Inheritance, Variation and Evolution Flashcards
Paper 2 - B6
1
Q
What is the purpose of meiosis?
A
Production of gametes (sex cells)
2
Q
How is mitosis different from meiosis?
A
Meiosis leads to production of 4 non-identical cells, mitosis leads to production of 2 identical cells
3
Q
Name the gametes (sex cells) in a) flowering plants b) animals
A
a) pollen and egg cells b) sperm and egg
4
Q
Why is sexual reproduction important?
A
It involves mixing of gametes which leads to variation
5
Q
What is asexual reproduction?
A
Reproduction involving only one parent and no fusion of gametes
6
Q
What type of offspring are produced in asexual reproduction?
A
Genetically identical organisms (clones)
7
Q
What does meiosis do to the number of chromosomes in gametes?
A
It halves the number
8
Q
Gametes have half the number of chromosomes as body cells. In what process is the full number restored?
A
Fertilisation
9
Q
What happens in the nucleus of a cell before meiosis?
A
Copies of the genetic information (DNA, chromosomes) are made
10
Q
How many gametes are produced in meiosis?
A
Four
11
Q
What type of cell division occurs AFTER fertilisation to lead to an embryo?
A
Mitosis
12
Q
What happens to the cells in an embryo to eventually cause organs etc. to develop?
A
Cells continue to multiply by mitosis and then they DIFFERENTIATE
13
Q
(Triple only) What is the advantage of sexual reproduction
A
Produces variation in offspring giving an advantage if the environment changes
14
Q
(Triple only) Give 4 advantages of asexual reproduction
A
Only 1 parent needed; more time/energy efficient as don’t need to find a mate; faster than sexual reproduction; many identical offspring produced when conditions are
favourable
15
Q
(Triple only) Why is genetic variation an advantage?
A
Natural selection can occur if the environment changes
16
Q
(Triple only) Name 3 organisms that can reproduce by both sexual and asexual reproduction
A
Malarial parasites; fungi; plants e.g. daffodils, strawberry plants
17
Q
(Triple only) Which type of reproduction (asexual or sexual) of malarial parasites occurs in the human host and which occurs in the mosquito?
A
Asexual in human host, sexual in mosquito
18
Q
What is the structure of DNA?
A
Double helix
19
Q
What is the genome?
A
The entire genetic material of an organism
20
Q
What is DNA?
A
A polymer made up of two strands in a double helix
21
Q
What structures contain DNA?
A
Chromosomes
22
Q
What is a gene?
A
A small section of DNA on a chromosome
23
Q
What does a gene code for?
A
A particular sequence of amino acids to make a specific protein
24
Q
Give 3 reasons why understanding the human genome is important
A
Search for genes linked to different diseases; understanding & treatment of inherited disorders; use in tracing human migration patterns from the past
25
(Triple only) What units make up DNA?
Nucleotides
26
(Triple only) What are the 3 components of a nucleotide in DNA?
Sugar, phosphate group, one of 4 bases
27
(Triple only) Name the 4 bases in DNA and say how they pair up
A, T, C, G; A pairs with T; C pairs with G
28
(Triple only) How many bases are the code for one amino acid?
Three
29
(Triple only) In DNA, what does the order of bases control?
The order in which amino acids are assembled to make a particular protein
30
(Triple only) Where are proteins synthesised?
On ribosomes
31
(Triple only) What happens in protein synthesis?
A copy of the DNA (a template called mRNA) attaches to a ribosome which reads the bases in threes. Carrier molecules (tRNA) bring the correct amino acids to add to the growing protein chain
32
(Triple only) What is a mutation and how might it affect a protein?
A change in DNA structure (different bases) which changes the shape/function of the protein produced
33
(Triple only) What happens to a protein to give it a unique function?
It folds up into a unique shape
34
(Triple only) List three types of proteins
Enzymes, hormones, structural
35
(Triple only) How might a mutation affect an enzyme?
It alters the shape of the active site so the substrate cannot bind
36
(Triple only) Give one role of the non-coding parts of DNA
Switch genes on and off
37
(Triple only) What effect might a mutation have to a non-coding part of DNA
It might affect how genes are expressed
38
What is the effect of most mutations?
Most have no effect, some may be harmful or beneficial
39
What are alleles?
Different forms of a gene
40
In genetics, what does dominant mean?
Only one copy of an allele is needed to produce a characteristic (always expressed)
41
In genetics, what does recessive mean?
Two copies of an allele are needed to produce a characteristic (only expressed if no dominant allele is present)
42
What is the genotype?
Pair of alleles for a characteristic
43
What is the phenotype?
The characteristic caused by a particular
pair of alleles
44
What does homozygous mean?
Two alleles of the same type for a characteristic (i.e. both dominant or both recessive)
45
What does heterozygous mean?
A genotype with one dominant and one recessive allele
46
Give an example of a characteristic in humans controlled by a single gene
Red-green colour blindness
47
Name the grid used to show the results of a genetic cross
Punnett square
48
Why do most characteristics have many different possible phenotypes (e.g. lots of different hair colours and types)?
They are caused by multiple genes, not just one
49
Name an inherited condition caused by a recessive allele
Cystic fibrosis
50
Name an inherited condition caused by a dominant allele and affecting the hands and feet
Polydactyly
51
How can embryo screening be used to prevent genetic disorders
Following IVF, embryos can be tested for genetic disorders before being implanted back into the mother
52
What is the ethical issue relating to embryo screening?
Deciding what counts as a 'genetic disorder' (level of severity etc.) and fact that embryo may then be destroyed
53
How many pairs of chromosomes are in ordinary body cells?
23 pairs
54
What pair of sex chromosomes are found in the nucleus of male body cells?
XY
55
What pair of sex chromosomes are found in the nucleus of female body cells?
XX
56
Aside from genes, what else can affect the overall phenotype of an organism?
Interaction with the environment
57
How does new genetic variation arise?
Mutations
58
What is evolution?
A change in the inherited characteristics of a population over time through natural selection
59
When did the first life forms on earth develop?
Over 3 billion years ago
60
What is natural selection?
When organisms with the most favourable genetic variants survive, reproduce and pass on their alleles, meaning that these increase in the population
61
When is a new species formed?
When two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring
62
What is a species?
Organisms with similar characteristics that can interbreed to produce fertile offspring
63
What is selective breeding?
When humans breed plants or animals for particular genetic characteristics
64
How is selective breeding carried out?
Choose parents with desired characteristics, breed together, select offspring and repeat over many generations
65
List 4 characteristics which might be chosen for selective breeding
Disease resistance in food crops; more meat or milk in animals; domestic dogs with gentle nature; large or unusual flowers
66
What is the main disadvantage of selective breeding
Inbreeding where some breeds are particularly prone to disease or inherited defects
67
What is genetic engineering?
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
68
Give two characteristics produced by genetic engineering in plants
Disease resistance; bigger, better fruits
69
What useful product is now produced by certain bacteria as a result of genetic engineering
Human insulin
70
Give three characteristics of genetically modified crops
Resistance to insect attack; resistance to herbicides; increased yield
71
Give two concerns relating to GM crops
Effects of wild populations of flowers and insects; effects on human health haven't been fully explored
72
How could genetic modification be used in humans?
To overcome certain inherited disorders (gene therapy)
73
In genetic engineering, what is used to isolate and remove the required gene?
Enzymes
74
In genetic engineering, what is usually used as a vector to transfer the gene into the new organism?
A plasmid or a virus
75
In genetic engineering, what is the purpose of the vector?
To transfer the gene into the required cells
76
Why is genetic engineering usually done during an early stage of the organism's development?
So that the organism develops with the desired characteristic
77
(Triple only) What is tissue culture?
Using small groups of cells from part of a plant to grow identical new plants
78
(Triple only) Give two methods of cloning plants
Tissue culture; taking cuttings
79
(Triple only) How is cloning carried out in animals?
Embryo transplants; nuclear transfer (adult cell cloning)
80
(Triple only) How are embryo transplants carried out in order to clone an animal?
Cells in an embryo are split apart before they become specialised, then the embryos are transplanted into host mothers.
81
(Triple only) How can cloning be carried out using adult cells?
Nucleus removed from unfertilised egg cell and replaced with nucleus from adult body cell. Electric shock given, so cell divides to form an embryo, then inserted back into womb of adult female
82
(Triple only) Who came up with the theory of natural selection and how?
Charles Darwin, on a round the world expedition and based on observations of fossils, geology and experimentation
83
(Triple only) Describe the stages in evolution by natural selection
Genetic variation, survival of the fittest, breeding and passing on characteristics
84
(Triple only) Name Darwin's book and the date of publication
On the Origin of Species, 1859
85
(Triple only) Give 3 reasons why Darwin's theory was only gradually accepted
It challenged ideas about God making all the animals/plants; insufficient evidence at the time; mechanism of inheritance (genes) was not known for another 50 years after publication
86
(Triple only) Who came up with an alternative theory to Charles Darwin?
Jean-Baptiste Lamarck
87
(Triple only) How did Lamarck's theory differ from Darwin's?
He proposed that characteristics developed during an organism's lifetime could be passed on (Darwin said only characteristics you were born with)
88
(Triple only) Who proposed natural selection independently to Darwin but also published papers with him?
Alfred Russell Wallace
89
(Triple only) Aside from evolutionary theory, what else did Alfred Russell Wallace work on?
Warning colouration in animals
90
(Triple only) What is speciation?
Development of a new species through natural selection occurring differently in isolated populations
91
(Triple only) What did Mendel do, and how did it influence the theory of evolution?
Experiments on plant breeding; Basic ideas about 'units' of inheritance (later known as genes)
92
Give two pieces of evidence for evolution
Fossils; antibiotic resistance in bacteria
93
How do fossils provide evidence of evolution?
Show gradual changes in organisms over time
94
How does antibiotic resistance provide evidence for evolution?
It shows how an organism can change when the environment changes
95
What are fossils?
Remains of organisms from millions of years ago which are found in rocks
96
How do fossils form (three ways)?
Parts of organisms don't decay; parts of organisms are replaced with minerals as they decay; preserved footprints etc.
97
Why don't all organisms form fossils?
Many organisms are soft bodied and don't form fossils easily; some are destroyed by geological activity
98
What is extinction?
When there are no individuals of a species left on earth
99
List some factors that may contribute to extinction of a species
Climate change; hunting; disease; new predators etc.
100
What is MRSA?
A particular microorganism that is resistant to antibiotics
101
How can we reduce antibiotic resistance?
Only prescribe antibiotics when necessary; patients must complete the course; reduce agricultural use of antibiotics
102
Why is antibiotic resistance a concern?
People are not immune to the bacteria but it cannot be treated with antibiotics; Development of new antibiotics is costly and slow - can't keep up with emergence of resistant strains
103
Who developed the first system for classification of organisms?
Carl Linnaeus
104
List the levels in the classification system proposed by Carl Linnaeus
Kingdom, phylum, class, order, family, genus, species
(King Philip Came Over For Good Soup)
105
What are the two parts of an organism's binomial name?
Genus and species
106
Give two reasons why our ideas about classification have changed since Carl Linnaeus first proposed his system
Development of microscopes advances knowledge of structures inside cells; understanding of biochemical processes progressed
107
Who proposed the 'Three Domain system' of classification?
Carl Woese
108
What are the three groups of the 'three domain system' of classification?
Archaea, bacteria, eukaryota
109
What are the archaea (in the 'three domains system' of classification)?
Primitive bacteria usually living in extreme environments
110
How can we show in a visual way how organisms are related?
Evolutionary trees
111
What information is needed to construct an evolutionary tree?
Classification data for living organisms and fossil data for extinct organisms
