Introduction to Genetics

Introduction to Genetics What is this all about?

What is Genetics all about? • Genetics is the study of how traits are passed from parent to offspring .

What do you mean traits? • Traits are characteristics of each person such as hair color, eye color, shape of face or nose, height, predisposition to certain diseases.

Why do we study genetics? • We study genetics so that we can determine why we have certain traits. • Studying genetics can also lead us to find cures for hereditary diseases that may be passed down from parent to child.

Heredity, another new word?? • Heredity simply means passing traits from parent to offspring. • Sounds like genetics and heredity are the same thing. • Yes, but basically genetics is the study of heredity and genes and the traits passed down.

Like blue jeans??? • NO. It is spelled differently, • G E N E S • Genes are sets of instructions that tell what traits you will have. • Remember talking about fertilization? • Remember that the sperm fertilizes the egg? • Ok, your dad’s sperm had certain genes that combined with your mom’s egg that had certain genes.

I thought we were finished with Reproduction. • We are, but it was the reproductive process that allowed you to become a person and through that process your dad gave you some of his genes and your mom gave you some of her genes.

So that’s why I look like my dad, right. • Exactly. But it isn’t quite that simple. • Let me explain a few things.

Your cells • Your cells all have something called chromosomes which are located in the nucleus of your cell. • Most of the cells in your body have chromosomes which hold the information for who you are and what you look like.

All of your BODY cells have 46 chromosomes (23 pairs) • Each of those chromosomes have genes on them that hold information to determine your traits. • Each of those genes contains your specific recipe called your DNA.

Draw this quickly on Your paper.

So we understand your cells contain your personal information • WHOA… Not so fast…. • What does this have to do with genetics and heredity? • Well, it is the study of genetics that lets us know which traits were passed to you from mom and dad.

Go back to the sperm and the egg • Dad gave a sex cell called the sperm and Mom gave a sex cell called the egg to make you. • Right and each cell has 46 chromosomes, right. • NO. Only body cells.

I’m confused • Your body cells include all cells except your sex cells. Remember, Sperm and Egg. • Oh yeah. Sex Cells. • So, mom’s egg combined with dad’s sperm. Each of those sex cells had 23 chromosomes so that when they combined to make you, it gave your cells 46 chromosomes • 23+ 23= 46

So, what next?? • So, now you see how we all have 46 chromosomes and half of them is from mom and half from dad.

What does this all mean for genetics? • If half of you is from your dad and half from your mom, you have to have some genes from each of them. • Remember, genes are located on Chromosomes and you got half from mom and half from dad. • Genetics is the study of which genes (traits) showed up in you.

Each chromosome contains hundreds of genes for hundreds of different traits. • Some of those traits, we don’t even see or really know that much about. • Ex: • Eye Color Height • Hair Color

So how did I get my hair color? • NOW, WE’RE TALKING GENETICS. • Words to know. • Genes--- Alleles--- dominant---recessive • A gene determines a trait • An allele is a form of the gene. (so a gene is made up of alleles • dominant means stronger • recessive means weaker

Strong vs. WeakDominant vs. Recessive • If I hand you a gene that determines eye color and one part says Brown and the other part says blue, you will end up with Brown eyes. • This is because Brown eyes are dominant over blue.

Let’s call brown B and blue b • So your gene for eye color may look like Bb and you have Brown eyes. Each letter represents a form of the gene which we call an allele. B==allele b==allele

Ok, let’s focus on Hair Color. • Mom gave you an allele for hair color and Dad gave you an allele for hair color. • We are going to give each hair color allele a letter. It’s ok to use the same letter as before if we know what they are standing for. • Let’s say Brown is B • Let’s say blonde is b • Which hair color is dominant? Recessive?

So, B=Brown hair • b=blonde hair • Mom gave you a B allele • Dad gave you a b allele • What hair color gene do you have? • Bb=brown (hair color)

Let’s ReviewWrite and answer each question. • 1. What is a chromosome? • 2. What is genetics? • 3. What is the difference in a gene and an allele? • 4. How many chromosomes do our body cells have? • 5. How many chromosomes do our sex cells have? Why? • 6. What is the difference in dominant and recessive?

Now that you have the basics… • You want to know why you have blonde hair but dad and mom both have brown hair. • This is where it gets fun…….. • Ever heard of a Punnett Square?

Introduction to Genetics