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BIO > DNA (2.7 to HL) > Flashcards

DNA (2.7 to HL) Flashcards

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1
Q

What is the Central Dogma

A

Describes the flow of genetic information
-DNA replication
-DNA transcribed into mRNA
-mRNA translated to produce proteins

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2
Q

Why is DNA replication Semi-Conservative?

A

Each nitrogenous base can only pair with its complementary partner

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3
Q

How did Meselson-Stahl Experiment prove that DNA replication is Semi-conservative

A

-After 1st division: DNA contained both N15 & N14 isotopes (disproves conservative model)

-After 2nd division: Some DNA consists solely of N14 (disproves dispersive model)

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4
Q

What does Helicase do?

A

Separates double helix strands by breaking the Hydrogen bonds between them

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5
Q

What does Polymerase III do?

A

Synthesizes new strand from template DNA strand
Covalently joins the nitrogenous bases together.

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6
Q

Key steps of PCR

A

-Denaturation: Heat separates strands
-Annealing: Primers designate copying sequence
-Elongation: Taq Polymerase copies the sequence

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7
Q

What is transcription?

A

Synthesis of mRNA copied from the DNA base sequence by RNA polymerase

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8
Q

What does RNA Polymerase do?

A

Binds DNA and separates the strands by breaking the H bonds
Covalently joins RNA nucleotides together to form a new strand (U instead of T)

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9
Q

What is the Anti-Sense Strand?

A

The strand that is transcribed (complementary to RNA transcript)

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10
Q

what is the Sense Strand?

A

The strand that is not transcribed (identical to RNA -except T/U)

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11
Q

What is Translation?

A

The synthesis of polypeptides on ribosomes

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12
Q

What is a condon?

A

Triplet of nucleotide bases

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13
Q

What is the Process of Translation?

A

-mRNA is transported to a ribosome to read the sequence in codons

-Transfer RNA molecules carry specific amino acids, which contains anticodons that will align opposite a specific Condon on the mRNA

-Ribosomes moves along the mRNA and join the amino acids together with peptide bonds.

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14
Q

What is the Genetic code?

A

Rules by which mRNA sequence are converted into protein

-Condon correspond to a particular amino acid
-The order of codons determines the amino acid sequence of a polypeptide

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15
Q

Key Features of the Genetic Code

A

Universality: All organisms use the same code

Degeneracy: More than one codon can code for the same amino acid
|- 64 codon combinations, 20 amino acids
|- Allows for silent mutations-Mistakes might result in the same protein.

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16
Q

What is the Start Codon for Translation?

A

AUG

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17
Q

What is Translation terminated by?

A

A stop Codon

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18
Q

Where does degeneracy occur in the Transfer RNA

A

in the 3rd base postion

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19
Q

What is the Wobble Hypothesis?

A

Shape of transfer RNA is not optimal for base pairing at third position, the interaction between the anticodon and codon might “wobble”. This permits the tRNA to recognize more than one codon (Degeneracy)

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20
Q

What is a frameshift mutations?

A

When a reading frame is interrupted by insertion or deletions of a base pair. Causing the triplets to be read differently.

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21
Q

Why is Genetic Code universal?

A

almost every organism uses the exact same code
genetic information can be transferred between deferent species

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22
Q

What is a proof of the universality of the Genetic Code?

A

production of human insulin in bacteria

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23
Q

Three Main parts of a gene

A

-Promoter: The non coding sequence that is responsible for the initiation of transcription and where RNA polymerase binds

-Coding sequence: The region of DNA that is transcribed by RNA polymerase

-Terminator: The sequence that is responsible for terminating transcription

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24
Q

Outline the Process of Transcription

A

-RNA polymerase binds to the promoter and separates the DNA strands

-Nucleoside triphosphates (NTPs) bind complementary bases (antisense strand) |- RNA uses U and stead of T

-RNA polymerase moves in a 5’ to 3’ direction and covalently binds the NTPs together (involves the release of the two extra phosphates)

-When RNA polymerase reaches the terminator sequence, both enzyme and RNA sequence dissociate from he DNA and the double helix reforms

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25
Q

Exon

A

Expressing sequence (codes for polypeptide)

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26
Q

Introns

A

intruding sequences/non coding

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27
Q

Proteome

A

All the proteins that can be expressed by a genome

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28
Q

What type of cells go through Post transcription Modification?

A

Eukaryotes

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29
Q

Three post transcriptional evens

A

-Capping: A 5’ methyl cap is added to RNA, prevents degradation out of the Nuclease

-Polyadenylation: The 3’ end is polyadenylated, improves stability and export

-Splicing: Introns are removed in order to form a continuous mRNA sequence

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30
Q

What is Alternative splicing?

A

Selective removal of exons and normal removal of introns

different polypeptides can be generated from the same gene

creates a larger proteome

31
Q

Transcription factors/regulatory protiens

A

-Activator proteins bind to enhancer sites and increases rates of transcription

-Repressor proteins bind to silencer sites and decrease rates of transcription

32
Q

How does Nucleosomes regulate transcription rate?

A

Histones proteins determine how DNA is packaged
-Acetylation: Makes DNA les tightly packed and more accessible to transcriptional machinery.

-Methylation: Makes DNA more tightly packed and less accessible to transcriptional machinery.

33
Q

What happens to methylation patterns over time?

A

It changes

34
Q

Epigenetics

A

Study of changes in organism as a result of different genes expressed due to environmental factors (changes in phenotype not genotype)

35
Q

Examples of Epigenetics

A

hydrangea flowers changing colour based on pH conditions of the soil

Human producing different amounts of melanin based on UV exposure

36
Q

Two sub units of Ribosomes

A

-Small subunit: Contains an mRNA binding site

-Large subunit: Contains three tRNA binding sites (A, P, E)

37
Q

tRNA activation

A

tRNA activating enzymes attach tRNA to amino acids

Active site on each enzyme is specific to the correct amino acid and tRNA

ATP (adenosine triphosphate) is needed to attach amino acids to tRNA

The amino acid is activated by forming a bond with adenosine monophosphate

The provides energy for the amino acid to form a covalent bond with the tRNA

38
Q

Four Stages of Translation

A

-Initiation: creating a active ribosomal and mRNA complex

-Elongation: A new amino acid is added to a growing peptide chain

-Translocation: The ribosome moves to the next condon position

-Termination: Ribosomal complex and polypeptide dissociate from mRNA

39
Q

Translation Initiation

A

-Small subunit binds mRNA
-tRNA binds to start codon
-Large subunit binds tRNA via P site
-Ribosome able to translate

40
Q

Translation Elongation

A

-New tRNA enters A site
-Amino acid transferred frim tRNA in the P-site
-Peptide bond is formed between the amino acids in A site

41
Q

Translation Translocation

A

-Ribosome moves one codon position (5’ to 3’)
-tRNA from P site translocated to E site, then released
-new tRNA enteres A site

42
Q

Translation Termination

A

-Stop codon is reached
-Release factor recruited
-ribosome disassembled
-polypeptide released

43
Q

what is a Polysome?

A

polysomes are a group of two or more ribosomes translating an mRNA sequence simultaneously

44
Q

How does translation occur in prokaryotes?

A

immediately after transcription due to no nuclear membrane

In eukaryotes translation occurs in Free (cytoplasm) and bound ribosomes (rER)

45
Q

Signal recognition Particle

A

-In eukaryotes proteins destined for the rER will produce a specific amino acid sequence on their nascent polypeptide chain

This sequence recruits a signal recognition particle (SRP) that transfers ribosomes to the ER network- the polypeptide is then translated into the ER lumen.

46
Q

Primary Protein Structure

A

Describes the order of amino acids in a polypeptide sequence, formed by covalent peptide bonds between adjacent amino acids

47
Q

Secondary protein structure

A

Folding the chain into repeating arrangements
-Formed by H bonds between non adjacent amino acids

-forms alpha helices or beta pleated sheets

48
Q

Tertiary protein Structure

A

3D shape of a protein due to R group interactions and surrounding water

-positive and Negatively charged R groups form Ionic bonds

-hydrophobic amino acids orient inwards, vice versa for Hydrophilic

-Polar groups can H bond with one another

-R group in cysteine can from a covalent bond with another cysteine, forming a disulfide bridge.

49
Q

What was the Hershey-Chase experiment?

A

To determine if the genetic material is protein or DNA (it was known viruses insert genetic material into cells)

-Viruses grown in S35 had radiolabeled proteins that did not transfer

-Viruses grown in P32 had radiolabeled DNA that transferred.

50
Q

What did the data from franklin infer about the DNA model?

A

-DNA is double stranded
-Phosphates form outer backbone
-Molecules forms a double helix

51
Q

What did Franklin and Wilkins use to investigate the structure of DNA?

A

X-ray defraction

52
Q

Non Coding Function of DNA

A

S.T.I.N.G
-Satellite DNA (short tandem repeats)
-Telomeres (regions at end of chromosomes)
-Introns (non coding sequence on a gene)
-Non coding genes (code for tRNA and rRNA)
-Gene regulatory sequence (promoters)

53
Q

What is STR profiling?

A

Satellite DNA has recurring elements.
-The length of these repeats is unique to individuals
-STR loci can aid in DNA profiles

54
Q

What do nucleosomes do?

A

Histones proteins compacts DNA to form nucleosomes for effective storage.
-Further compressed to 30nm fibre, Chromatin and finally chromosome

55
Q

Nucleosomes are wrapped around an ?

A

Octamer of histone proteins

56
Q

Nucleosomes become linked together by the presence of an additional

A

H1 histone protein

57
Q

Why does DNA associate with histone proteins?

A

DNA is negatively charged and the amino acids on the surface of histones are positively charged

58
Q

What does anti-parallel strands allow?

A

Replication to occur bi directionally

59
Q

What does complimentary base parings allow?

A

Sequence is conserved during replication, makes it possible to use one strand as a template to create the other.

60
Q

Topoisomeras

A

Reduces torsional strain on DNA

61
Q

RNA Primase

A

Adds RNA primers

62
Q

DNA polymerase I

A

Replaces RNA primer

63
Q

DNA ligase

A

joins fragments together

64
Q

SSB protein

A

prevents DNA from reforming double helix

65
Q

DNA gyrase

A

a type of Topoisomerase

66
Q

DNA pol III moving towards Helicase

A

synthesis is continues (leading strand)

67
Q

Okazaki Fragments

A

Discontinuous segments on the lagging strand are called okazaki fragments (the gaps)

68
Q

DNA pol III moving away from helicase

A

synthesis is discontinuous (lagging strand)

69
Q

DNA pol I

A

Replaces RNA primers with DNA

70
Q

DNA ligase

A

Covalently joins okazaki fragments together

71
Q

What does ddNTPs do in sequencing?

A

ddNTPS (dideoxynuleotides) lack the 3’ hydroxyl group needed to form a phosphodiester bond

Terminates DNA replication

The length of a sequence will reflect the position of ddNTP

72
Q

Sanger Method

A

-Four sets of normal nucleotides (A, C, G, T) and one ddNTP (A) is prepared.
-PCR is run and whenever A is incorporated the sequence terminates, every possible terminating fragment is generated. (CA) (CTGAGA)

-Fragments run through gel electrophoresis to determine base sequence by the ordering of fragments based on their length

73
Q

RNA primase

A

adds RNA primers, starting point for replication process

BIO (9 decks)

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