Human Inheritance & Genetic Mutations

At the End of Today, You Should Know: Connect the terms gene, chromosome & DNA. Explain how humans get their traits. Include two main sources. Classify human traits into three groups. Define mutation. Describe harmful mutations. Identify what makes a mutation neutral. Provide examples of beneficial mutations.

1. Living things are made of cells, which are the smallest structural and functional unit of the organism. Here are some examples…

Plant Cells Onion Cells Cork Cells

Animal Cells Frog Blood Cells Human Cheek Cell

• Inside the nucleus of most cells are the chromosomes, which are composed of DNA. • Small sections of DNA are called genes. • These are the instructions for absolutely everything that goes on within the organism.

How is a chromosome like a roll of toilet paper?

Random Fact… If you took all the DNA from each of the cells in your body and stretched it out end to end, it would be long enough to reach from the earth to the sun and back – about 60 times!

• The approximately 25,000 genes in each of our cells is responsible for determining all of the initial traits about a human. Remember… these genes came from our parents. • Once born, the environment plays just as a significant role in shaping who you are.

There are three kinds of traits: Physical Behavioral Predisposition to Disease We all inherit an initial set of each, but the environment and the choices we make can change how these traits are displayed.

A change in a gene or a chromosome What is a Mutation? Definition: A change in a gene or a chromosome The term mutation comes from the Latin word for “change”

What is a Mutation? Abrupt changes in a single gene or a region of a chromosome that may be passed genetically. Mutations are the fuel for evolution and are the basis for the variation in population… we will be talking more about this! Whether a mutation is harmful, helpful, or neutral depends on the organism’s environment.

SURVIVE AND / OR REPRODUCE Harmful Mutations A mutation is considered harmful to the organism if it impedes the organism’s ability to… SURVIVE AND / OR REPRODUCE

Some Mutations Cause Disorders…

One Wrong Letter As you watch this video clip, please think about… • Taye-Sachs Disease is caused by a mutation. One letter is incorrect in the affected child’s DNA. It is a recessive mutation. What does that mean? • What does it mean to be a carrier of a disease? 8:57

Genetic Modification As you watch this video clip, please think about… • We have a generic map of the human genome… Eventually we will know which parts of the genome cause certain traits. What are some of the positive and negatives to this practice? This is something you will be facing in your lifetime… 4:28

Should We Screen for Cancer? As you watch this video clip, please think about… • It is becoming more common (and cheaper) to map your genome. Is this something you’d be interested in doing? Why or why not? 3:55

Not all Mutations 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. Most mutations within the DNA are “covered” or compensated for by other, normal genes. 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 Neutral Scientists can trace blue eyes to one person who originally had the mutation. The same is true for people with red hair. That trait is caused by a genetic mutation. Are these beneficial or harmful? Chances are one would say… Not really either. They would be considered neutral. Most neutral mutations aren’t even known to the organism… Think of it as an email or a text message with a typo. The meaning is still understood, unless it is a MAJOR typo.

SURVIVE AND / OR REPRODUCE Neutral Mutations A mutation is considered neutral to the organism if it neither impedes nor benefits the organism’s ability to… SURVIVE AND / OR REPRODUCE

Yes, There Are Beneficial Mutations

Mutations Can Be Beneficial Bacterial resistance to antibiotics (beneficial to the bacteria, not to humans) Insecticide resistance in bugs (beneficial to bugs, not to humans) Seedless watermelon (beneficial to humans, difficult for the watermelon to reproduce) Ability to digest lactose… Did you know it is a mutation that give humans the ability to digest cow’s milk? Scientists think that this originated from farmers who needed to drink animal milk to survive (and reproduce)

SURVIVE AND / OR REPRODUCE Beneficial Mutations A mutation is considered beneficial to the organism if it benefits the organism’s ability to… SURVIVE AND / OR REPRODUCE

Double Immunity • Why is this segment titled, “Double Immunity?” • For which organism is this mutation considered harmful? • What might be done with the knowledge of this mutation? 2:22

Sometimes There’s a Trade-Off Sometimes you can get a beneficial mutation that has a drawback. 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.

A Mutation Story Would this mutation be considered harmful, neutral, or beneficial Defend your answer… 4:50

Check Yourself: Can you answer… Connect the terms gene, chromosome & DNA. Explain how humans get their traits. Include two main sources. Classify human traits into three groups. Define mutation. Describe harmful mutations. Identify what makes a mutation neutral. Provide examples of beneficial mutations.