Life Sciences: Fundamentals of Genetics

Life Sciences: Fundamentals of Genetics

Your genes are unique and determine everything about you. In this lesson, we will learn what genes are, how they are inherited from your parents, and how to determine which traits will actually be expressed if you inherit a certain combination of genes.

What color are your eyes?

We all know that people inherit certain traits from their parents, like eye color, hair color, and skin color. How exactly does this work? Do you always inherit exactly the same traits as your parents? If this were true, then two brown eyed parents would always have brown eyed children. While this does happen often, it's not the only possible outcome. My own daughter has blue eyes even though both of her parents have brown eyes, and I'm sure you have seen many other children who look different from their parents in many ways. So, how was I able to have a blue eyed child even though I have brown eyes? Understanding genetics will help us to answer this question.

What are Genes?

Inside every cell in your body, there is a secret code that determines everything about you. DNA (deoxyribonucleic acid) is the material that determines all your traits, and it is found inside the nucleus of all your cells. Genes are short pieces of DNA that determine a specific trait, like eye color or hair color. You have about 20-25 thousand genes total, each one responsible for a different characteristic.

What are Genes?

A gene is a short segment of DNA that codes for a specific traitThe genes in your cells are different from your parents' genes because you inherit one copy of each gene from your father and one from your mother. As a result, the particular combination of genes in your cells is different from everyone else in the world. This recombination of genetic material not only determines visible traits like your eye and hair color, but also can cause you to be more (or less) susceptible to certain diseases.

Multiple Choice

What is located in the nucleus of your cells and contains all of your genetic information?

• DNA

• prorozomes

• gametes

• RNA

Process of Reproduction

In order to create a baby with a unique genetic code, each parent must first produce a special type of cell that only has one copy of each gene. These special cells are called gametes, and a random process determines which copy of each gene gets put into each gamete.

Multiple Choice

Reproductive cells that only contain one copy of each gene are called ____.

• dominant cells

• gametes

• Punnett cells

• recessive cells

Dominant vs. Recessive Gene

Many traits are determined by dominant and recessive genes.

Punnett Squares

A tool that we can use to determine which traits will be expressed in the offspring of two parents is called a Punnett square. To create a punnet square, list the genes of one parent vertically on the left side and the genes of the other parent horizontally above the square. Then combine the genes in the four sections of the square to determine all possible gene combinations that the child could have.

Multiple Choice

If one parent has two genes for brown eyes (BB) and the other has two genes for blue eyes (bb), what is the chance that their offspring will have blue eyes?

• 50%

• 25%

• 0%

• 100%

Multiple Choice

If both parents have blue eyes, what percentage of children are likely to also have blue eyes?

• 50%

• 25%

• 0%

• 100%

Multiple Choice

If the genotype is a capital letter (BB) it means the trait is ________

• dominant

• recessive