Transcript Recessive

Heredity and Genetics
How it all works
 Dominant is the expressed trait. (That
means the trait we see. So it gets a
capital letter.)
 Recessive is the unexpressed trait.
(That’s the one we don’t see. So it gets
a lower case letter.)
 Codominant is when both traits
are equally dominant and are
equally expressed.
What is Genetics?
 Genetics explains how traits are passed
on from generation to generation.
 Traits are either Dominant or Recessive
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(Look at the Laboratory Investigation sheet)
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Tongue RollerWidow’s peak
Hitchhikers thumbRed/not hairHand ClaspEarlobes FreeEye Color
Who is Mendel and What Does a Pea Plant Have to
do with ME?
 Mendel became the father of genetics.
 He did not realize it then, but his study of pea
characteristics or traits gave us the basics for genetics
today.
 He studied traits like how tall they grew, the color of
seeds, and the shape of the seeds.
 He tried to cross traits to see what
would happen. (He found things like a
tall and a short made 4 tall.. This led
to the idea of dominant and recessive.
 The Genotype is the “gene” make-up of
an organism.
 The Phenotype is the “physical” look that
the genes created.
What is his phenotype and
genotype?
Dark Hair –BB or Bb
Light Hair-bb
Pairs- the traits are put is pairs: one from mom
and one from pops. The pairs are either
heterozygous (different Dd) or
homozygous (same DD or dd).
We use the punnett square to figure out what
an offspring's genotype and phenotype will
be. Draw this on your graph paper.
d
D
d
Dd
dd
d
Now try this:
Gg
dd
gg
DD
continue
Hh
Ss
hh
Ss
Genotype and Phenotypes
 H is blue, h is yellow: What is Hh?
 T is tall, t is short: what is TT? Tt? tt?
 What is the only way to make the
recessive gene show?
Word Bank for Heredity Quiz
Trait
Allele
Phenotype
heterozygous allele
Genotype
homozygous allele
Dominant allele
heredity
Recessive allele
genetics