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45 Cards in this Set
- Front
- Back
What is the central dogma of of molecular biology?
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DNA > RNA > Protein
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What is the problem with the central dogma?
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does not take into account that RNA is sometimes the finished product (rRNA, tRNA, iRNA, miRNA)
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What are Ribozymes?
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RNA's that have cralytic activity, function LIKE enzymes. Accociated with translation in making the peptide bonds.
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What are Retroviruses? Can it occur normally?
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Transcribe RNA into DNA, also known as reverse transcription.
Yes example Telomearse enzyme. |
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What are Nucleotides and what made of?
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They are subunits of nucleic acids. Consist of sugar (ribose or deoxyribose, lacks an O), phosphate and nitrogenouse base (Pyrimidines & Purines).
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What is a Pyrimidine?
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Single Ring three types: Uracil (RNA), Cytosine, and Thymine (DNA)
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What is the difference between Thymine and Uracil, Cytosine and Uracil?
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Thymine has a methyl group and Cytosine has an Amine group.
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What are Purines?
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2 ring structure, Adeine and Guanine. And Adenine like cytosine has an Amine group.
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What happens if Cytosine or Adenine is deaminated?
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Turns into Uracil, which is picked up easily because DNA does not have Uracil. Same with Adeine forms hypoxanthine.
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What if Cytosine gets methylated and deaminated?
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If a bunch in one area then shuts down gene expression. When you deaminate a methulated cytosine turns into Thymine harder to repair and take out.
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Describe Phosphates role in Nucleotides?
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Up to 3 attached to 5' Carbon inan ester link. Each phosphate has a negative charge which gives DNA and RNA a negative charge.
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What makes up DNA and what is the polarity?
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Nucleotides strung together by phosphodiester bonds
Both RNA and DNA are polar. |
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What are complementary base pairs?
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Adenine is always paried with Thymine/Uracil and Gaunine alsway aoired with cytosine.
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How many hydrogen bonds pair A-T and G-C?
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A-T have two hydrogen bonds and G-C have 3. Areas of seperation or Origin of Replication occrus at A-T rich b/c easier to seperate.
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What are the advantages of an alpha helix?
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Make it more compact, more thermodynamically stable, more surface area for proteins to recognize it.
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What is the difference between the sequence of the two stands and the two strands?
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The sequence are complementary and the two strands are antiparallel
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Where does protein recognition occur?
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In the Major Groove between two turns (particular structure) and the Minor Groove between two strands (particular nucletide sequence)
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What is chromatin?
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DNA in the nucleus combined with proteins (histones), that make up chromosomes
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Whare is Heterochromnatin?
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Most compacy form of chromatin particulary compact area is nucleoli whare ribosomes are synthesized
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What is Euchromatin?
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Most open form of chromatin, has to do with whether of not DNA is being actively used or not.
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What is the nuclear envelope?
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Double membrane that separates the nucleus form the cytosol.
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What are Nuclear Pores and how are they used in RNA processing?
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Where molecules travel between the cytosol and nucleus protected by proteins.
Important in RNA processing will not let RNA out of nucleus into cytosol until fully processed. |
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What are Histones?
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small POSITILVELY charged proteins that DNA wrap around nearly tice to form NUCLEOSOME BEADS.
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How are Histones linked together/seperated?
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They are seperated by about 50 base pairs of DNA called LINKER DNA which is bound together by HISTONE H1.
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How do you seperate the two stands to use for replication/transcription?
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Post-Transitonal Modification
Lysine AA on termnmal end of Histone have + charge and interact with - charge of phosphate on DNA. They are neutralized by addion of acetyl group (acetylation). This weakens the attraction. Done by the ENZYME HAT |
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Once replication / transcription is finished what happens with histone interaction?
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The acetyl group is removed and histone can re-bind to DNA dpme ny tje Emzyme HDAC.
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When is nuclear DNA replicated?
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Only during a discrete phase called the S Phase.
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What is Mitosis?
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When the cell actually divides
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What is proto-oncogenes?
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Protein that stimulates cell cycle progression
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What is Tummor Suppressors (p53)?
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Products of the this inhibit cell cycle progression.
Control checkpoints where cell checks that everthing was done beofore moving on. |
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When are regions of the genome actively transcribed and when are untranscribed regions replicaed?
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Regions of the genome that are actively transcribed are replicated early in S phase
Untranscribed regions are replicated later in S |
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What are cell cycle events controlled by?
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Controlled by proteins called cyclins and cyclin dependent kknases (CDK's)
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What is semiconservative?
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It is in DNA replication where each daughter cell contain one parental strand and one newly synthesized strand.
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What direction does DNA synthesis occur and in what direction and from where?
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Only in the 5' to 3' direction
There are multiple origins along a chromosome and more bi-directional |
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What is the replication fork and the replication bubble?
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The region of trnasition between the unwound parent duplex and the newly replicaed daughter DNA
Unwound region is the bubble |
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When does cell licensing occur and what is it?
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Occurs in G1
It is when "licensed" to replicate and when Cdc6 binds ORC and recruits Mcm to form pre-RC |
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What does Mcm contain?
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It contains helicase activity whcih separates two stands of DNA and migrates with the replication fork
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When does the origin fire?
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When it is phosphorylated by S-Cdk (Cdc6) in the S phase
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What prevents positive supercoiling and what are the 2 types?
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Topoismerase make reversible nicks and then reseal the gap
Type I = make single stranded nicks Type II = make double stranded nicks |
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Decribe DNA synthesis by DNA Polymerase:
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Both parental stands are used as templates
Complementary nuclotides are added one at a time t othe 3' OH DNA Polymerase requires pre - existing 3' OH, provided by an RNA primer by the primase Joined by phosphodiester bonds |
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What direction is DNA synthesized and what dierction does it move along the template?
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Synthesized in the 5' to 3' and DNA Pol. moves along the template in 3' to 5'
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How does DNA Pol. proofread?
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DNA pol. has 3' to 5' exonuclease activity and excise the last nucleotide if it doesnt base pair correctly with the template strand
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What does the RNA primer (primase) do?
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Provides the 3' OH for DNA pol. so DNA synthesis can begin. RNA pol. does not have this requirement
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How does the proofreading remove an unwanted nucleotide?
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Failure to form a proper ase pair triggers a conformational change in the DNA pol. so falls into hte exonuclease pocket where the last nucleotide is removed
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What is the leading strand?
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moves forward in the smae direction the forks
away from the origin contineous |