Genetic Mutations

• What is a mutation?• What are some examples of harmful mutations?• Neutral Mutations are…• What are some examples of beneficial mutations?

At the End of Today, You Should Know:

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.

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

What is a Mutation?

• More or less chromosomes than 46• 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

Some Mutations Cause Disorders…

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

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)

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

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

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

Effects of Klinefelter Syndrome

• Sparse facial and body hair• Underdeveloped muscles• Wide hips• Tall height• Long legs & arms• Higher-pitched voice

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

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

http://www.floquetdeneu.es/

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 50-100 mutations within

their DNA - most (if not all) are neutral or beneficial

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”

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.

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