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Biology 12 > Molecular Genetics > Flashcards

Molecular Genetics Flashcards

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1
Q

S-Strain

A

Highly pathogenic but can be made non-pathogenic by heating it up (mouse dies when injected).

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2
Q

R-Strain

A

Non-pathogenic (mouse lived when injected).

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3
Q

Protease

A

Enzyme that destroys protein

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4
Q

RNase

A

Enzyme that destroys RNA

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5
Q

DNase

A

Enzyme that destroys DNA (mouse lives when injected.

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6
Q

Bacteriophages

A

Viruses that infect bacteria, used to confirm that DNA is hereditary material. Structurally simple, inner nucleic acid core and outer protein core.

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7
Q

Chargaff’s Rule

A

Variations in the composition of nucleotides among species. All DNA maintain certain properties, the amount of thymine = adenine, amount of cytosine = guanine.

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8
Q

Purines

A

Adenine, guanine (2 fused rings)

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9
Q

Pyrimidines

A

Thymine, cytosine (single rings) (RNA uracil)

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10
Q

Chromosome condensation

A

Nuclear envelope breakdown. Occurs at the end of G2 phase of replication.

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11
Q

Chromosome decondensation

A

Reformation of nuclear envelopes.Occurs in cytokinesis.

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12
Q

Phases of DNA replication

A

Initiation, elongation, termination

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13
Q

Initiation Phase (DNA Replication)

A

A portion of DNA double helix is unwound to expose the bases for new base pairings.
- Replication starts at origin of replication
- Several initiator proteins bind to DNA and begin unwinding double helix
- Creates an unwound, even-shaped area called a replication bubble
- Creates two y-shaped regions called replication forks at the end of each unwound area

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14
Q

Elongation Phase (DNA Replication)

A

Two new strands of DNA are assembled using the parent DNA as a template. The new DNA molecules - each composed of one strand of parent DNA and one strand of daughter DNA, forms into double helices.
- Synthesises new DNA strands by joining free nucleotides together

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15
Q

Termination Phase (DNA Replication)

A

Replication process is completed and the two new DNA molecules separate from each other. At that point the replication machine is dismantled.

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16
Q

Helicase

A

Enzyme involved in the unwinding process. Helices cleave together the hydrogen bonds that link complementary structures together.

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17
Q

Single Stranded Binding Proteins (SSBP)

A

Help to stabilise the newly unwound single strands, otherwise strands would reform the double helix. Serve as templates that will be used to guide the synthesis of new polynucleotide strands.

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18
Q

Topisomerase

A

Enzyme that helps to relieve the strain on the double helix sections ahead of the replication forms. Result from unwinding process.

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19
Q

DNA polymerase III

A

Enzyme that catalyses the addition of new nucleotides, one at a time, to create a strand of DNA complementary to a parental strand.
- Only attaches new nucleotides to the free 3’ hydroxyl end of a pre-existing chain of nucleotides
- Synthesises a new strand from this parent strand in the 5’-> 3’ towards the replication fork
- Synthesises new DNA from parent strand that does not have free 3’ hydroxyl end (AKA lagging strand)

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20
Q

RNA Primer

A

Short strand of RNA that binds and begins the synthesis of lagging strands.
- Complementary to a section of the parent DNA being copied
- New primers must be added as replication proceeds

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21
Q

Primerase

A

Enzyme that synthesises RNA primer.

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22
Q

Okazaki Fragments

A

Newly synthesised DNA fragments.

23
Q

DNA polymerase I

A

Removes RNA primer and fills space by extending neighbouring DNA fragments.
- Proofreading function for genetic errors (as does DNA polymerase II)

24
Q

DNA Ligase

A

Joins Okazaki fragments together.

25
Q

Errors in Code

A

1 per billion nucleotide base pairings
i.e. Incorrect base pairings (A-C), strand slippage
- DNA polymerases excise incorrect base from new strand and add correct base, using parent strand as template (99% of code corrected)
- 1 gene = 200 bases of coding info (2 mistakes in cell division)

26
Q

Misplaced Bases

A

Cause deformities in newly synthesised DNA. Corrected by mismatch repair. Deformities recognised by a group of enzymes that bind to DNA and remove incorrect bases from daugther strands.

27
Q

Eukaryotes vs Prokaryotes

A

Eukaryotes: Linear DNA, 23 pairs (46 chromosomes), slower replication (40 nuclei/s), 13 DNA polymerases, thousands of origins of replication, lose ends of DNA replication if primer isn’t exactly lined up

Prokaryotes: Circular DNA (plasmid), no nucleus, 4x10^6 base pairs, faster replication (1000 nuclei/s), 5 DNA polymerases identified, 1 origin of replication

Both: DNA double stranded, have origins of replication, ribosomes, move 5’ -> 3’, Leading and lagging strands, use Okazaki fragments, use DNA polymerases

28
Q

Prokaryote Replication

A

Replication can occur in two directions at once because DNA is circular.

29
Q

Semi-Conservative DNA replication

A

One old strand, one new strand after replication.

30
Q

Gyrase

A

Wriggles along DNA, allowing it to unwind.

31
Q

Leading Strand

A

DNA polymerase III and replication fork move in the same direction. DNA copied continuously.

32
Q

Lagging Strand

A

DNA polymerase III and replication fork move in opposite directions. DNA copied in discontinuous segments.

33
Q

Exonuclease

A

Removes RNA primer

34
Q

Telomerase

A

(Eukaryotes) Rebuilds ends of daughter strands so that it’s not shorter (DNA pol. III), can’t reach ends because it takes up space.

35
Q

Triplet Hypothesis

A

Proposal that the genetic code is read three nucleotides bases at a time.
- mRNA codons and corresponding amino acids were determined

36
Q

Characteristics of Genetic Code

A
  1. Redundant (1 codon can code for the same amino acid, only 3 codons do not code for any amino acid)
  2. Continuous
  3. Universal
37
Q

Central Dogma of Genetics

A

Theory that genetic information flows from DNA -> RNA -> proteins

38
Q

Transcription

A

RNA polymerase makes a copy of template strand. mRNA synthesised based on DNA template gene.
- Cells receives chemical signal indicating promoter region (“upstream” from gene to be copied)
- Enzyme uncoils and unzips DNA in localised region

39
Q

Translation

A

Production of a protein with an amino acid sequence, based on nucleic acid sequence of mRNA.

40
Q

Promoter

A

DNA sequence that tells RNA polymerase where to start transcription, which DNA to translate, direction to take from start (TATA boxes).

41
Q

Steps in Transcription

A
  1. Initiation
  2. Elongation
  3. termination
42
Q

Initiation (Transcription)

A

Transcription machinery (made of RNA polymerase) is arranged on the template strand and binds to the promoter region.

43
Q

Elongation (Transcription)

A

RNA polymerase complex unwinds and opens in a section of the double helix. Transcription begins at the initiation site. RNA polymerase adds buses at 3’ end 5’ -> 3’

44
Q

Termination (Transcription)

A

Specific DNA sequences signal the end of the transcription. RNA polymerase falls off, mRNA free to leave. Newly synthesised mRNA from elongation complex.

45
Q

Precursor mRNA -> mature mRNA

A
  • 5’ guanine cap added (allows for easy ribosome recognition)
  • 3’ poly-A tail added (allows for ribosomes to stay on)
  • Introns spliced out exons = code
46
Q

Spliceosomes

A

Enzymes that splice the pre-mRNA, alternative splicing allows for one gene to produce multiple proteins.

47
Q

Phosphodiester Bonds

A

Covalent bond between hydroxyl group and phosphate groups on nucleotides.

48
Q

Mouse Study (WILL BE TESTED ON THIS)

A

Rough strain - mouse lives
Smooth strain - mouse dies
Heat-killed smooth strain - mouse lives
Rough strain + heat killed smooth strain - mouse dies

Heat-killed smooth bacteria
+ RNase = mouse dies
+ protease = mouse dies
+ DNase = mouse lives

49
Q

Dispersive DNA replication

A

Conserved helix breaks up and sections replicate

50
Q

Conservative DNA replication

A

Both strands are conserved and two replicate.

51
Q

Initiation (Translation)

A
  • 2 subunits (1 large and 1 small) of ribosome assemble (by initiation factors) and bind mRNA.
  • mRNA is fed through unit until it reaches start codon
  • Lines up at specific A-site
  • tRNA w/ anticodon (UAC) will enter the A site
52
Q

Elongation (Translation)

A
  • tRNA moves into p-site (growing polypeptide chain)
  • Next codon enters the A site (read by ribosome)
  • Amino acid attracted to tRNA joined via polypeptide bond
  • tRNA passes from A-site to P-site
53
Q

Termination (Translation)

A
  • When A-site contains “stop” (UAG, UAA, UAC) polypeptide is released, cleave the polypeptide from the last tRNA
54
Q

5 Levels of Control Mechanisms

A
  1. Epigenetic, 2. Transcriptional, 3. Posttranscriptional, 4. Translational, 5. Posttranslational

Biology 12 (3 decks)

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