What are stem cells?
Stem Cells are undifferentiated, they can develop into different types of cells depending on what instructions they’re given.
(differentiation is the process by which a cell changes to become specialised for its job)
Where are stem cells found?
Stem cells are found in early human embryos, adults also have stem cells but they’re only found in certain places for example bone marrow. However, they can’t turn into any cell type at all, only certain ones.
What are adult stem cells used for?
Adult stem cells can be used to cure disease, for example by bone marrow transplants, Bone Marrow contains stem cells that can turn into new blood cells to replace the faulty ones.
What are embryonic stem cells used for?
Stem cells can be extracted from early human embryos and grown to replace faulty cells.
What do genetic diagrams show?
The possible combination of gametes
What did Mendel discover during his genetic experiment with pea plants?
Mendel discovered that characteristics in plants are determined by ‘hereditary units’.
which are passed on from both parents, one hereditary unit is passed on from each parent.
Hereditary Units can be dominant or recessive- if an individual has both units for a characteristic, the dominant characteristic will be expressed.
What are alleles?
alleles are different versions of the same gene for example an eye gene could have a green eye colour allele and a blue eye colour allele.
What does it mean if an organism is homozygous?
if an organism is homozygous it has two alleles that are same for a particular gene.
What does it mean if an organism is heterozygous?
If an organism is heterozygous it has two alleles that are different for a particular gene.
What is a genotype?
the alleles that an individual contains
What is a phenotype?
the actual characteristics of an individual
What is cystic Fibrosis?
cystic fibrosis is a genetic disorder of the cell membrane. It results in the body producing a lot of mucus in the air passages and the pancreas.
The allele which causes cystic fibrosis is a recessive allele, because its recessive, people with only one copy of the allele won’t have the disorder- they’re known as carriers.
For a child to have the disorder both parents must be either carriers or sufferers.
What is polydactyl?
polydactyl is a genetic disorder where a baby’s born with extra fingers or toes. The disorder is caused by a dominant allele and so can be inherited if just one parent carries the defective allele- they’re also a sufferer.
What is DNA?
substance containing all the instructions to put an organism together and make it work. Found in the nucleus of cells in chromosomes.
What are chromosomes?
Chromosomes are really long molecules of DNA
What is a gene?
a gene is a section of DNA, it contains the instructions to make a specific protein.
What chromosomes do men and women have?
all men have a x and y chromosome
all women have two x chromosomes
What is embryo screening?
before an egg is implanted during ivf, it is possible to remove a cell from each embryo and analyse its genes. This is called embryo screening. Many genetic disorders can be detected this way such as cystic fibrosis. Embryos with ‘good’ alleles would be implanted into the mother and bad alleles destroyed.
What are the arguments AGAINST embryo screening?
- There may come a point where everyone wants to screen their embryos so they can pick the most desirable ones.
- Rejected embryos destroyed- could have developed into humans.
- it implies that people with genetic problems are ‘undesirable’ this could increase prejudice.
- screening is expensive.
What are the arguments FOR embryo screening?
- It will help to stop people suffering.
- There are laws to stop it going too far (currently, parents are not allowed to choose the sex of their child)
- During IVF most of the embryos are destroyed anyway- screening just allows the selected ones to be healthy.
- Treating disorders cost the gov a lot of money.