B1b 6 Variation
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Genetic information is inherited (passed on to you) from your parents.
This genetic information is carried
within the sex cells (sperm I
eggs). The scientific name for sex
cells is gametes.
Every cell of living things contains a nucleus. Within this nucleus there are
thread like structures called chromosomes
Every chromosome contains packets of information that code for particular
characteristics. These packets are called genes.
Humans have 23 pairs of chromosomes in normal body cells. Other organisms
will have different number of chromosomes.
Human sex cells contain 23 chromosomes in total.
A single pair of genes or many genes functioning together can determine
personal characteristics.
Types of reproduction
Sexual reproduction involves two individuals. This type of reproduction leads to
greater variety in the offspring. By producing offspring with variety there is a
greater chance some will survive different versions of the same gene are known as
alleles.
Asexual reproduction requires only one parent and results in identical offspring
(clones). Many plants and small organisms carry out this type of reproduction.
Cloning
Gardeners carry out cloning when they fake a cutting from a plant. The resulting plant
has exactly the same genetic make up as the original parent. The advantages of this
method are that it is cheap, easy and relatively quick to produce new plants. Tissue
culture is concerned with taking a sample of cells from a plant and then encouraging
those cells to .each grow into new plants using special hormones. All the plants grown
will have the same genetic information as the parent plant.
Embryo cloning concerns taking a very early developing embryo and then dividing the
cells into smaller clusters. At this stage of development the cells have not become
specialised and therefore are still able to become any body part. Each cluster will
then develop into a new embryo, which can then be placed back into a host mother.
Fusion cell cloning — the stages:
The nucleus is removed from an adult cell
Nucleus is also removed from an egg cell from an animal of the same species
Nucleus from the original cell is placed inside the egg cell
A small electric shock fuses the egg and nucleus together
The new fused nucleus and egg cell start dividing (cell division) to create a new
embryo
6. Develops as per normal - identical to the original animal from which the adult
cell was removed
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Adult cell cloning - the above method used to produce cloned entire animals.
Advantages
Disadvantages
Possible to save animals that are
threatened or extinct
Reduces variation
Able to produce great numbers of
medically useful cloned animals
Ethical / moral concerns
Genetic Engineering - Genetic engineering is concerned with the altering of the
genetic information within an organism
Advantages
Disadvantages
Possible to manufacture large amounts of
desired proteins (such as insulin)
Unknown long-term effects. What if
the genes escape into the wild, do
they cause any harm when these
modified foodstuffs are eaten Being
a relatively new science there are
many questions that are not yet
answered.
Improves growth rates and quality of
foodstuffs. Able to get plants to grow in
difficult conditions
Future possibilities — will people
want to genetically engineer their
children for particular traits?
May be possible in the future to cure
illnesses by inserting unaffected DNA.
Moral / ethical concerns