Looking closer at DNA …

Journal question …

• If you could have ONE animal trait genetically given to you, what would it be?

Finish trait activity …

• Honors … please take your science fair boards home ASAP! They get donated to Ms. Kuhl at the end of the week!!

• Retakes for Genetics Quiz #2 require a passport sheet. Need to finish to retake quiz.

Make a BINGO card

• Gene• Trait• Allele• Dominant• Recessive• Phenotype• Genotype• Purebred

•Homozygous•Heterozygous•Heredity•Mendel•Haploid•Diploid•Punnett Square•Hybrid

We will get definitions as we go today …

• HeredityHeredity : the passing of traits from

parent to offspringparent to offspring

Traits are controlled by genes genes ((small section of DNAsmall section of DNA)) SO what is GENETICS?

Genetics: The study of how

traits are inheritedinherited.

Traits

Hair color is a perfect example of a trait

Prince Charming is blond

Snow White has dark hair

What color hair should their children have?

Genes

There are two basic kinds of genes:– Dominant - A gene that is always

expressed and hides others– Recessive - A gene that is only expressed

when a dominant gene isn’t present

WHAT ARE ALLELES?WHAT ARE ALLELES?

o Are ONE FORM FORM of a gene (one form can be dominant and the other is recessive)

oSex cells (sperm and egg) have one one form of each gene on their 23 chromosomes

When the sperm fertilizes the egg, the two alleles that match come

together and …

A couple more vocabulary words…

• Haploid = half of the number of chromosomes. (ex. 23 in a human) Eggs and sperm have a haploid number of chromosomes

• Diploid = the full number of chromosomes for a cell (ex. 46 in a human) Most of your body cell have a diploid number of chromosomes.

ExampleExample: Eyecolor—Brown color is dominantdominant and blue is

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

but still have brownbrown eyes because the brown allele is dominant and “hideshides” the blue allele.

Make a trait!!

Example:RR= dominant rr = recessive

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

Let’s look at the Munster family

Dominant and Recessive Genes

Eddie has a widow’s peak.

• A “widows peak” is dominant, not having a widows peak is recessive.

• If one parent contributes a gene for a widows peak, and the other parent doesn’t, the off- spring will have a widows peak.

Widows Peak

Wait a minute … distant relative??

o “Purebred” species have two exact alleles for the samesame traito Represented by two of the same

letters. This is called homozygoushomozygous. For instance: BB or bb.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

“lettersletters” and is called “heterozygous”. For instance: BbFor instance: Bb

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

o What the trait looks like to us is referred to as it’s phenotype. Example: blue eyes or brown eyes

A widows peak, dominant, would be symbolized with a capital “W”, while no widows peak, recessive, would be symbolized with a lower case “w”.

Father - No Widows Peak – w

Mother - Has a Widows Peak - W

Since Herman has no widows peak, he must be “ww” (one allele from Mom and one from Dad). Lilly has a widows peak she could be either “WW” or “Ww” (remember the dominant or capital letter is expressed)

Definitely ww = Homozygous

recessive

Either Ww = Heterozygous

or WW = Homozygous dominant

UnofficialVocabulary

Quiz

1. Which of the following is a possible abbreviation for a

genotype?

A. BC B. Pp C. Ty D. fg

2. What is the best way to determine the phenotype of the

feathers on a bird?

A. analyze the bird's DNA (genes) B. look at the bird's feathers C. look at the bird's beak D. examine the bird's droppings

3. Which of the following pairs is not correct?

A. hybrid = heterozygous B. heterozygous = Hh C. homozygous = RR

D. kk = hybrid

4. The genes present in an organism represent the organism's __________.

A. genotype B. phenotype C. physical traits

5. Which choice represents a possible pair of alleles?

A. k & t B. K & T C. K & k D. K & t

6. How many alleles for one trait are normally found in the genotype of an organism?

A. 1 B. 2 C. 3 D. 4

Probability Beast

• Get your homework worksheet and draw your beast on the back of it.

• Finish your BINGO card for homework too!

Genetics

So, back to the original question. What color hair will the offspring of Prince Charming and Snow White have?

Genetics

Hair color is different from widows peak, no color is truly dominant. – Brown and blond are the two, true traits– Homozygous conditions produce either

brown or blond hair– Heterozygous conditions produce red hair

(called codominant)

Genetics

For Snow White to have brown hair she must be homozygous dominant, “BB”, a blond Prince Charmin must be homozygous recessive, “bb”.

Bb

Bbb

b

B B

Bb

Bb

Genetics

All the offspring from Prince Charming and Snow White will therefore be heterozygous, “Bb”, and since hair color is codominant….. all their children will have red hair.

+

GREGOR MENDELGREGOR MENDELo First known geneticist and

“father father of genetics”

o Was an Austrian monk and was born in 18221822

o Did most of his genetic studies on peapea plants

• By looking at the color of flowers and the heights of his plants, Mendel noticed that different traits showed up a different percent of the time.

• Using his superior math skills, he figured out which traits were dominant and which ones were recessive.

PROBABILITYPROBABILITY

o Helps predict the chance chance that something will happen

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

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

Punnett SquaresPunnett Squares

o Used to help predict Mendelian genetics

Steps for using the Punnett square:

1) One parent’s alleles (genotype) (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:Steps for using the Punnett square:

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

genotype). What would be their phenotype?

Brown EyesBrown EyesB b

B

b

So you would predict:

¼ offspring to be BB, or Brown Eyes

2/4 or 1/21/2 to be Bb, or BrownBrown Eyes

and ¼ to be bb or BlueBlue eyes

BB

bbBb

Bb

Let’s try some practice Let’s try some practice problems…problems…

Practice Problem #1Practice Problem #1

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

• Use any letter you like.

Practice Problem #1Practice Problem #1

Bb bb

Bb bb

B b

bb

Practice Problem #2Practice Problem #2

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

• Use any letter you like.

Practice Problem #2Practice Problem #2

bb bb

bb bb

b b

bb

Practice Problem #3Practice 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 #3Practice Problem #3

GG Gg

Gg gg

G g

Gg

Practice Problem #4Practice 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 #4Practice Problem #4

Rr rr

Rr rr

R r

rr

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

XX XY

XX XY

X Y

XX