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Presentation on theme: "Mutations."— Presentation transcript:

1 Mutations

2 Any change in the DNA base sequence
What is a mutation? Any change in the DNA base sequence

3 What are the two different classes of mutations?
Gene Mutations Chromosomal Mutations

4 What is a gene mutation? A change in the base sequence of one gene

5 What causes gene mutations?
Errors in DNA replication Chemicals UV/X-ray Radiation

6 Types of Gene Mutations
Substitution Deletion Insertion Original DNA Strand

7 Two types of Gene Mutations
Point mutation A change in ONE nitrogenous base, the overall number of bases stays the same (Substitution) Frame shift mutation A change in the number of overall nitrogenous bases in the genetic code (Insertion or Deletion)

8 Substitution Mutation
Substitution – One nitrogenous base is substituted for another.

9 Deletion and Insertion Mutations
Deletion – One or more nitrogenous bases are removed Insertion – Extra nitrogenous bases are added to the genetic code.

10 Sickle Cell Anemia

11 How does a mutated protein affect a cell?
If the shape of the protein is altered, it MIGHT disrupt its normal activity OR (functioning).

12 What type of mutation is it?

13 How can gene mutations be passed down to future offspring?

14 What are some characteristics of gene mutations?
They can be dominant or recessive They can occur on autosomal chromosomes (pairs 1-22) or sex chromosomes (pair 23)  People that are heterozygous for a recessive genetic disorder are called carriers  Carriers have one normal allele and one diseased allele; They do not show symptoms for the disease but may pass the allele to future offspring


16 Genetic Diseases caused by gene mutations:
Cystic Fibrosis Faulty gene produces a defective protein that does not allow for the proper removal of mucous lining the cells of the lung and GI tract.

17 Gene Mutations: Tay-Sachs Disease
Faulty gene produces a defective enzyme which cannot help remove fat from nerve cells.

18 Sickle-Cell Anemia: One base is substituted for another and this causes the production of a distorted hemoglobin molecule (protein) which cannot function properly.

19 What do these three gene mutations have in common?
They all affect the shape of proteins!! If we change the shape of proteins (enzymes) they will not function properly and this will affect our phenotype.

20 How do we trace/identify gene mutations in a population or family?
Pedigree Charts: - A diagram that shows the presence or absence of a particular trait through each generation. Genetic Testing: Ability to diagnose vulnerabilities to various genetic disorders

21 Recessive Gene Pedigree Chart
Cc Cc cc

22 A – Dominant Allele; a - Recessive
aa Aa Aa Aa aa aa Aa Aa aa ? aa ?

23 H – Dominant Allele; h - Recessive
Hh hh hh Hh Hh hh hh hh hh hh hh hh hh Hh

24 What is a chromosomal mutation?
Any change in the number or structure of chromosomes

25 Chromosome Damage: Part of a chromosome is repeated.
missing. Reversing a fragment of the chromosome. A fragment of one chromosome attaches to a nonhomlogous chromosome.

26 Abnormal Numbers of Chromosomes
Polyploidy: Having many sets of chromosomes – 1.5n, 3n, 4n, 5n

27 Abnormal Numbers of Chromosomes
Aneuploidy: The addition or loss of a whole chromosome

28 How do these mutations occur?
NONDISJUNCTION: occurs when homologous chromosomes or sister chromatids fail to separate during meiosis.

29 Normal Karyotype

30 Trisomy 21 – Down Syndrome

31 Trisomy 18 – Edward’s Syndrome

32 Monosomy X – Turner Syndrome

33 Chrom. #5 deletion: Cri-du-Chat Syndrome

34 Klinefelter’s Syndrome

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