1. Compiled by Siti Sarah Jumali Room 14, Level 3 06-4832123
Mutations
Compiled by Siti Sarah Jumali
Room 14, Level 3

2. Changes in Heredity- Mutations

3. Nothing is perfect…
Mutation – any changes (alterations) in the sequence of DNA that affects genetic information and the appearance of offspring. Caused by: UV Light, X-Rays, etc.

4. Types of Mutations
Gene mutation – a mutation that occurs in a single gene and affects one trait. Ex: Eye color, Sickle cell Anemia, Hemophilia Chromosome mutation – a mutation that occurs in many genes and affects many traits at once. Ex: Down Syndrome (an extra 21st chromosome)

5. How Can Mutations Affect an Organism?
Body cell mutations can cause cancer. - only the individual is affected. Gamete cell mutations affect the egg and the sperm. - all offspring of the individual can be affected.

6. Gene Expression
An individual’s trillions of body cells all come from one cell (zygote). In differentiation the cells become different tissues. (ex: skin, muscle, organ) Certain cells will “turn on” or activate only the genes they need. This is called gene expression.

7. Factors that Affect Gene Expression
The internal and external environment of a cell can influence which genes are “turned on”.
Ex: - Hormones can “tell” a cell to activate a specific gene.
- Outside temperature changes fur color in rabbits.

8. End of Today, You Should Know:
What is a mutation?
What are some examples of harmful mutations?
Neutral Mutations are…
What are some examples of beneficial mutations?

9. What is a Mutation?
Abrupt, heritable changes in a single gene or a region of a chromosome, can also include alterations in chromosome number
Mutations are the fuel for evolution and are the basis for the variation in population.

10. What is a Mutation?
Can be when one letter is switched - accidentally copied incorrectly within the DNA.
When one section of the DNA, sometimes an entire gene, is not properly connected to the rest of the DNA; sometimes it even reconnects to another chromosome
One section of DNA, sometimes an entire gene, appears more than once

11. What is a Mutation?
Will only get passed on to offspring when the sex cells contain the mutation
Can be caused after birth by environmental factors like radiation and chemicals, which can alter a person’s DNA, even in their sex cells, causing their offspring to have disorders

12. Mutation.. Affects molecular changes in the DNA sequence of a gene
Alter the coding sequence within a gene
Causes permanent change in DNA sequence
Involve insertion or removal of 1 or more base pairs
Point mutation is a change in single base pair within DNA sequences
Base substitution changes is in pair
2 types of changes
Transition (within same group AT and GC)
Transversion (between 2 groups)

13. Transition vs Transversion

14. Changes in coding sequence
Silent mutation –does not alter the amino acid sequence of the polypeptide although the nucleotide sequence was changed
Missense mutation- base substitution causes change in amino acid eg sickle cell anemia (Glu to Val)
Nonsense mutation – change from normal to stop codon. Translation is termination in abrupt producing truncated protein
Frameshift mutation – additional or deletion of a number of nucleotides that will not be realized if 3 nucleutides because 3 bases code for 1 aa. But if it is not in multiple 3, will be very dangerous, changes the whole aa sequence

15. Missense mutation

16. Nonsense mutation

18. Silent or neutral mutation
Silent mutation can result in enhancing new protein, but all other mutations reduce the function
Missense mutation generally affect mutation, it is also known as neutral mutation

19. Silent mutation

20. Frameshift mutation

21. Frameshift mutation

22. Some Mutations Cause Disorders…

23. Down’s Syndrome • Offspring receives 3 copies of 21st chromosome
90% of the time the extra chromosome comes from the mother
Affects 1 in 800 live births

24. Effects of Down’s Syndrome
Different in each person
Does not usually pass this onto children
Common effects include
Learning Disabilities
Heart defects (can usually be corrected with modern technology)

27. Turner’s Syndrome 45 (instead of 46) chromosomes
offspring are born with one X chromosome (no Y; only one X)
only affects women
In about 80% of cases the X comes from the mother and the father’s sperm has no Y
Affects 1 in 2500 live births

28. Effects of Turner’s Syndrome
• Sometimes a lack of ovarian development
• Can have more masculine qualities (stronger), although are female
In some cases:
Webbed neck
Arms that turn in at the elbow
Low hairline on the back of the head

31. Klinefelter’s Syndrome
• Offspring inherit a Y chromosome and two X chromosomes
Because there is a Y all offspring are male
Sometimes the extra X comes from the egg and sometimes it comes from the sperm
Occurs in 1 out of every 500 – 1000 live births

32. Effects of Klinefelter Syndrome
Sparse facial and body hair
Underdeveloped muscles
Wide hips
Tall height
Long legs & arms
Higher-pitched voice

34. Albinism Caused by a recessive gene
Causes genes to release unusual amounts of melanin (chemical that provides color)
Affects 1 in 17,000 people
People of all races are susceptible
All animals are susceptible

35. Effects of Albinism Light skin Light hair
Reddish or violet eyes (in some albinos)
Lack of eye pigment leads to vision problems
Skin cancer – especially in third world countries

43. There are MANY other mutations…

44. Not all Mutations Are Bad…

45. Mutations Can Be Neutral
They may have little or no effect on the survival of an organism or on its ability to reproduce.
They may result in the same kind of organism - meaning that the change still tells the cell to do what it should, so there is no difference.
It is estimated that the average human has mutations within their DNA - most (if not all) are neutral or beneficial

46. Mutations Can Be Beneficial
Bacterial resistance to antibiotics
Insecticide resistance in bugs
Rapid mutation rates in virus’s proteins allowing them to adapt to new “hosts”

47. Mutations Can Be Beneficial
In humans, it can be a different set of circumstances… Here’s an example:
Sickle-Cell Anemia is a genetic disorder in which there is a defect in the structure of red blood cells. This leads to fatigue and anemia when not treated.
However, it has been found that people who are carriers for Sickle-Cell Anemia also has some genetic protection against another disease, malaria.

48. Mutations Can Be Beneficial
• In evolutionary studies, scientists have connected the presence of a brain chemical microcephalin (a proposed mutation) with the human’s development of art, music, and complex tool-making practices
This same research indicates that the human brain is still evolving and becoming more and more capable of more complex tasks
Some humans have been found to have mutations that protect them from other diseases, such as AIDS