Do Now: When we talk about traits, what are we talking about?

Trait  A visible attribute or characteristic. Eye color Hair color Height This is something that is not changed (greatly) by the environment. Our traits come from DNA (our genetic code) We have genes that make up our DNA that make our traits For example, these things are NOT traits in genetics: Tattoos Hair length Piercings

Some traits can be changed by the environment: BUT: that still doesn’t change your DNA. The environment effects our traits, but the DNA remains the same. For example: Height – this can be affected by diet. You might have a greater chance to be tall because of your DNA, but if you don’t eat enough, you will never reach that height. Weight – this can be affected by diet and exercise.

We have two copies of every gene… We get one from mom and one from dad. For example: My dad has blue eyes, so I probably got a blue eye gene from him. My mom has brown eyes, so I probably got a brown eye gene from her. We call these different versions: alleles. So why do I have brown eyes if I have a blue eye allele?

Dominant and Recessive Some alleles are dominant – or cover up – the other alleles. The ones that get covered up are called recessive. So my mom’s brown eye allele must have covered up my dad’s blue eye allele. When we talk about the alleles, we use letters to represent them – remember, these letters represent different versions of a gene. For example: Brown eyes might be: BB or Bb Big B represents brown and brown covers up blue. Blue eyes might be: bb Little b represents blue so you have to have both for blue to show up.

So, for our cats: L (hair length) LL Ll ll short hair short hair long hair W (white) WW Ww ww completely white hair completely white hair some colored hair S (piebald spotting) SS Ss ss some white hair some white hair no white hair D (dense pigment)DD Dd dd black, brown or orange black, brown or orange gray, light brown or cream Homozygous Heterozygous

Punnett squares This is a way to predict the probability of offspring (or children) having certain traits. It is based on large sample sizes. So, for example…