B1.7 Genetic Variation and its Control Flashcards
What is genetic variation?
The inheritance of characteristics from parents - these are determined by genes
What are genes?
Codes inside your cells that control how you’re made
How are genes passed onto offspring?
Sex cells containing genes from the mother and father combine to develop offspring
Why are no two species genetically identical?
Due to the genes which determine an offspring’s characteristics coming from two different individuals
What are examples of characteristics inherited only by genes - in both plants and animals? (4)
A flower being violet in colour (plants), eye colour, blood group and inherited disorders (animals)
What is environmental variation?
The environment an organism lives and grows in, can cause differences between members of the same species
What are examples of environmental variation?
Your toes being eaten off, getting a suntan, having yellow leaves - anything which is caused by the conditions of the environment
Is height determined by environmental variation or genetic variation?
Both - an animals or plants max height is determined by genes, but weather it actually reaches that height is determined by the environmental factors e.g. how much food it gets.
Is intelligence determined by environmental variation or genetic variation?
Both - there are theories that show your maximum possible IQ is determined by genes, but whether you reach this level of IQ is determined by environmental factors e.g. your upbringing and school life
Is health determined by environmental variation or genetic variation?
Both - some people are more likely to get certain diseases due to their genes, but environmental factors like whether you smoke or much junk food you eat can also affect health
What do the nuclei in cells contain?
Genetic material - the instructions you need to grow and develop
How is genetic material stored in nuclei?
In chromosomes
How are chromosomes found?
In pairs
How many chromosomes does a human cell contain?
23 pairs - 46 in total
What are chromosomes long lengths of?
Chromosomes are long lengths of a molecule called DNA
Where is DNA found in chromosomes?
It is coiled up to form the arms of the chromosomes
What does chromosomes carry?
Genes - which are short sections of DNA
What are different versions of the same genes called?
Alleles
What is sexual reproduction?
The combination of genetic information from two organisms (a father and a mother) to produce offspring which are genetically different to either parent
What are gametes? What do they contain?
Sex cells e.g. egg and sperm cells in animals - each gamete contains 23 chromosomes which is half the number of chromosomes in a normal cell
What is fertilisation?
The fusion of gametes to form a cell with the full number of chromosomes (half from the father and half from the mother)
Why do offspring inherit features from both parents?
Because they receive a mixture of chromosomes from both parents
Can you sum up sexual reproduction?
Sexual reproduction involves the fusion of male and female gametes. Because there are two parents, the offspring contain a mixture of their parents’ genes and are genetically different to their parents
What is asexual reproduction?
When an ordinary cell divides in two - the new cells have exactly the same genetic information as the parent celll
How does asexual reproduction work?
- X-shaped chromo’ have 2 identical halves
- Each chromo’ is split down the middle to form two identical sets of ‘1/2 chromosomes’ - a membrane forms around each set
- The DNA then replicates itself to form two identical cells with completes sets of X-shaped chromosomes
How do plants and animals grow and produce replacement cells?
With asexual reproduction
How do bacteria and certain plants produce offspring?
With asexual reproduction
Can you sum up asexual reproduction?
There’s only one parent. There’s no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offspring are genetically identical to the parent - they’re clones
What is cloning?
The making of an exact (genetically identical) copy of an organism
What are the two ways of cloning a plant?
Cuttings and tissue culture
Describe the process of ‘cuttings’ when cloning a plant
Cuttings from a good parent plant, are used to produces genetically identical copies of the parent plant
What benefits are there to using ‘cuttings’ to clone plants? (2)
The plants can be produced quickly and cheaply
Describe the process of ‘tissue culture’ when cloning a plant
Plant cells are put in a growth medium with hormones, and they grow into new plants (or clones of the parent plant)
What benefits are there to using ‘tissue culture’ to clone plants? (3)
They grow very quickly, they require very little space and they can be grown all year
What are the two ways of cloning an animal?
Embryo transplants, and adult cell cloning
Describe the process of ‘embryo transplants’ when cloning an animal
An embryo is created, then split many times in the early stages to form clones - the cloned embryos can then be inserted into a host mother to continue developing
Describe the process of ‘adult cell cloning’ when cloning an animal
An unfertilised egg has its genetic material removed (its nucleus), and then a complete set of chromosomes from an adult body cell is inserted into the ‘empty’ egg cell - an electric shock is then used to make the egg divide like a normal embryo
What happens after the embryo has received an electric shock in ‘adult cell cloning’?
Once it has become a ball of cells, it’s implanted into the uterus of a surrogate mother, where it grows into a genetically identical copy of the original adult body cell
What benefits are there to cloning? (3)
It allows you to achieve an ideal offspring with known characteristics e.g. a cow which produces a lot of milk can be cloned for a farmer, the study of cloning gives us a greater understanding of the development of the embryo, and cloning could be used to preserve endangered species
What are the concerns with cloning?
Gives a ‘reduced gene pool’, so a new disease could potentially wipe out a population as they may all have no allele resistant to the disease, cloned animals aren’t as healthy as the originals and people are worried that humans might be cloned in the future
What is genetic engineering?
The idea to copy a useful gene from one organism’s chromosome into the cells of another
How does genetic engineering work? (2 steps)
- A useful gene is ‘cut’ from one organism’s chromosome using enzymes
- Enzymes are then used to cut another organism’s chromosome and then to insert the useful gene
What is an example of when genetic engineering is used?
The human insulin gene can be inserted into bacteria to produce human insulin, which can then be given to be people with diabetes
What are GM crops?
Genetically modified crops which have had their genes modified
Why are crops genetically modified? (3)
To make them resistant to viruses, insects and herbicides
What is gene therapy?
The treatment of disorders by inserting working genes into sufferers
What is an example of genetic engineering used in animals?
Sheep have been genetically engineered to produce drugs in their milk that can be used to treat human diseases
What are the benefits of GM crops? (2)
They can increase the yield of a crop, and they can be engineered to contain nutrients which there is a lack of in developing countries e.g. ‘golden rice’
What are the concerns with GM crops? (3)
They affect biodiversity around farmland as they affect the number of weeds and plants in the area (and so the population of insects), not everyone is convinced that growing GM crops are safe, and it is thought that transplanted genes may get out into the natural environment e.g. herbicide resistant weeds, making ‘superweeds’
