Transcript Powerpoint for Traits Traits weve all got themx

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:
Heterozygous
Homozygous
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
SS
Ss
ss
some white hair
some white hair
no white hair
DD
Dd
dd
black, brown or orange
black, brown or orange
gray, light brown or cream
S (piebald spotting)
D (dense pigment)
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…