Transcript Dom_Recessive geno phenox

Dominant vs.
Recessive
and
Genotype vs.
Phenotype
Can roll your tongue?

Yes:
No:
Do you have a widow’s peak?

Yes:
No:
Do you have unattached earlobes?

Yes:
No:
 These
are all DOMINANT
traits.
 We tend to see these traits
more often in society.
 Why is that?
 YOU
WILL LEARN TODAY!
 Things
we already know:
◦Chromosomes are made up of
GENES
______________
◦Genes code for ____________
TRAITS
◦A pair of genes that interact to code
for a trait are called ________
GENE PAIRS
OR ALLELES
Skin tone is an example of a
trait that is controlled by
multiple genes.
That’s why we have a variety of skin tones in
the world!
So let’s focus on some traits
that are only controlled by
ONE gene.

These are the traits that you either have
one form or the other.

There’s no in-between.

What are some examples of traits
controlled by only ONE gene (from your
HW!)
Hairline: Two forms?
Widow’s peak vs. straight
Handedness: Two forms?
Right handed vs. left handed
Earlobes: Two forms?
`
Attached vs. unattached
Curliness of hair: Two forms?
Curly vs. straight
Freckles: Two forms?
Freckles vs. no freckles
Dimples: Two Forms?
Dimples vs. no dimples
Cleft Chin: Two Forms?
Cleft chin vs. no cleft chin
 How
do we inherit either form of one of
these traits?
 KP#1:
There are two types of genes:
dominant (CAPITAL LETTER) and
recessive (lowercase letter).
This guy
represents a
recessive gene.
recessive means
weak
This guy
represents a
dominant gene.
Dominant means
strong
LETS PRACTICE!
Is it a Dominant or a Recessive Gene?
b
RECESSIVE
f
RECESSIVE
T
DOMINANT
g
RECESSIVE
r
RECESSIVE
L
DOMINANT
Our two genes combine to make a trait:
◦ AA = two dominant genes = shows dominant trait
◦ aa = two recessive genes = shows recessive trait
◦ Aa = one dominant and one recessive gene
What do you think will show?
DOMINANT! DOMINANT BEATS RECESSIVE
Which guy do you
think represents the
dominant gene and
which guy represents
the recessive gene?
WHAT’S THE RULE??
KP #2: A dominant trait will show if you
have ONE or TWO dominant genes.
 AA or Aa
KP #3: A recessive trait will show ONLY
if you have TWO recessive genes.
 aa
LETS PRACTICE!
Will these gene combinations show a
Dominant or a Recessive Trait?
bb
RECESSIVE
Ff
DOMINANT
TT
DOMINANT
Gg
DOMINANT
rr
RECESSIVE
LL
DOMINANT
Who’s tired of saying GENE COMBINATION?
KP# 4:
Another word for gene combinations is
GENOTYPE. (THINK GENE)
EX:
Aa = genotype
Another word for trait or the way an
organism looks or behaves is
PHENOTYPE. (THINK PHYSICAL)
Ex: Curly hair = phenotype
LETS PRACTICE!
Genotype or Phenotype?
Jj:
Genotype
Freckles:
Tt:
Phenotype
Genotype
Straight
hair line:
Cc:
Phenotype
Genotype
Dimples:
Phenotype
What about wavy hair? What gene
combination do you think creates
wavy hair?
-Aa
KP #5: Sometimes the
dominant gene does
not completely
overpower the
recessive gene. This is
called incomplete
dominance.
CANDY QUESTION: Could it be possible
for this little girl to have her own
daughter some day with straight hair?
YES! HOW?
If the curly haired girl has a genotype that
shows INCOMPLETE DOMINANCE, she still
has an allele for straight hair. She could pass
that on to her own child.
What
genotype
MUST this
little girl
have?
What genotype must this
girl’s MOTHER have?
aa =
straight
hair
aa = straight hair
or
Aa = wavy hair
YOUR TURN TO SHOW
WHAT YOU LEARNED!
START YOUR
INDEPENDENT PRACTICE
NOW.