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MCAT Bio > Genetic code and DNA > Flashcards

Genetic code and DNA Flashcards

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1
Q

Nucleic acids

A

contain DNA and RNA
DNA: store and transmit
RNA: transcribe to make proteins

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2
Q

The 4 nucleotides

A

-DNA encode info using 4 nucleotides (A, C, G, T (T is U in RNA)
- Generate all messages needed to build proteins and cells

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3
Q

Nucleotides (have 3 parts)

A
  1. nitrogenous base
  2. pantose- 5 carbon sugar (In RNA, use 5-C sugar called ribose, in DNA use similar sugar but lack hydroxyl group)
  3. at least 1 high-energy P group ( P group - change due to lots of electrons)
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4
Q

Nucleosides

A
  • nitrogenous base
  • pentose sugar
  • no p group
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5
Q

ATP

A
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6
Q

cAMP

A

cyclic adenosine monophospahte
- similar to ATP but include only 1 P group that is attached to pentose sugar at 2 point
cAMP: chemical signaling molecule inside cells

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7
Q

Nitrogenous Base

A
  • Experience. hydrophobic intercation with. adjacent bases stacked on top of each other. Enhancing stability of nucleic acid
    N base is what make DNA and RNA unique
  • N base: cyclic with a lot of N base
  • Pyrimidines are nitrogenous base with 1 ring
  • Purines: 2 rings
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8
Q

Nitrogenous base DNA pyrimidines

A

In DNA, the pyrimidines are cytosine and thymine

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9
Q

Nitrogenous base DNA purine

A

adenine and guanine (PURE As Gold)

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10
Q

Nitrogenous base RNA

A

Adenine, guanine, cytosine, uracil ( Cut the PY)

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11
Q

Pairing

A

Thymine pair with Adenine (or uracil)
- Cytosine pair with Guanine ( 3 H bonds: complementry held by hydrogen bond, weak intercation but many togther form a stable molecule) Gc pairs stick best

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12
Q

Chargaff’s Rule

A
  • a double starnd DNA molecule contain 1:1 ratio of A:T; C:G
    ex: 20% A: 20% T
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13
Q

how nucleotide held together?

A

Sugar phosphate backbone: a linear string: pento sugar and P group connected by a phosphodiester linkage
- the P group link nucleotide togther by binding 3’c to a 5’c

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14
Q

complementary sequence

A

must be complementary and antiparallel running in the 3’ to 5’
- ex: 5’ ACTG-3’ (A=T, C=G, T= A, G=C) - 3’TGAC5’

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15
Q

Separating 2 strands of double-starnds DNA molecule

A
  • use heat or. urea to denature
  • melting DNA:Tm
    overcoming the H bond that hold base pairs together
  • Annealing: reverse process
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16
Q

DNA double helix

A

have grooves:
- wider grooves are ‘major groove’
- narrower grooves: ‘ minor grooves”
- these grooves bind sites for transcription factors

17
Q

Central dogma:

A

DNA to RNA to proteins

18
Q

Alfred Hershey & Chase experiment

A
  • DNA is inherited and source of genetic info
  • viruses incubated with radioactive sulfur that labeled their proteins
    other viruses were incubated with radioactive phosphorus that labeled their DNA
  • These viruses (microphages: were allowed to infect bacteria)
  • ## after the infected bacteria is isolated, they contained radioactive material only when infected by the PHOSPHORUS-LABELED VIRUSES ( the DNA but not the protein was tranferred
19
Q

Heterogenous nuclear RNA (hnRNA)

A

precursor to mRNA that is modifies to the mature mRNA form

20
Q

mRNA

A

template to synthesis protein

21
Q

tRNA ( transfer RNA)

A
  • transfer aminos to growing polypeptide chains
  • recognize specific codons or sequences on mRNA
22
Q

Ribosomal RNA (rRNA

A
  • synthesized in nucleoli
  • making more than 50% of ribosomes by weight
    some molecules act as ribozymes have Inherent enzymatic activity
  • siRNA and miRNA gene expression inhibit gene expression
23
Q

Reverse transcription

A
  • enzymes reverse transcriptse in viruses reverse trasncriped rna back to DNA
    that help the virus propagate in its host
24
Q

genetic code: degenerate

A
  • more than one different codon can encode for the same amino
25
Q

Conservative mechanism (DNA replication)

A
  • the entire DNA molecule is completely duplicated to create a entire new DNA molecule
26
Q

Dispersive mechanism

A

the DNA backbone would be broken in multiple places as two strands unwind
both the old and new molecule would contain section of old and new DNA

27
Q

Semi-conservative

A

the two DNA strands separate and each serve as a template for synthesis of a new strand \
- both old and new contain one old and one new strand

28
Q

Meselson-Stahl experiment

A

E.coli bacteria were grown in medium contain nitrogen-15 isotope( heaver than the much more nitrogen 14 isotope)
- after many gen, the 15N had been completely incorporated into bacterial DNA
The bacteria were transferred to medium contain the 14N and replicated
- after centrfuging and testing on salt to see density:
if the DNA replicated vis conservative mechanism: after 1 round replication, we expected to see 2 separate bands ( 1 for 15N and 1 14N)
- instead all of the new DNA molecule had intermediate density (contain part of the old and new DNA)

29
Q

prokaryote replication:

A
  • have 1 origin replication (specific sequence that recognized the pre-replc complex
30
Q

eukaryotic replc

A
  • much more complex genomes
  • multiple origin replication
  • DNA replication produce identical sister chromatid connected to original DNA at chromosome centromere
31
Q

Helix unwinding

A
  • accomplished by helicase enzyme which unwind 2 strands and the replication fork
  • single stranded binding proteins: prevent the new separated one from coming back together
32
Q

Topoisomerase enzyme (DNA gyrase)

A
  • alleviate supercoiling created by helicase by making incision in 1 of the DNA strands and rotate the cut around the other then rejoin them to relax DNA
33
Q

primase

A
  • synthesize a short RNA primer with free 3 hydroxyl group that is a starting point
34
Q

Prokaryotic DNA polymerases

A
  • DNA polymerase I: removes rna primer, replace primer with DNA and repairs DNA
  • DNA polymerase II: repair DNA
  • DNA poly III: synthesizes new DNA and proofread DNA via 3’-5’
35
Q

eukaryotic DNA polymerase

A
  • DNA poly alpha: initiate synthesis
  • DNA poly delta: synthesize new DNA and replace RNA primer with DNA
  • DNA poly ę epsilon: extend leading starnds and repair
  • DNA poly gamma: replicating mitochondrial DNA
    -DNA poly: beta: repair DNA
36
Q

Ligase:

A

responsible for joining DNA fragments or Okazaki fragments together that are produced as a result of the DNA replication process. As such, if a cell contains disconnected DNA fragments, nonfunctioning ligase may be the culprit.

37
Q

telomeres

A
  • exetend telomeres to preventt chromoses arms from shortening that prevent loss of genetic materia
  • telomeres protect against degradation at end of chromoses in the cells that divide and replicate. Cells that divide have more telomeres activities
38
Q

telomeres

A
  • exetend telomeres to preventt chromoses arms from shortening that prevent loss of genetic materia
  • telomeres protect against degradation at end of chromoses in the cells that divide and replicate. Cells that divide have more telomeres activities
39
Q

Stop codons

A

UGA, UAA, and UAG are all stop codons.

  • U go away
    U are annoying
    U are ghastly

MCAT Bio (3 decks)

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