+

Genetics and

Inheritance

+Intro to Genetics

Every living thing—plant or animal,

microbe or human being—has a set of

characteristics inherited from its

parent or parents.

Your DNA holds the genetic code for

every TRAIT (physical characteristic)

you have.

+Remember!

DNA RNA Protein

+Heredity and Genetics

Passing characteristics (traits) from

parent to offspring is called heredity.

The scientific study of heredity, known as

genetics, is the key to understanding

what makes each organism unique.

Key Question: How can we know, just

by looking at our DNA, what we

physically look like?

+Brainstorm: Why is one flower

white and one flower purple?

It’s because of each flower’s unique DNA genetic code!

Looking closely at the genetic message…

Chromosomes carry GENES (most have at least 1,000 genes)

Gene: a section of a chromosome that codes for a specific trait (ex. hair color)

GENE

Example: FLOWER COLOR, hair color, etc.

CHROMOSOME

Each gene can have different forms/options!

The alleles determine an organism’s TRAIT

TRAIT: physical appearance (what it looks like!)

Example: purple OR white flowers

Allele: different forms of a gene

PUTTING IT ALL TOGETHER

Match each statement with its

key term (gene, allele, trait)

1)Flower color looks purple

2) DNA segment coding for

flower color

3) DNA segment coding for

purple flower color

TRAIT

GENE

ALLELE

+STOP AND JOT!

In your own words, describe the relationship between the terms below. An example may help your description!

1. Chromosome

2. Gene

3. Trait

4. Allele

+The Experiments of Mendel

Genetics was founded by

an Austrian monk named

Gregor Mendel.

Mendel correctly figured

out that parents pass

traits on to their offspring.

Mendel studied peas

+Genetic Crosses

When doing genetic crosses, we call

the original pair of organisms the

P, or parental, generation.

+Genetic Crosses

Their offspring (kids) are called the

F1, or “first filial,” generation.

+Mendel’s Crosses

Mendel did experimental crosses for seven

different traits

Each parent had a different version of each trait

One of the traits “disappeared” in the F1 generation

+Dominant and Recessive Traits

Principle of Dominance: Some traits are dominant to other traits

When both dominant and recessive alleles are present, we only see the dominant trait.

We write dominant alleles with an UPPERCASE letter

We write recessive alleles with an lowercase letter

+Example

Plant Height

Tall = Dominant

Short = Recessive

+Learning Check

Seed Color

Yellow =

Green =

Dominant

Recessive

+F2 Generation

Did the recessive

alleles go away?

NO! They come back

in the F2 Generation

Dominant?

Tall

Recessive?

Short

+

• Every sexually reproducing organism

inherits two alleles for every trait

• One allele from MOM and one from DAD

From Mom From Dad

Examples:

B = curly hair

b = straight hair

B = freckles

b = NO freckles

Dominant and Recessive Alleles

+

1. How many alleles do you have for a

single trait?2

2. If your mother gave you a dominant allele

(E) and your father gave you a recessive

allele (e), what gene combination would

YOU have? Ee

Check for Understanding

4. Based on these questions, what are the ONLY

three possible allele combinations that you

could have?

EE ee EeDominant

came from

BOTH parents

Recessive

came from

BOTH parents

Dominant from

one parent and

recessive from

the other parent

3. If your mother gave you a dominant allele (E)

and your father also gave you a dominant allele

(E), what gene combination would YOU have?

EE

+Check for Understanding

In Chinchillas, Grey is

a recessive fur color.

What would the

alleles of the grey

chinchilla be?

ff

+Check for Understanding

In Chinchillas, Grey is

a recessive fur color.

If two grey chinchillas

had babies, what

color would they be?

Grey

+Check for Understanding

In Chinchillas, Beige is a

dominant fur color.

What would the alleles of

the grey chinchilla be?

FF or Ff

+Check for Understanding

In Chinchillas, Beige is a

dominant fur color.

If two Beige chinchillas

had babies, what color

would they be?

Depends…

+ Check for Understanding

What vocabulary word match the following definitions?

Gene, Allele or Trait

1. Your physical appearance

2. A specific form of a gene

3. A part of DNA that codes for a trait

4. The DNA section that codes for a dog’s fur color

5. The DNA section that codes for brown fur

6. The dog’s fur appears brown

7. Dominant or Recessive?

1. Aa 2. TT 3. ee 4. Ff 5. bb 6. RR

TRAIT

ALLELE

GENE

GENE

ALLELE

TRAIT

DOM DOM REC DOM REC DOM

+Genotype and Phenotype

Every organism has a genetic makeup as

well as a set of observable characteristics

Phenotype – physical expression of traits (result of environment and genotype)

What you SEE

Genotype – genetic makeup (inherited)

The DNA

+Determining Phenotypes

How do you determine traits based on the allele combination?

Dominant alleles will always appear as the physical trait.

Recessive alleles will only appear if they come from BOTH parents.

EE= Dominant trait shown

Ee= Dominant trait shown

ee= Recessive trait shown

+

• Hh

• Blue eyes

• AA

• Kk

• Brown Hair

• Small ears

G

P

G

G

P

P

Genotype or Phenotype?

+Homozygous and Heterozygous

Homozygous: two of the same alleles

Homozygous Dominant: AA

Homozygous Recessive: aa

Heterozygous: two different alleles

Aa…What phenotype?

Dominant

Definition: Having two copies of

the SAME allele

1) Homozygous:

AA BB aa bb

HOMO MEANS SAME!!

EXAMPLES:

What type of trait can this code for?

Dominant (AA) or Recessive (aa)

Definition: Having two DIFFERENT

alleles

2) Heterozygous

Aa Tt

Gg Bb

HETERO MEANS DIFFERENT!!

EXAMPLES:

What type of trait can this

code for?

ONLY DOMINANT

+Heterozygous (He) or

Homozygous (Ho)

AA ______ EE _____ Ii _____ Mm _____

Bb ______ ff _____ Jj ______ nn ______

Ho Ho

Ho Ho

He He

He He

+

1. If two dominant alleles are inherited (DD),

the _______________ trait will be expressed.

2. If one dominant and one recessive allele

is inherited (Dd), the ____________________

trait will be expressed.

3. If two recessive alleles are inherited (dd),

the _______________ trait will be expressed.

Dominant

Dominant

Recessive

Check for Understanding

+

Circle ALL of the allele

combinations below that will

show the dominant trait.

Dd dd DD Bb bb RR Rr

Check for Understanding

+Check for Understanding

Label using the correct terms:

Homozygous v. Heterozygous

EE=

Ee=

ee=

Now add Dominant or Recessive

Homozygous

Homozygous

Heterozygous

Dominant

Recessive

Genotype HeterozygousorHomozygous? DominantorRecessive?

AA

Bb

Cc

dd

LL

Pp

hh

Practice on YOUR OWN!

HOMOZYGOUS DOM

HETEROZYGOUS DOM

HETEROZYGOUS DOM

HOMOZYGOUS REC

HOMOZYGOUS DOM

HETEROZYGOUS DOM

HOMOZYGOUS REC

+Check for Understanding

1. Which of these is an example of a homozygous

genotype?

A. Rr B. RR C. wrinkled D. round

2. Which of these is an example of a heterozygous

genotype?

A. Rr B. RR C. wrinkled D. round

+Determining PHENOTYPE from

GENOTYPE

Unattached earlobes are dominant to attached earlobes

EE_______________________ Ee_______________________ ee_______________________

Brown eyes are recessive to blue eyes.

BB_________________________ Bb_________________________ bb_________________________

Unattached earlobesUnattached earlobesAttached earlobes

Blue eyesBlue eyesBrown eyes

+Check for Understanding

In Chinchillas, Grey is a recessive fur color.

Genotype?

ff

Phenotype?

Grey orHomozygous Recessive

+Check for Understanding

In Chinchillas, Ebony is a dominant fur color.

Genotype?

FF or Ff

Phenotype?

Homozygous Dominant or Heterozygous

+Challenge!

In Chinchillas, White is a dominant fur color

Homozygous White (FF) is LETHAL, so there are no Homozygous White Chinchillas.

Genotype?

Ff

Phenotype?

Heterozygous

+

In humans the trait of having freckles (F)

is dominant to not having freckles (f).

Which genotype and phenotype are

correctly paired?

FF—no freckles

Ff—no freckles

Ff—freckles

ff—freckles

Check for Understanding

+

In humans, the allele for being a tongue curler is dominant (T) and the allele for not being a tongue curler (t) is recessive. A woman who is homozygous dominant for this trait marries a man who is homozygous recessive.

What is the genotype of the mom?

What is the genotype of the dad?

What is the phenotype of the mom?

What is the phenotype of the dad?

TT

ttTongue

curler

Not a tongue

curler

Check for Understanding

+

A __________ is a physical appearance. A ________________ is a sequence of

DNA that codes for a specific trait. An ______________ is a specific form of a

gene.

A person inherits _________ genes for each trait. One gene comes from the

______________________ and one gene comes from the ___________________.

The genetic makeup of an individual, usually represented by two letters, is

called the individual’s _____________________________. How a person looks

as a result of this genotype is called a ______________________________.

When the two alleles are the same (BB or bb), a person is _________________

for that trait. When the two alleles are different (Bb), a person is

__________________________________ for that trait. These genes can be

_________________________________ or ________________________________,

depending on the combination of alleles.

two

mother father

genotype

phenotype

homozygous

heterozygous

recessivedominant

allele

trait gene

Putting it all together: Fill in the blanks

with the key terms you’ve learned!