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4)genetic variation > the genetic code > Flashcards

the genetic code Flashcards

1
Q

what is a gene?

A

a base sequence of DNA that codes for, the amino acid sequence of a polypeptide. a functional RNA (including ribosomal RNA and tRNAS)

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2
Q

how are genes arranged?

A

they are separated by non-coding regions between genes. these non coding regions contains VNTRs (variable number tandem repeats)

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3
Q

what are alleles?

A

a version of a gene eg mouse have a gene for fur but some alleles code for black hair some white etc

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4
Q

what is a locus?

A

the position a gene occupies on a chromosome

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5
Q

how many chromosomes do humans have?

A

humans have 23 pairs of chromosomes. these are arranged into homologous

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6
Q

what is a homologous pair?

A

means they have the same loci but alleles may differ

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7
Q

if they are attracted by centromere

A

sister chromatids (replicas of same chromosome)

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8
Q

same gene at same loci

A

homozygous pair

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9
Q

different gene at same loci

A

heterozygous

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10
Q

the features of the genetic code

A

universal, non-overlapping, degenerate

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11
Q

universal

A

the triplet code codes for the same amino acids in all organisms

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12
Q

triplet code

A

a sequence of three bases which codes for specific amino acid

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13
Q

degenerate

A

same amino acids have more than one triplet code which codes for them

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14
Q

non-overlapping

A

each base belongs to just one triplet code

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15
Q

genome

A

the complete set of genes in a cell/organism

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16
Q

proteome

A

the range of proteins that a cell/organism can produce

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17
Q

how does DNA exist in eukaryotes?

A

wrapped around histone proteins, contains introns, long, linear, contains non coding sequence between genes

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18
Q

what are histones?

A

proteins that DNA wrap around

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19
Q

what are introns?

A

base sequence within a gene that do not code for amino acids. introns are removed during splicing and the axons are joined

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20
Q

how does DNA exist in prokaryotes?

A

short , circular (not linear/ no free strands) not associated with proteins, no introns few non-coding regions between genes also have plasmids (small circles of DNA)

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21
Q

what is the DNA in chloroplasts and mitochondria like?

A

circular and not associated with proteins

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22
Q

coding strand

A

contains the code for a polypeptide or functional RNA

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23
Q

template strand

A

complimentary to the coding strand and is used to make mRNA from

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24
Q

triplet

A

a sequence of three DNA bases on the coding strand that codes for a specific amino acid

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25
Q

codon

A

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

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26
Q

what are the two stages of protein synthesis?

A

transcription ans translation

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27
Q

transcription

A

1)DNA helices attach to a specific DNA sequence at the start of the gene (promoter region) and unwinds the double helix
2)DNA helices breaks hydrogen bonds between complimentary base pairs
3)RNA polymerase attacks to start sequence
4)free floating RNA nucleotides attach to the template strand of DNA according to the rules of complimentary base pairings
5) RNA polymerase joins adjacent nucleotides together creating phosphodiester bonds
6)the RNA polymerase moves down the DNA molecule until it reaches a stop sequence
7) as RNA polymerase moves down the DNA strand, hydrogen bonds reform between complimentary base and strands coil together
8)the pre-mrna strand is spliced to remove introns. axons are joined together forming mature mRNA
9)mature mRNA leaves via a nuclear pore

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28
Q

splicing

A

before the mRNA leaves the process of splicing occurs to remove introns and join up the externs. the mRNA leaves via a nuclear pore

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29
Q

translocation

A

1)mRNA attachs to a ribosome
2)ribosome reads the first codon (start codon)
3)tRNA with complimentary anticodon attach to the codon. This requires ATP
4)tRNA carries a specific amino acid for that codon
5)a second tRNA and amino acid arrives at the ribosome and binds to the next codon
6)process continues and amino acids from peptide bonds via condensation reactions until stop codon is reached
7)the polypeptide is now made. the ribosomes mRNA complex disassembles

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30
Q

mRNA

A

long stranded, singles stranded, coils into helix and RNA organic bases

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31
Q

tRNA

A

short, single stranded, H bonds between own nucleotides forms clover leaf shape, anticodon at one end which complimentary base pairs to codons. One end of the chain extends beyond the other forming an amino acid binding site

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32
Q

where does transcription occur

A

the nucleus

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33
Q

where does translocation occur

A

ribosomes/cytoplasm

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34
Q

what might mutations result in

A

a different amino acid sequence in the encoded polypeptide. a different amino acid means hydrogen bonds form in different places and alter the secondary structure, hydrogen, ionic, disulfie bonds form in different places ad affect the tier chary structure

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35
Q

what is the definition of a mutation

A

a change to the DNA

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36
Q

what are the different types of mutations that can occur

A

gene mutation (a change to the base sequence of DNA) and chromosome mutation (changes to the numbers of whole chromosome)

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37
Q

what causes gene mutations?

A

gene mutations arise spontaneously during DNA replication chromosome mutations occur due to non-dysfunction during meiosis

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38
Q

how doe mutation effect t enzymes?

A

they change the tier chary structure, the active site. therefore the active site is no longer complimentary to substrate

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39
Q

what does degernate mean and how does this affect the protein produced?

A

degenerate means more than triplet codes for the same amino acid. if a mutation occurs changing one triplet to another-it may still code for the same amino acid so the mutation has no effect

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40
Q

silent mutation

A

some gene mutations change only one triplet code. due to degenerate nature of the genetic code, this still may code for the same amino acid

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41
Q

what is a frame shift?

A

some gene mutations change every codon downstream fro the mutation

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42
Q

what causes mutations?

A

random errors when DNA replicate. Chemical mutagens. Mutagenic agents eg x rays

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43
Q

how do mutagenic agents cause mutations

A

change the structure of the DNA double Helix, bases may be altered and chemicals may act as bases

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44
Q

what happens in non-dysfunction?

A

means the chromosomes fail to segregate during meiosis. this produces a gamete with two copies of a chromosome and a gamete with no copies of a particular chromosome

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45
Q

east id the biological sex of this individual?

A

female-XX
male-XY

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46
Q

species definition

A

organisms with similar characteristics which are able to interbreed to produce fertile offspring

47
Q

population definition

A

a group of individuals of the same species living in the same geographical range which are able to interbreed to produce fertile offspring

48
Q

allele frequency

A

the number of times an allele appears in the population as a proportion of the toil number oc alleles

49
Q

genetic diverisity definition

A

is the number of different alleles of a gene in a population/gene pool

50
Q

what are different versions of a gene called?

A

alleles

51
Q

what is meant by the term genetic diversity?

A

the number of different alleles of a gene in a population/gene

52
Q

what are the factors that increase the genetic diversity within a population?

A

mutation, meiosis and random fertilisation

53
Q

what are the factors that reduce genetic diversity within a population?

A

-genetic drift (only in small population)
-interbreeding (small population)
-bottle necking
-founder effect

54
Q

what is a gene pool?

A

all the alleles of all the individuals in a population

55
Q

what is genetic bottleneck?

A

an abrupt and severe reduction in the number of individuals due to a random event

56
Q

what happens to the genetic diversity of a population after a genetic bottleneck?

A

reduces diversity of a gene pool

57
Q

what is the founder effect?

A

loss of genetic variation that occurs when a new population is established by a very small number of individuals from larger population. because the founders start a new population in a different area the ones better adapted to that area survive and reproduce increasing the Elle and reducing the allele frequency of the less advantageous allele

58
Q

what is genetic drift?

A

a decrease in allele frequency

59
Q

what populations does genetic drift have the biggest impact on and why?

A

small populations

60
Q

what is the affect of genetic drift on the frequency of alleles?

A

it decreases the frequency of alleles

61
Q

what drives natural selection in a population?

A

selection pressures, pressures I an ecosystem that create a struggle for survival

62
Q

why are all individuals within a population different?

A

genetic variation due to meiosis and random fertilisation and mutations

63
Q

how does natural selection affect the frequency of alleles in a population?

A

the allele frequency of the advantageous allele increases

64
Q

what kind of alleles occur?

A

new alleles

65
Q

the theory of evolution by natural selection

A

-random mutation can result in new alleles of a gene
-many mutations are harmful but in certain envrionments the new allele of a gene might benefits its possessor giving its a selective advantage in the presence of selection pressures
-(state specific selection pressure)
-this leads to increased reproductive success over other members of the population
-the advantagous allele is inherited by members of the next generation
-as a result the frequency of the advantageous allele increase in the gene pool

66
Q

what are adaption?

A

adaptions are anotominal, physiological our behavioural characteristics that enable an organism to survive its geographical range

67
Q

behavioural adaption

A

migration of birds, hibernation, courtship behaviours, huddling

68
Q

physiological adaptions

A

processes in the body such as chemical processes that enable a part of the body ti function, eg changes to metabolic rate or more of an enzyme

69
Q

anatomical adaptions

A

structures on the body, sharp teeth, blubber, thick fur, camouflage, long neck

70
Q

what are the three types of selection

A

-directional
-stabilising
-disruptive

71
Q

what is directional selection?

A

-one extremes of the phenotype is selected for, curve moves to the left ir right. often occur when there is a change in environment

72
Q

Example of directional selection?

A

a mutation occurs in a bacterium that makes it more resistant to the antibiotic methicillin. this provides a survival advantage to that one bacterium in the population they are exposed to methicillin (selection pressure)

73
Q

what is stabilising selection?

A

the average of the phenotype is selected for both extremes, curve narrows often occurs when the environment remains constant

74
Q

what is an example of stabilising selection?

A

human birth rates

75
Q

what is disruptive selection?

A

-both extremes of the phenotype are selected for, the peak of the curve flattens are both extremes increase

76
Q

what is an example of disruptive selection?

A

large salmon are predators, small salmon are better at sneaking up on eggs nests too release gametes. both have a survival advantage . middle size fish are selected against

77
Q

what is classification?

A

putting organisms into groups

78
Q

what are the groups based on?

A

artificial-observable characteristics current-evolutionally relationships (phenogenetic)

79
Q

how many different levels of classification are there?

A

8 (domain, kingdom, phylum, class, order, family, genus, species)

80
Q

taxonomic groups are based on hierarchy. what is meant by the term hierarchy?

A

smaller groups are placed within larger groups with no overlap between groups. Each groups is called a taxon

81
Q

how do scientific advances affect classification?

A

similarities and differences in base sequences of DNA and mRNA. similarities and differences in the amino acid sequence of proteins. advances in these technologies has resulted in reshuffling of the organisms in each group since they were previously based on oberservable characteristics. We can now base them on evolutionary relationships

82
Q

acronym to remember the classification system

A

delicious king prawn curry or fat greasy sausages

83
Q

why classify organism?

A

organise them

84
Q

what is phylogeny?

A

attempts to arrange species into groups based on their evolutionary relationships

85
Q

what do branches of a phylogenetic tree represent?

A

specification occurring (when one species diverges into two separate species)

86
Q

Name the kingdom’s represented in this phylogenetic tree

A

living things (archeae, bacteria, eukaryotic (plant animal fungi, protist)

87
Q

suggest how animo acid sequence in amino acid sequences could be used top construct a phylogenetic tree

A

%similarity in amino acid sequence between a common protein and insulin

88
Q

what is a species?

A

a class of things of the same kind and with the same name

89
Q

what is a binomial name?

A

the genes and species, universal

90
Q

how can you identify the genus and the species?

A

the last 2 classification taxa (genus and species)

91
Q

how can courtship rituals be used to classify organisms?

A

classification is the process of putting organisms into groups eg bird, fish, reptiles. The more similar courtship ritual, the more closely related they are

92
Q

what are the essential features of a courtship ritual?

A

-recognise members of their own species, identify a mate that is capable of breeding, form a pair bond, synchronise mating, become able to breed

93
Q

recognise members of their own species

A

ensures interbreeding only occurs with members go the same species so fertile offspring can be produced

94
Q

identify a mate that is able for breeding

A

eliminates individuals that are not sexually mature who are not fertile anymore

95
Q

form a pair bond

A

strengthens the bond between parents to help raise young or nurture matting

96
Q

synchronic mating

A

mating ensures mating takes place when there is maximum probability of the sperm nd the egg meeting

97
Q

what were original classification system based on?

A

analogous structures

98
Q

what are the current classification. system based on?

A

comparing amino acid sequences, immunological comparison, genome sequencing. comparing mRNA sequences

99
Q

comparing animo acid sequences

A

similarities and differences in the amino acid sequences of proteins, percentage similarity or percentage difference can be calculated

100
Q

immunological comparison

A

selling if an immune response is caused by injecting proteins in a. different species when would indicated the degree of similarity or seeing ig the antibiotics produced can recognise the protein from other species

101
Q

genome sequencing

A

mapping the whole genome to see how it compares to another species genome

102
Q

comparing mRNA sequences

A

similarities and differences in the base sequence of DNA or mRNA-proteins-percentage similarity or percentage difference can be calculated

103
Q

community definition

A

the different species living in the same geographical range

104
Q

habitat definition

A

place where an organism normally lives and is categorised by physical conditions and the other types of species present

105
Q

biodiversity definition

A

is a measure of the number of different species in a community (the species richness) and number of individuals in each species

106
Q

species richness

A

the number

107
Q

How does farming affect biodiversity?

A

Removal of hedgerows, woodland clearance, use of herbicides, use of pesticides, monoculture

108
Q

What is a monoculture?

A

Artificial fertiliser which can pollute water courses causing eutrophication

109
Q

What is a monoculture?

A

Artificial fertiliser which can pollute water courses causing eutrophication

110
Q

How can biodiversity be increased?

A

Maintains existing hedgerows at the not beneficial height and shape. An a shape provides better habitats than a rectangular one. Plant hedges rather than erect hedges as field boundaries. Maintain existing ponds and where possible create new ones. Leave wet corners of fields rather than draining them

111
Q

What is variation?

A

Differences between member of the same species

112
Q

What causes variation?

A

Genetic factors and environmental factors

113
Q

Genetic factors

A

The allies and combination of alleles can differ as a result of meiosis and random fertilisation or mutation

114
Q

Environmental factors

A

The environment can influence characteristics

4)genetic variation (10 decks)

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