Variation Flashcards
Causes of variation
- alleles that individuals have inherited
= genetic causes eg hair colour - environment
= eg language - combination of genes and the environment
= height
Define mutations
Random changes to DNA
Examples of selective breeding
- dogs
= more gentle - food crops
= disease resistant - cows
= more milk - plants
= larger flowers
Stage 1 of selective breeding
- take a mixed population of species and select largest female and male
- breed together
= sexual reproduction produces variation in offspring - offspring will be mix of larger and smaller
- select largest male and female offspring and breed together
- breed until all offspring large
Problem with selective breeding
If we breed closely related animals or plants then we can get inbreeding
= cause some breeds to be prone to disease or inherited defects
Describe genetic engineering
Genes from one organism are cut out and transferred to cells of a different organism eg bacteria
GM crops function
Produce a greater yield than normal
Stages of genetic engineering
- identify the gene we want to transfer
- use enzymes to isolate gene
- transfer gene into vector eg virus or plasmid
- desired gene transferred into target organism
- organism cells take up vector and useful gene it contains
= produce protein that gene codes for
Why do we do genetic engineering at early stages of embryo
Make sure all of the cells receive the transferred gene
= organism develops with characteristic that we want
Adv of cloning plants
Because clone is genetically identical to original plant we know exactly what clone’s characteristics will be
Describe cuttings cloning method
- small piece of plant removed and dipped into rooting powder
= contains plant hormones
= encourages plant to develop roots
= produce genetically identical clone of starting plant
Describe tissue culture cloning method
- take plant we want to clone and divide plant into hundreds of tiny pieces
- each piece contains small number of cells
- small groups of cells incubated with plant hormones
= stimulate plant to grow and develop into fully grown clones - conditions must be sterile
= reduce entry of microorganisms
Why do we need sterile conditions
Don’t want to introduce any microorganisms such as bacteria or fungi
Why is tissue culture used in commercial farming
Allows growers to produce thousands of genetically identical plants quickly and cheaply
= can be certain they will get desired characteristics as they’re clones
Preserve rare species of plants
Describe embryo transplants
- start with sperm of animal with desired characteristics
- fertilisation produces fertilised egg
- allow egg to develop into an early stage embryo
- cells must not start to specialise
- use glass rod to spilt embryo into 2
- transplant embryos into host mothers
= two identical clones
Problem with embryo transplant
As we start with sperm and an egg
= can’t be certain that offspring will have desired characteristic
Benefit of adult cell cloning
Cloning from an adult
= we know characteristics clone will have
Stages of adult cell cloning
- remove a cell from animal we want to clone
- remove nucleus of cell that contains genetic info of animal were cloning
- take unfertilised egg cell from same species
- remove nucleus from unfertilised egg and throw it away
- insert nucleus from original adult body cell into empty egg cell
- give egg cell an electric shock
- makes egg cell divide to form an embryo
- when embryo developed it’s inserted into the womb of an adult female to continue development
Why was Darwin’s theory not accepted
- at time people believed god made all animals and plants
- not enough evidence
- not understand how genetics are inherited
Describe Lamark’s theory
When characteristic regularly used it becomes more developed
= strengthened characteristic passed on to offspring
Why was Lamark wrong
Changes that occur in an organisms lifetime can’t be passed onto offspring
How does speciation work
Need a geographical barrier to separate a population into 2
= prevent interbreeding between populations
Describe gene therapy
Giving person the healthy version of a gene
Problem and solution of gene therapy
Faulty gene would be in all cells
= hard to transfer new gene to every cell
Could transfer the gene at early stage of development eg egg or embryo stage
= as person grows healthy gene passed into all other cells
Pros and cons of GM crops
Pros
- crops with desirable characteristics
= more fruits for LICs
- can make sure plants make special nutrients
Eg golden rice has beta carotene to prevent blindness
- increase growth rates of plants and yield
Cons
- don’t know how they can affect health
- chance plants make way to wild and out compete local plants
= change whole ecosystem
Examples of genetic engineering
- bacteria produce hormone insulin to treat diabetes
- crops resistant to disease, insects etc
- drugs in sheep milk to extract and treat diseases
Pros and cons of cloning
Pros
- produces lots of offspring with specific desirable feature
- study of clone could help research into embryo development
- bring back species that are extinct
Cons
- may lead to human cloning
- clones have low survival rate
- clones have genetic problems
- reduced gene pool
Why does clone of adult cell cloning look nothing like mother
Clone contains none of her genetic material
