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Biology AS Level > DNA + Nucleic Acid > Flashcards

DNA + Nucleic Acid Flashcards

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1
Q

TRANSCRIPTION 1-6

A

1.RNA polymerase unwinds DNA
2. RNA polymerase attaches to beginning of gene being copied at PROMOTOR REGION
2. DNA helicase unzips + breaks H+ between CBP; A- T (2H+) and C-G (3H+)
3. 1 DNA strand = TEMPLATE STRAND
4. Activated free floating RNA nucleotides
5. CBP with exposed DNA strand
6. A=U; C-G (3 H-bonds)

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2
Q

DNA REPLICATION PHASE 1-6 + how does ss of DNA allow it

A
  1. DNA helicase unwinds DNA
  2. H+ break between CBP BROKEN
    - 2 DNA strand = template strand
  3. Activaed DNA nucleotides will CBP with exposed DNA strand bases
  4. DNA ligase = PDB between nucleotides via condensation reaction
  5. DNA polymerase ONLY acts in 5’ to 3’ direction for addition of nucleotides = LEADING STRAND
  6. produces 2 identical DNA mol
  7. SCR
  • CBP= AT,GC
  • free pair nucleotide on both strands
  • both strands act as template strands = 2 identical DNA mol identical to each other
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3
Q

TRIPLET CODE

A

1 codon codes for 1 amino acid
4x4×4 = 64 combinations.
- Lots of variety
- 4 = A,C,G,T

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4
Q

Non overlapping code

A
  • 2 codons code for 2 amino acids IF non-overlapping
  • If overlapping, then 2 codons code for 4 amino acids (AGT, GTA, TAG, AGT)
  • 1 base mutated = all AA in sequence changes
  • Non-overlapping code = protection from mutations
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5
Q

DEGENERATE CODE

A

MANY codons code for 1 AA
- ONLY if the LAST base changes, the SAME AA will be coded for
- Same AA will be inserted into polypeptide chain = silent mutations= protecting from mutation.
All code for same amino acid
If the 1st or 2nd base change by substitution = MUTATION

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6
Q

TRANSLATION 1-8

A
  1. mRNA binds to small subunit of ribosome
  2. mRNA contains codons
  3. 2 codons at any one time in the ribosome
  4. 1st codon is AUG which is start codon
  5. tRNA with anticodon (UAC) goes to ribosome with specific AA
  6. for the START codon is methionine
  7. codon CBP with anticodon (A=U; C-G (3 H-bonds)
  8. this holds the AA in place
  9. 2nd tRNA with specific amino acid binds to next codon
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7
Q

POST transcriptional changes - mRNA

A
  1. Primary transcript - mRNA (in neculus)
    - introns + exons
    - Exons protein coding
    - introns junk non coding DNA
    - splicesomes used to splice out introns
    - exons joined tgt
    - If exons join in correct order —> post mRNA strand
    - post mRNA STRAND BINDS TO SMALL SUBUNIT OF RIBOSOME IN CYTOPLASM
    - if exons wrong order –> diff protein made
    - RNA/DNA splicing
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8
Q

Role of tRNA in production of polypeptide

A
  1. tRNA transports/attatched specific AA to ribosome
    - AA activation before attachment
  2. tRNA enters at 2 sites Peptidyl and A(Aminoacyl)sites of ribosome
  3. Anti-condon on tRNA binds + CBP w codon on mRNA
    - anticodon identifies specific AA
  4. AA in correct position in polypep chain + forms primary ss
  5. Peptide bonds formed between AA
  6. tRNA reused
  7. 2 tRNAs at one time
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9
Q

Consequence of mutation that deletes U from codon 2 on polypeptide chain

A
  1. diff sequence of AA from codon 2 onwards
  2. Every subsequent codon changed
    - diff polypep chain from codon 2 onwards
  3. Premature chain termination
  4. Change in primary ss/ secondary ss
  5. loss of enzyme/protein function
    6.Frameshift mutation
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10
Q
  1. Suggest why in vitro (test tube) translation is less efficient than in Vivo translation (5)
A
  • Ribosomes lost/damaged
  • Fewer AA available
  • No respiration
  • Organelles not replaced
  • hard to replicate internal cell conditions
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11
Q
  1. Describe role of tRNA in synthesis of as protein
A
  • AA activation
  • TRNA attached/transports to specific AA
  • Anticodon identifies specific AA + binds to codon on mRNA
  • tRNA entering site in ribosome
  • Specific AA in correct position in polypep chain
  • Helps to form primary structure
  • tRNA reused
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12
Q

When does DNA replication occur + role

A
  • ‘S’ Phase of interphase - cell NOT dividing IN NUCLEUS
  • Ensures genetic continuity between generations of cells so ALL genetic info is passed on hereditarily.
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13
Q
  1. Describe the role of ribosome in translation
A
  • attachment to mRNA
  • 2 codon attachment/sites
  • MRNA has code for sequence of AA in polypeptide
  • Each tRNA has specific AA
  • MRNA codon- anticodon tRNA binding
  • CBP
  • Formation of peptide bonds
  • Ribosome moving along mRNA 1 codon at a time
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14
Q

DNA “carrier of coded info” why?

A
  1. Info in different sequence/order of bases in polynucleotide strand
  2. DNA/gene contains info for synthesis is of polypeptide/protein
  3. Info becomes sequence of AA + passed in cell to cell
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15
Q

Hba vs Hbs allele difference?

A
  • different sequence of bases/nucleotides
  • mutation
  • base substitution
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16
Q

Explain why cells are chosen based on their high levels of protein synthesis fro translation

A
  • lots of RER = cells can produce protein at high rate
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17
Q

Explain why using own cells mRNA must be destroyed to produce new mRNA in translation?

A
  • only desired protein produced
  • inefficient
  • cells protein will inhibit (enzyme)
18
Q

Explain why mRNA from any source can be translated into any type of extract

A
  • ribosomes function not altered
  • translation same in all cells
  • genetic code is universal
  • all cells use mRNA for protein synthesis
19
Q

Explain why cell wall + CM need to broken down for translation if present

A
  • MRNA easier access to ribosomes/RER
  • cells dna/mRNA can be accessed
  • easier to extract proteins
20
Q

Gene mutation

A

-change in DNA base sequence/nucleotides
- random
- framsehift
- substitution + addition
- change in mRNA base sequence during transcription
- change in tRNA
- different codons/AA sequence/ primary structure
- DIFFERENT POLYPEPTIDE/PROTEIN PRODUCED

21
Q

REPLICATION VS TRANSCRIPTION

A
  • DNA formed VS mRNA formed
  • 2 identical DNA mol vs 1 mRNA mol
  • all dna replaced vs part of dna mol involved
  • DNA polymerase vs rna polymerase
  • CPB A-T vs CBP A-U
  • ‘S’ phase vs throughout interphase
  • mitosis vs protein synthesis
22
Q

DNA vs rna

A
  • double strand v single strand
  • double helix v straight chain
  • T + A vs. U+A
  • Oxygen present on 3rd carbon/one hydroxyl group vs 2 hydroxyl groups
  • deoxyribose vs ribose
  • nucleus vs cytoplasm
  • produced via transcription vs. produced by semi conservative replication
23
Q

ATP (Adenosine triphosphate)

A
  • 3 phosphate bases
  • one ribose pentode sugar
  • adenine nitrogenous base
  • ribose +adenine = nucleoside
  • not part of DNA/RNA
  • nucleotide
  • Adenine can be combined we 1,2,3 phosphate group = ADP/ATP etc
24
Q

Purine vs pyrimidne

A
  • Adenine and Guanine = purine double carbon-nitrogen ring structure (BIGGER)
  • Cytosine, Thymine and Uracil = pyriminde single carbon-nitrogen ring (SMALLER)
25
Q

Nucleotide consists of…

A

Phosphate group
Pentose (5 carbon ) sugar: RNA or DNA
Nitrogenous base - A,T,G,C in DNA or U in RNA
Linked by covalent bonds on each 5’ end of polymer

  • antiparallel
26
Q

Sickle cell anemia

A
  • mutation
  • base substation
  • gene that codes for b polypeptide chain has base T instead of A (triplet different) = diff AA used when polypep made in ribosome
  • 2 different forms of allele/gene
27
Q

what is meant by a STOP codon?

A

1) codon that terminates translation
2) does not specify any amino acid
3) has no complementary tRNA/anti-codon
4) causes the release of a completed polypeptide chain

28
Q

Explain why the hydrogen bonding between the two strands of DNA is important for it to carry out its functions vs normal ss

A

2) many H+ bonds = stability
3) H+ bonds MORE EASILY BROKEN (than covalent bonds)
4) H+ bonds WEAK so can be broken= strands can be separated for DNA replication
6) H+ bonds form between, specific bases = few mistakes
7) H+ bonds can easily re-form

  1. CBP = holds strands together (polynucleotide opposing) one strand 5’ to 3’ and vice versa
    - puréing always against pyrimidine
  2. Many H+ bonds
  3. SPB
  4. Double helix protects bases
29
Q

What does the process of transcription require?

A

ATP, DNA and free nucleotide bases

30
Q

Suggest the significance of mRNA being highly labile

A

1) translation will stop when mRNA breaks down
2) allows re-use of nucleotides (for other mRNAs)
3) ref. to control of gene expression
4) ref. to control of cell activity / fast response to changing requirements
5) ref. to efficiency in energy use

31
Q

Outline the role of DNA polymerase in the replication of DNA

A

1) joins a nucleotide to polynucleotide chain
2) Only allows complementary base pairing
3) Forms phosphodiester bonds between nucleotides

32
Q

true or false
RNA is found thoughout cell and DNA only found in nucleus

A
  • FALSE
33
Q

in what position would dna be found aft cells divided once + divided twice?
Semi conservtaive rep

A
  • Dividing once= All in middle
  • Dividing twice= Half in middle + half on top
34
Q

Hemoglobin mutation in b-globin polypeptide AA base change + function/structure

A
  • diff AA = diff R group
  • glu to val
  • prevents formation of bonds between R groups
  • may form new bonds between R groups
  • change in secondary/tertiary ss
  • change in globular ss
    -lower affinity to oxygen
  • carry less oxygen
35
Q

suggets 2 ways streptomycin acts at ribosome to inhibit protein synthesis (TB)

A
  • binding of trna/mrna prevented - binds to small subnit of ribosome (inhibits enzymes in translation)
  • no anticodon-codon binding
  • peptide bond NOT formed
  • NO TRANSLATION = no protein synthesized
  • NO ribosomes move along MRNA
36
Q

why use Mitochondrial DNA instead of Linear DNA to work out who ancestors are

A
  • more mitochondria found in cell vs nucleus
  • larger sample DNA obtained
  • naked DNA in M. vs linear DNA w/ 8 histones
  • any mutations should have occured will ocur in naked DNA = histone proteins protect DNA against mutations
  • M. DNA has no enzymes to cut mutations occured vs linear DNA has enzymes cutting out mutations in G2= MD more accurate
37
Q

function of introns

A
  • non coding dna
    CODE FOR:
  • telomeres
  • centromere
  • promotor region
  • tRNA
38
Q

describe Messelon and stahl exp

A
  • Grow ecoli bacteria in medium containing 15N
  • baccteria tesk up 15N + synthesizes new DNA
  • repeat for many generatiobs growing in 15N untill all bac DNA labeled w/ 15N
  • bacteria placed in medium w 14N + growed for 7 gens
  • collect small samples at each gen + extract and purify
  • measure density of DNA via DENSITY GRADIENT CENTRIFUGE
  • seperate mol of DNA bands by spinning them at high speed
39
Q

Explain how DNA labelled w/ 15N can be seperated + diffrentiated from 14N

A
  • DNA centrifuged depending on its mass/density
  • compare w position of band formed in 14N and 15N AT BOTTOM of tube
40
Q

explain how DNA can be damaged and repaired in cells

A
  • damage to DNA occur in SCR = CBP not occuring + change in base sequence
  • caused by mutagen e.g ionising radiation
  • DNA polymerase surveys DNA
  • in G2, other enzymes cut out mismtached nucleotides
  • correct nucleotides inserted via DNA ligase
41
Q

explain how ss of nucleus allows its function of containing DNA

A
  • two membranes FORMING nucelur enevlope
  • nucleur pore too small for DNA to escape
  • protects DNA from hydrolytic enzymes
42
Q

post translation changes

A
  • occurs in golgi
  • removal of methionine from primary ss
  • modification of protein occurs = FOLDING of primary ss = tertiary ss

Biology AS Level (12 decks)

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