Term
| The Central Dogma of gene expression |
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Definition
DNA is transcribed to RNA, which translated to amino acids forming a protein
DNA -> RNA -> protein |
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Term
| DNA (deoxyribonucleic acid) |
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Definition
a polymer of necleotides ->phosphodiester bonds
Phoshate; 5-carbon sugar; nitrogenous base |
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Term
| DNA's four nitrogenous bases |
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Definition
Adenine and Thymine
Guanine and Cytosine |
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Term
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Definition
| two ring structure: Adenine and Guanine [image]and [image] |
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Term
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Definition
one ring structure: Thymine and cytosine
[image]and [image] |
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Term
| How many hydrogen bonds do Adenine and Thymine create? |
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Definition
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Term
| How many hydrogen bonds do Cytosine and Guanine create? |
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Definition
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Term
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Definition
5' -> 3' directionality
-- carbon # on the sugars |
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Term
DNA replication is semi-conservative
What does that mean? |
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Definition
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Term
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Definition
| Replication proceeds in both directions from an origin. Each direction produces a leading and a lagging strand. |
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Term
| What group of proteins governs the process of DNA replication? |
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Definition
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Term
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Definition
| Replisome attach on the chromosome at this location |
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Term
| Which enzyme unwinds the double helix? |
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Definition
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Term
| Which enzyme addes deoxynucleotides to the primer and moves along each DNA strand creating a new complementary strand. |
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Definition
DNA polymerase
- can only add to an existing strand
- reads 3' -> 5' creating new 5' -> 3' |
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Term
| Which enzyme creates an RNA primer to initiate the strand? |
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Definition
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Term
| What is being removed from a deoxynucleotide triphosphate as each nucleotide is added to the new strand? |
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Definition
| a removal of a pyrophosphate group |
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Term
| DNA ligase moves alone the lagging strand and ties the OKAZAKI fragments together. Okazaki fragments are semidiscontinuous, what does that mean? |
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Definition
| Formation of one strand is continuous and one is fragmented. |
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Term
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Definition
Removes nucleotides
automatic proofreader
repairs mismatch nucleotides
Therefore, DNA replication is fast and accurate |
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Term
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Definition
- carbon #2 on the pentose is not deoxygenated
- single-stranded
- uracil
- can move through the nuclear pores
- mRNA, rRNA, tRNA |
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Term
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Definition
| delivers DNA code for amino acids to the cytosol where the proteins are manufactured |
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Term
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Definition
combined the proteins to form ribosomes
synthesized in the nucleolus |
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Term
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Definition
| collects amino acids in the cytosol, and transfers them to the ribosome for incorporation into a protein. |
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Term
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Definition
| Makes RNA from a DNA template. It requires a promoter instead of a primer in replication. |
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Term
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Definition
| A spot on the DNA that tells RNA polymerase where to begin transcription |
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Term
| Transcription: Initiation |
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Definition
Proteins fins a promoter and assemble a transcription initiation complex.
The transcription bubble forms and elongation begins |
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Term
| Transcription: Elongation |
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Definition
| RNA polymerase transcribes only one strand of the DNA nucleotide sequence into a complementary RNA nucleotide sequence. |
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Term
| Transcription: Termination |
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Definition
Requires a special termination sequence and special proteins to dissociate RNA polymerase from DNA
Activators and repressors bind to DNA close to the promoter, and either activate or repress the activity of RNA polymerase
-> regulated by small molecules (cAMP) |
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Term
| Gene regulation Primary function in Prokaryotes |
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Definition
| Respond to environmental changes ~ change in concentration of nutrients in and around the cell |
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Term
| Gene regulation primary function in eukaryotes |
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Definition
| control the intra- and extracellular environments of the body |
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Term
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Definition
genetic unit consisting of the operator, promoter, and gene
ex. Lac Operon coding for E. Coli to import and metabolize lactose when glucose is not present |
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Term
| Post-transcriptional Processing 1 |
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Definition
-Primary transcript: addition and deletion of nucleotides; modification of nitrogenous bases
5' end capped using GTP as an attachment site in protein synthesis and as a protection against degradation by exonuleases
3' end is polyadenylated with a poly A tail same purpose |
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Term
| Post-transcriptional Processing 2 |
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Definition
Before leaving the nucleus, primary transcripted is cleaved into introns and exons
SnRNP form splicesome where introns are looped bringing the exons together |
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Term
| Post-transcriptional Processing: exons |
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Definition
| codes for a polypetide and exits the nucleus to be translated |
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Term
| Post-transcriptional Processing: Introns |
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Definition
| do not code for protein and remains in the nucleus |
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Term
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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
| degenerative (more than one series of three nucleotides may code for any amino acid) and unambiguous (any single series of three nucleotides will code for one and only one amino acid) |
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Term
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Definition
Process of protein synthesis directed by mRNA
nucleus -> cytosol (mRNA)
anticodon (tRNA)
makes ribosome (rRNA) |
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Term
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Definition
| tRNA possessing the 5'-CAU-3' anticodon sequesters the amino acid methionine and settles in at the P site (peptidyl site) signaling for the large subunit to join and form the initiation complex. |
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Term
| Translation: Elongation 1 |
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Definition
| tRNA with its corresponding amino acid attaches to the A site (aminoacyl site) at the expense of two GTPs. C-terminus of methionine attach to N-termious of Amino acid. Dehyration reaction catalyzed by peptidyl transferase processed by the ribosome |
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Term
| Translation: Elongation 2 (translocation) |
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Definition
Translocation: ribosome shifts 3 nucleotides along the mRNA toward the 3' end
tRNA with methionine moves to E site to leave ribosome
tRNA with nascent dipeptide moves to the P site
another GTP is used and this step continues until a stop codon reaches the P site |
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Term
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Definition
Stop codon reaches the A site, release factors (protein) bind to the A site
-> H20 can then add to the end of the polypeptide chain
Polypeptide is freed from the tRNA and ribosome
Chaperones are proteins aiding in the folding process of polypeptides. |
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Term
Which of the following is always true concerning the base composition of DNA?
a. In each single strand, the number of adenine residues equals the number of thymine resideues.
b. In each single strand, the number of adenine residues equals the number of guanine residues.
c. In a molecule of double stranded DNA, the ratio of adenine residues to thymine residues equals the ratio of cytosine residues to guanine residues.
d. In a molecule of double stranded DNA, the number of adenenine residues plus thymine residues equals the number of cytosine resides plus guanine residues. |
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Definition
C is correct. Since A always binds with T and G always binds with C, both the ratio of A/T and the ratio of G/C equal one. |
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Term
An mRNA molecule being translated at the rough endoplasmic reticulum is typically shorter than the gene from which it was transcribed because:
a. the primary transcript was cut as it crossed the nuclear membrane
b. normally multiple copies of the mRNA are produced and spliced
c. introns in the primary transcript are excised.
d. several expressed regions of the primary transcript have equal numbers of base pairs. |
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Definition
C is correct. The introns (intervening sequences) are removed during posttranscriptional modification |
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Term
In PCR amplification, a primer is hybridized to the end of a DNA fragment and acts as the initiation site of replication for a specialized DNA polymerase. The DNA fragment to be amplified is shown below. Assuming that the primer attaches exactly to the end of the fragment, which of the following is most likely the primer? (Note: the N stands for any nucleotide)
5'-ATGNNNNNNNNNNNNNNNNGCT-3'
DNA fragment
a. 5'-GCT-3'
b. 5'-TAC-3'
c. 5'-TCG-3'
d. 5'-AGC-3'
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Definition
D is correct. This question requires no knowledge of PCR. It requires only that you know that a DNA polymerase replicates from 5' to 3', and that you know the complementary bases. DNA polymerase can only read from 3' to 5', so it must start at the 3' end of the DNA fragment. |
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Term
Which of the following is NOT true concerning DNA replication?
a. DNA ligase links the Okazaki fragments.
b. Helicase unwinds the DNA double helix
c. Only the sense strand is replicated
d. DNA strands are synthesized in the 5' to 3' direction. |
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Definition
C is correct. DNA replication is semiconservative, which means that both strands are replicated, and each old strand is combined with a new strand. |
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Term
The gene for triose phosphate isomerase from maize (a corn plant) spans over 3400 base pairs of DNA and contains eight introns and nine exons. Which of the following would most likely represent the number of nulceotides found int eh mature mRNA after posttranscriptional processing?
a. 1050
b. 3400
c. 6800
d. 13, 600 |
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Definition
A is correct. Introns are remove from the primary trancript during posttransciptional processing. The number of nucleotides in the mature mRNA would have to be less than the number of base pairs of the gene. |
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Term
Complementary strands of DNA are held together by:
a. phosphodiester bonds
b. covalent bonds
c. hydrophobic interactions
d. hydrogen bonds |
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Definition
D is correct. Note that the question asks about complementary strands, which are the two strands in a double strand of DNA. |
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Term
Eukaryotic mRNA production occurs in the following sequence:
a. Transcription from DNA in the cytoplasm followed by post transcriptional processing on the ribosome
b. Transcription from DNA in the nucleus followed by post transcriptional processing in the nucleus.
c. Translation from DNA in the nucleus followed by post-transcriptional processing in the nucleus
d. Translation from DNA in the cytoplasm followed by post-transcriptional processing on the ribosome |
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Definition
B is correct. You should know that mRNA leaves the nucleus in it's finished form and that the process of RNA production is called transcription. |
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Term
In Souther blotting, DNA fragments are separated based upon size during electrophoresis. Which of the following is true of this process?
a. Positively charged DNA fragments move toward the cathode
b. Positively charged DNA fragments move toward the anode
c. Negatively charged DNA fragments move toward the cathode
d. Negatively charged DNA fragments move toward the anode. |
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Definition
| D is correct. Electrophoresis uses an electrolytic cell with a positively chraged anode and negatively charged cathode. The phosphate group of the DNA fragment gives it a negative charge that is attracted to the positively charged anode. |
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Term
If each of the following mRNA nucleotide sequences contains three codons, which one contains a start codon?
a. 3'-AGGCCGUAG-5'
b. 3'-GUACCGAAC-5'
c. 5'-AAUGCGGAC-3'
d. 5'-UAGGAUCCC-3'
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Definition
B is correct. The start codon is AUG. mRNA is translated 5'->3'. (Note: YOu did not need to know that to answer this question correctly.) We are looking for AUG 5'->3'. Only A, B, and C have an AUG sequence. However, if there are three codons in C, they must be: AAU, GCG, and GAC. The three in A must be: GAU, GCC, and GGA. |
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Term
Translation in a eukaryotic cell is associated with each of the following organelles or locations EXCEPT:
a. the mitochondrial matrix
b. the cytosol
c. the nucleus
d. the rough endoplasmic reticulum |
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Definition
C is correct. Translation does not take place within the nucleus. |
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Term
The large subunit of an 80S ribosome is made from:
a. rRNA only
b. protein only
c. rRNA and protein only
d. rRNA and protein bound by a phospholipid bilayer |
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Definition
C is correct. The ribosome is made in the nucleolus from rRNA and protein. It does not have a membrane |
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Term
Which of the following is true concerning the genetic code?
a. There are more amino acids than codons.
b. Any change in the nucleotide sequence of a codon must result in a new amino acid.
c. The genetic code varies from species to species.
d. There are 64 codons. |
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Definition
D is correct. There are 43 possible different codons. There are more codons than amino acids (used in proteins). This means that any amino acid could have several codons. The genetic code is evoluntionarily very old, and almost universal. Only a few species use a slightly different genetic code. |
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Term
A tRNA molecule attaches to histidine. The anticodon on the tRNA is 5'-AUG-3'. Which of the following nucleotide sequences in an mRNA molecule might contain the codon for histidine?
a. 3'-GCUAGGCCU-5'
b. 3'-GGTACCTAC-5'
c. 5'-CATTCTTAC-3'
d. 5'-UCAUGGAUC-3'
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Definition
D is correct. The complementary sequence to 5'-AUG-3' is 5'-CAU-3'. Only D contains this sequence in any order. Remember thymine is only ofund in DNA, not RNA so B and C are wrong. |
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Term
One difference between prokaryotic and eukaryotic translation is:
a. eukaryotic ribosomes are larger containing more subunits
b. prokaryotic translation may occur simultaneously with transcription while eukaryotic translation cannot
c. prokaryotes don't contain supra molecular complexes such as ribosomes
d. prokaryotic DNA is circular so does not require a termination sequence. |
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Definition
B is correct. Only choice B is both true and concerns translation. RIbosomes contain two subunits for both eukaryotes and prokaryotes, so choice A is incorrect. Prokaryotes do contain ribosomes, so choice C is wrong. Translation does not concern DNA, so choice D is incorrect. |
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Term
During translation the growing polypeptide can be found attached to a tRNA at which site on the ribosome?
a. the E site
b. the P site
c. the A site
d. the Z site |
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Definition
B is correct. The P stand for peptiyl site, where the growing peptie chain attaches to the tRNA. |
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