Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochem Y1 > Molecular Biology And Biochemistry DNA > Flashcards

Molecular Biology And Biochemistry DNA Flashcards

1
Q

Characteristic components of nucleotides

A

Nitrogenous base
One or more phosphates
A Pentose sugar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is ribose sugar more reactive the deoxyribose

A

It’s more reactive and unstable because of the OH group on the 2 carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which bases are purines

A

Adenine and guanine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which bases are pyrimidines

A

Thymine, uracil and cytosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a pyrimidine

A

Single ring nitrogenous base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Structure of dna

A

Two anti parallel strands
Each strand has a 5’ (phosphate) and 3’ end (hydroxyl)
Held together by hydrogen bonds
Antiparallel nature allows for h bond formation
Bases planar to sugar phosphate backbone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What evidence proved dna helical structure

A

X ray diffraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does the x ray diffraction of dna show a helical structure

A

X shape which is indicative
Layer line which shows the length of one complete turn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The common features of B-DNA

A

Right handed double helix
Hydrophobic core
Hydrophilic backbone
Major and minor groves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Factors towards the stability and structure of the double helix

A

Backbones separated as far apart as possible to avoid electrostatic repulsion
Bases form stablizing h bonds
Bases stack to maximise aromatic ring interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How many hydrogen bonds form between the bases

A

A +t 2
C + g 3 (

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why doesn’t non standard base pairing work

A

Distorts the geometry of the double helix the bases are no longer 1.1 nm apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are their aromatic stack interactions

A

Benzene contains an e in all p orbitals which can delocalise and form a ring of electron density around the planar ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is displacement stacking better then eclipse stacking

A

Maximises attractive interactions between dipoles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why are there major and minor groves

A

The glycosidic bonds between bases are the same distance apart so nucleotides must be at an angle
They allow for dna bonding proteins to read dna without unwinding the helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why does DNA have thymine not uracil

A

Cytosine can delaminate to uracil therefore uracil is identified and removed in dna repair processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why does RNA have uracil not thymine

A

Thymine is more energetically costly to produce as a methylated uracil
There’s no bio synthetic pathway for it to be produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is rna less stable then dna

A

OH group on c2 acts as an internal nucleophile and causes the breakage of the phosphodiester backbone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What end are nucleotides added to in replication

A

3’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does chain elongation occurs

A

The OH group on c3 has a nucleophilic attack on the primary phosphate group of another nucleotide. Hydrolysis of the other two phosphates provide energy for the reation

21
Q

What are the steps to separate the double helix

A

Helicase opens the helix by breaking the weak h bonds between bases
Topoisomerase releaves the tension in the helix by breaking the dna and reasealing to the right of the replication fork ahead of the helicase
Single stranded dna binding proteins bind to separate strands to prevent annealing

22
Q

How does dna get a 3’ OH end to start replication

A

Short rna primer is made by dna primase

23
Q

How does the antiparallrl nature of dna cause problems

A

Lagging strand is synthesised discontinuously

24
Q

What are the discontinuous stands of dna in the lagging strand called

A

Okazaki fragments

25
Q

How does replication occurs on lagging strand

A

Dna primase creates rna primers
Dna polymerase III extends the dna from 3’ OH and makes Okazaki fragments
Dna polymerase I removes RNA primase and fills gaps
Dna Ligase joins discontinuous gaps

26
Q

What’s in place to prevent dna polymerase detaching

A

Sliding clamp protein complex

27
Q

Source of error in dna repl

A

Frameshifts
Substitution mutations

28
Q

How are incorrect bases corrected

A

Dna polymerase has exonuclease activity that can remove the wrong base

29
Q

What different in the replication of circular dna

A

2 replication forks as single place of origin
Dna has multipul origins of replication

30
Q

Base requirements of transcription

A

Ribonucleoside triphosphates (NTPs)
A template
Rna polymerase
An energy source

31
Q

How is the correct place in the genome found for transcription

A

Promoter region containing specific sequences for rna polymerase and regulatory proteins

32
Q

How does rna polymerase bind to promoter

A

Sigma subunit between -35 and -10

33
Q

How does transcription stop

A

Rna polymerase has a hairpin structure of that are complementary to termination area causing release

34
Q

What the protein coding region also called

A

Open reading frame

35
Q

Transcription in prokaryotes

A

Proteins coded for that have similar function are located next to each other and transcribed together in a single mRNA called an operon

36
Q

Features of translation

A

Code must translate to one of twenty amino acids
Involves ribosomes and tRNA
mRNA read as triplet codons

37
Q

What are the three stop codons

A

UAA UAG UGA

38
Q

How are amino acids attached to tRNA

A

Aminoacyl-tRNA enzymes

39
Q

What are the three binding sites in ribosomes

A

Peptidyl
Exit
Aminoacyl

40
Q

How is translation initiated in prokaryotes

A

In the 5’ untranslated region, the shine-dalgarno pairs with the 16S rRNA which places the AUG in the p site of ribosome
A modified methionine is used for the initiating amino acid

41
Q

How is translation initiated by eukaryotes

A

The small ribosomal subunit and initiating tRNAi-Met bonds to 5’ cap and scans until AUG

42
Q

Translation elongation

A

A charged aminoacyl tRNA enters the A site and pairs with anticodon
Peptide bond is formed between the two amino acids which breaks the covalent bond between the amino acid and tRNA at p-site
The tRNA that was in the p site leaves by e site and the tRNA with the peptide chain moved to P site freeing A site
This repeatedly occurs untill a stop codon enters the a site
Release factors stimulate hydrolysis of polypeptide from tRNA

43
Q

How is DNA amplified

A

Polymerase chain reaction (PCR)
Created by Kary Mullis

44
Q

What process is PCR based on

A

Dna replication

45
Q

How many primer are needed for PCR

A

2 one for each stand of dna

46
Q

What is the process of PCR

A

Heated to 96 to denature and break hydrogen bonds
Cool to approximately 55 to allow rna primers and extremophile dna polymerase (taq polymerase) to bond
Heat to 72 for extention

47
Q

What type of DNA sequencing is used for dna tech

A

Sanger sequencing

48
Q

What can be inserted to prevent further extention

A

Dideoneucleotides because it has only hydrogen on c3 so sugar phosphate backbone can’t form

49
Q

How does Sanger sequencing work

A

A mixture of dNTP and ddNTPs are added the ddNTPs with Florescent tags
Dna polymerase extends strand complementary to template
Generated multipul fragments of different lengths different by one nucleotide so the sequence can be discovered
Fragments are separated by size by capillary electrophoresis

Biochem Y1 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions