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Mutations 1.

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Presentation on theme: "Mutations 1."— Presentation transcript:

1 Mutations 1

2 What Are Mutations? Changes in the nucleotide sequence of DNA
May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring 2

3 Are Mutations Helpful or Harmful?
Mutations happen regularly Almost all mutations are neutral Chemicals & UV radiation cause mutations Many mutations are repaired by enzymes 3

4 Are Mutations Helpful or Harmful?
Some type of skin cancers and leukemia result from somatic mutations Some mutations may improve an organism’s survival (beneficial) 4

5 Types of Mutations 5

6 Chromosome Mutations May Involve:
Changing the structure of a chromosome The loss or gain of part of a chromosome 6

7 Five types exist: Chromosome Mutations Deletion Inversion
Translocation Nondisjunction Duplication 7

8 Deletion Due to breakage A piece of a chromosome is lost 8

9 Chromosome Mutations Cri-du-chat
Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps

10 Inversion Chromosome segment breaks off Segment flips around backwards
Segment reattaches 10

11 Duplication Occurs when a gene sequence is repeated 11

12 Translocation Involves two chromosomes that aren’t homologous
Part of one chromosome is transferred to another chromosomes 12

13 Translocation 13

14 Nondisjunction Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes Disorders: Down Syndrome – three 21st chromosomes Turner Syndrome – single X chromosome Klinefelter’s Syndrome – XXY chromosomes 14

15 15

16 16

17 Chromosome Mutation Animation

18 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. 18

19 Types of Gene Mutations
Include: Point Mutations Substitutions Insertions Deletions Frameshift 19

20 Point Mutation Change of a single nucleotide
Includes the deletion, insertion, or substitution of ONE nucleotide in a gene 20

21 Point Mutation Sickle Cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene 21

22 Frameshift Mutation Inserting or deleting one or more nucleotides
Changes the “reading frame” like changing a sentence Proteins built incorrectly 22

23 Frameshift Mutation Original: The fat cat ate the wee rat.
Frame Shift (“a” added): The fat caa tet hew eer at. 23

24 Amino Acid Sequence Changed

25 Gene Mutation Animation

26 HOX GENES A series of genes that control the differentiation of cells and tissues in the embryo. Hox genes determine an animal’s basic body plan



29 FYI

30 Normal Male 2n = 46 30 30

31 Normal Female 2n = 46 31 31

32 Male, Trisomy 21 (Down’s) 2n = 47 32 32

33 Female Down’s Syndrome
33 33

34 Female with Down’s Syndrome

35 Klinefelter’s Syndrome
35 35

36 Sex Chromosome Abnormalities
Klinefelter’s Syndrome XXY, XXYY, XXXY Male Sterility Small testicles Breast enlargement


38 Sex Chromosome Abnormalities
XYY Syndrome Normal male traits Often tall and thin Associated with antisocial and behavioral problems

39 Turner’s Syndrome 2n = 45 39 39

40 Sex Chromosome Mutations
Turner’s Syndrome X0 Female sex organs don't mature at adolescence sterility short stature

41 Sex Chromosome Mutations
XXX Trisomy X Female Little or no visible differences tall stature learning disabilities limited fertility

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