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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
order of the bases calles
particular protien
26
Describe how nucleotides interact to form a molecule of DNA
● 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
27
Explain how a gene codes for a protein
● 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.
28
Why is the ‘folding’ of amino acids important in proteins such as enzymes?
determines the shape of the active site
29
what happens if the DNA base structure changes
the protien created will be different
30
describe protien synthesis
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
31
what are mutations
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
32
what is gene expression
non-coding parts of DNA can switch genes on and off so variations in these affect how genes could be expressed
33
What are alleles?
Different versions of the same gene.
34
What is a dominant allele?
A version of a gne where only one copy is needed for it to be expressed.
35
What is a recessive allele?
Two copies of the allele need to be present for the phenotype to be expressed.
36
What is meant when an organism is homozygous?
When an organism has two copies of the same allele (two recessive or two dominant)
37
what do alleles present
genotype operate at a molecular level develop physical characteristics expressed as a phenotype
38
What is meant when an organism is heterozygous?
When an organism has two different versions of the same gene (one dominant and one recessive).
39
What is the genotype?
The genes present for a trait
40
What is the phenotype?
The visible characteristic.
41
Give 2 examples of inherited disorders
● Polydactyly (having extra fingers or toes) - caused by a dominant allele. ● Cystic fibrosis (a disorder of cell membranes) - caused by a recessive allele.
42
what can alliviate genetic disorders
embryo screening gene therapy
43
What is variation?
Differences in the characteristics of individuals in a population
44
What are the causes of variation within a species?
● Genetics ● Environment ● A mixture of both of the above
45
What is genetic variation?
● Variations in the genotypes of organisms of the same species due to the presence of different alleles. ● Creates differences in phenotypes.
46
what happens if a mutation leads to a new phenotype
rapid change in the species will occur is favourable to the oenvironment
47
How may a gene mutation affect an organism’s phenotype? (3)
48
what is evolution
a change in inherrited characteristics over time through a process of natural selection can produce new species
49
Outline the theory of natural selection
All species of living things have evolved from simple life forms that first developed more than 3 billion years ago
50
how does natural selection work
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
How do two populations become different species?
When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring.
52
What is selective breeding?
humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
53
process of selective breeding
parents chosen from mixed population they are bred offspring with desired characteristics are bred together continues over many generations
54
what are the characteristics of selective breeding
disease resistance in crops animals producing more milk and heat large unusual flowers
55
Outline the disadvantages of selective breeding (4)
● 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
why was darwins theory not accepted
genes and dna havent been discovered not enough evidence
57
how were fossils destroyed
Technomic activity not discovered yet
58
model answer genetic variation
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
describe the process of genetic engineering
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
how can plants be cloned
● Taking plant cuttings ● Tissue culture
61
Describe how plants are grown using tissue culture
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
Describe the benefits of genetic engineering (3)
● 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
Describe the risks of genetic engineering (4)
● 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
What must be ensured when preparing tissue cultures?
Ensure aseptic conditions to prevent contamination by microorganisms.
65
What are the advantages of growing plants by tissue culture? (4)
● 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
What are the disadvantages of growing plants by tissue culture? (4)
● Reduction in the gene pool. ● Plant clones often have a low survival rate. ● Could unknowingly increase the presence of harmful recessive alleles.
67
describe the process of adult cell cloning
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
What was Jean-Baptiste Lamarck’s theory of inheritance
That changes during the lifetime of an organism can be inherited.
69
What is the definition of a species?
A group of organisms with similar characteristics which are able to interbreed to produce fertile offspring.
70
describe the process of speciation
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
How did Mendel study inheritance?
Through carry breeding experiments on plants and analysing the ratio of characteristics in offspring
72
Why was Mendel’s work not recognised until after his death?
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
how do species become extinct
- catastrophic event - new predator - new disease pathogen - speciation
74
how are fossils formed
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
Outline the process of antibiotic resistance bacteria evolving
● 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
Why are resistant strains of bacteria dangerous?
People have no immunity to them and there is no effective treatment.
77
State an example of a resistant strain of bacteria
MRSA. to reduce the rate of development
78
disadvantages of RB
new antibiotics are costly and slow and cant keep up
79
What can be done to reduce the rate of development of antibiotic resistant bacteria?
Refrain from inappropriately prescribing antibiotics eg. for viral diseases. ● Patients should complete the prescribed course of antibiotics. ● Restrict agricultural uses of antibiotics.
80
What are the classes of organisms as determined by Carl Linnaeus?
Kingdom, phylum, class, order, family, genus, species.
81
Which features are living creatures traditionally classified by
By their structure and characteristics
82
What is the binomial system of naming organisms?
Genus name followed by species name.
83
Why were new classification models proposed?
● Developments in microscopy allowed better examination of internal structures. ● Improvement in understanding of biochemical processes
84
State the three domains.
● Archaea - primitive bacteria ● Eukarya ● Bacteria
85
what are evolutionary trees
By examining the DNA of different species and analysing how similar the sequences are

biology paper 2 (3 decks)

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