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.