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Biology > Nuclei Acids > Flashcards

Nuclei Acids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Structure of DNA

A
  • DNA is double-stranded
  • DNA molecules twist as regular intervals to form helix
  • Nitrogen bases are closely packed together & phosphate forms an outer backbone on the outside.
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2
Q

purines

A

A + G

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3
Q

pyrimidines

A

C + T - 1 carbon-nitrogen ring

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4
Q

DNA replication

A

Helicase
DNA Gyrase
Single Stranded binding (ssb) protein
DNA primase
DNA polymerase III
DNA Polymerase I
DNA Ligase

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5
Q

Helicase

A

Unwinds the DNA and breaks the hydrogen bond in the base to separate double-stranded DNA

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6
Q

DNA Gyrase

A

Reduces tension and strain during unwinding by relaxing the positive super coils

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7
Q

Single Stranded binding (ssb) protein

A
  • Binds to the DNA strands to prevent strands from re-annealing
  • Stops it from being digested by nuclease
  • Gets dislodged when new complementary strands by DNA polymerase III
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8
Q

DNA primase

A
  • Generates short RNA primer (10-15 nuceolides) on each template strand
  • RNA primer provides an initiation point of DNA polymerase III to extend it
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9
Q

DNA polymerase III

A
  • Free nucleotides align opposite their complementary base
  • attaches to a 3’ of primer and covalently joins the free nucleotide together in a 5’ -> 3’ direction
    -> leading strand - towards replication fork and synthesize continuously
    -> logging strand - away from the replication fork & synthesize in parts
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10
Q

DNA polymerase 1

A

Lagging strand has multiple RNA primase and it removes them to replace with DNA nucleotides

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11
Q

DNA ligase

A

Joins Okazaki fragments to form continuous strands. Done by covalently joining sugar-phosphate backbone with a phosphodiester bond

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12
Q

Okazaki Fragments

A

DNA polymerase cannot initiate replication and can only add nucleotides to an existing strand
-> Add to 3’ end of a primer
-> uses energy released to form a phosphodiester bond

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13
Q

Lagging Strand (Okazaki fragments)

A
  • moving away from the helicase meaning It returns to copy a new strand
  • copied as short fragments
  • Primers replaced with the DNA bases and joined together by a combination of DNA polymerase 1 & DNA ligase
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14
Q

What is the most widely used method for DNA sequencing

A

Dideoxynucelotides
lacks the 3’-hydroxyl group necessary for forming a phosphodiester bond which prevents elongation and terminates replication

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15
Q

Non-coding DNA

A

Satellite DNA - repeating sequencing of DNA
Telomeres - protect against deterioration during replication
Introns - Remove by RNA splicing prior to the formation fo MRNA
Non-coding RNA genes - RNA molecules not translated into protein
Gene regulatory sequences - involved in the process of transcription

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16
Q

Nucleosomes

A

Help to supercoil the DNA, resulting in a greatly compacted structure that gives more sufficient storage.
Protects from DNA damage

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17
Q

Organisation of Eukaryotic DNA

A
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18
Q

3 sections of genes

A

Promoter
Coding Sequence
Terminator

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19
Q

Promoter

A
  • responsible for the initiation of transcription
  • Binding site of RNA polymerase
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20
Q

Coding sequence

A
  • After RNA binds to the promoter DNA strand will unwind and separate
  • Region of DNA that is transcribed by RNA polymerase is the coding sequence
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21
Q

Terminator

A

Transcription will continue until it reaches the terminator sequence

22
Q

anti-sense (template strand) VS sense

A

there are two polynucleotide strands, but only one is transcribed into DNA

anti-sense
- transcribed into RNA
- complementary to the RNA sequence and is the DNA version of the anticodon sequence

sense
- not transcribed into the RNA
- DNA version of RNA sequence (identical swap T & U)

23
Q

transcription

A

DNA sequence is copied into a complementary RNA sequence by RNA polymerase

24
Q

what does RNA polymerase do in transcription

A

binds the NTPs together which will release two phosphates

25
Q

Free nucleotides in transcription

A

exist as nucleotide triphosphate (NTPs) and line up oppositely to complimentary pairs

26
Q

In what direction does binding occur

A

5’ -> 3’ direction

27
Q

Transcription Processes

A
  1. Initiation
  2. Elongation
  3. Termination
28
Q

Initiation

A

RNA polymerase binds to the promoter causing the unwinding and separating DNA strands

29
Q

Elongation

A

RNA polymerase moves along coding sequnce

30
Q

Termination

A

RNA polymerase reaches the terminator. DNA rewinds

31
Q

Messenger RNA (mRNA)

A

carry the genetic information needed to make proteins. They carry the information from the DNA in the nucleus of the cell to the cytoplasm where the proteins are made.

32
Q

mRNA (capping)

A

addition of the methyl group to 5’ end
protect against degradation
allows transcript to be recognized by the cells translation material

33
Q

mRNA (polyadenylation)

A

Addition for a long chain of adenine nucleotides
Improved stability of RNA transcript

34
Q

mRNA (spicing)

A

non coding sequence called introns - removed before forming mature RNA
coding sequence called exons - fused together when introns removed

35
Q

alternative splicing

A

exons also removed causing different polypeptides from a single genetic sequence

36
Q

Gene Expression

A

the process by which the information encoded in a gene is turned into a function

includes
- Transcription factor
- Regulatory Protein

37
Q

Transcription factor

A
  • Form complex with RNA polymerase at the promoter
  • Cannot be initiated without these factors so their levels regulate gene expression
38
Q

Regulatory Protein

A

Binds to DNA sequences outside of promoter and interacts with transcription factors

Activator Protein - Bind to enhancer sites and increases rate of transcription
Repressor protein - binds to silencer sequence and decreases the rate of transcription

39
Q

Control element

A

DNA sequence that the regulatory protein binds to

Regulatory protein - binds to distal control
Transcription factor - binds to proximal

40
Q

Epigenetics

A

study in change in phenotype as a result of variation

41
Q

ribosomes

A

consist of a large subunit

large subunit - contains mRNA binding site
small subunit - contains three tRNA binding sites (E, P, A)

42
Q

Translation (tRNA)

A

folds into a cloverleaf structure with four key regions
- acceptor stem carries an amino acid
- anticodon associates with mRNA codon
- T arm associated with ribosomes
- D arm associates with the tRNA activating enzyme. (add amino acid to acceptor stem)

43
Q

Binding in the tRNA

A

an amino acid binds to a specific amino acid

  1. Enzyme binds ATP to amino acid to form amino acid AMP complex
  2. Amino Acid is now coupled to tRNA and AMP is released. This means tRNA can now be used
44
Q

tRNA how it works

A
  1. tRNA activating enzyme
  2. Enzyme binds to ATP and a specific amino acid
  3. Amino acid ATP complex is formed and a specific tRNA molecule is recruited
  4. the tRNA is bound to the amino acid and AMP is released
  5. Charged tRNA is introduced
45
Q

Translation steps

A
  1. Initiation
  2. Elongation
  3. Translocation
  4. Termination
46
Q

Initiation

A

assembly of three components that carry out the process
- Ribosomes subunit binds to the 5’-end of the mRNA and moves along it until it reaches the start codon
then : tRNA bind to the codon via its anticodon
then : large ribosomal subunit aligns itself to the tRNA molecule at the p site and forms a complex with the small subunit

47
Q

Elongation

A
  • second tRNA pains with next codon in the A site
  • amino acid in P attaches to amino acid in A covalently
  • tRNA in p site now has no amino acid but A site carries peptide chain
48
Q

Translocation

A
  • Ribosomes move along mRNA strand
  • tRNA with no amino acid moves to E sire and is released while the molecule carrying peptide chain moves to p site
  • another tRNA molecule attaches to next codon and is now occupied in A site
49
Q

Termination

A

disassembly of the components and release of a polypeptide chain

continues until a stop codon is reached
- release factor signalling for translation to stop
- polypeptide is released and ribosome disassembles into 2 independent subunits

50
Q

polysomes

A

is a group of ribosomes translating an mRNA sequence simultaneously

Biology (12 decks)

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