Protein synthesis, cell division and mutations

What is the function of DNA?

It codes for the production of proteins

Where in a eukaryotic cell is DNA stored?

In the nucleus; as chromosomes

Where in a cell are proteins synthesised?

in the ribosomes

What is the relationship between the number of DNA bases and the number of amino acids?

3 DNA bases in a row code for 1 amino acid

Protein synthesis step 1

A template molecule is made from the DNA of a gene on a chromosome

Protein synthesis step 2

The template molecules leaves the nucleus and travels to a ribosome

Protein synthesis step 3

In the cytoplasm, there are carrier molecules that are each attached to a specific amino acid

Protein synthesis step 4

At the ribosome, a specific carrier molecules carrying a specific amino acid binds to 3 complementary bases on the template molecules (C pairs with G, A pairs with U)

Protein synthesis step 5

The process is repeated along the whole length of the template molecule, determined by the base sequence

Protein synthesis step 6

The amino acids are joined together, and the polypeptide chain folds up to form a protein

Protein synthesis step 7

The carrier molecules leaves the ribosomes and template molecule, and pick up more amino acids in the cytoplasm

Where does the energy required for photosynthesis come from?

Aerobic respiration in the mitochondria

Anaerobic respiration in the cytoplasm

What is a mutation?

A rare, random change in the genetic code of an organism

What are the 2 types of mutation?

1. A change in a gene

2. A change in a chromosome

When do mutations occur?

During cell division or DNA replication

flow chart of effect of a mutation

mutation -> change in a DNA base sequence -> change in the base sequence of the template molecule -> change in the amino acid sequence of the protein -> change in the shape/structure of the protein -> change in the function of the protein -> change in a characteristic/the phenotype of an organism

Substitution mutation

A single base is replaced -> could result in a different amino acid being synthesised and therefore possibly a different protein

Insertion mutation

bases are added to a gene -> changes the amino acid sequence -> a different amino acid being synthesised, and therefore possibly a different protein

Deletion mutation

DNA bases removed -> changes AA sequence -> a different amino acid being synthesised, and therefore possibly a different protein

Examples of neutral mutation

Heterochromia, polydactyly (in cats)

Examples of a harmful mutation

Sickle cell anaemia, albinism in reindeer (visible to predators), down syndrome

Examples of beneficial mutations

Melanism in peppered moths (less visible to predators)

When are mutations inherited?

Only mutations in sex cells (gametes) or cells that divide to form sex cells will be passed on to the next generation

What affects might a mutation have on an enzyme?

1. no effect

2. lose activity (protein changes shape -> change in active site)

3. Change the activity -> catalyse a different reaction

4. Improve the activity

What is non-coding DNA?

Controls whether certain genes are on or off

What is the function of non-coding DNA?

If a gene is on, the protein is made

If a gene is off, the protein is not made

What could happen if there's a mutation in non-coding DNA?

Too many proteins made or too few proteins made