what is a gene variant? - ANSWERSa version of a gene which can exhibit multiple different phenotypes
but it is for the same trait, such as the dominant and recessive alleles mixing in either homozygous or
heterozygous manners. An example of multiple allelism is blood type.
,What is the importance of the minor and major grooves of the DNA molecule? - ANSWERSthey allow for
proteins to bind to the helix and recognize base pairs from the outside of the molecule in the major
grooves. the presence of the minor grooves allow the major grooves to have room for this binding and
recognition to occur rather than all being the same distance apart per turn.
What was wrong with Linus Pauling's DNA structure molecule? - ANSWERSIt did accurately show the
negatively charged phosphate groups on the interior of the twist, but it showed that there were three
strands and that the phosphates were neutral and bound to each other in the middle of the twist.
What is crossing over and why is it important? Why can the distance between genes in the same
chromosomes affect genetic mutation? - ANSWERScrossing over occurs during meiosis and it creates
unique expressions of alleles and genes that is unique to the offspring and not identical to either parent.
the distance between genes affects recombination because if the genes are further apart they are more
likely to recombine independently and are not linked to one another. If they are close together they are
most likely linked and have a greater chance of crossing over together.
When a ribosome is translating a mRNA, what is the reading orientation? - ANSWERSThe mRNA is read in
a 5' to 3' manner and in the left to right direction (usually).
On which molecule and on which atom is the nitrogenous base attached? What kind of bond is formed? -
ANSWERSThe nitrogenous base is attached to the 1st carbon and a glycosidic bond is formed.
On which molecule and on which atom is the phosphate bond attached? What kind of bond is formed? -
ANSWERSThe phosphate is attached to Carbon 5 with a hydrogen bond.
one DNA turn has how many major grooves and how many minor grooves? - ANSWERSone major groove
and one minor groove
Why does the number of CG pairs affect the stability of the DNA molecule? - ANSWERSThe C and G have
3 hydrogen bonds between their base pairs in comparison to 2 between A and T which makes them
more stable due to the increased number of n=bonds which increases their strength.
What are melting and annealing temperatures? - ANSWERSmelting: temp where the DNA strand begins
to unwind and become denatured
,annealing: temp where the DNA can begin to reform its normal structure; known as "renaturation"
Why do we load DNA samples closer to the negative electrode in a gel electrophoresis assay? -
ANSWERSthe current flows from negative to positive which shows the length of the DNA sequence and
bigger DNA lengths travel slower and smaller travel faster. This is due to the negatively charged
phosphate backbone which allows it to travel to the positively charged side of the electrophoresis gel.
The number of genes in an organism doesn't explain the difference in DNA size. What does the C-value
paradox say about this? - ANSWERSThe C-value paradox states that more complex organisms do not
always need more genes and most likely organisms with very high C-values have a lot of extra non-
coding DNA.
What is meant by upstream and downstream? - ANSWERSupstream: ahead of the referenced section of
the sequence
downstream: after the referenced sequence.
What is the difference between the transcription initiation site and the initiation codon? -
ANSWERStranscription initiation site: location in the chain in which transcription begins and the first RNA
nucleotide is transcribed.
initiation codon: specific 3 letter code on the template that tells the mRNA to begin transcription.
Is the gene encoded on both DNA strands? Explain. - ANSWERSThe gene is technically encoded on both
DNA strands, but only one is actually being transcribed at a time and the other is known as the non-
coding strand.
What is the difference between the transcription termination site and the stop codon? - ANSWERSThe
transcription termination site is the section of the template in which transcription stops.
The stop codon is a three letter code of the template that tells the mRNA to code for stopping the
process of transcription.
Why does RNA have U instead of T? - ANSWERSRNA has U instead of T because RNA is less stable and
does not need to last as long as DNA. Uracil is resistant to oxidation and can exist outside the nucleus,
whereas thymine is easily oxidized so outside the nucleus it is quickly destroyed.
, What does 5'-UTR and 3'-UTR refer to? - ANSWERSThe 5'-UTR is the region upstream of the initiation
codon that is not translated and the 3' UTR is the region right after the stop codon in which the codons
are not translated.
What are the sizes of each ribosome subunit? What is the size of the whole ribosome? Why doesn't the
total size match the sum of the individual subunit sizes? - ANSWERSThe sizes of each ribosome subunit
are 50s and 30s and the whole subunit is 70s because the numbers of the parts are a sedimentation
coefficient and it is not proportionate to particulate mass, so they don't add together.
What is a protein domain and why is the concept important? - ANSWERSA protein domain is a compact
structural region of protein and they may contain structural motifs such as zinc fingers that bind to zinc
or hydrophobic pockets that bind to hydrophobic molecules.
What are codons and anticodons? - ANSWERScodons: groups of three bases that are read in a 5'-3'
direction and they are translated into amino acids using the three letter code.
anticodons: the complement to the codon and are often found in the bottom loop of the tRNA molecule
that matches with the codon in translation.
What is one reason that a harmful mutation such as sickle cell anemia can persist in a population? -
ANSWERSit becomes dominant in the population and all members will either have the gene or they will
have the heterozygous phenotype in which the trait becomes either present or carried in all offspring.
don't forget about conventions: how are RNA and DNA sequences written? - ANSWERSthey are ALWAYS
written from 5' to 3'
What are restriction enzymes and what are the different ways they can cut DNA? - ANSWERSthey are
endonucleases that prevent the invasion of foreign DNA by cutting it into pieces. They cut at site in
foreign DNA rather than from ends.
What is the "modification system" and why does it exist? - ANSWERSIt is the pair of the restriction
endonucleases and the methylases and they pair in order to protect the host DNA from being cut by
methylating it after replication in order to mimic the parent strand.
What is the role of the origin on the plasmid? Why is it needed? Why does it have to replicate? What is
"transformation"? - ANSWERSThe origin on a plasmid serves as the start place for replication
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