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What are some genetic mutations and what is their affect?
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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
There are MANY other mutations…
Not all Mutation
s Are Bad…
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
