Protein synthesis and selection Flashcards

1
Q

What is a mutation? (1)

A

Change to the DNA base sequence

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2
Q

How and when do mutations occur? (2)

A

Randomly and spontaneously
During DNA replication

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3
Q

Why might a mutation not lead to change in the amino acid sequence (2)

A

Genetic code is degenerate (mutation may end up coding for the same amino acid as the original triplet)
Mutation may occur in an intron

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4
Q

What is a silent mutation?

A

Alters a base but does not change the amino acid coded for (the code is degenerate)

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5
Q

What is a substitution mutation? (2)

A

One nucleotide takes place of another - usually leads to no change in the amino acid sequence

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6
Q

What is an addition mutation? (1)

A

When one or more bases are added

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7
Q

What is a deletion mutation? (2)

A

One nucleotide is removed from a gene or DNA sequence - harmful and significant because it leads to a frameshift which means the entire amino acid sequence will be different

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8
Q

What does an addition/deletion mutation cause? (1)

A

Results in alteration of the base triplets from the mutation onwards and so is known as a frameshift

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9
Q

How do mutations lead to non-functional proteins? (5)

A

Alter the primary structure of polypeptides
So alter the secondary structure and change the positions of the weak hydrogen bonds affecting alpha helixes and beta pleated sheets
Alter the tertiary structure (change positions of H-bonds, ionic bonds and disulphide)
Alter the binding site of proteins and make them non-functional

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10
Q

What are mutations responsible for in the forces of natural selection and in speciation? (1)

A

Genetic diversity of populations

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11
Q

What are mutagenic agents? (1)

A

Outside factors that increase the rate of spontaneous mutation

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12
Q

Examples of mutagenic agents? (3)

A

High energy ionizing radiation (X-rays, UV light, gamma rays)
DNA reactive chemicals (benzene, hydrogen peroxide)
Biological agents such as some viruses and bacteria

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13
Q

What is a chromosomal mutation and what does it cause? (2)

A

Mutations that produce changes in whole chromosomes
Causes chromosome non-disjunction

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14
Q

What is chromosome non-disjunction? (2)

A

When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal.

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15
Q

What is inversion mutation? (1)

A

When a segment of bases is reversed end to end

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16
Q

What is duplication mutation? (2)

A

Doubling of a part of chromosome or of an entire chromosome or even the whole genome
When one or more bases are repeated

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17
Q

What is translocation mutation? (1)

A

When groups of base pairs relocate from one area of the genome to another, usually between non-homologous chromosomes
Moves a segment from one chromosome to another, nonhomologous one

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18
Q

What is a phenotype? (1)

A

The expression of the genetic constitution and its interaction with the environment

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19
Q

What is a genotype? (1)

A

Genetic makeup of an organism (all the alleles an organism has)

20
Q

What is genetic diversity? (1)

A

The number of different alleles in a population

21
Q

What advantage does high genetic diversity provide? (2)

A

Ability to adapt to a change in environment
Allows natural selection to occur

22
Q

What are selection pressures? (1)

A

External agents which affect an organism’s ability to survive in a given environment

23
Q

Describe natural selection (6)

A

Variation due to mutation
Different environmental/selection pressures
Selection for advantageous allele
Differential reproductive success/(selected) organisms survive and reproduce
Leads to change in allelic frequency
Occurs over a long period of time

24
Q

When does stabilising selection occur? (1)

A

When environment is stable/the same

25
What is stabilising selection? (2)
When the environment favours the average (most common characteristic - eliminates extremes) Reduces diversity and reduces opportunity for evolutionary change
26
What is directional selection and when does it occur? (2)
Favour an extreme phenotype Occurs when environmental conditions change
27
What does a mean in population represent? (1)
Optimum phenotype for existing conditions
28
What is disruptive selection? (1)
Favours 2 extreme phenotypes
29
What is evolution by natural selection? (1)
Change in allelic frequencies within a population
30
What is the genome? (1)
Complete set of genetic information contained in the cell of an organism
31
What is a proteome? (1)
Full range of proteins that a cell is able to produce
32
What does loci mean? (1)
Position of a gene within the chromosome
33
What is a gene? (1)
DNA base sequence coding for a single polypeptide
34
What are exons and introns? (2)
Exons - sequence of nucleotides that code for the amino acid sequence Introns - non-coding sequence of nucleotides
35
Where are introns found? (1)
Between exons within genes
36
Describe transcription (5)
DNA helicase breaks hydrogen bonds so that the strands separate Only one strand acts as a template RNA nucleotides attracted to exposed bases Adenine - Uracil and Guanine - Cytosine RNA polymerase joins adjacent nucleotides together forming phosphodiester bonds through condensation reaction pre-mRNA spliced to remove introns
37
Describe translation (8)
mRNA binds to ribosome Ribosome finds the start codon Only 2 codons can fit the ribosome at one time tRNA with complementary anticodon binds to the codon on mRNA tRNA brings a specific amino acid Catalyses formation of peptide bonds between amino acids, held by tRNA, using energy from ATP tRNA released as ribosomes move along Ribosome releases polypeptide when the stop codon is reached
38
What are ribosomes made of? (2)
rRNA and ribosomal proteins
39
What is the genetic code? (2)
Order of bases on DNA Consists of codons
40
Identify and describe the features of the genetic code (3)
Non-overlapping - Each base is read once in a triplet Degenerate - more than one triplet can code for the same amino acid Universal - The same 3 bases on mRNA/DNA code for the same amino acids in all organisms
41
What is a population? (1)
All the organisms of a particular species that live in the same habitat
42
Give and explain an example of directional selection (3)
Antibiotic resistance Bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce Frequency of the allele will increase and the population will shift to have greater antibiotic resistance
43
Give and explain an example of stabilising selection (2)
Birth weight Babies that weigh around 3kg are more likely to survive than those at lower or higher weights
44
Define a niche (1)
Role of a species within its environment Species sharing the same niche will compete with each other
45
What are the three types of adaptation and give an example of each (6)
Anatomical (changes to body structure) - oily fur Physiological (changes to bodily processes) - venom production Behavioural (changes to actions) - hibernation