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biology topic 4 Flashcards

1
Q

what are the properties of prokaryotic DNA?

A

DNA loose in cytoplasm, smaller, circular, not associated with proteins, sometimes in plasmids

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2
Q

what are the properties of eukaryotic DNA?

A

linear, associated with histone proteins, long

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3
Q

what is a gene?

A

sequence of bases in DNA that code for the amino acid sequence in a polypeptide

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4
Q

what is the structure of DNA?

A

pentose sugar, deoxyribose, nitrogenous base

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5
Q

what is coding DNA known as?

A

exons

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6
Q

what is non coding DNA known as?

A

introns

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7
Q

what is an allele?

A

different version of the same gene

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8
Q

what is a proteome?

A

range of proteins that the cell can produce

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9
Q

what is a genome?

A

complete set of genes in a cell

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10
Q

what does it mean by the genetic code being a triplet code?

A

3 bases code for 1 amino acid

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11
Q

what does it mean by the genetic code being degenerate?

A

each amino acid can be coded for by more than one set of amino acids

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12
Q

what does it mean by the genetic code being non overlapping?

A

each base is only part of one triplet

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13
Q

what does it mean by the genetic code being universal?

A

in all living organisms the genetic code is the same

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14
Q

how does transcription occur?

A

RNA polymerase attaches to the DNA double helix
DNA helicase breaks hydrogen bonds between DNA strands
one DNA strand acts as a template
free RNA nucleotides align by complementary base pairing
RNA polymerase joins nucleotides by phosphodiester bonds
pre mRNA spliced to form mRNA
mRNA moves out of the nuclear pore and attaches to a ribosome in the cytoplasm

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15
Q

what is the role of transcription?

A

mRNA made from DNA, occurs in the nucleus

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16
Q

how does translation occur?

A

mRNA attaches to a ribosome
tRNA has an anticodon which is complementary to the mRNA codon
tRNA brings a specific amino acid
amino acids are joined by peptide bonds using ATP
tRNA is released
the ribosome moves along the mRNA to form a polypeptide

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17
Q

what is the DNA in chloroplasts and mitochondria similar to?

A

prokaryotic DNA

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18
Q

what is a homologous pair of chromosomes?

A

same size chromosomes with the same genes but different alleles

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19
Q

what is mRNA?

A

messenger RNA, made in transcription, carries the genetic code from DNA to ribosomes, makes a protein during translation, single polynucleotides, 3 bases known as codons

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20
Q

what is tRNA?

A

transfer RNA, involved in translation, carries amino acids to ribosomes, single polynucleotide, clover shape

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21
Q

what are the differences between mRNA and tRNA?

A

mRNA is straight whereas tRNA folds into a clover
mRNA is longer than tRNA
tRNA contains some base pairs and hydrogen bonds whereas mRNA doesn’t

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22
Q

what happens in splicing?

A

introns removed, exons joined

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23
Q

what type of DNA doesn’t contain introns?

A

prokaryotic

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24
Q

what is a gene mutation?

A

change in the base sequence of DNA, can arise spontaneously in interphase

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25
how does a mutation lead to a non functional protein?
change in base sequence changes the order of amino acids, which changes the tertiary structure (and the active site if it is an enzyme)
26
what happens in base deletion?
a base is deleted which leads to frameshift as the genetic code is non overlapping
27
what happens in base substitution?
one base is substituted with another which could introduce a new amino acid
28
what are the possible results of a gene mutation?
new/superior protein neutral no/inferior protein
29
what are the possible causes of mutations?
spontaneous in DNA replication, mutagenic agents eg) radiation, chemicals
30
what is a chromosome mutation?
change in the number/structure of chromosomes- chromosomes fail to separate
31
what is the difference between meiosis and mitosis?
in meiosis 4 daughter cells whereas mitosis has 2 daughter cells meiosis is sexual so there is variation, mitosis is asexual so there is no variation
32
what are gametes?
sex cells
33
what are the stages of meiosis?
Meiosis 1= P-DNA replication occurs, homologous chromosomes pair M- chromosomes align on the equator A- pairs of chromosomes separate together T- nuclear envelopes may reform Meiosis 2- P- spindle fibres form, chromosomes move to the centre of the equator M- chromosomes line up on the equator A- chromosomes are pulled apart like in mitosis T- gametes are formed
34
how does crossing over create genetic variation?
alleles are exchanged, creating a new combination of alleles on chromosomes
35
how does independent segregation cause genetic variation?
random which chromosome goes to each daughter cell, different combination of chromosomes and alleles
36
why is meiosis important?
two divisions create haploid gametes, diploid restored at fertilisation, maintains chromosome number across generations, genetic variation
37
how do you calculate the number of combinations of chromosomes after meiosis?
2^n
38
what is genetic diversity?
number of different alleles/genes in a species/population
39
what is a population?
group of interbreeding individuals of the same species
40
how does natural selection occur?
more offspring than can be supported, some organisms have alleles that make them more able to survive, these are better competitors so out survive organisms without these alleles, so reproduce and pass on successful alleles, this continues over generations to produce more advantageous alleles
41
what happened with Darwin's Finches?
stopped at the Galapagos islands, discovered unique species like finches, depending on the environment evolved to suit their niche
42
what are behavioural adaptations?
how organisms act to increase their survival
43
what are physiological adaptations?
how organisms change their body to survive
44
what are anatomical adaptations?
structural features of an organism to increase their chance of survival
45
what is directional selection?
alleles for an extreme phenotype are more likely to survive and reproduce
46
what is stabilising selection?
alleles towards the middle of the range are more likely to survive and reproduce
47
what is disruptive selection?
either extreme ends of the phenotype are preferred
48
how is the number of alleles in a population reduced?
selective breeding/artificial selection
49
what is a genetic bottleneck?
event that causes a large reduction in a population, the reduced population reproduces with fewer alleles, so the new population has reduced genetic diversity
50
what is the Founder effect?
a few organisms from a population start a new colony, small number of alleles in the initial gene pool, could lead to a higher chance of a genetic disease, initially show less variation
51
what is classification?
when living organisms are organised into groups
52
what is a species?
similar organisms that share identifiable characteristics and breed with each other to produce fertile, living offspring
53
why may offspring from 2 different species be infertile?
odd number of chromosomes so cannot perform meiosis
54
how does the binomial naming system work?
first name= generic name= genus- capitalised second name= specific name= species, not capitalised in italics or underlined
55
what is natural classification?
based on evolutionary relationships, classes species based on shared features from ancestors, arranged into a hierarchy
56
what is a hierarchy?
groups contained within larger groups, no overlap
57
what is artificial classification?
divides organisms by physical characteristics, eg size
58
what is phylogeny?
the evolutionary history of groups of organisms
59
what is a group known as?
a taxon
60
what is the order of the classification system?
``` domain kingdom phylum class order family genus species ```
61
what is the benefit of synchronised mating?
maximum chance of fertilisation occurring
62
what is courtship behaviour?
actions taken to aid successful mating, determines whether the female is at the receptive stage, able to recognise members of the same species, establishes a pair bond
63
how does DNA/genome sequencing help to see relationships between organisms?
closer related species have a higher percentage of similarities in their DNA base order, during evolution mutations accumulate more differences
64
how can immunological comparisons help to see relationships between organisms?
if an antibody binds to a specific antigen then it is closely related as they have a similar tertiary and therefore primary structure
65
how does comparing amino acids help to see relationships between organisms?
related organisms have similar DNA base sequences so similar amino acid sequences
66
what is DNA hybridisation?
make a hybrid DNA made of one strand of DNA from one species and another strand from another species where bases line up hydrogen bonds will form more strands matching= more hydrogen bonds form closer 2 species are related- stronger and more bonds
67
how do gene technologies work?
can measure genetic diversity, can see different alleles etc
68
what was the disadvantage of before gene technologies where scientists looked at observable characteristics?
characteristics are polygenic so hard to distinguish, characteristics could be modified by the environment
69
what is genetic diversity?
the variety of genes within a species
70
what is species diversity?
number of different species/number of individuals of each species
71
what is ecosystem diversity?
range of habitats within an area
72
what is biodiversity?
the variety of living organisms within an area
73
what is local biodiversity?
variety of species living in a small habitat
74
what is global diversity?
the variety of species living in the world
75
what is a habitat?
the place where an organism lives
76
what is a community?
all the populations of different species within a habitat
77
why is biodiversity important?
food chains need a variety of organisms to keep them balanced, species depend on each other for food and oxygen, plants help to protect the soil, carbon/nitrogen cycles depend on biodiversity, plants produce oxygen and remove carbon dioxide, plants could be a source of medication
78
what is species richness?
number of different species within a community
79
what is species evenness?
number of individuals within each species
80
what does a larger value of D (species diversity index) show?
greater diversity
81
what do conservation schemes do?
protect endangered species, created protected areas, encourage farmers to conserve biodiversity
82
how do farmers reduce biodiversity?
remove hedgerows, use pesticides, use herbicides, monoculture

biology (5 decks)

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