Term
| Enzyme that breaks hydrogen bonds between bases during DNA replication |
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Definition
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| Enzyme that prevents supercoiling during DNA replication |
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Definition
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Term
| Number of base pairs per complete turn of the helix in B-DNA |
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Definition
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Term
| What is the electrical charge of histones? |
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Definition
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Term
| What is the enzyme that joins RNA or DNA fragments together |
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Definition
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Term
| What is the bond between sugar and phosphate in DNA |
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Definition
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Term
| Suger used to halt DNA synthises during Sanger sequencing |
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Definition
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Term
| What is the promoter sequence found between -60 and -120 position in plants |
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Term
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Definition
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Term
| Processing Heterogenous Nuclear RNA in Eukaryotes involves. (3) |
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Definition
addition of 7-methylguanosine cap
addition of poly-A-tail
Removal of interons (splicing)
RNA Editing |
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Term
| Type two diabetes is... (3) |
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Definition
controlled by multiple genes
a threshold trait
the majority of the population has inherited at least some of the genes implicated in this type of diabetes |
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Term
| Griffith's transformational experiment |
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Definition
| used mice and strep. bacteria to seethat S-type cells killed but R-type and ehated s-type did not kill the mouse. |
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Term
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Definition
| found that only DNase killed trasformants not RNase |
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Term
| Hershey and Chase experiment |
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Definition
| used T-4 bacteriophage and found that phosphorus entered the cells while sulfur did not |
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Term
| Adenine and thymine pair with 2 hydrogen bonds |
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Definition
| Guanine and Cytosine pair with 3 hydrogen bonds |
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Definition
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Definition
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Definition
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Term
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Definition
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Term
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Definition
| 4 carbons and 1 O and 1 CH3 |
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Term
| A DNA nucleotide is made up of.... (3) |
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Definition
| sugar + Base + phosphate group |
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Term
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Definition
high salt concentrations or when dehydrated
right handed with 11 bases |
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Term
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Definition
| most frequent DNA in living cells |
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Term
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Definition
may represent temporary down regulation of genes in living cells
left handed with 12 bases |
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Term
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Definition
coded for in the genome
polynucleotide
anticodon is complementary to t RNA |
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Term
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Definition
| excess DNA is present that does not seem to be essential to the development or evolutionary progression of eukaryotes |
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Term
| High repeat DNA sequences in eukaryotes.... (3) |
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Definition
protect the centromere region of the chromosome
protect the telomeres
act as spacers between groups of transcribed genes |
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Term
| What occurs during the process of polypeptide elongation in translation... (3) |
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Definition
The charged tRNA enters the A site in the ribosome
The A site in the ribosome is then positioned over the next codon on the mRNA
uncharged tRNA exits the ribosome |
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Term
| termination of Translation occurs when... |
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Definition
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Term
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Definition
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Term
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Definition
inverted repeat in DNA downstream of the stop codon
folds into a hair pin
RNA polymerase encounters poly A-series |
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Term
| DNA replication is termed semiconservative because... |
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Definition
| the new DNA HELICES contain one old strand and one new strand |
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Term
| DNA in solution is weakly acidic because... |
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Definition
| H ions are released from the Phosphate molecules |
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Term
| The octamer of histones within the nucleosome core particle contains.... |
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Definition
| two molecules each of H2A, H2B, H3, and H4 |
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Term
| tRNA has the sequence _______ at the end of the acceptor stem. |
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Definition
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Term
| In gel electrophoresis of DNA, the ______ fragments move the furthest through the gel toward the positive electrode. |
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Definition
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Term
| When eukaryote mRNA is processed, the splicosome cuts the recognition sequence at the _______ first |
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Definition
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Term
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Definition
circular
looped onto a central protein scaffold
and not complexed with histones |
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Term
| closey-coupled transcription/translation is possible in prokaryotes because... (3) |
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Definition
there is no nuclear membrane
the mRNA does not require processing before translation
the 5' end of the mRNA is transcribed first. |
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Term
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Definition
| the process of "switching on" a gene to obtain the product the gene codes for. |
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Term
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Definition
| the production of an mRNA copy of the coding strand of a gene's DNA sequence. It is the first step in gene expression. |
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Term
| Is the base sewquence of the RNA transcript the same as the gene's DNA template strand or coding strand? |
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Definition
| coding strand (but with Us instead of Ts) |
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Term
| Is the base sewquence of the RNA transcript complementarty to the DNA template strand or coding strand? |
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Definition
| the RNA transcript is complementary to the DNA template strand. |
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Term
| What components must be present for transcription to proceed? |
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Definition
DNA template strand,all 4 nucleotides in equal amounts (A, U, C, G as
triphosphate nucleotides with ribose as the sugar), and RNA polymerase. |
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Term
| What is the function of the promoter sequences in transcription? |
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Definition
Promoter sequences are the "on" switch for the gene. They guide the RNA
polymerase into the correct position immediately upstream of the start
codon of the gene to be transcribed. |
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Term
What is a consensus sequence? What are the promoter consensus
sequences for
a) prokaryotes b) animals c) plants? |
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Definition
Consensus sequences are key functional DNA or RNA sequences that
vary very little from one species to another.
The promoter consensus sequences for (a) prokaryotes are TATAAT at the
-10 position and TTGACA at the -35 position; (b) for animals TATA at -25
and CAAT at -60 to-120; (c) for plants TATA at -25 and AGGA at -60 to -
120. |
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Term
| What is the role of the sigma factor in initiating transcription in E. coli? |
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Definition
| What is the role of the sigma factor in initiating transcription in E. coli? |
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Term
What happens when the RNA polymerase reaches a stop codon in
transcription? |
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Definition
The RNA polymerase transcribes the STOP codon into the mRNA and
keeps on going, so that some of the DNA sequence downstream of the
STOP codon is also transcribed. The STOP codon terminates translation
but not transcription (there are other mechanisms for terminating
transcription, such as those involving hairpin formation or the rho protein). |
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Term
What is an inverted repeat in DNA? If you found one downstream of a STOP
codon, what would it tell you about transcription of that gene? |
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Definition
An inverted repeat is a section of DNA with the same sequence repeated
forward and backward in opposite directions on the two strands. RNA
transcribed from an inverted repeat can bend around and pair with itself to
form a "hairpin" structure, so the presence of an inverted repeat
downstream from a STOP codon indicates that RNA hairpin formation is
part of the mechanism for terminating transcription of that gene. |
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Term
Which enzyme carries out transcription of mRNA in a) prokaryotes b)
eukaryotes? What exactly does this enzyme do? |
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Definition
a) A single RNA polymerase transcribes all kinds of RNA (mRNA, tRNA,
rRNA) in prokaryotes; (b) RNA polymerase II transcribes mRNA in
eukaryotes. RNA polymerases form phosphodiester bonds between the
ribose sugar of one nucleotide and the phosphate group of the next
nucleotide to make a strand of RNA. |
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Term
| How is transcription in prokaryotes different from transcription in eukaryotes? |
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Definition
Different promoter consensus sequences; in prokaryotes the RNA
polymerase binds directly to the promoter and does not need extra protein
transcription factors; prokaryotes do not have enhancers; prokaryotes
have only one RNA polymerase; in prokaryotes the primary RNA transcript
is the "ready to go" mRNA and can be translated immediately because it
does not need additional processing or editing. |
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Term
What is heterogenous nuclear RNA in eukaryotes? How is it processed after
transcription? |
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Definition
Heterogenous nuclear RNA in eukaryotes is the raw primary transcript
product made by the RNA polymerase. Before translation it has to have a
methylated guanosine cap added to the 5' end; a poly-A tail added to the 3'
end; introns have to be spliced out; and RNA editing to replace, add or
remove some bases may take place. |
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Term
What is closely-coupled transcription-translation? Why is it possible in
prokaryotes but not in eukaryotes? |
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Definition
This is when the new RNA is translated as fast as it is transcribed, with
translation starting even before the mRNA is complete. It is not possible in
eukaryotes because the nucleus is separated from the cytoplasm by a
nuclear membrane that the ribosomes cannot pass through, and because
eukaryote RNA must be processed before it can be translated. |
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Term
| What is supercoiling? How is it prevented when DNA unwinds? |
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Definition
| supercoiling is literally coiling of coils- the DNA helix coils up on itself. This is prevented by DNA gyrase cutting through ('nicking') the sugare-phosphate backbone ahead of the replication fork to release the tension, and then resealing the sugar-phosphate bonds. |
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Term
| What is the role of the SSBs? Why are they necessary? |
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Definition
| The SSBs attach to the separated DNA strands to prevent the hydrogen bonds reforming between the paired bases. They are necessary because DNA is more stable as a double helix and will always try to assume this configuration. |
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Term
| Unwinding of prokaryote DNA for replication. |
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Definition
| Prokaryote DNA is circular and there is less of it to unwind, so unwinding and replication begins at a single point of origin and proceeds in both direction, forminga a theta structure of two linked circular DNA molecules. |
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Term
| Unwinding of Eukaryote DNA for replication. |
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Definition
| Eukaryote DNA is linear and much greater in quantity, so miltiple replicons of unwinding and replicating DNA form at intervals along the strand. Adjacent replicons fuse when they meet. |
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Term
| Why is it not possible for DNA to replicate continuously on both strands? |
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Definition
| Because the DNA strands are antiparallel and DNA polymerase synthesizing the new strand can only add nuvleotides to the 3' end so only one strand is orinted the right way. |
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Term
| Why are RNA primers necessary for synthises of new DNA? |
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Definition
| Because DNA polymerase cannot place a nucleotide in position unless there is already a 3' OH group to attach it to. This is what the RNA primer provides. |
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Term
| What is an Okazaki fragment? |
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Definition
| a piece of new DNA about 200 base pairs long with its own RNA primer. |
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Term
| How are Okazaki fragments formed? |
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Definition
| they are formed on the lagging (discontinuous) strand by the old DNA strand looping to temporarily reverse its orientation. This brings the 3' end of the new DNA strand withing reach of the DNA polymerase in the replisome. |
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Term
| Why does eukaryote DNA lose 10 bases everytime it replicates? Which end does it lose the bases from? can this ever be repaired? |
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Definition
| When the RNA primer is removed from the 5' end of each strand of the new DNA it leaves a one-seided gap that DNA polymerase cannot fill. Telomerase can replace the missing bases but not all cells make this enzyme. |
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