1
Q
What is DNA?
A
The chemical that makes up all genetic material in a cell and contains coded information for an organism’s characteristics & behaviour
2
Q
What are chromosomes?
A
Coils of DNA that usually come in pairs
3
Q
What shape is DNA?
A
Double helix
4
Q
What is a gene?
A
A small section of DNA within a chromosome
5
Q
What do genes do?
A
Code for a particular sequence of amino acids to make up a certain protein
6
Q
How does DNA determine what type of cell a cell is?
A
It determines which protein the cell produces/ what job it does
7
Q
What is a genome?
A
The entire set of genetic material in an organism
8
Q
3 reasons discovering the human genome is beneficial?
A
- Identification of genes related to certain diseases
- Effective treatments for hereditary diseases
- Migration of earlier populations can be traced
9
Q
What are DNA strands made of?
A
Nucleotides
10
Q
What are the 2 components of a nucleotide?
A
- Phosphate sugar backbone
- Bases
11
Q
How do the two nucleotides in DNA join?
A
T and A bases join & C and G bases join
12
Q
How many pairs of bases code an amino acid?
A
3
13
Q
How does code from DNA get to the ribosome for protein synthesis?
A
mRNA copies code from the DNA and carries the correct amino acids
14
Q
3 functions of proteins?
A
- Enzymes
- Hormones
- Structural proteins
15
Q
What is a mutation?
A
A random change in an organism’s DNA which may be inherited
16
Q
How is mutation chances increased?
A
Some radiation or substances
17
Q
2 ways mutations can negatively affect proteins?
A
- Enzymes’ active sites can be altered so the substrate doesn’t fit
- Structural proteins can lose their strength
18
Q
Why may the function of proteins be affected by mutation?
A
Mutations change the sequence of bases, leading to a change in amino acids in a protein
19
Q
What are the 3 types of mutation?
A
- Insertions - A new base is inserted where it shouldn’t be
- Deletions - When a random base is removed from the sequence
- Substitutions - When a random base in the sequence is changed to another
20
Q
What is the offspring of sexual reproduction?
A
Genetically different (variation in characteristics)
21
Q
How does sexual reproduction work?
A
Gametes are produced through meiosis with half the chromosome count of a regular cell
- The male and female cells fertilize together and join to create the regular number of chromosomes
22
Q
What are the offspring of asexual reproduction?
A
Genetically identical to parents
23
Q
How does asexual reproduction happen?
A
Mitosis of an ordinary cell
24
Q
Explain meiosis in 5 steps.
A
- Genetic information is duplicated
- Chromosome pairs line up down centre of the cell
- Pairs are pulled apart so each new cell has one copy of each chromosome
- Chromosomes line up again for second division
- Arms of the chromosome are pulled apart, resulting in 4 daughter cells each with a single set of chromosomes
25
How does an embryo create more cells?
Mitosis and differentiation
26
4 advantages of sexual reproduction over asexual?
1. Organism inherits genes from each parent - variation
2. Variation means offspring is more likely to survive a change in the environment
3. Species adapted to the environment are more likely to survive and pass on beneficial genes
4. Selective breeding can speed up natural selection
27
4 advantages of asexual reproduction over sexual?
1. Only one parent required
2. Less energy is used as organisms don't have to find a mate
3. Faster than sexual
4. Lots of identical offspring can be produced in favourable conditions
28
3 organisms which can reproduce both sexually and asexually?
1. Malaria reproduces sexually in the mosquito, but asexually in a human
2. Fungi spores
3. Plants produce seeds sexually, but also asexually e.g strawberry runners
29
How can possible gamete combinations be shown
Punnet square
30
What are alleles?
Genes existing as different versions inside the body
31
How many alleles do you have for every gene in the body?
2
32
What does homozygous mean?
The 2 alleles existing for one gene are the same
33
What does heterozygous mean?
The 2 alleles existing for a gene are different
34
Which allele is presented if they are the same?
The dominant allele
35
How can a recessive gene be presented?
If both alleles are recessive
36
What is a genotype?
The combination of alleles someone possesses
37
What is your phenotype?
The combination of alleles presented
38
How is cystic fibrosis caused?
Two recessive alleles carrying the disease
39
How is polydactyl (extra fingers or toes) caused?
Someone carrying a dominant allele for the disease
40
What is embryo screening?
Removing a cell from an embryo and checking its genes for a disease
41
3 arguments for embryo screening?
1. Can stop people suffering
2. Treating disorders is expensive once baby is born
3. Laws to stop it going to far
42
3 arguments against embryo screening?
1. Implies people with genetic problems are undesirable
2. Could lead to desirable characteristics being picked
3. Screening is expensive
43
What did Mendel do?
Noted how characteristics in pea plants were passed on from one generation to the next
44
Mendel's 3 conclusions?
1. Characteristics are determined by hereditary units
2. Hereditary units are passed on unchanged from each parent
3. Hereditary units can be dominant or recessive
45
Why wasn't Mendel believed?
People didn't have the background knowledge to understand his work
46
What is genetic variation?
A mixture of genes from mother and father lead to a unique mix of genes in the offspring
47
What is environmental variation?
Organisms adapting to live in the conditions of their environment
48
What can introduce variation?
Mutation
49
What is Darwin's "survival of the fittest" theory?
The theory that organisms most suited to the environment are more likely to survive
50
Explain evolution in 6 steps
1. Mutation causes variation
2. Some variation leads to better suited adaptations to an environment
3. The species with better suited adaptations are more likely to survive and pass on their characteristics
4. Over time beneficial adaptations become more popular and the organism evolves
51
What is speciation?
An entirely new species as natural selection changes an organism so much
52
How can you tell when a new species has been created?
The new species cannot interbreed to create fertile offspring
53
3 reasons species go extinct?
1. Catastrophic event
2. New disease
3. New predator
54
2 reasons no one supported Darwin?
1. His ideas went against religious beliefs
2. Darwin couldn't explain how new, useful characteristics appeared
55
What did Lamarck believe?
That environmental changes will be passed onto offspring
56
What is selective breeding?
Choosing which organisms have desired characteristics and breed these together, until desired characteristics become more frequent
57
4 advantages of selective breeding?
1. More meat/milk
2. Crops with disease resistance
3. Dogs with good temperament
4. Decorative plants with unusual flowers
58
Main drawback of selective breeding?
Reduced gene pool meaning less chance of resistant alleles
59
What is genetic engineering?
Taking the gene for a desired characteristic from one organism and putting it into another
60
3 examples of genetic engineering
1. Bacteria can now produce insulin
2. Genetically modified crops to become disease resistant
3. Sheep can produce disease curing drugs in their milk
61
3 concerns about GM crops
1. Could reduce biodiversity in farmland
2. Transplanted genes may be picked up by environment
3. Eating them may affect human health
62
2 cloning methods?
1. Growing cuttings
2. Tissue culture
63
What are embryo transplants?
Egg and sperm cells are taken from desirable organisms and the the embryo created is split to create many clones
64
What is adult cell cloning?
1. The nucleus is removed from an unfertilised egg cell
2. Nucleus from an adult body cell is inserted into the egg
3. The egg is electrically shocked to make it divide to make an embryo
4. The embryo is then implanted into a womb
65
2 advantages of cloning?
1. Ideal offspring
2. Could be used to preserve endangered species
66
2 disadvantages of cloning?
1. Reduced gene pool
2. Human cloning
67
3 ways fossils are formed?
1. Hard substances can be replaced by minerals as they decay
2. An organism left i a soft substance like clay can leave an impression as the clay hardens
3. Preservation is materials which don't decay e.g amber
68
2 reasons we don't have fossils from how the world began?
1. Many early forms of life were soft-bodied
2. Fossils have been destroyed by geological activity
69
A way speciation can occur other than natural speciation?
Geographical isolation - physical barriers have slightly different conditions either side
70
How can bacteria become antibiotic resistant?
Mutation and passing on of resistant genes to offspring
71
2 reasons antibiotic resistance is increasing?
1. Doctors unnecessarily prescribing antibiotics
2. Patients not fully finishing a course of antibiotics
72
How do antibiotics lead to resistance?
They create a situation in which naturally resistant bacteria have an advantage and so increase in numbers
73
What is the Linnaen classification?
Kingdom, Phylum, Class, Order, Family, Genus, Species
74
What are the 3 domains?
1. Archaea
2. Bacteria
3. Eukaryota
75
How does the binomial naming system work?
The first part of the Latin name is the genus, the second part is the species
Biology
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