1. Lesson starter Write down three differences between translation and transcription

2. How can mutations affect phenotype (physical appearance) and genotype
How can mutations affect phenotype (physical appearance) and genotype? Are mutations a good or bad thing?

3. Mutations Learning objectives:
State that mutations cause changes to the sequence of nucleotides in DNA molecules
Explain how the mutations can have beneficial, neutral or harmful effects on the way a protein functions
Mutations
Success criteria:
Give examples of different types of mutation
Describe the effect they have on DNA sequencing
Describe the effects that mutations have on protein structure and function, giving named examples
Summarise how mutations can affect protein structure and function

4. Mutations
A mutation is a change in the structure or quantity of an organism’s genetic material.
A gene mutation is a change in one or more nucleotides in a strand of DNA
A chromosome mutation is a change to the structure, such as deletion, inversion or translocation, or a change to the number of chromosomes in a nucleus
Mutations can vary from a small change in DNA or a gene or be a large change in chromosome structure or number

6. DNA mutations – point mutations
Substitution: one nucleotide is replaced by another with a different base
Inversion: nucleotides change position with each other

7. DNA mutations – frameshift mutations
Deletion: one nucleotide is removed from the chain and the chain joins up again
Insertion: one extra nucleotide is inserted into the chain

8. Types of Mutation
Point mutations: these are only minor mutations that will affect the organism only slightly or not at all
Substitution
Inversion
Frameshift mutations: these lead to major changes as large portions of DNA are misread
Insertion
Deletion
Remember SIDI for mutations! Substitution, Inversion, Deletion, Insertion

9. Frameshift Mutation Inserting or deleting one or more nucleotides
Changes the “reading frame” like changing a sentence
Proteins built incorrectly

10. Frameshift Mutation Original: The fat cat ate the wee rat.
Frame Shift (“a” added):
The fat caa tet hew eer at.

11. Amino Acid Sequence Changed

12. Inversion – bases swapped around
Deletion – no G
Insertion – extra C
Substitution – A for G
Inversion – bases swapped around

13. Framshift mutations result in minor changes to DNA
Mini Plenary
Framshift mutations result in minor changes to DNA
True
False

14. Point mutations only cause minor effects to changes in DNA
Mini Plenary
Point mutations only cause minor effects to changes in DNA
True
False

15. True False Mini Plenary
Insertion mutations add an extra amino acid to the sequence
True
False

16. Mini Plenary
Mutations can affect genes or chromosomes
True
False

17. Examples of Mutations Sickle cell anaemia Cystic Fibrosis
Protooncogenes in cancer

19. Frequency of Mutations & Mutagenic Agents
Without external influences, mutations occur randomly and spontaneously
Mutations of this kind are very rare as most mutant genes are recessive.
A person would have to be homozygous to display the mutant trait in their phenotype
Mutagenic agents can increase the rate at which mutations occur
Mustard gas
Types of radiation e.g. gamma rays, X-rays and UV light

20. Chromosome Mutation Animation

22. Gene Mutations Change in the nucleotide sequence of a gene
May only involve a single nucleotide
May be due to copying errors, chemicals, viruses, etc.

23. Point Mutation
Sickle Cell disease is the result of one nucleotide substitution
Occurs in the hemoglobin gene

24. Gene Mutation Animation

25. Cell division
Cell division is tightly controlled by genes, there are two types involved in this
Tumour suppressor genes – that slow cell division
Proto-0ncogenes - that stimulate cell division
These ensure that cells divide at a fairly constant rate, and those cells that are worn out or dead are replaced

27. Proto oncogenes
These are normally only switched ‘on’ when growth factors are detected by protein receptors on the cell surface membrane. These cause relay proteins in the cytoplasm to switch these genes on.

28. Oncogenes
A mutation can cause proto oncogenes to mutate into oncogenes
This is when these genes are permanently switched on, even in the absence of growth factors that would normally stimulate appropriate cell division
The receptor on the cell surface membrane could be permanently activated
A growth factor is produced in excessive amounts

29. Tumour Suppressor Genes
These inhibit cell division
This maintains normal cell division and prevents tumours from developing
If these genes become inactivated a tumour can develop

30. Describing how mutations happen
Study the diagrams below. Using these diagrams to help you, describe the mutation that has occurred and the consequence it has for the protein formed.
Sickle cell anaemia
Cystic Fibrosis

31. Describing how mutations happen
Sickle cell anaemia: a result of a point mutation on codon 6 of the gene for the beta polypeptide chain of haemoglobin.
CF: a deletion deleting ONE amino acid out of 1480 in a polypeptide chain

32. How can mutations affect phenotype (physical appearance) and genotype
How can mutations affect phenotype (physical appearance) and genotype? Are mutations a good or bad thing?

33. Neutral, beneficial or harmful?

34. Example(s) of mutation Description of how it works
Neutral, beneficial or harmful? Copy and complete the table below, using pages to help you. Aiming for an A: use the information in the stretch and challenge box to help you complete this table.
Mutation type
Example(s) of mutation
Description of how it works
Useful
Harmful
Neutral
(B/C grade) Complete questions 1 and 2 on page 111
(A grade) complete question A from the purple box

35. Plenary Write down a key word from today’s lesson on mutations.
Find someone else with a different key word.
Swap boards and use their key word to construct a sentence about today’s lesson.