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A-level Biology > classification and diversity > Flashcards

classification and diversity Flashcards

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1
Q

gene definition

A

section of DNA that contains
code for making polypeptide
+ functional RNA

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2
Q

locus definition

A

location of particular gene
on chromosome

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3
Q

allele definition

A

a different version of same
gene

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4
Q

chromosome definition

A

threadlike structure
composed of tightly coiled DNA
wrapped around histones (if it is eukaryote)

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5
Q

Homologous
chromosome definition

A

pair of chromosomes that
have same genes
therefore- same
size

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6
Q

Prokaryotic
DNA

A

Shorter
Circular
Not associated w/histones
No nucleus
May have plasmids
Only exons

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7
Q

Eukaryotic
DNA

A

Longer
Linear
Associated w/ histones
Contains nucleus
No plasmids
Have introns + exons

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8
Q

Codon

A

3 bases on mRNA- code for
amino acid

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9
Q

Start codon

A

3 bases at start of mRNA
sequence which help initiate
translation

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10
Q

Similarities of eukaryotic + Prokaryotic DNA

A

Both DNA are polynucleotides
Both DNA are double stranded
Both held by phosphodiester bonds
Both have same nitrogen bases

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11
Q

stop codon

A

3 bases at end of every gene
that don’t code for amino
acid- ribosomes to
detach + therefore stops translation

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12
Q

Genetic code

A

amino acid is coded for by 3
DNA bases which- described
as “triplet code”

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13
Q

What is meant by
‘the genetic code
is degenerate?

A

each amino acid is coded for by
more than one triplet of bases

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14
Q

What is the advantage
of the genetic code
being degenerate?

A

if a substitution mutation occurs, the new triplet of bases may still code for the same amino acid
therefore the mutation will have no impact on the final protein produced

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15
Q

What is the advantage of the genetic code being universal?

A

genetic engineering is possible a human gene can be inserted into another organism
e.g human gene for insulin inserted into bacteria to make insulin

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16
Q

What is the advantage of the genetic code being non- overlapping?

A

if a point mutation occurs, it will only affect one codon and therefore one amino acid

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17
Q

Triplet code

A

an amino acid is coded for by 3 bases

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18
Q

Mutation

A

a change in the DNA
can be a gene or chromosome mutation

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19
Q

What is meant by ‘the genetic code is non-overlapping?

A

each base in a gene is only part of one triplet of bases that codes for one amino acid therefore each codon is read as a discrete unit

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19
Q

What is meant by ‘the genetic code is universal?

A

the same triplet of bases codes for the same amino acid in all organisms

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20
Q

Introns

A

non-coding sequence of DNA

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21
Q

Exons

A

sequences of DNA that code for amino acids

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22
Q

What is splicing?

A

post-transcription modification
removing introns

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23
Q

Genome

A

the complete set of genes in a cell

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24
Q

tRNA function

A

a specific amino attaches at the binding site
transfers this amino acid to the ribosome to create the polypeptide chain

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24
Q

Proteome

A

The full range of proteins that a cell is able to produce

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24
Q

Anticodon

A

3 bases on the tRNA which are complementary to the codon on mRNA.

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25
Q

mRNA function

A

a copy of a gene from DNA created in the nucleus, and it
then leaves the nucleus
to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm

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25
Q

tRNA structure

A

single-stranded, folded to create a cloverleaf shape
held in place by hydrogen bonds
has an anticodon and amino acid binding site

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25
Q

mRNA structure

A

single-stranded
made up of codons
a copy of one gene

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26
Q

Transcription

A

the first stage in protein synthesis
one gene in DNA is copied into mRNA
occurs in the nucleus

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27
Q

Translation

A

the second stage in protein synthesis
the polypeptide chain is created using both the mRNA base sequence and the tRNA
occurs on ribosomes in the cytoplasm

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28
Q

Which enzymes are involved in transcription?

A

DNA helicase
RNA polymerase

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29
Q

DNA helicase

A

catalyses the breaking of hydrogen bonds between the two strands of DNA

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30
Q

RNA polymerase

A

joins adjacent RNA nucleotides
together
forming a phosphodiester bond

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31
Q

pre-mRNA

A

mRNA in eukaryotes that still
contains the introns

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32
Q

How is pre- mRNA modified?

A

the introns are removed by a protein called a spliceosome
this leaves just the exons

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33
Q

What is ATP used for in translation?

A

forming the peptide bond between amino acids

34
Q

Haploid

A

one copy of each chromosome in a cell

35
Q

Diploid

A

two copies of each chromosome in a cell

36
Q

Meiosis

A

cell division that creates
genetically different gametes
there are two nuclear divisions in this process
results in four haploid daughter cells

37
Q

Independent segregation

A

homologous pairs of chromosomes randomly line up opposite each other at the equator of the cell
when they separate it creates a large number of possible combinations of chromosomes in the daughter cells produced

38
Q

Types of gene mutations

A

deletion
substitution
addition

39
Q

Crossing over

A

homologous pairs of chromosomes line up opposite each other at the equator in meiosis 1
parts of the chromatids twist, break and recombine with another chromatid
results in new combinations of alleles in the gametes

40
Q

What is a frameshift?

A

the removal of one base
changes all of the subsequent codons
all the bases shift back one position

41
Q

Gametes

A

sex cells (sperm and egg)

42
Q

How does meiosis introduce variation?

A

crossing over
independent segregation

43
Q

Chromosome mutation

A

change in the number of chromosomes
occurs during meiosis

44
Q

Deletion mutation

A

a gene mutation
a base is removed from a sequence
causes a frameshift

45
Q

Substitution mutation

A

a gene mutation
a base is swapped for a different one

46
Q

Non-disjunction

A

the chromosomes or chromatids do not split equally during anaphase

47
Q

Aneuploidy

A

a change in the number of individual chromosomes
e.g 3 copies of chromosome 21

48
Q

Polyploidy

A

changes in whole sets of chromosomes
e.g. when organisms have three or more sets of chromosomes mainly occurs in plants

49
Q

Down’s syndrome

A

causes by a chromosome mutation
an example of aneuploidy 3 copies of chromosome 21

50
Q

Genetic diversity

A

the number of different alleles in a population

51
Q

Natural selection

A

the process that leads to evolution in populations results in species becoming better adapted to their environment

52
Q

Gene pool

A

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

53
Q

Allele frequency

A

the proportion of organisms within the population carrying a particular allele

54
Q

Evolution

A

the change in allele frequency over many generations in a population

55
Q

Selection pressure

A

factors that affect the survival of an organism
the driving force of natural selection

56
Q

Types of selection

A

stabilising
directional

57
Q

Directional selection

A

one of the extreme traits has a selective advantage
occurs when there is a change in the environment
the modal trait changes

58
Q

Stabilising selection

A

the middle (median) trait has a selective advantage and continues to be the most frequent in the population represented by a normal distribution graph
range decreases as the extreme traits are lost over time

59
Q

An example of directional selection

A

antibiotic resistance

60
Q

An example of stabilising selection

A

human birth weight

61
Q

Binomial system

A

a universal naming system individuals are named after their genus and species
e.g. Homo sapiens

61
Q

Definition of a species

A

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

62
Q

Courtship behaviour

A

different sequences of behaviours that animals demonstrate to attract a mate each species demonstrates its own unique behaviour essential for successful mating

63
Q

Importance of courtship

A

helps to synchronise mating behaviour so that the animals are more likely to mate when the female is releasing eggs
increases the likelihood of successful mating
enables individuals to recognise members of the same species and opposite sex

64
Q

What is meant by a hierarchy?

A

smaller groups arranged within larger groups
there is also no overlap between groups

65
Q

Phylogenetics

A

the study of species’ evolutionary origins and relationships

65
Q

Taxon

A

the term for each group in classification

66
Q

Common ancestor

A

the species from which another species evolved

67
Q

Species diverstity

A

the number of different species and the number of individuals within each species in a community

67
Q

What are the taxa in the Linnaeus classification system?

A

domain
kingdom
phylum
class
order
family
genus
species

68
Q

Species richness

A

the number of different species in a particular area at the same time

69
Q

Index of diversity

A

a measure of species diversity
a calculation to measure the relationship between the number of species in a community and the number of individuals in each species

70
Q

Community

A

all the species in a particular area at a particular time

71
Q

Environment

A

the abiotic (non-living) factors in an area

72
Q

Habitat

A

The range of physical, biological and environmental factors in which a species can live

73
Q

Which farming techniques reduce biodiversity?

A

destruction of hedgerows
selective breeding
monocultures
over-grazing
filling in ponds and draining wetlands

74
Q

How is standard deviation more useful than a mean?

A

it gives you the spread of data (variance) around the mean\ overlaps in standard deviation indicate no significant difference in the means

74
Q

Biodiversity

A

a measure of the range of habitats
from a small local habitat to the entire Earth
a measure of species diversity
a measure of genetic diversity

75
Q

How do you make sure your sampling is representative of the population?

A

take a large sample (at least 30)
randomly sample to avoid bias

76
Q

How can you measure genetic diversity?

A

by comparing the base sequence of DNA, mRNA and the amino acid sequence of the proteins

77
Q

Genetic diversity

A

the mesure of how many different alleles there are for each gene

78
Q

Formula for Index of Diversity

A

D=N(N-1)
———
n(n-1)

79
Q

Compare the DNA in chloroplast/ mitochondria to prokaryotic DNA

A

the DNA is similar to prokaryotic DNA, in that it is: short
circular
not histone bound

79
Q

What is the role of ribosomes in translation?

A

it holds two tRNA molecules
to enable peptide bonds to form between the amino acids

80
Q

How does transcription differ between prokaryotes and eukaryotes

A

Transcription in prokaryotic organisms results in mRNA that requires no modification because prokaryotic DNA does not contain any introns eukaryotic transcription results in pre-mRNA that needs introns removed

81
Q

What is the role of tRNA in translation?

A

it carries a specific amino acid anticodons align opposite complementary codons on the mRNA

82
Q

Gene mutations

A

a change in the base sequence of DNA
substitution or deletion

83
Q

When in the cell cycle do gene mutations occur?

A

interphase (s phase)
this is when DNA is replicated

A-level Biology (8 decks)

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