Download - Dominant vs. Recessive and Genotype vs. Phenotype Dominant vs. Recessive and Genotype vs. Phenotype
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 code for ____________
◦A pair of genes that interact to
code for a trait are called ________
TRAITS
GENE PAIRS OR ALLELES
GENES
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!)
Widow’s peak vs. straight
Right handed vs. left handed
Attached vs. unattached
Curly vs. straight
Freckles vs. no freckles
Dimples vs. no dimples
Cleft chin vs. no cleft chin
Hairline: Two forms?
Handedness: Two forms?
Earlobes: Two forms?`
Curliness of hair: Two forms?
Freckles: Two forms?
Dimples: Two Forms?
Cleft Chin: Two Forms?
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 dominant gene. Dominant means strong
This guy represents a recessive gene. recessive means weak
LETS PRACTICE!Is it a Dominant or a Recessive Gene?
b
T
r
f
g
L
RECESSIVE
RECESSIVE
RECESSIVE
RECESSIVEDOMINANT
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 geneWhat do you think will show?
Which guy do you think represents the dominant gene and which guy represents the recessive gene?
DOMINANT! DOMINANT BEATS RECESSIVE
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
TT
rr
Ff
Gg
LL
RECESSIVE
RECESSIVE
DOMINANT
DOMINANTDOMINANT
DOMINANT
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
Who’s tired of saying GENE COMBINATION?
Genotype or Phenotype?
LETS PRACTICE!
Jj:
Cc:
Tt:
Genotype
Genotype
GenotypeFreckles: Phenotype
Straight hair line:
Phenotype
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?
aa = straight
hair
What genotype must this girl’s MOTHER have?
aa = straight hairor
Aa = wavy hair
YOUR TURN TO SHOW WHAT YOU LEARNED!
START YOUR INDEPENDENT PRACTICE
NOW.