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Genetic Mutations. Standards: CLE 3210.4.6Describe the connection between mutations and human genetic disorders. Objectives: Investigate the affect of.

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Presentation on theme: "Genetic Mutations. Standards: CLE 3210.4.6Describe the connection between mutations and human genetic disorders. Objectives: Investigate the affect of."— Presentation transcript:

1 Genetic Mutations

2 Standards: CLE Describe the connection between mutations and human genetic disorders. Objectives: Investigate the affect of mutations on protein production Differentiate between point mutations and chromosomal mutations.

3 What is a gene mutation? Mutations are changes in genetic material – changes in DNA code – which means changes in a gene(s) In gene mutations, the DNA code will have one or more bases missing, added, or exchanged in a codon.

4 How common are mutations? Mutations occurs at a frequency of about 1 in every 1 billion base pairs Everybody has about 6 mutations in each cell in their body!

5 Does that mean I have a chance to become a super hero/villian?

6 If I have that many mutations, why don’t I look weird? Mutations are not always seen. The affected gene may still function. Mutations may be harmful. Mutations may be beneficial. Mutations may have no effect on the organism.

7 How do mutations affect a population? Mutations are a major source of genetic variation in a population increasing biodiversity. Some variations may help them to survive better.

8 Beneficial or Harmful?

9 How are mutations inherited? Only mutations that occur in gametes are passed onto offspring. Mutations in body cells (somatic cells) only affect the organism in which they occur and are not passed on.

10 Types of Gene Mutations Point mutation occurs when the base sequence of a codon is changed. (ex. GCA is changed to GAA) Chromosome mutations - Changes in the number or structure of chromosomes

11 Types of Point Mutations Point mutation occurs when the base sequence of a codon is changed. (ex. GCA is changed to GAA) There are 3 types: Also called frameshift mutations Substitution Deletion Insertion

12 What will happen to the amino acids? Substitution Mutations Normal DNA: CGA – TGC – ATC Mutated DNA: CGA – TGC – TTC Alanine – Threonine - stop Alanine – Threonine - Lysine This is a substitution mutation The adenine was replaced with thymine What has happened to the DNA?

13 Substitution Mutations This is a substitution mutation. A single nitrogen base is substituted for another in a codon. It may or may not affect the amino acid or protein. Mutated DNA: CGA – TGC – TTC Alanine – Threonine - Lysine Normal DNA: CGA – TGC – ATC Alanine – Threonine - stop

14 TRY THIS! On your note paper write: The cat ate the rat Change one letter in the sentence to represent a substitution mutation.

15 Think – Pair - Share Why are we using 3 letter words? Share with your partner the substitution change that you made Can you still “read” your sentence fairly easily? How damaging is a substitution mutation?

16 Analogy The cat ate the rat. SUBSTITUTION #1 Thc cat ate the rat. May have little effect. You can still get the overall idea. Like a typo on a test. SUBSTITUTION #2 The hat ate the rat. Changes the thought of the sentence. The effect of the mutation depends on where the substitution happens

17 This is an insertion mutation, also a type of frameshift mutation. Insertion Mutations Normal DNA: CGA – TGC – ATC Mutated DNA: CGA – TAG – CAT – C Alanine – Threonine – stop Alanine – Isoleucine – Valine What will happen to the amino acids? An adenine was inserted thereby pushing all the other bases over a frame. What has happened to the DNA?

18 Insertion Mutations This is an insertion mutation. A nitrogen base is inserted/added to the sequence. It causes the triplet “frames” to shift. It always affects the amino acids and, consequently, the protein. Mutated DNA: CGA – TAG – CAT – C Alanine – Leucine - Valine Normal DNA: CGA – TGC – ATC Alanine – Threonine - stop

19 Think – pair - share Predict the effect an insertion mutation cause to our sentence: THE CAT ATE THE RAT

20 TRY THIS! On your notebook paper write: The cat ate the rat. Insert a letter into any word above. Rewrite the sentence. Each word must have only 3 letters to represent the codon. What were the effects of the insertion?

21 Analogy The cat ate the rat. Insertion The cca tat eth era t. Inserting the c causes a FRAMESHIFT THE SENTENCE NO LONGER MAKES SENSE!!

22 Think – pair - share Where in the gene sequence would an insertion mutation cause the most damage to the DNA code? At the beginning of the gene sequence

23 Let’s examine the effect of location THE CAT ATE THE RAT INSERTION #1 – THE CAT ATE THA ERA T – Would any of the codons code correctly? INSERTION #2 – TAH ECA TAT ETH ERA T – Would any of these codons code correctly?

24 What will happen to the amino acids? Mutated DNA: CGA – TCA- TC A guanine was deleted, thereby pushing all the bases down a frame. Alanine – Threonine – stop Alanine – Serine Deletion Mutations Normal DNA: CGA – TGC – ATC This is called a deletion mutation, also a type of frameshift mutation. What has happened to the DNA?

25 Deletion Mutations This is a deletion mutation. A nitrogen base is deleted/removed from the sequence. It causes the triplet “frames” to shift. It always affects the amino acids and, consequently, the protein. Mutated DNA: CGA – TCA- TC Alanine – Threonine – stop Alanine – Serine Normal DNA: CGA – TGC – ATC

26 TRY THIS! Write the sentence on your paper: The cat ate the rat. Delete one letter from any word. Rewrite the sentence. Remember: each word can only have 3 letters.

27 Analogy DELETION The cat ate the rat. Thc ata tet her at FRAMESHIFT The sentence no longer makes sense!! Deletions can have huge effects.

28 Standards: CLE Describe the connection between mutations and human genetic disorders. Objectives: Investigate the affect of mutations on protein production Differentiate between point mutations and chromosomal mutations.

29 Think – pair - share Which type of mutation would have the least damaging affect on an organism? Substitution has the least affect because it changes only one amino acid or it may change no amino acid. Mutated DNA: CGA – TGC – ATT Alanine – Threonine - stop Normal DNA: CGA – TGC – ATC Alanine – Threonine - stop Mutated DNA: CGA – TGC – ATG Alanine – Threonine - Tyrosine

30 An example of a substitution mutation is sickle cell anemia Only one amino acid changes in the hemoglobin. The hemoglobin still functions but it folds differently changing the shape of the rbc.

31 Think – pair - share Which type(s) of mutation would have the most affect on an organism? Insertion and deletion mutations have the most effect on an organism because they affect many amino acids and consequently the whole protein. Mutated DNA: CGA – TCA- TC Alanine – Threonine – stop Alanine – Serine Normal DNA: CGA – TGC – ATC Mutated DNA: CGA – TAG – CAT – C Alanine – Leucine - Valine

32 An example of a frameshift mutation disorder is Tay Sachs disease. Children born with this disorder cannot make an enzyme that is critical in breaking down fat and toxic substances in the brain. The disease is terminal. Most will die before age 4.

33 Think – pair - share In which cells would a gene mutation have the greatest affect on an organism? When it is inherited from the gametes or develops early in embryonic development (in stem cells or first few days). Four cell Zygote Embryo Egg being fertilized

34 Mutagens What causes mutations? –natural errors during replication –an environmental mutagen/carcinogen What is a mutagen (carcinogen)? something that causes the DNA code to change (mutate) – x-ray, chemicals, UV light, radiation, etc What happens to a person who has a mutation?

35 Gene Mutations Activity Complete the worksheet

36 Chromosomal Mutations think – pair - share How do you think we could mutate a chromosome? List at least 3 ways

37 Chromosomal Mutations Changes in the number or structure of chromosomes Deletions Duplication Inversion Translocation Nondisjunction

38 Deletions removal of a gene and/or entire chromosome

39 Duplication repeat of a gene or chromosome

40 Inversion gene sequences are switched on the chromosome

41 Translocation part of one chromosome breaks off and reattaches to a non-homologous chromosome

42 Think - pair - share Compare and contrast translocation with crossing – over – How are they similar? – How are they different?

43 Non-disjunction A chromosome fails to separate from its homologue during meiosis

44 Down’s Syndrome Result of nondisjunction of the chromosomes at pair #21

45 Homework Chromosome Mutation activity

46 Standards: CLE Describe the connection between mutations and human genetic disorders. Objectives: (DID WE…) Investigate the affect of mutations on protein production Differentiate between point mutations and chromosomal mutations.

47 Exit Ticket How do mutations affect the production of a protein?


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