Homework

• Exam style questions p.234-5 mark scheme in school library and on intranet

• Learn work so far test next week • Hand in essay from period 5

Gene mutation

Aqa p.230-233

Objectives

• What is a gene mutation?• How do deletion and substitution of

bases result in different amino acid sequences in polypeptides?

• Why do some mutations not result in a changed amino acid sequence?

• What are the causes of gene mutations?

• How is cell division genetically controlled?

Syllabus

• Gene mutations might arise during DNA replication. The deletion and substitution of bases.

• Gene mutations occur spontaneously. The mutation rate is increased by mutagenic agents. Some mutations result in a different amino acid sequence in the encoded polypeptide. Due to the degenerate nature of the genetic code, not all mutations result in a change to the amino acid sequence of the encoded polypeptide.

The ambassadors reception

• Students work in three groups to prepare a short presentation

• Students go off and visit other stations

• Compile a poster about mutations• Groups mark each others posters• Best poster voted for by students =

10 mins of their own music next lesson

Group 1

What are mutations and their causes?

Group 2

Substitution of bases

Group 3

Deletion of bases(include purple hint on

p.231)

Summary

• Complete the work sheet to give the correct word for each letter

• 3x OHT exam questions

Sheet answersA. DNAB. GeneC. mRNA (transcribed)

or a.acid(translated!)D. Amino acidE. WrongF. FunctionG. Non senseH. Missense

I. SilentJ. Amino acidsK. Missense (substitution)L. DeletionM. Missense (substitution)N. Replication carcinogens O. Mutagenic agents

Genetic mutationsA mutation is a change in the amount or structure of DNA. There are two types of mutation:

A gene or point mutation – a change in the base sequence of a gene, which can cause a change in the polypeptide chain. It is caused by errors that occur during DNA replication.

A chromosome mutation – a change in the number or structure of the chromosomes. It is caused by errors that occur during cell division.

Different types of point mutation

Mutagenic agentsThe natural spontaneous mutation rate is typically around one or two mutations per 100,000 genes per generation.

The mutation rate can be increased by mutagenic agents, which include UV radiation and harmful chemicals. These disrupt the structure of DNA or interfere with transcription.

Mutations provide the genetic variation needed for evolution, however they can produce harmful effects.