1. MUTATIONS

2. What causes a snake to be born with two heads?

3. Are Mutations common?
As scientists learn to read the instructions in our genes, they are discovering that much of our DNA is riddled with errors.
We each inherit hundreds of genetic mutations from our parents, as they did from their forebears.

4. In addition, the DNA in our own cells undergoes an estimated 30 new mutations during our lifetime, either through mistakes during DNA copying or cell division or, more often, because of damage from the environment.

5. When are Mutations Harmful?
During copying, bits of our DNA may be deleted, inserted, broken, or substituted.
Most mutations affect only the parts of DNA that do not contain instructions for making a gene, so we need not worry about them.

6. Problems arise only when an error in DNA alters a message that tells certain cells to manufacture a certain protein.
Such messages are spelled out in varying sequences of the four chemical bases that make up DNA: adenine (A), thymine (T), guanine (G), and cytosine (C).

7. Mutations
Mutations occur as random chance events and cause changes in the DNA sequence
If mutations occur in gametes, they can be passed on to offspring
Mutations may be caused by exposure to toxins or radiation (mutagens).

8. Some mutations cause disease, yet others may lead to variations in the organism that make it better adapted for their environment

9. Kinds of
Mutations

10. There are 2 kinds of Mutations:
Chromosomal Mutations
Gene Mutations

11. Chromosomal
Mutations

12. 1. Chromosomal Mutations
An abnormal change in the structure of all or part of a chromosome, OR in the number of chromosomes an organism has
Ex: normal humans have 46 chromosomes
Humans with Down Syndrome have 47

13. Trisomy 21

14. Down syndrome (Trisomy 21)
Extra 21 chromosome
Effects 1/700
Alters child’s phenotype– characteristic facial features, short stature
Usually some degree of mental retardation

16. Gene
Mutations

17. 2. Gene Mutation A change that affects a gene on a chromosome
Causes the cell to produce abnormal proteins
There are 2 types of gene mutations:

18. Point Mutation
Frame Shift Mutation

19. Point
Mutations

20. Point Mutation A gene mutation involving only a single nucleotide
Ex: ACA mutates to read ACT
mRNA codes ACT to be UGA which is a stop codon!
This will cause the necessary protein to not be made

21. Point Mutation:

22. Frame-Shift
Mutations

23. Frame Shift Mutation
This is the insertion or deletion of one or more nucleotides
Ex: THE CAT ATE
In a frame shift mutation it would read THE ATA TE which is meaningless!
Which letter was deleted? C

24. Genetic
Disorders

25. There are 3 different types of Human Genetic Disorders
Sex-linked Disorders
Autosomal Genetic Disorders
Chromosomal Genetic Disorders

26. Sex-linked
Traits

27. Sex-linked Traits
A trait that is controlled by a gene found on the sex chromosome

28. Why are Males more likely to inherit sex-linked genetic disorders?
On the other hand, men are more likely to inherit sex-linked disorders because they only have one X
They lack the protection of having 2 X’s as females do.

29. Each male child of a mother who carries the defect has a 50 % risk of inheriting the faulty gene and the disorder.
Each female child has a 50% chance of being a carrier like her mother.

30. The two sex-linked disorders we will be discussing are:
Color Blindness
Hemophilia

31. Color
Blindness

33. 1. Color Blindness
Color blindness is a condition in which the individual cannot perceive certain colors
Found mostly in males
Females can carry the gene for color blindness and are called carriers
Carriers have the gene for color blindness on one X chromosome

34. This is what a strawberry patch would look like to a color blind person

35. Hemophilia

36. 2. Hemophilia
Hemophilia is a genetic disorder that affects the ability of blood to form an effective clot and thereby results in prolonged bleeding.
Occurs almost exclusively in males.

37. Vessel damage, blood loss Coagulation, scab forms
                                                      
                                                         
Platelets form
Coagulation, scab forms

38. Why Blood Clots
A. Normal Blood Clot:
                                                   
B. Person with Hemophilia

39. Chances for Hemophilia

40. Autosomal
Genetic
Disorders

41. What are Autosomal Genetic Disorders?
Humans have 23 pairs of chromosomes
22 pairs are called Autosomes
The last pair are called sex chromosomes because they determine your gender
Autosomal genetic disorders therefore are mutations that occur on the first 22 pairs of autosomes

42. An Example of an Autosomal Genetic Disorder is:
Sickle Cell Anemia

43. Sickle-Cell
Anemia

44. Sickle Cell Anemia

45. 1. Sickle-cell Anemia
The genetic defect that causes sickle cell anemia affects hemoglobin, a component of red blood cells.
What causes this defect is a mutation when making a certain amino acid

47. How to Detect
Genetic Disorders

48. There are 2 ways to detect genetic disorders during pregnancy
Amniocentesis
Karyotype

49. Amniocentesis

50. 1. Amniocentesis
A long needle is inserted into the amniotic sac of a pregnant woman to obtain a sample of amniotic fluid
The cells of the fetus that are contained within the fluid are then examined to see if there are any abnormalities

52. Karyotyping

54. 2. Karyotyping A sample of blood cells is taken
Chromosomes are separated out, viewed with a microscope and photographed.
The photograph is then rearranged to show the paired chromosomes.
Size, shape and banding pattern are used to pair up the chromosomes.

55. Notice the differences in these chromosomes:
Differences in length
Differences in banding patterns
Differences in centromere locations (top, middle)