1
Q
nucleotides
A
the monomers that make up the DNA polymer
2
Q
what are nucleotide bases made of?
A
phosphate group bonded to a deoxyribose sugar bonded to a nucleotide base
3
Q
what are the 4 nucleotide bases and what do they all bond to?
A
- adenine (A)
- guanine (G)
- cytosine (C)
- thymine (T)
join to each sugar
4
Q
what are the complimentary base pairing?
A
T and A
G and C
(tewksberry abbey, gloucester cathedral)
5
Q
gamete
A
the female and male sex cells (sperm and egg)
6
Q
chromosome
A
thread like structure in the cell nucleus that contain dna (made up of 2 chromatids)
7
Q
gene
A
small section of dna found on a chromasome that contains the intructions for a particular characterstic
8
Q
what does each gene code for?
A
a particular sequence of amino acids = A PROTEIN
9
Q
what is the genetic code?
A
- sequences of 3 bases (neuclotide triplets called codons)
- triplets do not overlap
- there can be more than one triplet for each of the amino acids (the code is degenerate)
10
Q
mutation
A
change is the nucleotide base sequence (change in a codon)
11
Q
how does a mutation affect a protien? (5)
A
- changes nucleotide base sequence
- changes amino acid
- changes how protien folds
- changes protien shape
- may change function (could improve, worsen or have no effect on the function)
12
Q
what is 98% of the human genome?
A
- non-coding DNA
- not junk dna
- can act as mollecular switches
- can make up ribosomes
- can be translation and transcription factors
- and more…
13
Q
genome
A
complete set of dna, entire genetic material of an organism
14
Q
when was the human genome project?
A
1990 - 2003
15
Q
uses of information the human genome project discovered (4)
A
- identify genes linked to different diseases
- create better treatments and gene therapies for inherited diseases
- understand human migration pattterns
- ancestry/ paternity testing
16
Q
required practical
describe method for extracting dna
A
- peel the skin from a kiwi and mash it up (physically break down cell walls)
- add salt and washing up liquid (washing up liquid breaks down fatty cell membrane)
- heat this mixture at 60° for 5 mins (denature protiens )
- filter the mixture (to remove cell wall, cell membrane and denatured protiens) and retain filtrate only
- cool using an ice bath and gently pour chilled ethanol onto the top of the filtrate (percipitate the dna out)
17
Q
purpose of meiosis
A
production of gametes fof sexual reproduction
18
Q
where does meiosis happen?
A
sex cells in testes and ovaries
19
Q
what happens to the dna before division in meiosis?
A
replicates for first division only
20
Q
how many divisions in meiosis?
A
2
21
Q
how many daughter cells formed in meiosis?
A
4
22
Q
what happens in meiosis? (4)
A
- dna replicates
- homologous chromosomes align in middle, criss over between non-sister chrmatids and swap ends (source of genetic variation)
- homologous chromosomes pulled to opposite sides of cell without separating
- chromatids separated into chromosmes and second round of cell division occurs
23
Q
what does meiosis result in?
A
- results in 4 daughter cells that have half the dna of the parent cell
- all daughter cells (gametes) genetically different to each other and to the parent cell
24
Q
what are the 3 types of tissue?
A
- glands
- muscles
- epithelium
25
how is rna different to dna? (3)
1. RNA is single stranded while DNA is double stranded.
2. RNA has a sugar called ribose while DNA has a sugar called deoxyribose.
3. RNA has the base uracil (U) while DNA has the base thymine (T)
26
2 steps of protien synthesis
1. transcription
2. translation
27
where does transcription take place?
nucleus
28
steps of transcription
1. RNA polymerase moves along the DNA unwinding the strand.
2. Hydrogen bonds between base pairs break which allows the unzipping of the double helix.
3. As RNA polymerase breaks the bonds, it synthesises a primary transcript of mRNA using RNA nucleotides. These form hydrogen bonds with the exposed DNA strand by complementary base pairing.
4. The primary transcript of mRNA is processed to produce a mature transcript of mRNA.
5. The mature mRNA transcript is now ready to leave the nucleus and travel to the ribosome.
29
what is mRNA?
messenger RNA -> carries a copy of the gene to be expressed from the nucleus
30
steps of translation
1. The mRNA molecule travels through the cytoplasm and attaches to the ribosome.
2. tRNA molecules transport specific amino acids to the ribosome.
3. Each mRNA codon codes for a specific amino acid.
4. The first codon of an mRNA molecule is a start codon. This signals the beginning of translation.
5. The anti-codons and codons match up and form complementary base pairs.
6. Peptide bonds form between the adjacent amino acids to form the polypeptide (protein).
7. Used tRNA molecules exit the ribosome and collect another specific amino acid.
8. The last codon of an mRNA molecule is a stop codon which signals the end of translation.
31
what is tRNA?
transfer RNA -> has a triplet anti-codon site and an attachment site for a specific amino acid
32
3 types of rna
mRNA (messanger)
tRNA (transfer)
rRNA (ribosomal)
33
3 examples of uses of protien
1. enzymes - biological catalysts
2. hormones - carry messages through blood
3. structural protien - eg collagen which strengthens connective tissues like cartilage
34
plant gametes
pollen (produced in ather) and ova/egg (produced in ovule)
35
haploid
containing half the DNA of a normal somatic cell (eg gametes)
36
animal gametes
sperm (produced in testes) and egg/ovum (produced in ovaries)
37
in which process are gametes made?
meiosis
38
what happens in sexual reproduction? (3)
1. gametes produced through meiosis (2 PARENTS)
2. during fertilisation, gametes fuse to from a cell with a full genome
3. cell then divides by mitosis to grow into an organism
39
advantages of sexual reproduction
- increases genetic variation in population since each new organism is genetically different
- increases population's abilty to adapt to changes in the envrionment eg new disease
- population as a whole is moe likely to survive environmental change
40
how is variation achieved in sexual reproduction?
- crossing over in meiosis
- independent assortment of chromosomes during meiosis
- random fertilisation
41
disadvantages of selective breeding?
- reduced genetic diversity and variation
- less able to respond to envrionmental changes
42
how do farmers use selectuve breeding?
1. selection of desirable characteristics
2. breeding of individuals with that characteristic
3. breeding of offspring with desirable characteristics
4. repeated over several generations
5. desirable characteristics increases in proportion in the population
43
what happens in asexual reproduction?
- involves mitosis ONLY
- only 1 parent
- no fusing of gametes
- two daughter cells are genetically identical to each other and the parent cell (clones)
44
advantages of asexual reproduction
- faster (no need to find a mate)
- less energy required
- great under favourable conditions as more organisms produced more efficiently
45
examples of species that do both asexual and sexual reproduction
- malaria parasites
- fungi
- plants with bulbs eg dandelions
- plants with seed and runners eg straweberries
46
how do plants like stawberries reproduce sexually and asexually?
- plants use sexual reproduction to produce seeds (MEIOSIS, THEN MITOSIS)
- plants such as strawberries reproduce asexually by sending out runners, or daffodils when their bulbs divide (MITOSIS)
47
how do fungi reproduce both sexually and asexually?
- fungi reproduce sexually to generate variation
- fungi release spores by asexual reproduction
48
how do marial parasites reproduce sexually and asexually?
- malarial parasites reproduce sexually in the host mosquito
- malarial parasites reproduce asexually in the human host
49
allele
inherited characteristics are carried as pairs of alleles found on pairs of chromosomes (alternative version of a gene)
50
dominant
the allele for the characterstic that's always shown by an organism (always in its genotype) even if it is heterozygous (capital letter allele)
51
recessive
an allele that only shows up in the phenotype of the homozygpus is in the genotype (an allele whose characteristics only appears in an organsim if there are 2 copies present)
52
homozygous
where an organism has 2 alleles for a particular gene that are the same
(homo = same)
53
hetrozygous
when an organism has 2 alleles for a particular gene that are not the same (hetro = different)
54
genotype
the allele that an organism has eg Bb
55
phenotype
the characteristic an organism has eg blue eyes
56
somatic cells
body cells
57
male chromosomes
XY
58
female chromosomes
XX
59
when a gene is hetrozygous, which allele will an organism show in its phenotype?
dominant (captial letter)
60
what must be true for an organism to display a recessive characteristic?
both its alleles must be recessive (homozygous)
61
# inherited disorders
what is cystic fibrosis?
- genetic disorder of the cells membranes
- leads to lots of thick sticky mucus
- no cure and it can shorten your life
62
what kind of gene causes cystic fibrosis?
RECESSIVE
so for a child to have it, both parents must be carriers (have it as a recessive allele) or have it themselves (25% chance of baby having it if both parents are carriers)
63
what is polydactyly?
genetic disorder which causes a baby to be born with extra fingers or toes
64
what kind of gene causes polydactyly?
DOMINANT
can be inherited if one parent acrries the defective allele (and therefore has it themself)
(50% of baby having polydactyly if one parent has it)
65
2 types of embryoscreening
1. amnoscentesis
2. chronic villus sampling
66
# embryoscreening
what is amnioscentesis?
- needle inserted in amniotic sack to collect amniotic fluid
- offered at 15-20 wks
- risk of damaging fetus/ misscarriage
67
# embryoscreening
what is chronic villus sampling?
- sampling before implantation (IVF)
- no chance of miscarriage and can be done earlier
68
pros of embryoscreening
1. help stop people suffering
2. helps parents to plan for the care of their baby
3. individuals with genetic disorders are expensive to treat (reduces NHS cost)
4. there are laws to stop it becoming eugenics eg parents can't even choose gender of the baby
69
cons of embryoscreening
- expensive
- possible damage to embryo and mother
- parents have to make difficult choice about abortion
- could lead to eugenics/ 'desirable characteristics'
- implies those with genetic disorders are 'undesirable' which could increase prejudice
70
intraspecific variation
differences between individuals of the same species
71
interspecific variation
differences between individuals of different species
72
examples of intraspecific variation caused by only genetics
- fur/hair colour
- eye colour
- blood group
- sex chromosomes
- dimples
73
examples of intraspecific variation caused by genetics and the environment
- skin colour
- length of leaf
- height
- shoe sizee
- petal colour
74
3 factors required for evolution
1. variation
2. selection pressure
3. time
75
evolution
change in the inherited characteristics through a process of natural selection that may result in the formation of a new species
76
theory of evolution
all of today's species have evolved from simple life forms that first started to develop over 3 billion years ago
77
4 scientists who contributed to theories of evolution
1. mendel
2. lamark
3. alfred russel wallace
4. charles darwin
78
natural selection (7)
1. within a species, there is always intraspecific variation
2. random mutation occurs that alters the genotype and phenotype of some individuals
3. those with mutation have survival advantage in that environment
4. more likely to survive
5. more likely to reproduee and pass on allele for their desirable characteristic
6. repeats for many generations
7. over time, the new/ mutated phenotype become the normal
79
darwin's observations which led to his theory
theory of survival of the fittest
- struggle for survival
- variation between offspring
- numbers within a population tend to stay constant
80
81
lamarck's theory of evolution
- within a species, organisms all start very similar
- some individuals would change do to use/disuse of a body part eg repeated use of an arm would increase its size
- this would give individuals characteristics which they would pass onto their offspring
82
wallace's discoveries
- realised warning colouurs (when bright colours are used to deter predators) must be passed on by natural selection
- shaped modern ideas of mimicry
83
theory of survival of the fittest
organisms with most suitable characteristics for the envurinment would be more succesful competitors and more likely to survive, so their characteristics would be passed onto their offspring
84
what is extinction?
when no individuals of a species remain
85
5 causes of extinction
1. environment changes too quickly
2. new predator kills them all
3. new disease kills them all
4. they cannot compete with a new species for food/resources any more
5. catastrophic event kills them all eg asteroid
86
why were wallace and darwin's theories not accepted?
- gaps in fossil records
- no knowledge of genetics, inheritance, dna
- not enough evidence
- challenged religious belief of god as the creator
87
what are fossils?
remains of organisms from many thousands years ago found in rocks (older=lower in ground)
88
3 types of fossilisation
1. gradual replacement by minerals
2. casts and impressions
3. preservation in places where no decay happens
89
why is the fossil record incomplete?
- conditions of many fossils are damages/ incomplete
- usually organisms will decompose and not fossilise
- early life was mostly soft bodied, so decayed completely
- often fossils can be destroyed by geological activity
90
how can fossilisation happen? (mineralisation)
1. ancient organism
2. death
3. buried under sediment
4. decay of soft parts
5. more sediment deposited
6. mineralisation of bone (transforms from bone to rock-like substance)
91
how can fossilisation happen? (casts and impressions)
1. ancient organism
2. death
3. buried under soft material like clay
4. clay hardens around it and organism decays, leaving a cast of itself
92
how can fossilisation happen? (preservation in places where no decay occurs)
1. ancient organism
2. death in one of 3 places
3a. in amber and tar pits, there is no oxygen or moisture so decay microbes can't survive
3b. in glaciers, it is too cold for decay microbes to work
3c. peat bogs are to acidic for decay microbes
93
extinction
when there are no remaining (breeding) individuals of a species
94
12 causes of extinction
1. new predators
2. new pathogens
3. new competitors
4. lack of food
5. climate change
6. exponential population growth
7. overconsumption/hunting
8. destruction of habitat
9. illegal wildlife trade
10. natural disasters
11. overfishing
12. pollution
95
how does antibiotic resistance happen? (5 steps)
1. bacteria grows and reproduces by mitosis
2. by chance, dna mutates
3. when exposed to antibiotoics this leads to selection pressure
4. variants can survive antibiotic and pass on their genes/ mutation to the next generation
5. antibiotic resistant bacteria accumulate in population
96
what causes mutation in antibiotic resistant bacteria?
- chance mutation
- not caused by anrtibiotics (simply act as selection pressure)
97
how can doctors reduce antibiotic resistant strains?
- prescribe antibiotic only for bacterial infections (not for viral)
- prescribe length of time for the course
98
how can farmers reduce antibiotic resistant strains?
vaccinate livestock instead of giving antibiotics
99
how can patients reduce antibiotic resistant strains?
finish course of antibiotics
100
why is it important to reduce antibiotic resistant bacteria?
- to ensure antibiotics work when they are really needed
- it is slow, difficult and expensive to make new antibiotics
101
102
classification
grouping of organisms according to differences and similarities in their structures
103
what is the linnean classification method?
1. 5 kingdoms
2. phylum
3. class
4. order
5. family
6. genus
7. species
104
what are the 5 kingdoms?
1. animalia
2. plantae
3. fungi
4. protist
5. prokaryota
105
cell type of animalia
eukaryote, multicellular, no cell wall
106
cell type of plantae
- eukaryote
- multicellular
- cell wall is present
107
cell type of fungi
- eukaryote
- single and multi cellular
- cell wall
108
cell type of protists
- eukaryote
- single cellular
- sometimes have cell walls
109
cell type of prokaryota
- prokaryotes
- single celled
- have cell walls
110
which of the 5 kingdoms can move?
- animalia
- plantae
- prokaryota
- protists (sometimes)
111
which of the 5 kingdoms cannot move?
- fungi
- protists (sometimes)
112
which of the 5 kingdoms are only heterotropic?
- animalia
- fungi
113
which of the 5 kingdoms are only phototropic?
- plantae
114
which of the 5 kingdoms are both phototropic and heterotropic?
- protists
- prokaryota
115
what is selective breeding?
when humans artificially select plants/ animals to breed so that the genes for particular characteristics remain in the gene pool
116
process of selective breeding (6)
1. within a species there is always variation
2. humans identify variants with desired characteristics (altered phenotype)
3. variants with desired characteristics are bred together
4. offspring with desired characteristics are bred together
5. this repeats over many generations
6. overtime animals/plants with the new phenotype become the largest proportion of the population
117
desirable characteristics for animals
(why would animals be selectively bred?)
- non-shedding/hypoallergenic fur
- size (eg teacup pigs)
- docile/friendly nature
- higher meat/ milk yield
- no horns
118
desirable characteristics for plants
(why would plants be selectively bred?)
- unusual/ unique looking plants (for decorative plants)
- larger flowers/seeds/fruit
- disease/pest resistance
- seedless fruit
119
benefits of selective breeding
- higher crop yield
- animals become better (friendlier, faster, smarter, safer for humans
120
problems with selective breeding
- desired characteristics may be harmful for the animal/plant eg french bulldogs
- rare genetic disorders accumulate so more suffering for the animal
- reduced gene pool
- less resistance to pests and disease (less chance of some members having resistant alleles so all will die)
121
2 ways to clone plants
1. tissue cultures
2. cuttings
122
process of tissue cultuire to clone plants (6)
1. take a sample from a plant
2. cut sample into small pieces and sterilize with ethanol
3. place the pieces on a culture medium (ie agar plate) containing plant hormones
4. plantlets grow on medium
5. pot plantlets into compost
6. result in young plants planted out to grow and produce a crop that is identical to the original plant
123
2 applications of cloning plants via tissue culture
1. farmers - cloning crop plants
2. scientists - conservation of rare plants that are difficult to reproduce in captivity eg orchids
124
advantages of tissue culture to clone plants
- species can be conserved
- some crop plants do not produce viable seeds so must be cloned to reproduce eg bananas
- allows for consistent crop yield, flavour, sizes
125
disadvantages of tissue culture to clone plants
- requires specialist techniques and training (skilled labour)
- expensive
- inbreeding depression
- decreased gene pool
126
process of using cuttings to clone plants
1. cut off a branch of the parent plant near a meristem (new bud)
2. dip the stem into rooting power containing plant hormones
3. pot in compost and then plant
127
advantages of using cuttings to clone plants
- quick
- cheap
- simpler method than tissue culture (no skilled labour needed)
- species can be conserved
- some crop plants do not produce viable seeds so must be cloned to reproduce eg bananas
- allows for consistent crop yield, flavour, sizes
128
disadvantages of using cuttings to clone plants
- damages parent plant
- inbreeding depression
- decreased gene pool
129
2 ways to clone animals
1. embryo transplants
2. adult cell cloning
130
process of adult cell cloning (4)
1. nucleus is removed from an unfertilised egg cell
2. nucleus is extracted from a somatic cell and inserted into the nucleus-less egg cell
3. an electric shock stimulates the egg cell to divide to form an embryo (which contain the same dna as the somatic cell)
4. when the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to develop into a clone of the specimen which provided the somatic cell#
EG DOLLY THE SHEEP
131
pros of adult cell cloning
- maintains population and prevents extinction
- useful if species is difficult to breed in captivity
132
cons of adult cell cloning
- low success rate
- requires skilled labour and specialist equipment
- expensive
- development issues in clone
- reduces gene pool, causing inbreeding depression
133
embryo transplant
splitting apart cells from a developing animal embryo before they become specialized, then transplanting the identical embryos into host mothers
134
process of embryo transplant to make animal clones (5)
1. sperm cells and egg cells are taken from 2 'prize' animals
2. the sperm is used to artificially fertilise the egg cell
3. embryo develops and then is split many times to form clones before any cells become specialised
4. these cloned embryos are then each implnted into different surrogate wombs
5. this will make all of the offspring genetically identical (clones)
135
speciation
when population of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
136
what leads to speciation?
1. isolation (where populations of the same species are separated due to physical barriers eg earthquake forms a mountain)
2. natural selection
137
genetic engineering
transferring a gene responsible for a desirable characteristic from one organism's genome into another organism so that it also has the desired characteristic
138
process of genetic engineering (3)
1. cut out/ isolate useful gene from one organism's genome using enzymes
2. insert gene into vector (bacterial plasmid or virus)
3. insert vector into host, so that the useful gene is inserted into its cells
139
examples of genetic engineering
flavr savr tomatoes - stay fresh for longer due to lack of ethene
golden rice - enriched rice with vitamin a to reduce vitamin deficiency is subsistence farmers
140
uses of genetic engineering in plants
- increasing yield
- increasing disease/ pest/ frost/ drought/flood resistance
141
uses of genetic engineering in animals
- increase in milk/meat/egg yield
- increasing disease resistance
- changing fat/ protein /carb conc. in milk
- produce hormones in milk
142
uses of genetic engineering in bacteria
can be used to make many protein products eg hormones
143
uses of genetic engineering in fungi
can be used to make vegetarian insulin for diabetics (otherwise from pigs' livers)
144
disadvantages of genetic engineering
- reduced gene pool
- inbreeding depression
- very expensive
- requires skilled labour
- gene leakage into wild population
- not well tested so unforseen consequences
- ethics (worries of eugenics)
- would consumers buy gene-edited food?
145
advantages of genetic engineering
- quicker than selective breeding
- human hormones can be produced, be vegan and less likely to cause an immune response
- allows for production of crops/ animals with desired traits
146
what is inbreeding depression?
inbreeding depression is the reduced biological fitness of a population caused by mating between closely related individuals (reduced gene pool), leading to increased expression of harmful recessive alleles
gcse biology
flashcards
Decks in class (12)
# Cards
-
cell biology and microscopes42
-
heart and circulatory system45
-
cell specialisation and division47
-
disease106
-
digestion and ezymes34
-
transport in cells25
-
plant tissues, organs and systems36
-
bioenergetics - respiration and photosynthesis37
-
homeostasis and control149
-
inheritance,variation and evolution146
-
ecology47
-
required practicals9
