BELL WORK:

1. Take out piece of paper and pen/pencil.

2. Put all notes away.

1. What do we call different forms a gene may have for a trait?

2. What height of pea plant (tall or short) did Mendel find to be dominant?

3. How are dominant and recessive traits represented? (upper or lower case)

Give an example!

• Heredity : the passing of traits from

parent to offspring

Traits are controlled by genes, SO what is GENETICS?

Genetics: The study of how

traits are inherited.

GREGOR MENDELo First known geneticist and

“father of genetics”

o Was an Austrian monk and was born in 1822

o Did most of his genetic studies on pea plants

o He performed cross-pollinationo He became the pollinator himselfo He controlled which plants mixed.

o Some traits Mendel worked with were shape of pea and it’s pod, color and shape of seeds, plant height, flower position and flower color.

WHAT ARE ALLELES?o Alleles are ONE FORM of a gene (there

can be more than one form)

o Sex cells have one form of a gene on their chromosomes

o Body cells have two forms or ALLELES for a single gene (you got one from Mom and one from Dad)

o One may be dominant over another. If this happens, the dominant gene is the one expressed or shown. If not, the recessive trait is expressed.

DOMINANT AND RECESSIVE

o A Dominant trait: will always be expressed or shown and will

“mask” a recessive trait

o A recessive trait can only be expressed if there are no dominant alleles present.

Example: Eyecolor—Brown color is

dominant and blue is recessive. A person can have a brown allele

and a blue allele but still have brown eyes because the brown allele is dominant and “hides” the blue allele.

Example:R= dominant r = recessive

• Generally, dominant alleles are represented with a capital letter, and recessive alleles are represented with a lower case letter.

Each organism is represented

by TWO letters, one

for each allele.

o “Purebred” species have two alleles of the same traito Represented by two of the same letters.

This is called homozygous. For instance: BB or bb.

o Species with two different alleles or two different forms of the gene would be “hybrid”o Represented by two different “letters” and

by called “heterozygous”. For instance: Bb

o The alleles present in the organism are referred to as its genotype. For instance, BB, Bb, or bb.

o The PHYSICAL trait that shows, regardless of genotype is called a PHENOTYPE.

o For instance, Blue or Brown Eyes.

Mom has blue eyes (bb)

Dad has brown eyes (BB or Bb)

Daughter has blue eyes (bb)

Therefore, Dad must have the Bb genotype, because he must have given her the “b” allele. His “b” allele is masked by his “B”/dominant allele.

Genetics by Brainpop

PROBABILITY

o Helps predict the chance that something will happen

o Example: the probability of throwing heads or tails on a coin is 50% (1/2 chances)

o Your predictions become more accurate with the more trials you run!

Using a Punnett Square…

o Used to help predict Mendelian genetics

Steps for using the Punnett square:

1) One parent’s alleles (genotype) go along the top

2) The other parent’s alleles go down the side.

3) You fill in the squares like doing the communicative property of multiplication.

B b

B

b

BB

bbBb

Bb

Steps for using the Punnett square:

Let’s say the parents are Bb and Bb (the same

genotype). What would be their phenotype?

Brown EyesB b

B

b

So you would predict:

¼ offspring to be BB, or Brown Eyes

2/4 or 1/2 to be Bb, or Brown Eyes

and ¼ to be bb or Blue eyes

BB

bbBb

Bb

So, if 2 adults were to have children …what color eyes would they have?

Mr. X

Brown eyes (BB)

Mrs. X

green eyes (bb)

All of their kids could have brown eyes, but we have to remember that our grandparents genes are also part of this process.!

Bb Bb

Bb Bb

B B

b

b

Using a Punnett Square Clip

Let’s try some practice problems…

Practice Problem #1

• Predict the fur color of the offspring of a brown heterozygous hamsters and a white homozygous hamster. Brown is dominant. White is recessive.

• Use any letter you like.

Practice Problem #1

Bb bbBb bb

B bb

b

Practice Problem #2

• Predict the offspring of 2 white homozygous cows. Black is dominant over white.

• Use any letter you like.

Practice Problem #2

bb bbbb bb

b bb

b

Practice Problem #3

• Predict the offspring of 2 Grey Heterozygous rats. Gray is dominant over white, which is recessive.

• Use any letter you like.

Practice Problem #3

GG GgGg gg

G gG

g

Practice Problem #4

• Predict the pea shape of the offspring of one Heterozygous Round Pea plant and one homozygous wrinkled pea plant. Round is dominant over wrinkled.

• Use any letter you like.

Practice Problem #4

Rr rrRr rr

R rr

r

Practice Problem #5you don’t have to write this one down…

• What are the chances of having a boy or a girl?

• How would you solve this one?

Practice Problem #5

XX XYXX XY

X YX

X

Heredity by Brainpop

Heredity by Brainpop

1 . What do we call different forms a gene may have for a trait?

2 . What height of pea plant (tall or short) did Mendel find to be dominant?

3 . Which kind of trait can’t be passed from parent to child?a )Eye color b) height c) broken arm