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AQA A-LEVEL BIOLOGY > 4. Genetics, Biodiversity and Classification > Flashcards

4. Genetics, Biodiversity and Classification Flashcards

1
Q

Gene

A

section of DNA base sequences that code for a polypeptide or functional RNA

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2
Q

Allele

A

a different version of the same gene, codes for slightly different versions of the same polypeptide

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3
Q

Exons

A

base sequences of DNA that code for polypeptide

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4
Q

Introns

A

base sequences of DNA that don’t code for polypeptide

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5
Q

Non-coding multiple repeats

A

repeating base sequences of DNA that don’t code for polypeptide, positioned between genes

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6
Q

Eukaryotic DNA

A

found in the nucleus, long linear molecule, wrapped around histones, coiled up into a chromosome, introns present

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7
Q

Prokaryotic DNA

A

found in the cytoplasm, short circular molecule, not associated with histones, condenses to fit into cell by supercoiling, introns not present

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8
Q

Degenerate

A

the same amino acid can be coded for by more than one triplet

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9
Q

Universal

A

the same triplets code for the same amino acids in all living organisms

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10
Q

Non-overlapping

A

each triplet is only read once

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11
Q

Genome

A

complete set of genes in a cell

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12
Q

Proteome

A

full range of proteins a cell is able to produce

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13
Q

mRNA

A

single stranded, linear polynucleotide strand, made of codons, carries the genetic code from the nucleus to the ribosome

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14
Q

tRNA

A

single stranded, clover shaped polynucleotide strand held in place by hydrogen bonds, has an anticodon at one end and an amino acid binding site at the other end, brings specific amino acid to the ribosome

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15
Q

Transcription

A

DNA helicase breaks hydrogen bonds between complementary base pairs, unwinding helix into two single strands, one strand acts as a template, free RNA nucleotides bind to exposed based on template by complementary base pairing, RNA polymerase joins adjacent nucleotides forming phosphodiester bonds, forming pre-mRNA

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16
Q

Splicing

A

introns are removed from pre-mRNA to form mRNA, only occurs in eukaryotes

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17
Q

Translation

A

ribosome binds to mRNA at the start codon, tRNA brings specific amino acid to the ribosome, tRNA anticodon binds to mRNA codon by complementary base pairing, amino acids join by condensation reactions forming peptide bonds using energy from ATP, ribosome moves along mRNA to form the polypeptide

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18
Q

Gene mutation

A

change to the base sequence of DNA, occurs during DNA replication (eg. addition, deletion, substitution)

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19
Q

Substitution

A

one base is replaced by another, triplet may still code for the same amino acid as DNA is degenerate

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20
Q

Deletion

A

one base is removed, causes a frame shift which alters all subsequent triplets

21
Q

Chromosome mutation

A

change to the number of chromosomes, occurs during meiosis (eg. chromosome non-disjunction)

22
Q

Chromosome non-disjunction

A

chromosomes don’t separate properly during meiosis, leads to an uneven number of chromosomes in the gametes

23
Q

Mutagenic agents

A

factors that increase rate of mutations (eg. UV radiation, ionising radiation)

24
Q

Diploid

A

two copes of each chromosome in a cell

25
Q

Haploid

A

one copy of each chromosome in a cell

26
Q

Random fertilisation

A

random which haploid sperm fuses with which haploid egg to form a diploid zygote, increasing genetic diversity

27
Q

Homologous pairs

A

pairs of chromosomes that carry the same genes but different alleles

28
Q

Meiosis

A

cell divides twice to produce four genetically different haploid daughter cells, occurs in the reproductive organs of eukaryotic organisms

29
Q

Meiosis process

A

DNA replicates and condenses into double-chromosomes (appearing as two sister chromatids joined by a centromere), in the first division homologous chromosomes separate, in the second division sister chromatids separate

30
Q

Independent segregation

A

homologous pairs randomly line up at the equator so it’s random with chromosome from each pair ends up in each daughter cell, creating daughter cells with different combinations of chromosomes, increasing genetic diversity

31
Q

Crossing over

A

homologous pairs line up at the equator during meiosis I, parts of the chromatids twist round each other, break off and exchange alleles, creating gametes with different combinations of alleles, increasing genetic diversity

32
Q

Genetic diversity

A

number of different alleles in a population, measured by comparing the base sequence of DNA, mRNA and the amino acid sequence of proteins

33
Q

Gene pool

A

all the genes and alleles in a population at a particular time

34
Q

Evolution

A

gradual change in allele frequency over time

35
Q

Adaptations

A

features that help organisms survive in their environment, can be behavioural, physiological or anatomical

36
Q

Natural selection

A

variation exists in the population due to mutation, individuals who are better adapted to their environment are more likely to survive and reproduce (differential reproductive success), passing the beneficial allele onto their offspring, over many generations frequency of the beneficial allele increases

37
Q

Stabilising selection

A

individuals with alleles for the middle range phenotype are more likely to survive and reproduce, mean remains the same but range decreases

38
Q

Directional selection

A

individuals with allele for an extreme phenotype are more likely to survive and reproduce, occurs when there is a change in environment, mean changes but range stays the same

39
Q

Species

A

a group of similar organisms that can breed to produce fertile offspring

40
Q

Phylogeny

A

the study of a species evolutionary origins and relationships, phylogenetic trees show the evolutionary relationships between species with each branch point representing a common ancestor

41
Q

Taxonomy

A

the science of classification, organisms are grouped into taxa according to their evolutionary relationships, arranged in a heirachy (smaller groups within larger groups) with no overlap

42
Q

Binomial system

A

scientific universal naming system, named according to their Genus and species

43
Q

Courtship behaviour

A

behaviours that increase chance of successful mating, allows members of the same species to recognise each other, allows recognition of opposite sex, indicates sexual maturation, stimulates release of gametes

44
Q

Biodiversity

A

the variety of species in a habitat

45
Q

Species richness

A

a measure of the number of different species in a habitat

46
Q

Index of diversity

A

a measure of the number of different species in a habitat and the number of individuals of each species, calculated by dividing N(N-1) by total n(n-1)

47
Q

Effect of agriculture

A

destruction of hedgerows, selective breeding, monocultures, use of pesticides and herbicides, decreasing biodiversity (fewer plant species, fewer food sources, fewer habitats)

48
Q

Sampling

A

quantitative investigation allowing estimation of the number of individuals in a habitat, use a large sample size so representative and random sampling to avoid bias

49
Q

Conservation

A

protection and management of ecosystems in a sustainable way (eg. seed banks, captive breeding, fishing quotas, restricting urban development)

AQA A-LEVEL BIOLOGY (8 decks)

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