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Biology > 12.4 Protein Synthesis > Flashcards

12.4 Protein Synthesis Flashcards

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1
Q

eukaryotes DNA

A
  • has ends - linear
  • very long
  • human DNA 3.2 B nucleotides
  • histone proteins (package it into cells wraps it around proteins)
  • 1 strand contains genes
  • exons and introns
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2
Q

prokaryotes DNA

A
  • dont contain a nucleus
  • shorter DNA
  • eukaryotic mitochondria + chloroplasts
  • DNA similar to eukaryotes
  • 1 strand contains genes
  • exons but no introns
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3
Q

exon definition

A

coding DNA base sequence found within a gene

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4
Q

intron definition

A

non-coding DNA base sequence found within a gene

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5
Q

similarities in prokaryotic DNA and eukaryotic DNA

A
  • P + E DNA have similar organelles
  • both made from nucleotides
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6
Q

differences in prokaryotic DNA and eukaryotic DNA

A
  • E is linear whereas P is circular
  • E is associated with histone proteins whereas P is not associated with histone proteins
  • E contains introns whereas P does not contain introns
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7
Q

4 types of RNA

A
  • mRNA
  • tRNA
  • rRNA
  • RNAi
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8
Q

codon definition

A

a sequence of 3 bases on mRNA that codes for a specific amino acid

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9
Q

anticodon definition

A

a sequence of 3 nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon

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10
Q

mRNA characteristics

A
  • single stranded
  • complementary copy of a single gene from the TEMPLATE strand of DNA
  • shorter than DNA
  • sequence of bases on mRNA complementary to sequence of bases of the gene its copying
  • G-C and A-U
  • codons
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11
Q

differences in DNA and mRNA

A
  • DNA double stranded whereas mRNA single stranded
  • DNA longer whereas mRNA shorter
  • thymine DNA whereas uracil mRNA
  • deoxyribose DNA whereas ribose mRNA
  • H bonds DNA whereas no H bonds mRNA
  • introns DNA whereas no introns mRNA
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12
Q

tRNA characteristics

A
  • polynucleotide chain of about 75 nucleotides
  • single stranded
  • cloverleaf structure held by H bonds
  • amino acid attachment site where only a specific amino acid binds
  • anticodons
  • role is to carry a specific amino acid to the ribosome
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13
Q

what does the anticodon do on the tRNA molecule

A
  • anticodon is specific to the amino acid carried by the tRNA and is complementary to the codon on the mRNA
  • the anticodon base pairs with the codon on the mRNA molecule
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14
Q

genome definition

A

complete set of genes in a cell / complete base sequence of all the DNA from a cell of an organism

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15
Q

proteome definition

A

full range of proteins that a cell is able to produce

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16
Q

loci definition

A

position of a gene within chromosome

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17
Q

allele definition

A

a different version / form of a gene

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18
Q

gene definition

A

a DNA base sequence that codes for a sequence of amino acids in a polypeptide

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19
Q

2 processes involved in protein synthesis

A

transcription and translation

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20
Q

transcription definition

A

making a copy of the base sequence of a specific gene (DNA) onto the base sequence of an mRNA molecule

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21
Q

translation definition

A

the conversion of the base sequence of mRNA (at a ribosome) into the specific amino acid sequence of a polypeptide chain (primary structure)

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22
Q

transcription of prokaryotes occurs in the…

A

cytoplasm

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23
Q

transcription of eukaryotes occurs in the…

A

nucleus

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24
Q

how does pre-mRNA turn into mature MRNA

A

its ‘spliced’

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25
Q

what is the process of ‘splicing’

A

introns removed and the exons are re-joined

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26
Q

stop codon

A

AUG

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27
Q

key processes of transcription

A
  • forming a pre-mRNA molecule from the DNA
  • removing introns to create a mature mRNA molecule
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28
Q

describe transcription

A

1 (DNA helicase) H bonds are broken so strands separate
2 only one DNA strand acts as template
3 RNA nucleotides are attracted to the exposed bases
4 (attraction) according to base pairing rule A-U, C-G
5 RNA polymerase joins (RNA) nucleotides together forming phosphodiester bonds through condensation reactions
6 Pre-mRNA spliced to remove introns (in eukaryotes)

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29
Q

what are ribosomes made from

A

rRNA and ribosomal proteins

30
Q

what does RER stand for

A

rough endoplasmic reticulum

31
Q

describe translation

A

1 mRNA binds to ribosome
2 ribosome finds the START codon
3 idea of 2 codons / binding sites
4 (allows) tRNA with complementary anticodons to bind / associate with codon
5 (catalyses) formation of peptide bond between amino acids (held by tRNA molecules) using energy from ATP
6 tRNA released as ribosome moves along (mRNA to the next codon) / translocation described
7 ribosome releases polypeptide into RER when the STOP codon is reached

32
Q

3 bases on DNA

A

triplet

33
Q

3 bases on mRNA

A

codon

34
Q

3 bases on tRNA

A

anticodon

35
Q

the genetic code characteristics

A
  • universal
  • non-overlapping
  • degenerate
36
Q

the genetic code is universal what does this mean

A

the same 3 bases on mRNA (codon) / DNA (triplets) code for the same amino acids in all organisms

37
Q

the mechanism of transcription and translation are…

A

universal throughout all organisms

38
Q

the genetic code is non-overlapping what does this mean

A
  • each base is only part of 1 triplet (DNA) / codon (mRNA)
  • during translation the ribosome reads each base only once in the codons on the mRNA - 1st 3 bases read, followed by 2nd 3 bases, then the 3rd 3 bases and so on in sets of 3
39
Q

the genetic code is degenerate what does this mean

A
  • more than 1 triplet (DNA) / codon (mRNA) codes for an amino acid
  • 20 amino acids and 64 combinations of triplets / codons
  • the 1st 2 bases are the most important when coding for amino acids
40
Q

evidence for triplet codes

A
  • 20 different amino acids and only 4 bases in any polynucleotide
  • sequence of these bases determines the 20 different amino acids
  • 4^1 = 4, 4^2 = 16, 4^3 = 64
41
Q

Mutation definition

A

Any change to the DNA base sequence

42
Q

Gene mutation definition

A
  • Single-point mutation
  • a change to a single base in the DNA base sequence of a gene.
43
Q

When do gene mutations occur and happen

A

Occur Randomly and happen spontaneously

44
Q

What would a mutation in DNA result in

A

A change in the primary structure of polypeptides, sequence of amino acids in the polypeptide chain

45
Q

What MAY the consequence be of a mutation of DNA

A
  • may alter the secondary structure (change the position of the weak H bonds affecting the alpha helices and beta-pleated sheets)
  • may alter the tertiary structure (change the position of the weak H, ionic bonds between the R groups of amino acids and the disulphide bonds) and may alter the binding site or active site of enzymes and make the protein non-functional.
46
Q

Where do mutations occur

A

During DNA replication

47
Q

3 types of mutations

A

Substitution, deletion, addition

48
Q

effect of substitution in the 3rd base

A
  • wouldn’t alter the amino acid coded for (as the 3rd codon can either be A, C, T, G)
  • silent mutation
  • mutation doesn’t change the amino acid coded for -> no effect on polypeptide chain
  • code is degenerate (more than 1 codon can code for an amino acid - the 3rd base can differ for some amino acids)
49
Q

effect of substitution in the 1st base

A
  • will change the amino acid sequence -> will alter the sequence of amino acids on the polypeptide chain -> may alter its specific tertiary structure / shape and function
50
Q

effect of substitution from a triplet to a STOP codon

A

causes the growing polypeptide chain to terminate prematurely and may not be able to perform it’s intended function (depending how early the termination occurred)

51
Q

addition / deletion mutations definition

A

1 full DNA nucleotide is gained or lost (within the gene)

52
Q

result of an addition / deletion mutation

A
  • results in an alteration of the base triplets from the mutation onwards
  • frame shift occurs (the reading frame has been shifted to the right / left by 1 base)
53
Q

effect of an early addition / deletion mutation in the sequence

A

more of the triplets coding for a polypeptide could be affected -> more of the amino acids would be altered

54
Q

effect of an late addition / deletion mutation in the sequence

A

lesser effect -> would still alter some amino acids at the end of the gene

55
Q

when do mutations occur

A
  • spontaneously during DNA replication
  • occur at a set rate (different for different species)
56
Q

mutations definition

A

natural and random events and cause permanent changes to the DNA base sequence which is passed on to future generations

57
Q

mutations are responsible for the genetic diversity of populations both in forces of…

A

natural selection and in speciation

58
Q

mutations can be 3 things

A
  • advantageous
  • disadvantageous
  • neutral
59
Q

what do mutations often produce

A

organisms that are less well adapted to their environment and can alter cellular activities

60
Q

mutation in gametes often proves…

A

fatal

61
Q

mutagenic agents increase the rate of…

A

spontaneous mutation

62
Q

3 mutagenic agents

A
  • high energy ionising radiation
  • DNA reactive chemicals
  • Biological agents
63
Q

what is high energy ionising radiation and what does it do

A
  • X / gamma rays, alpha / beta particles
  • damage the DNA molecule (bases) and chemicals that alter the DNA structure or interfere with DNA replication
64
Q

what are DNA reactive chemicals and what do they do

A
  • benzene, bromine, hydrogen peroxide
  • nitrous acid can remove an NH2 group from cytosine in DNA, converting the bases to uracil
65
Q

what are biological agents

A

some viruses and bacteria

66
Q

what are chromosomal mutations

A
  • within meiosis the cell divides -> each daughter cell contains 1 of each homologous chromosome
  • this can go wrong -> daughter cells produced containing too many chromosomes
  • a pair of homologous chromosomes may fail to separate during metaphase 1 or sister chromatids fail to separate during metaphase 2 (chromosome non-disjunction)
67
Q

example of chromosome dis-junction

A

down syndrome caused by non-disjunction of chromosome 21 (when gametes fuse at fertilisation offspring has 3 copies of chromosome 21 rather than 2)

68
Q

inversion mutations definition

A

when a segment of bases is reversed end to end

69
Q

duplication mutations definition

A

a doubling of a part of a chromosome, of an entire chromosome, or even the whole genome

70
Q

translocation mutations definition

A

when groups of base pairs relocate from 1 area of the genome to another, usually between non-homologous chromosomes

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