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Biology Noor > 12.13 Proteinsynthesis and Selection > Flashcards

12.13 Proteinsynthesis and Selection Flashcards

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1
Q

What bonds are nucleotides joined by?

A

Phosphodiester bonds

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2
Q

Structures in DNA nucleotide

A

Phosphate group
Deoxyribose sugar
Nitrogenous base

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3
Q

Purine bases

A

Adenine
Guanine

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4
Q

Pyrimidine bases

A

Thymine
Cytosine

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5
Q

Adenine pairs with…

A

Thymine

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6
Q

Cytosine pairs with…

A

Guanine

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7
Q

Difference between eukaryotic DNA and prokaryotic DNA

A

Linear vs Circular
Histones vs No histones
Introns vs No introns

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8
Q

Structures in RNA nucleotide

A

Phosphate group
Ribose sugar
Nitrogenous base

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9
Q

In RNA, Adenine pairs with…

A

Uracil

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10
Q

Differences between mRNA and DNA

A

Double-stranded vs Single-stranded
Longer vs Shorter
GC + AT vs GC + AU
Hydrogen bonds vs NO Hydrogen bonds
Introns vs NO Introns
Triplet vs. Codon

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11
Q

mRNA Characteristics

A

Single-stranded
Shorter than DNA
GC + AU
Ribose
No hydrogen bonds
No introns
Codon

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12
Q

tRNA characteristics

A

Single stranded
Shortest- 75 nucleotides
Uracil
Ribose
Some hydrogen bonds
Amino acid attachment site
Anticodon

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13
Q

Two processes in protein synthesis

A

Transcription
Translation

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14
Q

Describe Transcription in Eukaryotes

A
  1. Hydrogen bonds (between DNA bases) break;
  2. (Only) one DNA strand acts as a template;
  3. (Free) RNA nucleotides align by complementary base pairing;
  4. (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
  5. RNA polymerase joins (adjacent RNA) nucleotides;
  6. (By) phosphodiester bonds (between adjacent nucleotides);
  7. Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
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15
Q

Describe Transcription in Eukaryotes

A
  1. Hydrogen bonds (between DNA bases) break;
  2. (Only) one DNA strand acts as a template;
  3. (Free) RNA nucleotides align by complementary base pairing;
  4. (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
  5. RNA polymerase joins (adjacent RNA) nucleotides;
  6. (By) phosphodiester bonds (between adjacent nucleotides);
  7. Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
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16
Q

Describe Translation

A
  1. (mRNA attaches) to ribosomes and ribosome finds start codon to attach to.
  2. (tRNA) anticodons (bind to) complementary (mRNA) codons;
  3. tRNA brings a specific amino acid;
  4. Amino acids join by peptide bonds with the use of ATP;
  5. tRNA released (after amino acid joined to polypeptide);
  6. The ribosome moves along the mRNA to enable other complementary tRNA molecules to attach to next codon on mRNA;
  7. Ribosome releases polypeptide into RER;
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17
Q

Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).

A

. mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
2. mRNA does not have an amino acid binding site, tRNA does;
3. mRNA has more nucleotides;
4. (Different) mRNAs have different lengths, all tRNAs are similar / same length;
5. mRNA has codons, tRNA has an anticodon;

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18
Q

3 ways to describe genetic code

A

Universal
Non-overlapping
Degenerate

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19
Q

Universal genetic code

A

The same 3 bases on DNA code for the same amino acid in all organisms

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20
Q

Non-overlapping genetic code

A

A base from one triplet cannot be used in an adjacent triplet

21
Q

Degenerate genetic doe

A

More than one triplet/codon codes for an amino acid

22
Q

What is a gene mutation?

A

Change to a single base/nucleotide (sequence of chromosomes/DNA resulting in a mutation
Mutations occur randomly and could happen spontaneously
Results in the formation of new allele

23
Q

What can a mutation result in?

A
  1. Change in the PRIMARY STRUCTURE OF POLYPEPTIDES sequence of amino acids in the polypeptide chain
  2. May alter the SECONDARY STRUCTURE by changing the position of the weak hydrogen bonds affecting the alpha helixes and beta-pleated sheets
  3. May alter the TERTIARY STRUCTURE by changing the position of the weak Hydrogen, Ionic bonds between the R groups of amino acids and the Disulphide bonds
  4. May alter the ACTIVE site of enzymes and make the protein non-functional.
24
Q

What is a silent mutation?

A
  • Mutation does not change the amino acid coded
  • So will have no effect on the polypeptide chain
  • As DNA code is degenerate
25
Q

3 types of gene mutation

A

Substitution
Addition
Deletion

26
Q

Substitution mutation

A

Substitution of a base with another base

27
Q

What happens if there is a mutation for the STOP codon?

A
  • Causes the growing polypeptide chain to terminate prematurely
  • May not be able to perform its intended function
28
Q

Addition/Deletion Mutations

A
  • Nucleotide added or deleted
  • Alteration of base triplet from the mutation onward
  • Reading frame has been shifted and is known as a frameshift
  • Addition/deletion that occurs towards the end of a sequence of bases would have a lesser effect but still alter some amino acids at the end of a gene
29
Q

Examples of mutagenic agents

A
  1. High energy ionising radiation x-ray and gamma-rays
  2. DNA reactive chemicals such as benzene or bromine
  3. Biological agents such as viruses and bacteria
30
Q

What do mutagenic agents do?

A

Increase rate of spontaneous mutation

31
Q

Define chromosome non-disjunction

A

Where daughter cells are produced containing too many chromosomes.
Pair of homologous chromosomes may fail to separate during metaphase 1 OR sister chromatids may fail to separate in metaphase 2.

32
Q

Types of chromosomal mutations

A

Inversion
Duplication
Translocation

33
Q

What is an inversion mutation?

A

When a segment of bases or a chromosome is reversed end to end.

34
Q

What is a duplication mutation?

A

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

35
Q

What is a translocation mutation?

A

When groups of base pairs relocate from one area of the genome to another. This usually is between non-homologous chromosomes

36
Q

Allele definition

A

Different) form/type/version of a gene / different base sequence of a gene;

37
Q

A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how

A
  1. Change in base sequence (of DNA/gene);
  2. Change in amino acid sequence / primary structure (of enzyme);
  3. Change in hydrogen/ionic/ disulphide bonds;
  4. Change in the tertiary structure/active site (of enzyme);
  5. Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
38
Q

Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.

A
  1. Triplets code for same amino acid
  2. Occurs in introns /non-coding sequence;
39
Q

Genetic diversity/gene pool definition

A

Number of different alleles of genes in a population

40
Q

Natural selection definition

A

The process by which organisms better adapted to their environment will survive and reproduce in greater numbers, increasing the frequency of advantageous alleles within the population.

41
Q

Explain how selection occurs in living organisms

A
  1. Variation due to mutation;
  2. Different environmental/abiotic/biotic conditions / selection pressures;
  3. Selection for different/advantageous, features/characteristics/mutation/ /allele;
  4. Differential reproductive success / (selected) organisms survive and reproduce;
  5. Leads to change in allele frequency;
  6. Occurs over a long period of time;
42
Q

Describe stabilising selection

A
  • Occurs in all populations where the environment is stable.
  • Selection pressures at both ends of the distribution.
  • Favours the average.
  • Tends to eliminate extremes.
  • Reduces variability (the range within pop smaller)
  • Reduces opportunity for evolutionary change.
    E.G. human birth mass. Heavy and light babies show higher neonatal mortality= over time reduction in the number of heavy and light babies.
43
Q

Describe directional selection

A
  • Mean in population represents optimum phenotype for existing conditions.
  • Environmental change may produce new selection pressure that favours an extreme phenotype.
  • Change in conditions will favour the allele combination/extreme necessary for survival.
  • Some organisms possess optimum allele combinations.
  • Over time, selection will mean this allele combination will predominate and mean phenotype will shift.
    E.G. light coloured moths turning to dark coloured moths after industrial revolution
44
Q

Describe disruptive selection

A
  • Opposite of stabilising selection.
  • Environment has selection pressures that favour 2 extreme phenotypes.
  • When conditions change, the optimum phenotypes necessary for survival will also change.
  • Some organisms will possess new extreme phenotypes, and over time selection means that these - 2 extremes will dominate and mean will shift in both directions towards 2 extremes.
  • Least common type of selection, most important in evolution.
    E.G. mice living at a beach with light-coloured sand and tall patches of grass so two extremes of light-coloured mice and dark-coloured mice camouflage in two areas.
45
Q

What are viable counts of bacteria

A

Counts living cells only

46
Q

How to calculate bacteria after given number of replications

A

2^n
n= number of divisions of bacteria

47
Q

How to find number of divisions when given number of bacteria

A

Log(2)n
n= number of bacteria present

48
Q

Define ‘gene mutation’ and explain how a gene mutation can have:
- no effect on an individual
- a positive effect on an individual

A

(Definition of gene mutation)
1. Change in the base/nucleotide (sequence of chromosomes/DNA);
2. Results in the formation of new allele;

(Has no effect because)
3. Genetic code is degenerate (so amino acid sequence may not change);
OR
Mutation is in an intron (so amino acid sequence may not change);
4. Does change amino acid but no effect on tertiary structure;
5. (New allele) is recessive so does not influence phenotype;

(Has positive effect because)
6. Results in change in polypeptide that positively changes the properties (of the protein)
OR
Results in change in polypeptide that positively changes a named protein;
7. May result in increased reproductive success OR
May result in increased survival (chances);

Biology Noor (30 decks)

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