DNA (2.7 to HL) Flashcards

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
Exon
Expressing sequence (codes for polypeptide)
26
Introns
intruding sequences/non coding
27
Proteome
All the proteins that can be expressed by a genome
28
What type of cells go through Post transcription Modification?
Eukaryotes
29
Three post transcriptional evens
-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
30
What is Alternative splicing?
Selective removal of exons and normal removal of introns different polypeptides can be generated from the same gene creates a larger proteome
31
Transcription factors/regulatory protiens
-Activator proteins bind to enhancer sites and increases rates of transcription -Repressor proteins bind to silencer sites and decrease rates of transcription
32
How does Nucleosomes regulate transcription rate?
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
What happens to methylation patterns over time?
It changes
34
Epigenetics
Study of changes in organism as a result of different genes expressed due to environmental factors (changes in phenotype not genotype)
35
Examples of Epigenetics
hydrangea flowers changing colour based on pH conditions of the soil Human producing different amounts of melanin based on UV exposure
36
Two sub units of Ribosomes
-Small subunit: Contains an mRNA binding site -Large subunit: Contains three tRNA binding sites (A, P, E)
37
tRNA activation
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
Four Stages of Translation
-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
Translation Initiation
-Small subunit binds mRNA -tRNA binds to start codon -Large subunit binds tRNA via P site -Ribosome able to translate
40
Translation Elongation
-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
Translation Translocation
-Ribosome moves one codon position (5' to 3') -tRNA from P site translocated to E site, then released -new tRNA enteres A site
42
Translation Termination
-Stop codon is reached -Release factor recruited -ribosome disassembled -polypeptide released
43
what is a Polysome?
polysomes are a group of two or more ribosomes translating an mRNA sequence simultaneously
44
How does translation occur in prokaryotes?
immediately after transcription due to no nuclear membrane In eukaryotes translation occurs in Free (cytoplasm) and bound ribosomes (rER)
45
Signal recognition Particle
-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
Primary Protein Structure
Describes the order of amino acids in a polypeptide sequence, formed by covalent peptide bonds between adjacent amino acids
47
Secondary protein structure
Folding the chain into repeating arrangements -Formed by H bonds between non adjacent amino acids -forms alpha helices or beta pleated sheets
48
Tertiary protein Structure
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
What was the Hershey-Chase experiment?
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
What did the data from franklin infer about the DNA model?
-DNA is double stranded -Phosphates form outer backbone -Molecules forms a double helix
51
What did Franklin and Wilkins use to investigate the structure of DNA?
X-ray defraction
52
Non Coding Function of DNA
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
What is STR profiling?
Satellite DNA has recurring elements. -The length of these repeats is unique to individuals -STR loci can aid in DNA profiles
54
What do nucleosomes do?
Histones proteins compacts DNA to form nucleosomes for effective storage. -Further compressed to 30nm fibre, Chromatin and finally chromosome
55
Nucleosomes are wrapped around an ?
Octamer of histone proteins
56
Nucleosomes become linked together by the presence of an additional
H1 histone protein
57
Why does DNA associate with histone proteins?
DNA is negatively charged and the amino acids on the surface of histones are positively charged
58
What does anti-parallel strands allow?
Replication to occur bi directionally
59
What does complimentary base parings allow?
Sequence is conserved during replication, makes it possible to use one strand as a template to create the other.
60
Topoisomeras
Reduces torsional strain on DNA
61
RNA Primase
Adds RNA primers
62
DNA polymerase I
Replaces RNA primer
63
DNA ligase
joins fragments together
64
SSB protein
prevents DNA from reforming double helix
65
DNA gyrase
a type of Topoisomerase
66
DNA pol III moving towards Helicase
synthesis is continues (leading strand)
67
Okazaki Fragments
Discontinuous segments on the lagging strand are called okazaki fragments (the gaps)
68
DNA pol III moving away from helicase
synthesis is discontinuous (lagging strand)
69
DNA pol I
Replaces RNA primers with DNA
70
DNA ligase
Covalently joins okazaki fragments together
71
What does ddNTPs do in sequencing?
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
Sanger Method
-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
RNA primase
adds RNA primers, starting point for replication process