Biology 2 (iii) - Genetics

Biology 2 (iii) - Genetics, including DNA, Meiosis, Mitosis etc etc

HideShow resource information
  • Created by: Megan (:
  • Created on: 18-05-11 20:16



Stands for Deoxyribose Nucleic Acid

It contains 'instructions' to put an organism together and make it work

Found in the nucleus of animal and plant cells.

In really long molecules called CHROMOSOMES.




1 of 9



Its a section of DNA.

Contains the 'instructions' to a specific protein

Genes tell cells in what order to put amino acids together (to make the proteins)

DNA also determins what proteins the cell should produce: keratin, haemoglobin etc...

2 of 9



Makes new cells for repair and growth

Mitosis is when a cell reproduces itself by splitting to form two identical offspring

Used in asexual Reproduction

No variation between offspring in asexual reproduction, they're identical


(Next revision card shows the steps of Mitosis (: )

3 of 9

Steps of Mitosis

Steps of Mitosis

When the cell gets the signal to divide, it duplicates its DNA. The DNA is then copied and formed into X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.

The chromosomes then line up at the centre of the cell and cell fibres part them. The two duplicated arms are then at opposite sides of the cell.

Membranes form around each set of chromosomes. They are the nuclei of the two new cells

Finally, the cytoplasm divides.

(I'd recommend YouTube-ing the Mitosis song, you may learn something (: )

4 of 9



Gametes have half the usual amount of chromosomes

Used in sexual reproduction. Gametes have only one copy of each chromosome. A combination of the mother and father create a complete set

In humans, it happens only in the reproductive organs

Meiosis produces cells which have half the normal number of chromosomes


( Next revision card states the steps of Meiosis (: )

5 of 9

Steps of Meiosis

Steps of Meiosis

Before the cell splits, it duplicates it's DNA.

It includes 2 divisions. In the first, the chromosome pairs line up in the centre of the cell. The pairs are then pulled apart so each new cell only has one of each

Each cell will have a mixture of mother and father chromosomes. This creates variation.

In the second, they line up and part again, creating 4 gametes with a single set of chromosomes in it.

6 of 9

Stem Cells

Stem Cells

Found in early human embryos. (Embryonic stem cells)

Can also be found in adult bone marrow, not as versitile as Embryonic stem cells.

Differentiation is the process through which a stem cell changes into a specialised cell.

Have the ability to possibly cure many diseases.

Differetiation can be lost at an early stage in animals but is unlikely in plants

7 of 9

X and Y Chromosomes

X and Y Chromosomes

All men have X and Y chromosomes. Y causes male characteristics. All women have X and X chromosomes, this allows female characteristics.

In sperm production, X and Y are drawn apart (meiosis), meaning 50% have X and 50% have Y.

Y dominates the X. If an Y chromosome sperm fuses with a X chromosome creating XY, the offspring will be male

E.g                        XY = Boy                    ** = Girl


8 of 9

Genetic Diagrams

Genetic Diagrams

Alleles are different versions of the same gene

In genetic diagrams, letters are used to represent the genes. Dominant alleles are shown by a capital letter, and recessive alleles with a lower case letter. For example, Dad's genes are Blue, Mum's pink

                                         X               X              Dad's dominant X comes       

                             X       **             XX             above mum's recessive x.

                             x       Xx              **

9 of 9




cheers Megan that was very helpful 

Similar Biology resources:

See all Biology resources »See all DNA and inheritance resources »