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BIOCHEM DNA protein synthesis Flashcards

1
Q

what does DNA and RNA stand for and what polymers of subunits are they?

A

deoxyribonucleic acid
ribonuclueic acid
polymers of subunits known as nucleotides(nucleic acids)

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2
Q

why are DNA and RNA important?

A

important info carrying molecules
DNA holds gentic info
RNA transfers genetic infro from RNA to ribosomes

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3
Q

what is a nucletoide formed up from?

A

-pentose sugar
- phosphate group
- 1 of 4 nitrogen contianing bases

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4
Q

what is the structure of DNA and made it up?

A

wastson and crick
consists of 2 polynucleotide strands joined together by hdrogen bonding to make a doubke helix

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5
Q

what does each DNA nucleotide specifcally have?

A
  • pentose sugar (deoxyribose)
    -phosphate group
    -1 of 4 nitorgen contianing bases
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6
Q

what are the nucleotides within each strand joined by and in what reaction?

A

phosphodiester bonds in a condensation reaction

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7
Q

what is the sugar+phosphate together known as?

A

backbone

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8
Q

how are the ogranic bases positioned and why are they positioned like this?

A

orientated towards centre of helix to protect them from reacting with other chemicals

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9
Q

how do the bases on one stand join to the bases on the other strand and by which bonds?

A

joined by complementary base pairing A+T C+G, joined by hydorgen bonds on own weak however large number is good

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10
Q

with the DNA Helix being further coiled how is this a positive?

A

super helix so has compact store

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11
Q

how are genes linked to DNA and what do they determine?

A

-sections of DNA that have coded information as a speicifc sequence of bases which code for polypeptides

  • genes determine nature and development of organisms
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12
Q

what does DNA have the ability to do on its own and why is it vital what does it help?

A

self-replicate which is needed for cell division

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13
Q

can DNA have alternations within its base sequences, what are they and how is it a positive?

A

yes known as mutations, give gentic diversity + via natrual selection basis for evolution

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14
Q

how does structure of sugar-phosphate backbone, Helix, double starnded and large molecule, many H bonds, sequence of bases, complementary base pairing relate to its function?

A

-sugar-phosphate provides strength

  • helix- compact shape, protects bases
  • double stranded- used as template in replication, protection bases, more stable

large molecule- stores large amount info

many H bonds- gives stability as few its weak + easily unzip during replication

sequence of bases-code for speicifc sequence of amino acids in a polyppetide

Complementary base pairing- enables info to be replicated right

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15
Q

Describe process of semi-conservative mechanism of DNA replication?

A
  1. when DNA replicates, DNA HELICASE unwind double helix (breaks H bonds between complementary bases) of 2 polynucleotide strands
  2. both starnds are templates for formation of 2 new complementary strands
  3. indivudal DNA nucleotides allign+ attach by Hydrogen bonding to exposes bases ( specific complemetary base pairing) A+T C+G

4.DNA nucleotides in each NEW strand join together by phosphodiester bonds by DNA POLYMERASE to make new complementary starnds to original DNA strands

  1. 2 DNA molecules identicial to each othether + original DNA
  2. each newly made DNA molecule has 1 of original polynucleotide starnds + new starnds ( semi-conservative)
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16
Q

whi collected evidence for semi-conservative replication + how did they figure this out?

A

meselson+ stahl

1st gen/divison - each DNA molecule 1 starnd of heavy isotope 15n + 1 14n

2nd gen= 50% DNA molecules 1 starnd od 15n and 1 strand 14n
50 % had DNA starnds both 14n

3gen- 25% DNA molecules had 1 strand 14n and 1 starnd 15n
75% DNA molecule both strands 14n

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17
Q

give a short summary how meselson + stahl proves nelson+ cricks semi conservative replication?

A
  • grew bacteria in mediums with 2 different isoptopes nitrogen
    14n ligjhter and 15n heavier
  • nitrogen isotopes incorprotates in DNA nucelotides to make nitrogenous bases and seperates according to density using centrifuge
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18
Q

give structure of DNA

A

-short polynucleotide chains
- pentose sugar ( ribose)
- ogranic base uracil replaces thymine A+U C+G
-mRNA + tRNA single stranded unlike DNA which is dounle

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19
Q

give structure of mRNA ( messenger RNA)

A
  • linear structure
  • codons ( mRNA base triplets)
  • involved in protein synthesis
  • made nucelus during transcription
  • moves to ribosomes in cytoplasm where protein synthesis occurs
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20
Q

describe structure of tRNA

A
  • 20 different types
  • found cytoplasm
    -clover-leaf structure due to H bonds between complementary base pairs
  • one end of molecule has anticodon( 3 unattached tRNA nucelotide bases)
  • other end had binding site for speciifc amino group
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21
Q

what is rRNA made up of?

A

made of RNA + proteins

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22
Q

deacribe differences in structure beteen mRNA + tRNA

A

mRNA
- linear structure
-codons
-no binding site
-no H bonds

tRNA
- clover leaf structure
- anticodonds
-binding site
- H bonds

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23
Q

what type of structure does DNA molecules have in prokaryotes + eukaryotes and what type of DNA do mitcochondria + chlorplasts have?

A

DNA molecules in prokaryotes- short + circular not associated with proteins

DNA molecules in eukaryotes long+ linear + associated with proteins (histones)

  • mitochondria+ chloroplasts have own DNA like prokaryotes
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24
Q

what is a chromosome made up of?

A

DNA molecule+ protein

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25
what does gene do on chorosome?
-occupies fixed position (locus) on particular DNA chromosome
26
what is definition of an allele?
- form of GENE - code for different types of same characteristics
27
where are alleles of particular gene located ?
in same position locus on homologous chromosome
28
what type of genes do homologous chromosomes carry?
carry genes controlling same characteristics but not same alleles eg eye colour brown + blue
29
what do pair of homologous chromsomes consist of?
-paternal + maternal
30
Definition of gene and what do they also code for other than DNA
sequence of DNA bases code for speicifc amino acid sequence of polypeptide code for RNA too
31
what is a base triplet and what does it code for?
3 nucleotide bases codes for specific amino acid
32
what kind of base triplets are in mRNA and what are they known as?
DNA base triplets + RNA base triplets known as codons
33
what would 4 different nucelotides make?
4^3 = 64
34
why is triple code known as degenerate?
different triplets/cododons coding for same amino acid
35
what do stop codes do and what do they indicate?
stop code triplet code does NOT code for amino acid -indicates end of code for speciifc polypeptide
36
what is DNA triplet start code for all sequences coding for polypeptide?
ATG
37
what does it mean if the code is non-overlapping and universal?
non-overlapping so each base only read ONCE part of speciifc triplet universal= same triplet code for same amino acids in all organisms
38
does most of the DNA in eukaryotes code for polypeptides and what are they called?
- no only exons do - intronds base sequences within genes but do not code for speciifc amino acids unlike exos - multiple repeats- same base sequeneces present between genes often(non-coding) consists of same base sequence occuring again
39
what is the genome and proteome?
genomse- full set of genes (non-coding DNA) in a cell proteome-full range of proteins cell is able to make
40
what 2 main processes occur in protein synthesis and what do they do and where are they found?
trancription- occurs in nucleus + reqrites part of DNA into strand of MRNA translation occurs in cytoplasm + involves ribosomes synthesising proteins using info given by mRNA
41
describe process of transcription
1. in nucleus, rewrites part of DNA into mRNA strand 2. needed section of DNA molecule UNCOILS+ 2 starnds seperate as H bonds broken 3. ONE of starnds used as template 4.individual nucleotides line up alongisde DNA nucleotide bases on template strand ( speciifc complementary base pairing) U+A 5. sequence bases in mRNA starnd same as non-template except uracil replaces thymine 6. individual RNA nucleotides join togethher by enzyme RNA polymerase to make starnd of mRNA 7. mRNA strand follows splicing, leaves nucleus through nuclear pore + attaches to ribosomes in cytoplasm where translation occurs 8. strand of DNA recoil when sufficent mRNA made
42
what occurs in splicing and what is it known as and does it occur in prokaryotes too?
removal of introns + joining exons together to make mRNA known as post transcriptional processing doesnt occur in prokaryotes as there is o introns
43
what does translation do
- sequence of codons on mRNA starnd used to dtermine seuneces of amino acids in a polypeptide carried out by ribosomes in cytoplasm where there is 2o diff types of TRNA
44
describe process of translation?
1. mRNA binds to ribosome in cytoplasm 2. tRNA molecule with complementary anti-codon base sequence binds to first codon on mRNA strand at ribosomes, which has 2 binding sites so 2 tRNA molecules bind to 2 codons on mRNA 3. amino acid on first tRNA molecule attaches to amino acid on second t-RNA molecule by PEPTIDE bond, in condensation reaction ( needs hydrolysis of ATP to release energy +action of enzyme) 4. 1st tRNA molecule moves away from ribosome leaving amino acid behind+ collects another molecule of same amino acid in amino acid pood 5. ribosome moves alomg mRNA + other tRNA molecules in order determined by codons on mRNA starnd.process continues until all codons are read up to stop codon _ specific polypeptide has been made 6. polypeptide folds itself into secondary+ tertiary structure 7. sequence of amino acids in polypeptide has been determined by codons on mRNA strand 8. as mRNA transcribed from DNA template, sequence of DNA nucleotides determine speciifc polypeptide made
45
what are gene mutations and what is made?
change in sequence of nucleotide bases in DNA and new alleles made by mutations
46
how can gene mutations occur?
-occur spontaneously or by mutagenic agent - may arise during DNA replication - mutation rate increased by muatgenic agent -mutations can result in different amino acid sequence in encoded polypeptide due to altered base sequence
47
do muations change result in encoded amino acid?
not all due to degeneracy nature some change ony one triplet code however some change nature of all base tripleys dowstream from a mutation known as frame shift
48
what are the different ways sequence of nucelotide bases can be altered?
substitution, deletion, additon, inversion, duplication + translocation
49
what does substitution do and result in?
replacment of 1 or more bases ( single base) - new triplet coding for different amino acid (non-function) maybe - 1 different amino acid butstill functional protein -same amino acid coded due to degenrate nature eg COA + CGG code for same amino acid so polypeptide remains unchanged
50
what does deletion do and result in?
removal of 1 or more bases - results in frameshift so alternation n base tripleys from point of deletion, -sequence of amino acids altered from point of deletion + so protein made nearly always non-functional
51
what does addition do and result in?
adding 1 or more bases -results in frameshift too so sequence of amino acids altered point of addition so protein made nearly always non-functional
52
what does duplication do and result in?
1 or more bases repeated -frame shift from point
53
what do inversion + translocation do and result in?
inversion-sequence of bases reverses translocation- sequence of bases moved from one locaton to another part of genome
54
how do alleles occur and are they the same in theit base sequences
due to mutations - alleles of gene differ in base seuqnece + code for differenr sequence of Amin acids + sometimes this change in polypeptide makes protein made no-functional?
55
how does change in amino acid affect its structure + bonding?
affects position of hydrogen+ ionic bonds or disulfide which changes tertiary structure
56
if a protein codes for an enzyme what does change in the tertiary structure affect it?
change in its structure may change shape of active site + enzyme is then nonfunctional as substrate is not complementary and enzyme-substrate complex don't form
57
what are most common polypeptides coded by genes?
enzymes
58
how does gene muatation taht results in change of amino acids in polypeptide affect activity of an enzyme?
- amino acids changes may be at active site + substrate cant attach making enzyme non-functional - amino acids changes may be at active site and substrate can attach but less efficient (slowing down enzyme activity) - amino acids changes may be away from active site but affects tertiary strcuture and shaoe of active site so still affects enzyme activity -metabolic pathways often involve several enzymes and mutattion affectivity of 1 enzymes may block metabolic pathway
59
what type of mutation occurs in sickle cell anemia?
Substitution of single base, so change in base sequence amino acid gluatmin acid replaced by valine in beta polyppetide chains of haemoglobin molecule
60
what does change in beta polypeptide chain result in?
causes red blood cells carrying haemoglobin to develop sickle cell characteristics so altered haemoglobin less efficent at carrying O2
61
where is allele for sickle cell more prevalent in?
areas where malaria is endemic eg parts of Africa, also higher frequency of allele if individuals who are heterozygous have selective advantage only suffer marginal effects of it but lower infecton rate from malaria as parasite has difficulty penetrating sickle shaped red blood cells
62
what 2 main sets of genes control rate of division and what caan mutations of these 2 genes lead to?
proto-oncogenes : stimulate cell division tumour supressor genes- slow cell divisions mutations of these genes can lead to cancer as rapid uncontrollable cell division takes place making a tumour
63
how can mutations of oncogenes and tumour supressor genes lead to cancer?
oncogenes-stimulates cells divide too quickly- can cause a tumour tumour supressor gene- inactivates it allowing rate to increase
64
how can regulation of transcription of target genes be stimulates or inhibited?
when specific transcription factors move from cytoplasm to nucelus
65
what is a transcription factor?
protein present in cytoplasm + binds to speciifc sequence(promoter region) within DNA in nucelus that stimulates or inhibits transcription of gene
66
hormones can under go regulation of trancription how?
some hormones able to enter target cell and once inside function by stimulating or inhibiting expression of particular gene in target cell
67
how does oestrogen increase expression of a particular gene?
1. oestorgen= lipid soluble as its steroid hormone (from cholesterol) so can easily difffuse across cell membrane 2. oestrogen specifically binds to receptor prorein thats PART of transcription factor 3. transcription factor enters nucelus + binding of oestorgen changes shape of transcription factor + allows it to bind specifically to PROMOTER sequence of particular gene 4. allows RNA polymerase to attach to gene and catalyse transcription of gene 5. mRNA transcribed from gene which is translated into protein
68
how does oestrogen link to breast cancer and what drug can prevent?
-high blood conc of oestorgen leads to increase risk of breast canecer as stimulates uncontollable cell division - tamoxifen converted to endoxifen which has similar structure to oestorgen to sompetes with it binding to oestrogen receptor inhibiting its effect
69
what is regulation of translation?
translation of mRNA made from target genes can be inhiibted from RNA interference RNAi involves siRNA or small interfering RNA
70
what is structure of siRNA and what is its job?
siRNA molecules short,double stranded sections of RNA 20-25 basr pairs long siRNA regulates gene expression by causing mRNA to be broken down after transcription preventing translation
71
how does siRNA prevent translation ?
1. longer double stranded molecules of RNA are hydrolysed ( by enzyme) into shorter molecules 2. RNA becomes single stranded siRNA and siRNA bind to enzyme that hydrolyses mRNA 3. siRNA binds to specifc moleculoe of mRNA by complementary base pairing so siRNA guides hydrolytic enzyme to target molecule of mRNA 4. enzyme hydrolyses mRNA molecule which prevents translation of mRNA into protein

SEMESTER 1 (8 decks)

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