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biology paper 2 > topic 2 > Flashcards

topic 2 Flashcards

1
Q

What is sexual reproduction?

A

● Involves the production of gametes by meiosis.
● A gamete from each parent fuses to form a zygote.
● Genetic information from each gamete is mixed so the
resulting zygote is unique

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2
Q

What are gametes?

A

sex cells
sperm and egg in animals
egg and pollen in flowering plants

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3
Q

advantages of sexual repoduction

A

variation
survival advantage through natural selection and variation
natural selection can be speed up by seletive breeding

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4
Q

what are advantages of asexual production

A

only one parent needed
more time and energy efficient
faster
many identical offspring - in favourable conditions

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5
Q

what is meiosis

A

halves the number of chromosomes in gametes
when fertilisation occurs this doubles

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6
Q

What happens during the first stage of
meiosis?

A

● Chromosome pairs line up along the cell equator.
● The pair of chromosomes are separated and move to
opposite poles of the cell
● Chromosome number is halved.

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7
Q

how is variation created in meiosis

A

(the side to which each
chromosome is pulled is random, creating variation).

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8
Q

What happens during the second stage of meiosis?

A

● Chromosomes line up along the cell equator.
● The chromatids are separated and move to opposite
poles of the cell.
● Four unique haploid gametes are produced.

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9
Q

Why is meiosis important for sexual
reproduction?

A

● It increases genetic variation.
● It ensures that the zygote formed at
fertilisation is diploid.complete chromosome

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10
Q

meiosis vs mitosis

A

non identical cells
variation
mixing of genetic material

identical cells
cloned offspring
no mixing of genetic material

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11
Q

gamete production

A

copies of genetic material are made 2N
cell divides twice to form 4 gametes
each with a single set of chromosomes
so are genetically different

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12
Q

disadvantsges of SR

A

Two parents are required. This makes reproduction
difficult in endangered populations or in species which
exhibit solitary lifestyles.
● More time and energy is required so fewer offspring
are produced.

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13
Q

Describe the circumstances in which
Malarial parasites reproduce sexually
and asexually

A

Sexual reproduction in the mosquito.
Asexual reproduction in the human host

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14
Q

Describe the circumstances in which
fungi reproduce sexually and asexually

A

Asexual reproduction by spores.
Sexual reproduction to give variation.

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15
Q

Describe the circumstances in which
plants reproduce sexually and asexually

A

Sexual reproduction to produce seeds.
Asexual reproduction by runners (e.g.
strawberry plants) or bulb division (e.g.
daffodils).

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16
Q

what is DNA

A

chemical found in the nucleus
polymer
2 stands forming a double helix

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17
Q

Define genome

A

The entire genetic material of an organism.

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18
Q

Why is understanding the human genome important?

A

● Searching for genes linked to different types of disease.
● Understanding and treating inherited disorders.
● Tracing human migration patterns from the past.

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19
Q

What is a chromosome?

A

coiled molecule of DNA that
carries genetic information in the form of genes.

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20
Q

what is a gene

A

small section of DNA
each gene codes for a sequence of amino acids
to make a specific protien

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21
Q

dna structure

A

polymer
4 nucleotides
each nucleotide has a common sugar and phosphate group

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22
Q

What are the monomers of DNA?

A

Nucleotides

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23
Q

What are DNA nucleotides made up of?

A

● Common sugar
● Phosphate group
● One of four bases: A, T, C or G

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24
Q

what is a sequence of 3 bases called

A

amino acid

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25
Q

order of the bases calles

A

particular protien

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26
Q

Describe how nucleotides interact to form a molecule
of DNA

A

● Sugar and phosphate molecules join to form a
sugar-phosphate backbone in each DNA strand.
● Base connected to each sugar.
● Complementary base pairs (A pairs with T, C pairs with G)
joined by weak hydrogen bonds

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27
Q

Explain how a gene codes for a protein

A

● A sequence of three bases in a gene forms a triplet.
● Each triplet codes for an amino acid.
● The order of amino acids determines the structure
(i.e. how it will fold) and function of protein formed.

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28
Q

Why is the ‘folding’ of amino acids important in proteins such as enzymes?

A

determines the shape of the active site

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29
Q

what happens if the DNA base structure changes

A

the protien created will be different

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30
Q

describe protien synthesis

A

ribosomes made by a template
carrier molecules bring specific amino acids
to add to a protein chain
in the correct order
when its complete the chain folds up to produce a specific active sites
which allows them to be hormones enzymes or structures

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31
Q

what are mutations

A

happen continuously
most do not alter the protien
only alter it slightly in appearance
but few mutations code for a different protein
so will have a different shape and wont fit the substrate
so wont work

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32
Q

what is gene expression

A

non-coding parts of DNA can switch genes on and off
so variations in these
affect how genes could be expressed

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33
Q

What are alleles?

A

Different versions of the same gene.

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34
Q

What is a dominant allele?

A

A version of a gne where only one copy
is needed for it to be expressed.

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35
Q

What is a recessive allele?

A

What is a recessive allele?

36
Q

What is meant when an organism is
homozygous?

A

When an organism has two copies of the
same allele (two recessive or two
dominant)

37
Q

what do alleles present

A

genotype
operate at a molecular level
develop physical characteristics
expressed as a phenotype

38
Q

What is meant when an organism is
heterozygous?

A

When an organism has two different
versions of the same gene (one
dominant and one recessive).

39
Q

What is the genotype?

A

The genes present for a trait

40
Q

What is the phenotype?

A

The visible characteristic.

41
Q

Give 2 examples of inherited disorders

A

● Polydactyly (having extra fingers or toes) -
caused by a dominant allele.
● Cystic fibrosis (a disorder of cell
membranes) - caused by a recessive allele.

42
Q

what can alliviate genetic disorders

A

embryo screening
gene therapy

43
Q

What is variation?

A

Differences in the characteristics of
individuals in a population

44
Q

What are the causes of variation within a
species?

A

● Genetics
● Environment
● A mixture of both of the above

45
Q

What is genetic variation?

A

● Variations in the genotypes of organisms of
the same species due to the presence of
different alleles.
● Creates differences in phenotypes.

46
Q

what happens if a mutation leads to a new phenotype

A

rapid change in the species will occur is favourable to the oenvironment

47
Q

How may a gene mutation affect an organism’s
phenotype? (3)

A
48
Q

what is evolution

A

a change in inherrited characteristics over time through a process of natural selection
can produce new species

49
Q

Outline the theory of natural selection

A

All species of living things have evolved from simple life forms that
first developed more than 3 billion years ago

50
Q

how does natural selection work

A
  1. Genetic variation exists due to spontaneous mutations.
  2. Selection pressures (e.g. competition, disease) exist.
  3. Random mutation gives an organism a selective advantage.
  4. Organism is better adapted to the environment and survives.
  5. Organism reproduces, passing on its beneficial alleles.
  6. Frequency of advantageous alleles increase
51
Q

How do two populations become
different species?

A

When their phenotypes become different
to the extent that they can no longer
interbreed to produce fertile offspring.

52
Q

What is selective breeding?

A

humans artificially select
organisms with desirable characteristics and breed them to produce offspring with similar phenotypes

53
Q

process of selective breeding

A

parents chosen from mixed population
they are bred
offspring with desired characteristics are bred together
continues over many generations

54
Q

what are the characteristics of selective breeding

A

disease resistance in crops
animals producing more milk and heat
large unusual flowers

55
Q

Outline the disadvantages of selective breeding (4)

A

● Reduction in the gene pool
● Inbreeding results in genetic disorders.
● Development of other physical problems e.g. respiratory
problems in bulldogs.
● Potential to unknowingly select harmful recessive alleles

56
Q

why was darwins theory not accepted

A

genes and dna havent been discovered
not enough evidence

57
Q

how were fossils destroyed

A

Technomic activity
not discovered yet

58
Q

model answer genetic variation

A

mutation causes genetic variation
(example)
are now better adapted
and are more likely to survive and repoduce
and pass on the allele to their offspring
by natural selection

59
Q

describe the process of genetic engineering

A

cut out the desired gene from the dna of the host
using an enzyme
insert the gene to the vector (plasmid)
the vector is used to insert the DNA into the cell
at an early stage of development

60
Q

how can plants be cloned

A

● Taking plant cuttings
● Tissue culture

61
Q

Describe how plants are grown using
tissue culture

A
  1. Select a plant that shows desired characteristics.
  2. Cut multiple small sample pieces from meristem tissue.
  3. Grow in a petri dish containing nutrients and growth hormones
  4. Transfer to compost for further growth
62
Q

Describe the benefits of genetic engineering (3)

A

● Increased crop yields for growing population
● Useful in medicine e.g. insulin-producing bacteria, anti-thrombin
in goat milk, possibility to overcome some inherited disorders

● GM crops produce scarce resources

63
Q

Describe the risks of genetic engineering
(4)

A

● Long-term effects of consumption of GM crops unknown.
● Negative environmental impacts e.g. reduction in biodiversity,
● Late-onset health problems in GM animals.
● GM seeds are expensive. LEDCs may be unable to afford them or
may become dependent on businesses that sell them.

64
Q

What must be ensured when preparing
tissue cultures?

A

Ensure aseptic conditions to prevent
contamination by microorganisms.

65
Q

What are the advantages of growing
plants by tissue culture? (4)

A

● Fast and simple process.
● Requires little space.
● Enables the growth of many plant clones with the same
desirable characteristics.
● Useful in the preservation of endangered plant species

66
Q

What are the disadvantages of growing
plants by tissue culture? (4)

A

● Reduction in the gene pool.
● Plant clones often have a low survival rate.
● Could unknowingly increase the presence of harmful
recessive alleles.

67
Q

describe the process of adult cell cloning

A
  1. The nucleus is removed from an unfertilised egg cell.
  2. The nucleus from an adult body cell, such as a skin cell, is inserted into
    the egg cell.
  3. An electric shock stimulates the nucleated egg cell to divide and it forms
    an embryo.
  4. The embryo cells contain the same genetic information as the adult body
    cell.
  5. When the embryo is a ball of cells, it is inserted into the uterus of an adult
    female to continue developing
68
Q

What was Jean-Baptiste Lamarck’s
theory of inheritance

A

That changes during the lifetime of an
organism can be inherited.

69
Q

What is the definition of a species?

A

A group of organisms with similar
characteristics which are able to
interbreed to produce fertile offspring.

70
Q

describe the process of speciation

A

ansectors become separated by a geographical barrier
each population adapts to different environmental conditions
a genetic mutation causes more fur
giving them an advantage
so more likely to survive and repoduce
by natural selection
and pass mutated alleles to offspring
over a long period of time they can no longer interbreed to produce fertile offspring

71
Q

How did Mendel study inheritance?

A

Through carry breeding experiments on
plants and analysing the ratio of
characteristics in offspring

72
Q

Why was Mendel’s work not recognised
until after his death?

A

He could not explain the mechanism of inheritance, as chromosomes were only discovered after his death.
It was not communicated well to other scientists and not published in a reputable scientific journal.

73
Q

how do species become extinct

A
  • catastrophic event
  • new predator
  • new disease pathogen
  • speciation
74
Q

how are fossils formed

A

hard bones are preserved due to a lack of oxygen
parts of bone are replaced by minerals as they slowly decay
hard bones decay but leave an imprint

75
Q

Outline the process of antibiotic resistance bacteria
evolving

A

● Mutations occur in bacteria producing genetic variation.
● Certain strains are resistant to antibiotics and are not
killed when the antibiotic is applied.
● Resistant strains survive and reproduce.
● Over time, the population of the resistant strains increase

76
Q

Why are resistant strains of bacteria dangerous?

A

People have no immunity to them and
there is no effective treatment.

77
Q

State an example of a resistant strain of bacteria

A

MRSA.
to reduce the rate of development

78
Q

disadvantages of RB

A

new antibiotics are costly and slow and cant keep up

79
Q

What can be done to reduce the rate of development
of antibiotic resistant bacteria?

A

Refrain from inappropriately prescribing
antibiotics eg. for viral diseases.
● Patients should complete the prescribed course of
antibiotics.
● Restrict agricultural uses of antibiotics.

80
Q

What are the classes of organisms as
determined by Carl Linnaeus?

A

Kingdom,
phylum,
class,
order,
family,
genus,
species.

81
Q

Which features are living creatures traditionally
classified by

A

By their structure and characteristics

82
Q

What is the binomial system of naming organisms?

A

Genus name followed by species name.

83
Q

Why were new classification models
proposed?

A

● Developments in microscopy allowed better
examination of internal structures.
● Improvement in understanding of
biochemical processes

84
Q

State the three domains.

A

● Archaea - primitive bacteria
● Eukarya
● Bacteria

85
Q

what are evolutionary trees

A

By examining the DNA of different
species and analysing how similar the
sequences are

biology paper 2 (3 decks)

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