B1 (Biology Unit 1- B1)

Module B1- You and your genes (OCR)

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  • Created by: Kira
  • Created on: 23-12-11 11:15

Inherited or environmental?

Characteristics are a person's features- the things that make you who you are.

Some of your characteristics are decided just by the genes passed down from your parents. These are known as inherited characteristics, such as eye colour, hair colour, blood type, whether you have an attached ear lobe etc.

Environmental characteristics are features given to you from your environment, or upbringing. An example is being able to speak english.

Most of your characteristics are a mix of inherited and environmental. Things like weight and height are affected by your genes (heights/weights of parents) and your upbringing (if you are malnurished or eat too much junk food)

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DNA and Genes

Your genes are found in DNA.

Coils of DNA form the arms of chromosomes, which look a bit like X's

Humans have 23 pairs of chromosomes, 23 from each parent (46 in total).

These chromosomes are in the nucleus of most cells in the body.

Each gene codes for a protein. Proteins are used to build cells and enzymes in the body.

The sex cells (sperm and egg cells) only contain 23 single chromosomes. A persons chromosomes are randomly chosen to make eggs/sperm.

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A clone is the offspring of a parent which is genetically identical. This can usually only happen through asexual reproduction.

Asexual reproduction occurs in bacteria, some plants and some animals.

Any differences between clones can only be environmental.

Identical twins are clones, but only of each other, not of the parents.

Scientists can make clones by replacing the nucleus of an egg cell with the genetic information from a body cell and stimulating the cell.

Artificial cloning has not been very successful as it takes hundreds of attempts for it to work. For more info, research 'Dolly the Sheep'.

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Alleles are different versions of the same gene. A common example is with eye colour.

Some alleles are recessive (Blue eyes) and some alleles are dominant (Brown eyes)

People with blue eyes have to have the genotype bb

People with brown eyes can have the genotype BB or Bb and still have brown eyes, because the brown allele is dominant, or more powerful.

Your phenotype is the eye colour that people see- blue or brown.                 Your genotype is the alleles that make it up- BB, Bb, or bb

If you have different alleles (Bb) you are heterozygous

If you have identical alleles (BB or bb) you are homozygous

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Gene Therapy

Gene therapy could help to treat genetic disorders by inserting a healthy copy of a gene to make up for a faulty one.

A way of doing this is using a virus to insert the healthy copy of the gene into cells, but scientists could only do this if they know which genes control the disease.

It could also be dangerous. It is not certain what will happen.

Religious people have issues to do with playing God.

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Stem Cells

Stem cells are unspecialised cells.

Embryos have all unspecialised cells at first, then most cells become specialised. (They become red blood cells or muscle cells etc.)

Cells becoming specialised is called differentiation.

The cells in the body which do not beome specialised are found in the bone marrow. These could be used to cure diseases, by growing them into the cells needed to replace the faulty cells.

Because embryos have lots of unspecialised cells, there has been research into embryonic stem cells being used to cure diseases also.

However, there are many concerns about using embryos, as lots of people see them as life, and using them is wrong, even if most are left over from IVF, so would be disposed of anyway.

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Heidi Miraid Mills

These are really good, thank you :) 

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