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A-Level Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

Describe eukaryotic DNA

A

Large/long
Associated with histones
Found in linear chromosomes
Contained within the nucleus

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2
Q

Describe prokaryotic DNA

A

Shorter/single stranded
Not associated with histones
Single, circular loop
Free-floating in the cytoplasm

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3
Q

What is the genetic code?

A

Triplet code
Non-overlapping
Universal

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4
Q

What does it mean that the genetic code is a triplet code?

A

Every 3 bases forms a codon and one codon = one amino acid

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5
Q

What does it mean that the genetic code is non-overlapping?

A

It reads a sequence and separates it into 3s

123456 = 123, 456, 789 not 123, 234, 456

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6
Q

What does it mean that the genetic code is universal?

A

Each triplet code always codes for the dame amino acid

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7
Q

How many possible triplets is there?

A

64

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8
Q

How many different amino acids is there?

A

20

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9
Q

What does it mean that the code s.is degenerate?

A

Some amino acids are coded by more than one base

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10
Q

Do all triplet codes result in an amino acid?

A

No some act as start and stop codons

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11
Q

Describe the process of transcription

A

DNA helicase breaks H bonds
Free floating RNA nucleotides find complementary base pairs
RNA polymerase forms phosphodiester bonds between each mRNA nucleotide to form pre-mRNA

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12
Q

What is removed in splicing?

A

Introns

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13
Q

What are exons joined to form?

A

mRNA

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14
Q

What must be removed before mRNA leaves the nucleus?

A

Non-coding pieces of mRNA (introns)

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15
Q

What is translation?

A

The process by which mRNA is used to make a specific polypeptide

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16
Q

Describe the process of translation

A

mRNA moves out of the nucleus via nuclear pores
mRNA attaches to ribosome
Anti-codon forms temp H bonds with complementary bases on mRNA
Peptide bond forms between amino acids

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17
Q

When does the process of translation stop?

A

When a stop codon is reached

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18
Q

What will the other ribosomes that pass along the mRNA produce?

A

An identical polypeptide

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19
Q

What does tRNA do?

A

Transport specific amino acids

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20
Q

How many different types of tRNA is there?

A

20

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21
Q

What do all the different tRNA have in common?

A

The same structure

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22
Q

What is the structure of tRNA?

A 
Bases folded to form a clover structure
Attachment site for amino acids
Anti-codon
Base pairing
Consists of a single polynucleotide strand of RNA
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23
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of bases in DNA

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24
Q

What are mutations?

A

Random
Spontaneous
Natural

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25
Q

What are the three types of mutations?

A

Deletion
Insertion
Substitution

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26
Q

What is deletion?

A

A nucleotide is lost from the sequence

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27
Q

What is insertion?

A

A nucleotide is added to the sequence

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28
Q

What is substitution?

A

A nucleotide is replaced by another nucleotide with a different base

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29
Q

Which mutation will have the biggest impact and why?

A

Deletion and insertion as it will cause a frame shift (all amino acids effected)

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30
Q

Why will substitution have minimum impact?

A

As it will only effect one amino acid or non if it is degenerate

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31
Q

What are the two types of chromosomal mutation?

A

Polyploidy

Non-disjunction

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32
Q

What is polyploidy?

A

When organisms have three or more sets of chromosomes

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33
Q

What is non-disjunction?

A

When chromosomes fail to separate during meiosis

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34
Q

Which organism does polyploidy mostly occur in?

A

Plants

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35
Q

What is the role of mitosis meiosis in the animal body?

A

Growth and repair - MI

Production of gametes - ME

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36
Q

How many cell divisions is there in mitosis and meiosis?

A

1 - MI

2 - ME

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37
Q

How many daughter cells are produced in mitosis and meiosis?

A

2 - MI

4 - ME

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38
Q

What is the genetic composition of the daughter cells in mitosis and meiosis?

A

Diploid - MI

Haploid - ME

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39
Q

What is the similarity of the daughter cells to the parent cells in mitosis and meiosis?

A

Identical - MI

Similar but not identical - ME

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40
Q

What is meiosis?

A

The process by which a diploid nucleus divides to produce four haploid nuclei

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41
Q

What are the two forms of genetic variation during meiosis?

A 
Crossing over (exchange of alleles)
Independent segregation (Random arrangement of homologous chromosomes)
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42
Q

Describe meiosis

A

DNA unravels and replicates so there are two copies of each (chromatids)
DNA condenses to form double armed chromosomes formed by two sister chromatids
Joined by a centromere
Meiosis 1- chromosomes arrange themselves into homologous pairs
These are separated + halved
Meiosis 2- Sister chromatids are separated + centromere divided
4 genetically different haploid cells produced

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43
Q

What is genetic diversity?

A

The total number of different alleles in a population

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44
Q

What does it mean if there is greater genetic diversity in a population?

A

More likely organisms are going to be suited to their environment

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45
Q

What is phenotype?

A

Observable physical characteristics an organism has

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46
Q

What is genotype?

A

Genetic makeup of an organism

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47
Q

What is the gene pool?

A

The total number of alleles in a population at a specific time

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48
Q

What is allele frequency?

A

The number of times an allele occurs within the gene pool

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49
Q

What is a normal distribution curve look like?

A

Data surrounds a central point
Curve is symmetrical
Curve is bell shaped

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50
Q

What are most characteristics a result of?

A

Multiple genes (polygenes)

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51
Q

What are polygenes effected by?

A

The environment

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52
Q

If the environment changes what part of the distribution curve changes?

A

The mean

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53
Q

What is selection?

A

The process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted

54
Q

What are the two types of selection?

A

Directional

Stabilising

55
Q

Describe directional selection (on a distribution curve)

A

Extreme phenotypes are favoured
Changes in characteristics
Shifts left and right

56
Q

What is an example of directional selection?

A

Peppered moth

57
Q

Describe stabilising selection (on a distribution curve)

A

Mean phenotype favoured
No.of individuals with mean phenotype increases
Narrower + higher but no change in mean

58
Q

What is an example of stabilising selection?

A

Birth mass

59
Q

Explain directional selection

A 
Mutations = increased diversity
Changes in environment
Selection favours individuals that vary on one direction from the mean
Mean characteristic changes
Extreme phenotype is selected
60
Q

Explain stabilising selection

A

No change in environment
Extreme characteristics = less frequent
No.of individuals with trait increases
Mean phenotype favoured

61
Q

What is natural selection?

A

The process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted

62
Q

What is a species capable of?

A

Breeding to produce living, fertile offspring

63
Q

What system is used to identify organisms?

A

Binomial system

64
Q

What two taxons are used to name an organism?

A

Genus and species

65
Q

What does natural selection result in?

A

Adaptions in organisms that are better suited to their environment

66
Q

What are the adaptions?

A

Anatomical
Physiological
Behavioural

67
Q

What are courtship displays important for?

A

Organisms don’t live forever
Need DNA to be passed on
Occurs through reproduction
Increased likelihood of reproduction

68
Q

What are courtship displays?

A

A set of behaviours in which an animal attempts to attract a mate and exhibit their desire to copulate

69
Q

What do courtship displays include?

A

Vocalisation
Displays of beauty or strength
Ritualised movements

70
Q

Why are courtship displays important?

A

Enables member to recognise own species
Identify a mate that is capable of breeding
Form pair bonds
Synchronise mating season

71
Q

Describe a stimulus response

A 
Male communicates courtship signal
Acts as visual response
Female nervous system detects + responds with specific behaviour
Stimulus to male
Male responds
72
Q

What does pair bonds lead to?

A

Successful breeding + successful raising of offspring

73
Q

What does synchronised mating seasons ensure?

A

Maximum chance of fertilisation

74
Q

Why is it important for member to recognise their own species?

A

Prevent cross breeding + infertile offspring

75
Q

Why is it important for a mate to identify a mate capable of breeding

A

Since both need to be sexually mature, fertile and receptive

76
Q

What is classification?

A

The organisation of living organisms into groups

77
Q

What is taxonomy?

A

The theory and practice of biological classifications

78
Q

What principles are classification based on?

A

Artificial

Phylogenetic

79
Q

Describe artificial classification

A

Based on analogous characteristics

Not based on evolutionary relationships

80
Q

Describe phylogenetic classification

A

Based on homologous charcteristics

Based on evolutionary relationships

81
Q

What is an example of artificial classification?

A

Colour of flower

82
Q

What is an example of phylogenetic classification?

A

Limbs in animals (whether wings, arms, fins or legs) have similar structure

83
Q

What do phylogenetics arrange animals in?

84
Q

What are the features of a phylogenetic tree?

A

Small groups within larger groups
Taxons
Based on evolutionary relationships

85
Q

What is the order for the phylogenetic tree?

A 
Life
Domain
Kingdom
Phylum
Class
Order 
Family
Genus 
Species
86
Q

What is the most specific group?

87
Q

What are analogous structures?

A

They have the same function but different ancestors

88
Q

What are the three domains?

A

Bacteria
Eukarya
Archea

89
Q

Describe bacteria (domain)

A 
No membrane bound organelles
Unicellular
Cell wall = murein
70s ribosomes
DNA = single loop of nucleic acid not assiociated with hsitones
90
Q

Describe eukarya (domain)

A

Membrane bound organelles
Not all posses cell walls
80s ribosomes
DNA = associated with histones

91
Q

Describe archea (domain)

A 
Single celled prokaryotes
Similar size + shape to bacteria
Genes + protein synthesis similar to eukarya
Cell wall = no murein
More complex form of RNA polymerase
92
Q

What are the positives of just using observable characteristics?

A

Any one can classify an organism
Cheap
Easy to observe

93
Q

What are the negatives of just using observable characteristics?

A

May be a result of similar environment not similar evolutionary history
Pattern of inheritance is not always clear
Interpretation is subjective
Most genes are polygenetic

94
Q

What does modern classification compare?

A

Sequence of DNA
Sequence of mRNA
Amino acid sequence in proteins

95
Q

What are the disadvantages of using DNA and amino acid sequence in modern classification?

A

Expensive
Takes a long time
Some DNA is non-coding/non functional

96
Q

What does a DNA sequence determine in modern classification?

A

Exact order of nucleotides

How diverse an organism is

97
Q

What does amino acid sequence determine?

A

Order of DNA and mRNA

98
Q

What does it mean if amino acid sequences are similar in modern classification?

A

Species are similar

99
Q

Describe DNA hybridisation

A

Heat to break H bonds
Combine single strands of DNA
Cool to allow renaturation of double stranded DNA
Determine degree of hybridisation

100
Q

What does complete hybridisation mean?

A

Organisms identical

101
Q

What does partial hybridisation mean?

A

Organisms related

102
Q

What does no hybridisation mean?

A

Organisms aren’t related

103
Q

What does more hydrogen bonds reformed mean?

A

More related

104
Q

What does a higher temp mean?

A

Greater no. of H bonds formed
Greater similarity in DNA
Closer related they are

105
Q

Describe how immunology is used in genetics

A

Serum is injected into another species
Rabbits produce anti-human antibodies
They’re mixed with serum from another species
More similar species = more antibody-antigen complexes formed
Precipitate formed

106
Q

What does the larger amount of precipitate formed mean?

A

Closer evolutionary relationship

107
Q

What is species diversity?

A

The no.of different species and the no.of individuals of each species within any one community

108
Q

What is genetic diversity?

A

The variety of genes possessed by the individuals that make up one species

109
Q

What is ecosystem diversity?

A

The range of different habitats within a particular area

110
Q

If the diversity is higher what does that mean?

A

The more stable an ecosystem is since less of an impact an environmental change will have

111
Q

What will happen to an ecosystem with low diversity if there is an environmental change?

A

It will have a high degree of change

112
Q

What is biodiversity reduced by?

A

Agriculture
used land for homes + industry
Deforestation
Production of fossil fuels

113
Q

Why does agriculture reduce biodiversity?

A

Mono-culture = reduction in species
Using pesticides/fertilisers = enters water cycle + leads to eutrophication
Draining wetlands/marshes = removes habitats + nutrients and moisture from soil
Removing hedgerows = removing habitats

114
Q

What is deforestation?

A

The permanent clearing of forests and the conversion of land to other uses such as agriculture, grazing and settlement

115
Q

Why does deforestation reduce biodiversity?

A

Loss of species directly

Loss of habitats

116
Q

What are the two types of variation of species?

A

Intraspecific

Interspecific

117
Q

What is intraspecific variation?

A

Variation within a species

118
Q

What is interspecific variation?

A

Variation between species

119
Q

What are the two quantitative methods?

A

Quadrats

Transects

120
Q

What is the problem with these methods?

A

Unreliable
Untrustworthy
Unrepresentative

121
Q

How can you make it more reliable?

A

By taking multiple readings to find a mean

122
Q

How can you make it trustworthy?

A

Use random sampling

123
Q

Describe sampling bias

A

Choice made by the investigator
Sample is unrepresentative
Deliberate/unwilling

124
Q

How can sampling bias be avoided?

A

Random sampling

125
Q

Describe chance variation

A

Not representative sample

All individuals the same

126
Q

How can chance variation be avoided?

A

Increasing sample size

127
Q

What is standard deviation a measure of?

A

How much the data deviates from the mean

128
Q

What does SD enable you to do?

A

Improve the reliability of your results

129
Q

What does it mean if the SD is closer to the mean value?

A

More probable that your results are correct

130
Q

How do you find SD on a graph?

A

Measure the width of the curve

Where the graph goes from convex to concave

A-Level Biology (21 decks)

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