Inheritance, Variation and Evolution Flashcards
What is mitosis
The formation of two identical cells from one cell
What is meiosis
The formation of four non-identical cells from one cell
Give 3 advantages each for sexual and asexual reproduction
Sexual
- Produces variation is offspring
- Survival advantage when environment changes
- Possible to carry out selective breeding
Asexual
- Only one parent needed
- Many identical offspring
- Faster than sexual, uses less energy
Give 3 examples of organisms that reproduce sexually and asexually
- Strawberry- flowers(S) runners (A)
- Daffodil- Flowers (S) bulbs (A)
- Malarial parasite (A) in humans (S) in mosquitos
- Fungi (A) in spores, (S) in mycelium
Describe the structure of a DNA nucleotide
- Has a sugar (pentagon shape)
- Phosphate group (circle)
- Base
Give the 2 pairs of nitrogenous bases in DNA
Adenine and Thymine (A+T)
Cytosine and Guanine (C+G)
Describe how DNA codes for an amino acid
Bases come in groups of 3
Each “codon” codes for one amino acid
Explain how protein synthesis occurs
DNA is transcribed to make mRNA
mRNA leaves nucleus
Ribosomes “read” the codons and translate using tRNA
tRNA recruits the amino acid indicated by the triplet codon
Give 4 possible impacts of a mutation in the DNA
- No change
- Change to expression pattern, tells the cell how much of the protein to make
- Knock out mutation
- Change of structure. Protein still works, but differently. (evolution occurs)
Name 4 types of cloning
Tissue culture
Adult cell
Cuttings
Embryo transplant cloning
Describe how tissue culture is carried out
Small groups of cells are grown in a fluid or petri dishes with a grown medium to produce lots of identical plants
Give 2 examples of there tissue culture is used
Preserving rare plant species
Commercially in nurseries
Describe how cuttings are carried out
Small section of plants removed that contains meristem
Cutting placed in rooting powder before planting
Describe how embryonic transplant cloning is carried out
Sexual reproduction in petri dish to produce embryo
The embryo is split
Put separately into uterus of host mothers
Herd of identical offspring.
Describe how the offspring of embryo transplant cloning compare to one another and to their mother
- Offspring are identical
- Only share 50% of DNA with their mother
Describe the process of adult cell cloning
Enucleate egg cell (remove nucleus from egg cell)
Transfer nucleus of body cell from organism you want to clone
Electric shock to start division
Transfer embryo to uterus of host mother
Describe how the offspring of adult cell cloning compare to the somatic cell donor, the egg cell donor and the host mother
Somatic cell donor - 100%
Egg cell donor - 0%
Host mother - 0%
What is the theory of evolution
Charles Darwin’s theory that all species have evolved from simple life forms that first developed more than three billion years ago
What is evolution
Change in the inherited characteristics of a population over time through a process of natural selection
Describe the three key components of his theory
- Variation within a species
- Some are best suited to survive and breed
- characteristics are passed on to the next generation
Give three reasons why Darwin’s ideas were only gradually accepted
- Contradicted religion
- Insufficient evidence
- Mechanism not known for 50 years on how variation was happening
Describe Jean-Baptiste Lamark’s theory of evolution
- Theory of use and disuse
- If an organism used a body part in its lifetime, this would be enlarged in its offspring
- Theory doesn’t prove how evolution happens
What contribution did Alfred Russel Wallace make to evolutionary science?
Independently proposed theory of natural selection
Research about warning colouration
Speciation
What contribution did Gregor Mendel make to evolutionary science?
- Breeding experiments
- Early genetic theory
What name did Mendel give to genes
Units
Why would some plants have bright berries
To attract animals to eat it and help spread seeds
Explain why more deforestation for agriculture and fuel is occurring in tropical regions than temperate regions
increasing human population/ standard of living so more food/fuel required
Why is only 10% of the energy passed between trophic levels
- Some is lost in waste through processes like respiration
- Not all of the energy is consumed, for instance primary consumers don’t eat all the leaves from a tree
What structures in bacterial cells are likely to carry the genetic information that gives these bacteria resistance?
Plasmids
How to prevent antibiotic resistance
- do not prescribe antibiotics for mild infections because they will get better due to the body’s normal immune system
- do not prescribe antibiotics for viral infections / colds / flu because antibiotics do not kill viruses
How is a sperm cell adapted to its function
- Flagella so it can swim to the egg
- Lots of mitochondria to release energy for movement
Describe the process of meiosis
The cell makes copies of its chromosomes (double the amount of genetic information)
The cell divides into 2 cells, with half the chromosomes (46)
The cells divide again to give 4 gametes with 23 chromosomes
That are genetically different
What is a gene
A section of DNA that codes for a protein
What is a genome
All the genes coding for all of the proteins within an organism
What are enzymes
Biological catalysts that speed up rate of reaction
What are hormones
Chemical messengers that send signals around the body
What is a structural protein
Strong proteins in order to form structures, such as collagen
The three ways mutations in DNA sequences occur
- A base is inserted
- A base is deleted
- A base is substituted
Why may mutations alter a protein
Shape of protein is changed
So the substrate will no longer fit into the active site
A structural protein may lose its shape
What is a gamete
An organism’s reproductive cell which has half the numbers of chromosomes
What is a chromosome
A structure found in the nucleus which is made up of a long strand of DNA
What is an allele
The different forms of the gene - humans have two alleles for each gene as they inherit one from each parent
What is a dominant allele
Only one of the two alleles is needed for it to be expressed and for the corresponding phenotype to be observed
What is a recessive allele
Two copies are needed for it to be expressed and for the corresponding phenotype to be expressed
What is homozygous
When both inherited alleles are the same (2 dominant or 2 recessive)
What is heterozygous
When one of the inherited alleles is dominant, and the other is recessive
What is a genotype
The combination of alleles an individual has (Aa/AA/aa)
What is a phenotype
The physical characteristics that are observed in the individual (e.g eye colour)
What is polydactyly and what causes it
Having extra fingers or toes
Caused by a dominant allele
What is cystic fibrosis and what causes it
Disorder of the cell membranes
Caused by recessive allele, so both parents must be carriers
What is embryonic screening
When scientists can observe whether a child will have a genetic disorder
- Cells (+DNA) taken from embryos and its analysed
Arguments FOR embryonic screening
- Reduces the number of people suffering
- Treating disorders is very expensive for parents of child
- there are many regulations in place to stop it getting out of hand
Arguments AGAINST embryonic screening
Encourages people to pick characteristics
Expensive to carry out
Promote prejudice as it suggests people with genetic disorders are unwanted
Decisions abut terminating a pregnancy have to be made
The procedure can lead to miscarriage
What do the 23rd pair of chromosomes carry
Sex determining genes
What chromosome pair do women have
XX
Can only pass on X chromosomes in their egg
What chromosome pair do men have
XY
Can pass on X or Y chromosomes in their sperm
What 2 things affect the phenotype of a plant
- Genotypes
- Environment
Describe the process of natural selection
- Mutations occur which provides variation between organisms
- If the mutation provides a survival advantage, the organism is more likely to survive to breeding age
The mutation will then be passed onto offspring
Over many generations, the frequency of the mutation will increase within the population
how can selective breeding lead to problems
Inbreeding
Breeding those with similar characteristics meaning you are reducing the gene pool
So if the environment changes or there is a new disease, the species could become extinct
As there is a lower chance of survival advantage as they all have the same genetic make up
What is genetic engineering
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
Process of genetic engineering
-enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus
- The vector is used to insert the gene into the required cells
- Genes are transferred to the cells of animals, plants or microorganisms at an early stage, so they can develop with those characteristics
2 Methods of plant cloning
- Tissue culture
- Cuttings
How is tissue culture carried out
- Plant cells are taken
- They are placed in a growth medium with nutrients and hormones
- they grow into new plants, and intoclones as they are genetically identical to the parent
How are cuttings carried out
- A section of the meristem is taken from a plant with the desirable feature
- They are planted and produce clones as they are also genetically identical to the parent
How are embryo transplants carried out
- Sperm and egg cells from parents with desirable characteristics are obtained
- In a lab, embryo divides many times and is then inserted back into the mother
- The offspring is born genetically identical
Benefits of cloning
Produces lots of offspring with a specific desirable feature
The study of clones could help research into embryo development
Can help endangered species
Risks of cloning
The gene pool is reduced, less likely population will survive if there is disease
Clones have low survival rate
It may lead to human cloning
Charles Darwin
Scientist and naturalist
Put forward the theory of evolution
Supported by experimentation and his knowledge of geology and fossils
Published ‘On the Origin of Species’
Detailed theory of evolution
- Variation exists within species as a result of mutations in DNA
- Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed (survival of the fittest)
- The beneficial characteristics are passed on to offspring
- Over many generations, the frequency of alleles for this advantageous characteristic increases with the population
What is speciation
A new species developing through the selection of different alleles, increases genetic variation until the new population cannot breed with those in the old population to produce fertile offspring
who developed theory of speciation
Alfred Russel Wallace
Process of speciation
- Variation exists within population as a result of genetic mutations
- Alleles which provide a survival advantage are selected for through natural selection
- Populations of a species become isolated from one another, through a geological barrier
- Different alleles are advantageous in different environments with different selection pressures
- Natural selection occurs in different populations, increasing genetic variation between them
- When they are no longer able to breed together to produce fertile offspring, a new species has been formed
Why is theory of evolution now widely accepted
- Fossils
- Antibiotic resistance
What are fossils made up of
The remains of organisms from millions of years ago, which are found in rocks
Three ways how fossils are formed
Parts of an organism have not been decayed because one of more of the conditions needed for decay are absent
When parts of the organism are replaced by minerals
As preserved traces of organisms (footsteps)
Why can scientists not be certain about how life began on earth
- Many early forms of life were soft bodied, so they left few traces behind, any traces have been destroyed
Explain why sexual reproduction is an advantage for bluebells (4 marks)
genetic variation (in offspring)
(so) better adapted survive
(and) colonise new areas by
seed dispersal
many offspring so higher
probability some will survive
