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Biology 12 > Molecular Genetics > Flashcards

Molecular Genetics Flashcards

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
Errors in Code
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
Misplaced Bases
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
Eukaryotes vs Prokaryotes
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
Prokaryote Replication
Replication can occur in two directions at once because DNA is circular.
29
Semi-Conservative DNA replication
One old strand, one new strand after replication.
30
Gyrase
Wriggles along DNA, allowing it to unwind.
31
Leading Strand
DNA polymerase III and replication fork move in the same direction. DNA copied continuously.
32
Lagging Strand
DNA polymerase III and replication fork move in opposite directions. DNA copied in discontinuous segments.
33
Exonuclease
Removes RNA primer
34
Telomerase
(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
Triplet Hypothesis
Proposal that the genetic code is read three nucleotides bases at a time. - mRNA codons and corresponding amino acids were determined
36
Characteristics of Genetic Code
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
Central Dogma of Genetics
Theory that genetic information flows from DNA -> RNA -> proteins
38
Transcription
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
Translation
Production of a protein with an amino acid sequence, based on nucleic acid sequence of mRNA.
40
Promoter
DNA sequence that tells RNA polymerase where to start transcription, which DNA to translate, direction to take from start (TATA boxes).
41
Steps in Transcription
1. Initiation 2. Elongation 3. termination
42
Initiation (Transcription)
Transcription machinery (made of RNA polymerase) is arranged on the template strand and binds to the promoter region.
43
Elongation (Transcription)
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
Termination (Transcription)
Specific DNA sequences signal the end of the transcription. RNA polymerase falls off, mRNA free to leave. Newly synthesised mRNA from elongation complex.
45
Precursor mRNA -> mature mRNA
- 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
Spliceosomes
Enzymes that splice the pre-mRNA, alternative splicing allows for one gene to produce multiple proteins.
47
Phosphodiester Bonds
Covalent bond between hydroxyl group and phosphate groups on nucleotides.
48
Mouse Study (WILL BE TESTED ON THIS)
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
Dispersive DNA replication
Conserved helix breaks up and sections replicate
50
Conservative DNA replication
Both strands are conserved and two replicate.
51
Initiation (Translation)
- 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
Elongation (Translation)
- 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
Termination (Translation)
- When A-site contains "stop" (UAG, UAA, UAC) polypeptide is released, cleave the polypeptide from the last tRNA
54
5 Levels of Control Mechanisms
1. Epigenetic, 2. Transcriptional, 3. Posttranscriptional, 4. Translational, 5. Posttranslational

Biology 12 (3 decks)

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