inheritance ,variation snd evolution Flashcards
what is variation?
Differences in the characteristics of individuals in a population is called variation
what are the two causes of variation within species?
Genetics
Environment
A mixture of both of the above
what is genetic variation?
Variations in the genotypes of organisms of the same species due to the presence of different alleles
Create differences in phenotypes
What creates genetic variation in a species?
spontaneous mutations
sexual reproduction
what is a mutation?
A random change the base sequence in DNA which results in genetic variance
they occur continuously
State the three types of gene mutation
Insertion
deletion
substitution
how may a gene mutation affect an organism phenotype?
Neutral mutation does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype.
Mutations may cause a minor change in an organism phenotype, e.g. change in eye colour
Mutations may completely change the sequence of amino acid. This may result in a non-functional protein. Severe changes to phenotype.
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
What is evolution?
A gradual change in the inherited traits within a population overtime
Occur occurs due to natural selection which may result in the formation of new species
outline the theory of natural selection
- Genetic variation is this due to spontaneous mutations.
- Selection pressures e.g. competition disease exist
- Random mutation gives an organism as selective advantage.
- Organism is better adapted to the environment and survives.
- Organisms reproduce, passing on its beneficial alleles
- Frequency advantageous alleles increase.
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
What is selective breeding?
The process by which humans artificially select organisms with a desirable characteristics and breed them to produce offspring with similar phenotypes
outline the main steps involved in selective breeding
- Identify a desired characteristics.
- Select parent organisms that show the desire traits and breed them together.
- Select offspring with the desire trait and breed them together.
- Process repeated until all offspring have the desired traits.
give examples of characteristics selected for selective breeding
disease resistance in crops
Higher milk or meat production in animals
Gentle nature im domestic dogs
Large flowers
What is the main advantage of selective breeding?
crops produce a higher yield of grain
Cows produce a greater supply of milk
Plants produce larger fruit
Domesticated animals
other than in agriculture where else is selective breeding useful
In medical research
In sports, e.g. horse racing
outline the disadvantages of selective breeding
reduction in the gene pool
Inbreeding results in genetic disorders
Development of other physical problems, e.g. Respiratory problems in Bulldogs.
Potential to unknowningly select harmful recessive alleles
What is genetic engineering?
The modification of the genome of an organism by the insertion of a desired gene from another organism – genes from chromosomes of humans and other organisms can be cut out and transfer to cells of other organisms
Enable the formation of an organism with beneficial characteristics
Give an example of uses for genetically modified plants
disease resistance
Produce larger fruit
What is used for genetically modified bacteria cells?
To produce human insulin to treat diabetes mellitus
describe the benefits of genetic engineering
Increase crop yeilds for growing population
Useful in medicine
GM crops produce scarce resources
Describe the risk of genetic engineering
long-term effects on consumption of GM crops unknown
Negative environmental impacts e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming super weeds
late onset health problems in GM animals
GMC’s are expensive. LEDCs may be unable to find them or may become dependent on businesses that sell them.
what is the name for crops that have had their genes modified?
genetically modified crops, e.g. those modified to be resistant to insect attack and herbicides
what is Bacillus thuringiensis
insect larvae are harmful to crops
BT is a bacterium which secrets attacking that kills insect larvae
how is genetic engineering used to protect crops against insects?
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 lavae that feed on it
What are the benefits of BT crops?
increase crop yields
Lessons the need for artificial insecticides
BT Thompson is specific to a certain insect larvae so it is not harmful to the other organisms that ingested
What are the risk of BT crops?
long-term effects of consumption of BT crops unknown
Insect larvae may become resistant to the BT toxin
Killing insect larvae reduces by a diversity
describe the process of genetic engineering
- DNA is cut at a specific base sequences by restriction enzymes to create sticky ends.
- vector DNA cut using the same restriction enzymes to create complementary sticky ends 
3.ligase enzymes join the sticky ends of the DNA and DNA forming recombinant DNA - Recombinant DNA mixed with and” taken up“ by target cells
what is a vector?
A structure that delivers the desired gene into the recipient cell, e.g. plasmids, viruses
how can plants be cloned?
Taking plant cutting
Tissue culture
what is tissue culture?
Using small groups of cells from a part of a plant to grow identical new plants
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 growth medium.
4. Transfer to compost for further growth.
what must be insured when preparing tissue cultures?
Ensure aseptic conditions to prevent contamination by microorganisms
what does the growth medium contain?
Nutrients and growth hormones
What are the advantages of growing plant by tissue culture?
fast and simple process
Requires little space
Enables the growth of many plant clients with the same desirable characteristics
Useful in the preservation of endangered plant species
what are the disadvantages of growing plants by tissue culture?
Reduction in the gene pool
Plant clones often have low survival rate
could unknowingly increase the presence of harmful recessive alleles
describe the plant cutting methods of plant cloning
Older but simpler method than tissue culture
Gardeners use this method to produce many identical new plants from a parent plant
detail the process of the plant cutting method of plant cloning
- A branch is cut off from the parent plant.
- The lower leaves of the branch are removed and the stem is planted.
- Plant hormones are used to encourage new root development.
- A plastic bag is used to cover the new plant to keep it warm
- New route and a new plant is formed after a few weeks.
What does embryo transplanting involve?
pre-specialised cells from a developing animal embryo a split apart
The resulting separate but identical embryos are transplanted into host mothers
Describe how adult cell cloning is performed
- The nucleus is removed from an unfertilised egg cell.
- The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
- An electric shock stimulates the nucleated egg cell to divide and it forms an embryo.
- The embryo cell contains the same genetic information as the adult body cell.
- When the embryo is a ball of cells, it is inserted into the uterus of an adult female to continue developing.
Outline the theory of evolution by natural selection
individual of species show a wide range of variation for a characteristic
Those were the characteristic most suited to the environment will survive breed most successively
The desirable characteristic that has enabled the individual to survive a passed on to their offspring
Why was Darwin’s theory of evolution not accepted initially?
most people believed in creationism
Insufficient evidence to prove the theory
The mechanism of variation and inheritance was not known at the time
What was Lamark’s theory of inheritance?
That changes during the lifetime of an organism can be inherited
what is speciation?
The formation of a new species when two populations become so vary that they cannot interbreed to produce fertile offspring
What is the definition of species?
A group of organisms with similar characteristics which are able to inbreed to produce fertile offspring
Outline the process of speciation through geographic isolation
two populations of the same species are separated geographically
Geographic isolation prevent into breeding and mixing of genes between the populations
Due to different selection pressures, different mutations occur producing different phenotype is in each population
Overtime the two populations may evolve so that they are not able to interbreed
Why is genetic variation important in speciation?
genetic variation produces phenotypic variations some of which are better suited to the environment and are selected for
How did Mendel study inheritance?
breeding experiments on plants and analysing the ratio of characteristics in offspring
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
State two kinds of evidence used to show evolution
fossils
Antibiotic resistance in bacteria
How are fossils formed?
parts of an organism that have not decayed due to conditions needed for decay being absent
Parts of an organism that has been replaced by minerals as a decade, e.g. bones
Traces of organisms are preserved, covered in sediment and becoming rock
why are there few chases of early life forms left behind?
There are most softbodied
how do fossils act as evidence for evolution?
Scientists can identify the ages of the fossils and use them to show how organism change overtime
What do branches in evolutionary trees indicate?
Where speciation has occurred
what is extinction?
Where there are no individuals of species still alive
State the factor is that may lead to extinction
New disease
Predation
Competition
Changes to the environment
Catastrophic events
What enables bacteria to evolve quickly?
The fast rate of their reproduction
Outline the process of antibiotic resistant bacteria evolving
mutations occur in bacteria producing genetic variation
Certain strains are resistant to antibiotics and are not killed when they antibiotic is applied
Resistance strain survive and reproduce
Overtime the population of the resistant strains increase
why are resistant strains of bacteria dangerous?
People have no immunity to them, and there is no effective treatment
State an example of resistant strain of bacteria
MRSA
What can be done to reduce the rate of development of antibiotic resistant bacteria?
refrained from inappropriately prescribing antibiotics, e.g. viral diseases
Patient should complete the prescribed course of antibiotics
Restrict agriculture uses of antibiotics
why is it difficult to keep up with the emerging resistant strains?
Developing antibiotics have a high cost and take a long time to develop
What are the classes of organisms as determined by Carl Linnaeus?
Kingdom,phylum, class, order, family, genus,species
Which features are living creatures traditionally classified by?
By their structure and characteristics
what is the binomial system of naming organisms?
genus name followed by species name
Why were new classification models proposed?
development in microscopy allowed better examination of internal structure
Improvement in understanding of biochemical processes
State the three domains
archaea
eukarya
bacteria
which organisms belong in a domain archaea
Bacteria, usually living in extreme environments
Which organisms belong in the domain bacteria?
Bacteria
which kingdoms belong in domain eukartya
Plant
Animals
Fungi
Protests
how are evolutionary trees created?
By examining the DNA of different species and analysing how similar the sequences are
what is sexual reproduction
type of reproduction
Involves the production of gametes by meiosis
a gamete from each parent fusses to form a zygote
Genetic information from each guy is mixed so the resulting zygote is unique
what are gametes
sex cells
haploid
what is meiosis?
Form of cell division involved in the formation of gametes in reproductive organs
Chromosomes number is half
Involves two divisions
What must occur prior to meiosis?
interphase-cookies of genetic information made during this process
What happens during the first stage of meiosis?
chromosome pairs lineup along the cell equator
The pair of chromosome is separated and moved to opposite poles of the cell
Chromosome number is halved
what happens during the second stage of meiosis?
Chromosomes lineup along the cell equator
The chromatids are separated and move to the opposite poles of cell
For unique haploid gametes are produced
Why is meiosis important for sexual reproduction?
it increases genetic variation
It ensures that the zygote formed at fertilisation is diploid
describe fertilisation and its resulting outcome
Gametes joined together to restore the normal number of chromosomes and the new cell, then divides by mitosis
As the embryo develop cells differentiate
What is the advantage of sexual reproduction?
it creates genetic variation in offspring, increasing the probability of species adapting to surviving environmental changes
Natural selection can be speeded up by humans in selective breeding to increase food production
Describe the disadvantages of sexual reproduction
two parents are required. This makes reproduction difficult in endangered populations are in species which exhibit solitary lifestyles.
More time and allergies required to a few offspring are produced
what is asexual reproduction?
Type of reproduction
Involves mitosis only
Produce genetically identical offspring known as daughter cells
Describe the advantages of asexual reproduction
Only one parent is required
lots of offspring can be produced in a short period of time, enabling the rapport, colonisation of an area and reducing competition from other species
Requires less energy and time as do not need to meet
What is the disadvantage of asexual reproduction?
No genetic variation reducing the probability of a species being able to adapt to environment change
Describe the circumstances in which malaria parasites reproduce sexually and asexually
sexual reproduction in the mosquito
Asexual reproduction in the human host
describe the circumstances in which fungi reproduce sexually and asexually
Asexual reproduction by spores
Sexual reproduction to give variation
describe the circumstances in which plants reproduce sexually and asexually
Sexual reproduction to produce seeds
Asexual reproduction by runners or bulb division
What is DNA?
A double stranded polymer of nucleotides, wound to a form a double helix
The genetic material of the cell found its nucleus
describe genome
The entire genetic material of an organism
Why is it understanding the human genome important?
The whole human genome has been studied and is important for the development of medicine in the future
-Searching for genes linked to different types of disease
-understanding and treating and inherited disorders
-Chasing human migration patterns from the past
what is a chromosome?
A long coiled molecule of DNA that carries genetic information in the form of genes the hair
 how many chromosomes do human body cells have?
46
how many chromosomes do human gametes have?
23
define gene
A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
what are the monomers of DNA?
Nucleotides
what are DNA nucleotides made up of?
Common sugar
Phosphate group
One of four bases: A, T,C or G
State the full names of the far base is found in nucleotides
Adenine
Thymine
Cytosine
Guanine
Describe how nucleotides interact to form a molecule of DNA
sugar and phosphate molecules drawing to form a sugar phosphate backbone in each DNA strand
Base connected to each other
complementary base pairs joined by weak hydrogen bonds
Explain how a gene codes for a protein
A sequence of three bases in a gene forms a triplet
each triplet codes for amino acid
The order of amino acids determines the structure and function of protein formed
why is the ‘folding’ of amino acids important in proteins such as enzymes
The folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate
What is protein synthesis?
The formation of a protein from a gene
What are the two stages of protein synthesis?
transcription
Translation
what does transcription involve?
The formation of mRNA from a DNA template
Outline transcription
- DNA double helix unwinds
- RNA polymerase binds to specific base sequence of non-coding DNA in front of a June and moves along the DNA strand.
- RNA a polymerase joins three RNA nucleotides to complementary bases on the coding DNA strand
4.mRNA formation complete.mRNA detach and leaves the nucleus
what does translation involve?
A ribosome joints amino acids in specific order dictated by mRNA to form a protein
Outline translation
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
3.A polypeptide chain is formed from the sequence of amino acid which joined together
What is a mutation?
A random change in the base sequence of DNA which results mostly in no change to the protein coated for, or genetic variance of the protein
Mutations occur continuously
describe the effect of a gene mutation in coding DNA
if a mutation changes the amino acid sequence, protein structure and function may change
If a mutation does not change amino acid sequence, there is no effect on protein structure or function
what is non-coding DNA?
DNA which does not code for a protein but instead controls gene expression
describe the effect of a gene mutation in non-coding DNA
Gene expression may be alter, affecting protein production and the resulting phenotype
what are alleles
Different versions of the same gene
What is a dominant allele
A version of a gene were only one copies needed for it to be expressed
what is a recessive allele?
A version of a jim where two copies are needed for it to be expressed
What is meant when an organism is homozygous?
when an organism has two copies of the same allele
what is meant when an organism is heterozygous?
When an organism has two different version of the same gene
what is a genotype?
The genes present for a trait
what is the phenotype?
The visible characteristic
how are dominant alleles presented in a punnet square?
They are represented using uppercase letters
how are recessive alleles represented in a punnet square?
They use the lowercase version of the same letter as the dominant allele
what is the problem with single gene crosses?
Most characteristics are controlled by multiple alleles rather than just one
what is an inherited disorder?
A disorder caused by the inheritance of certain alleles
give two 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
how are embryo screened for inherited disorders?
during IVF, one cell removed and tested for disorder causing alleles. If the cell doesn’t have any indicator of alleles, then the originating embryo is implanted into the uterus.
what are the ethical issues concerning embryo screening?
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 within inherited disorder is seen by some as murder as these will go onto to become human beings
It could be viewed as part of the concept of designer babies as it may be the parents convenience or wishes rather than the child well-being
what are the economic issues concerning embryo screening?
Cost of possible treatment and medication will need to be considered if it is known that a child will have an inherited disorder and financial support explored if necessary
What are the social issues concerning embryo screaming?
social care for children with inherited disorders may need to be considered if parents are unable to provide care
If an employee is found to have an inherited disorder and is terminated, this can prevent a child and its parents from potentially suffering in the future due to this disorder
what is gene therapy?
The insertion of a normal allele into the cell of a person with inherited disorder to functionally replace the faulty allele
What are the ethical issues concerning gene therapy?
some people believe that is going against and playing God
The introduced genes could enter sex cells and so be past the future generations
what are sex chromosomes
a pair of chromosome that determine sex
males have X Y
females have two X
Why does the inheritance of a Y chromosome means that an embryo develops into a male?
Testee development in an embryo is stimulated by gene present on the Y chromosome
what is a sex linked characteristics
A characteristic that is coded for by an allele found on a sex chromosome 
why are the majority of genes found on the X chromosome rather than the Y chromosome?
The X chromosome is bigger than the Y chromosome so more genes are carried on it
Why are men more likely to show the phenotype for recessive sex linked trait than women
many genes are found on the X chromosome that have no counterpart on the Y chromosome
Woman XX have two alleles for each sex gene whereas men have XY often only have one alley
Only one recessive allele is required to produce a recessive phenotype in males
