Biology ~ B1

Module B1

HideShow resource information
  • Created by: Lucy
  • Created on: 29-12-11 15:17


Each gene is a code for making a certain protein.

Different versions of proteins make us have different characteristics.

2 Types:

Structual protein ~ eg. skin, hair, blood and cytoplasm in cells.

Functional protein ~ other proteins eg. enzymes (amylase)

1 of 11


 Alleles are different versions of the same gene.

Homozygous: 2 alleles the same. eg. BB bb

Hetrozygous: 2 different alleles. eg. Bb


Phenotype: The characteristics an organism displays/has. eg. eye colour, hair colour.

Geneotype: All the genes, alleles an organism has. eg. BB, hh, Ff, **.

2 of 11

Sex Cells

Are the sperm and the egg.

They contain 23 single chromosomes, one chromosome from each pair.

Sex chromosomes:

-All men have an X and a Y chromosome: XY

 The Y chromosome causes male characteristics.


-All women have two X chromosomes: **

 The lack of a Y chromosome causes female characteristics.

3 of 11


Found in the nucleus of cells.

Half a child's chromosomes come from each parent:

This is why most children look a bit like both of their parents.

Not the same because haven't got all the same alleles.

Sex Chromosomes:

23 pairs of chromosomes in every human body cell. The 23rd pair are labelled XY, these are sex chromosomes and decide whether you turn out male or female.

4 of 11

Genetic Diagrams

Parents' phenotypes:                  normal, but carrier         normal, but carrier

Parents' genotypes:                               Ff                                     Ff   


Sex cells' genotypes:                  F                 f                    F                   f


Possible genotypes                FF                   Ff                    Ff                    ff

of offspring:

Phenotypes:                        Normal            Carrier            Carrier           Sufferer

25% chance of a sufferer.

5 of 11

Punnet Squares

Carrier, sufferer parent


H                                   h


Hh                                 hh


Hh                                 hh


50% chance of carrier, sufferer.

6 of 11

Cystic Fibrosis

Caused by a faulty allele of a single gene which is recessive.

Is a genetic disorder of the cell membranes.


- Thick sticky mucus in the air passages, gut and pancreas.

- Breathing difficulty.

- Chest infections.

- Difficulty in digesting food.

7 of 11

Huntington's disorder

Caused by a faulty allele of a single gene which is dominant.


Is a genetic disorder.



- Tremours (shaking).

- Clumsiness.

- Memory loss.

- Mood changes.

- Poor concerntration.

8 of 11

Genetic Testing

IVF (in vertro fertilisation) - test tube baby

Doctors can test the embryos to check if they've got certain genetic disorders (Known as pre-implantation genetic diagnosis). Once tested only healthy embryos are chosen to be implanted into the mothers womb.

Also, Children and adults can be checked to see if they carry alleles for genetic disorders.

Some Issues:

1. Results of genetic tests may not be 100% accurate - there are often errors.         People might make decisions based on incorrect information.

2. If a test carried out during a pregnancy is positive, is it right to terminate the pregnancy?

3. Insurance companies might refuse to give life insurance to people with the 'wrong' alleles.

9 of 11


Clones are genetically identical organisms - they have the same genes, and the same alleles of those genes. Any differences are due to the environment.

Natural ~ Asexual - occurs mostly with; plants and bacteria.

Needs only 1 parent, and the offspring are genetically identical to each other and the parent.

Natural ~ Sexual - Identical twins

A normal embryo splits in half, and two separate embryos that are genetically identical begin to develop. Eventually two genetically identical twin babies are born.

In the lab ~ Animal clones eg. Dolly the sheep.

10 of 11

Stem cells

- cells that are unspecialised. They can develop into different types of cells depending on what instructions they are given.

1. Embryonic stem cells: unspecialised cells found in early embryos. Potentially specialise into ANY kind of cell at all.

2. Adult stem cells: unspecialised cells found in adult animals. Specialise into many cell types (but not all).

Treating illnesses

Embryonic stem cells could be used to replace faulty cells in sick people - you could make beating heart muscle cells for people with heart disease, insulin producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries, ect. These embryonic stem cell treatments are still being researched though, so they might not be available for a while yet.

11 of 11


No comments have yet been made

Similar Biology resources:

See all Biology resources »