P2- Topic 6- Inheritance, Variation and Evoloution Flashcards
(111 cards)
1
Q
What is sexual reproduction? 3
A
Type of reproduction
the joining of male and female gametes, each containing genetic information from the mother or father.
Sperm and egg cells in animals
Pollen and egg cells in flowering plants
2
Q
What are gametes?2
A
Sex cells (sperm cells and egg cells in
animals, pollen and egg cells in flowering
plants).
● Haploid (half the number of chromosomes)
3
Q
what does meiosis lead to 3
A
formation of four non-identical cells from one cell
Chromosome number is halved.
Involves two divisions
4
Q
What is asexual reproduction?
A
Involves mitosis only.
Produces genetically identical offspring
known as daughter cells.
5
Q
what happens in meiosis 4
A
a cell divides to form gametes
copies genetic information
cell divides 2x to form four gametes, each with a single set of
chromosomes
all gametes are genetically different from each other.
6
Q
Why is meiosis important for sexual
reproduction? (2)
A
increases genetic variation.
ensures the zygote formed at fertilisation is diploid
7
Q
Describe fertilisation and its resulting
outcome 2
A
Gametes join together to restore the normal
number of chromosomes and the new cell then
divides by mitosis (which increases the number
of cells).
As the embryo develops, cells differentiate.
8
Q
What is the advantage of sexual
reproduction?3
A
-produces variation in the offspring
-if the environment changes variation gives a survival advantage by natural
selection
• natural selection can be speeded up by humans in selective breeding to
increase food production.
9
Q
Describe the disadvantages of sexual
reproduction (3)
A
o parents are required.
-reproduction
difficult in endangered populations or in species which
exhibit solitary lifestyles
-More time and energy is required so fewer offspring
are produced
10
Q
Describe the advantages of asexual
reproduction (4)
A
only one parent needed
- more time and energy efficient as do not need to find a mate
- faster than sexual reproduction
- many identical offspring can be produced when conditions are favourable.
11
Q
What is the disadvantage of asexual
reproduction?2
A
No genetic variation (except from
spontaneous mutations)
reducing the
probability of a species being able to
adapt to environmental change.
12
Q
Describe the circumstances in which fungi reproduce sexually and asexually 2
A
Asexual reproduction by spores.
Sexual reproduction to give variation
13
Q
Describe the circumstances in which Malarial parasites reproduce sexually
and asexually 2
A
Sexual reproduction in the mosquito.
Asexual reproduction in the human host
14
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).
15
Q
Why is understanding the human genome
important?4
A
The whole human genome has been studied and is
important for the development of medicine in the future
search for genes linked to different types of disease
- understanding and treatment of inherited disorders
- use in tracing human migration patterns from the past
16
Q
Define genome
A
The entire genetic material of an organism.
17
Q
Describe the structure of DNA
A
- polymer
- made up of two strands
- forming a double
helix. - DNA contained in structures called chromosomes
18
Q
What are DNA nucleotides made up of?3
A
common sugar
phosphate group
one of four different bases attached to the sugar. A,T,C,G
19
Q
Define gene
A
-a small section of DNA on a chromosome.
Each gene codes
for a particular sequence of amino acids, to make a specific protein.
20
Q
what are the monomers of DNA?
A
Nucleotides
21
Q
Describe how nucleotides interact to form a molecule of DNA (3)
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
22
Q
Explain how a gene codes for a protein 3
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
23
Q
What is protein synthesis?
A
The formation of a protein from a gene
24
Q
What are the two stages of protein synthesis?
A
- Transcription
2. Translation
25
What does transcription involve?
The formation of mRNA from a DNA
| template
26
Outline transcription 4
1. DNA cannot move out of
the nucleus as it is too big.
2. The two strands pull apart from each other, and mRNA nucleotides
match to their
complementary base on the strand.
3. mRNA nucleotides joined together, creating a new
strand called the mRNA strand. This is a template of the original DNA.
4. The mRNA then moves out of the nucleus to the cytoplasm and onto
structures called ribosomes.
27
what does translation involve
ribosome joins in a specific order dictated by the mrRNA to form a protein
28
outline translation 4
1. mRNA attaches to a ribosome.
2. Ribosome reads the mRNA bases in triplets. Each triplet codes
for one amino acid which is brought to the ribosome by a tRNA molecule (carrier molecule).
3. A polypeptide chain is formed from the sequence of amino
acids which join togethe
29
What is a mutation? 2
A random change in the base sequence of DNA
results in no change to the protein coded for, or
genetic variants of the protein (slight alteration but
appearance and function remain)
30
Describe the effect of a gene mutation in coding DNA 2
the protein structure and function may change (an enzyme may no longer
fit its substrate binding site or a structural protein may lose its
strength).
● If a mutation does not change amino acid sequence, there is no effect on protein structure or function
31
What is non-coding DNA?
DNA which does not code for a protein but controls which genes are expressed
32
Describe the effect of a gene mutation in non-coding
| DNA (2)
Gene expression may be altered, affecting protein production and the resulting phenotype (physical charecteristics)
33
What are alleles?
Different versions of the same gene
34
What is a dominant allele?
A version of a gene where only one copy is needed for it to be expressed
35
What is a recessive allele?
A version of a gene where two copies are needed for it 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 is meant when an organism is heterozygous?
When an organism has two different versions of the same gene (one dominant and one recessive).
38
What is the genotype? and example 2
The genes present for a trait
The combination of alleles an individual has, e.g. Aa
39
What is the phenotype? and example 2
The visible characteristic eye colour
40
What is the problem with single gene crosses?
Most characteristics are controlled by
| multiple alleles rather than just one.
41
Give 2 examples of inherited disorders and allele cause
Polydactyly (having extra fingers or toes)
dominant allele.
Cystic fibrosis (a disorder of cell membranes
recessive allele.
42
How are embryos screened for inherited disorders? 3
In IVF, one cell is removed (from an 8 cell embryo)
tested for disorder-causing
allele
If the cell doesn’t have any indicator alleles, then the originating embryo is
implanted into the uterus.
43
What are the ethical issues concerning embryo screening?3
● It could lead to beliefs in society that being disabled or having a disorder is less human or associated with inferiority.
● The destruction of embryos with inherited disorders is seen by
as murder as these would go on to become human beings.
● concept of designer babies= parents convenience or wishes than the child’s wellbeing
44
What are the economic issues
| concerning embryo screening?1
Costs of hospital treatment and medication considered if it is known that a child will have an inherited disorder and financial support explored if necessary
45
What are the social issues concerning
| embryo screening?
● Social care for children with inherited disorders may
need to be considered if parents are unable to provide care.
● If an embryo is found to have an inherited disorder and is terminated, this can prevent a child and its parents from potential suffering in the future due to the disorder
46
What are the ethical concerning gene therapy
● believe that it is going
against and ‘playing God’.
● The introduced genes could enter sex cells and so be passed to future generations
47
What is variation?
Differences in the characteristics of
individuals in a population is called
variation
48
What are the causes of variation within a species? 3
-Genetics
● Environment
● A mixture of both of the above weight
49
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
50
What creates genetic variation in a species?2
● Spontaneous mutations
| ● Sexual reproduction
51
What is the consequence of a new phenotype caused by a mutation being suited to an
environmental change?
There will be a rapid change in the
| species.
52
How may a gene mutation affect an organism’s
| phenotype? (3)
No effect on phenotype.
some influence phenotype, change in eye colour
may determine phenotype by completely changing the sequence of amino acids.
53
What is evolution?2
change in the inherited characteristics of a population over time
by natural selection resulting in the formation of a new species
54
Outline the theory of natural selection 6
1. Genetic variation by 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
55
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.
56
What is selective breeding?
humans
| breed plants and animals for particular genetic characteristics
57
Outline the main steps involved in selective breeding 4
1. Identify a desired characteristic e.g. disease resistance.
2. Select parent organisms that show the desired traits and breed them together.
3. Select offspring with the desired traits and breed them together.
4. Process repeated until all offspring have the desired traits
58
Give examples of characteristics selected for selective breeding.4
Disease resistance in food crops.
• Animals which produce more meat or milk.
• Domestic dogs with a
gentle nature.
• Large or unusual flowers
59
What is the main advantage of selective breeding?4
Creates organisms with desirable features:
● Crops produce a higher yield of grain
● Cows produce a greater supply of milk
● Plants produce larger fruit
● Domesticated animals
60
Outline the disadvantages of selective
| breeding (4)
- Reduction in the gene pool (which becomes especially
harmful if sudden environmental change occurs).
● Inbreeding results in genetic disorders.
● Development of other physical problems e.g. respiratory problems in bulldogs.
● Potential to unknowingly select harmful recessive alleles.
61
What is genetic engineering?
modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
62
examples of genetic engineering in bacteria cells and plants 3
● Disease resistance
● Produce larger fruits
To produce human insulin to treat diabetes mellitus
63
Describe the benefits of genetic engineering (3
-Increased crop yields for growing population e.g.
herbicide-resistance, disease-resistance.
● Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk, possibility to overcome some inherited disordersproducing human insulin
● GM crops produce scarce resources e.g. GM golden rice produces beta-carotene (source of vitamin A in the body)
64
Describe the risks of genetic engineering
| (4
● Long-term effects of eatingGM crops unknown.
● Negative environmental impacts e.g. reduction in biodiversity, impact
on food chain, contamination of non-GM crops forming ‘superweeds’.
● health problems in GM animals.
● GM seeds are expensive
65
How is genetic engineering used to
protect crops against insects?
2
The gene for toxin production in Bt can be isolated and inserted into the DNA of crops.
● Bt crops now secrete the toxin which kills any insect larvae that feed on it
66
Describe the process of genetic
| engineering 5
enzymes are used to isolate the required gene
gene is inserted into a vector(bacterial plasmid,virus)
vector is used to insert the gene into the required cells
at an early stage of development genes are transferred to the cells of animals, plants or microorganisms so that they develop with desired characteristic
67
What is a vector?
A structure that delivers the desired gene
into the recipient cell e.g. plasmids,
viruses.
something that transmits (carries) something else.
68
explain genetic enginerring to produce human insulin?4
- human insulin gene is removed using a restriction enzyme.
- vector- bacterial plasmid is cut open using the same restriction enzyme to create sticky ends
-Ligase enzymes join the sticky ends of the DNA and vector DNA
forming recombinant DNA
-Recombinant DNA mixed with and ‘taken up’ by target cells.
69
How can plants be cloned? (2)
● Taking plant cuttings
| ● Tissue culture
70
What is tissue culture?
Using small groups of cells from part of a
| plant to grow identical new plants.
71
Describe how plants are grown using
| tissue culture 4
1. Select a plant that shows desired characteristics.
2. Cut multiple small sample pieces from meristem tissue.
3. Grow in a petri dish containing growth medium.
4. Transfer to compost for further growth.
72
What must be ensured when preparing tissue cultures?
Ensure aseptic conditions to prevent
| contamination by microorganisms.
73
What does the growth medium contain?
Nutrients and growth hormones
74
What are the advantages of growing
| plants by tissue culture? (3)
● 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
75
What are the disadvantages of growing plants by tissue culture? (2)
● Reduction in the gene pool.
● Plant clones often have a low survival rate.
● Could unknowingly increase the presence of harmful recessive alleles.
76
Describe the plant cuttings method of plant cloning
Older but simpler method than tissue culture.
Gardeners use this method to produce many
identical new plants from a parent plant.
77
Detail the process of the plant cuttings
| method of plant cloning 4
1. cuttins taken from parent plant.
2. lower leaves of the branch are removed and the stem is planted.
3. Plant hormones are used to encourage new root development. compost
4. A plastic bag is used to cover the new plant to keep it warm and
moist.
5. New roots and a new plant is formed after a few week
78
What does embryo transplanting involve?5
an embryo is removed from its mother's uterus before its cells have begun to specialise
female inseminated
embryo is then split, creating a large number of identical embryos.
embryos inserted into host mothers
embryos' cells become specialised in the host mothers and they develop into new organisms.
host mothers give birth to offspring identical to each other (clones).
79
Describe how adult cell cloning is performed 4
∙nucleus is removed from an unfertilised egg cell.
* nucleus from an adult body cell is inserted into the egg cell.
* electric shock stimulates the egg cell to divide to form an embryo.
* embryo cells has the same genetic information as the adult skin cell.
* When embryo has developed it is inserted into the womb of an adult female to continue its development.
80
Outline the theory of evolution by natural selection.
| 3
Individuals of a species show a wide range of variation for a characteristic.
Those with the characteristic most suited to the environment will survive breed most successfully.
The desirable and useful characteristic passed onto their offspring
81
Why was Darwin’s theory of evolution
| not accepted initially? 3
● Most people believed in creationism
● Insufficient evidence to prove the theory
● variation and inheritancewas not known at the time
82
What was Jean-Baptiste Lamarck’s
| theory of inheritance and example 2
That changes during the lifetime of an
organism can be inherited.
giraffe that stretches its neck a lot to reach the leaves on the tallest trees may develop a long neck
83
Outline the process of speciation through geographic isolation.
4
● Two populations of the same species are separated geographically
● Geographic isolation prevents interbreeding and mixing of genes
between the populations.
● Due to different selection pressures, different mutations occur producing different phenotypes in each population
.
● Over time, the two populations may evolve so that they are not able to
interbreed
84
Why is genetic variation important in speciation
produces phenotypic variation, some of which are better suited to the environment and are selected for
85
what is alfred wallace known for
independently proposed the theory of evolution by natural selection
86
How did Mendel study inheritance?2
carry breeding experiments on
plants (peaplants)
analysing the ratio of characteristics in offspring
87
Why was Mendel’s work not recognised
| until after his death?2
didn't explain the mechanism of inheritance, as chromosomes were only discovered after his death.
not published in a reputable scientific journal.
88
State two kinds of evidence used to show evolution
● Fossils
| ● Antibiotic resistance in bacteria
89
How are fossils formed?3
-when parts of organisms don't decay as
one or more of the conditions needed for decay are absent h20,oxygen
• when hard parts of the organism are replaced by minerals
• when organisms leave traces on the earth, which are then preserved in rock as footprints, burrows and
rootlet trace
90
Why are there few traces of early life-forms left behind?
They are mostly soft-bodied
geological events volcanoes
91
How do fossils act as evidence for evolution?
| 2
can identify the ages of the fossils and use them to show how organisms change over time
92
What do branches in evolutionary trees
| indicate?2
Where speciation has occurred
| common ancestor and ancestral species
93
State the factors that may lead to extinctions. 4/5
```
● New disease
● Predation
● Competition
● Changes to the environment
● Catastrophic events
```
94
What enables bacteria to evolve quickly?
The fast rate of their reproduction
95
Outline the process of antibiotic
| resistance bacteria evolving.4
● 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
96
Why are resistant strains of bacteria dangerous?
People have no immunity to them and
| there is no effective treatment
97
State an example of a resistant strain of bacteria.
MRSA
98
What can be done to reduce the rate of
development of antibiotic resistant
bacteria?3
● Refrain from inappropriately prescribing
antibiotics eg. for viral diseases.
● Patients should complete the prescribed course of antibiotics.
● Restrict agricultural uses of antibiotics
99
Why is it difficult to keep up with
| emerging resistance strains?
Developing antibiotics have a high cost
| and take a long time to develop
100
By what process do bacteria develop resistance to antibiotics 2
natural selection" or "mutation
101
What are the classes of organisms as
| determined by Carl Linnaeus? 7
```
Kingdom
phylum
class
order
family
genus
species
```
102
Which features are living creatures traditionally classified by?
By their structure and characteristics
| genus and species.
103
What is the binomial system of naming
| organisms?
Genus name followed by species name
104
Why were new classification models
| proposed?2
● Improved microscopes have allowed scientists to see more detailed internal structures of different organisms
● Improvement in understanding of
biochemical processes.
105
State the three domains. Carl Woese 3
● Archaea
● Eukarya
● Bacteria
106
Which organisms belong in the domain
| Archaea?
primitive bacteria usually living in extreme environments)
107
Which organisms belong in the domain
| Bacteria?
true bacteria)
108
Which kingdoms belong in domain
| Eukarya?
● Plants
● Animals
● Fungi
● Protists
109
How are evolutionary trees created?
examining the DNA of different
species and analysing how similar the
sequences are
110
What kingdom does Homo sapiens belong to?
"animals" or "animalia" or "animal kingdom"
111
How many kingdoms are there?5
```
animal,
plant,
fungi
protist
bacteria
```
