I can explain how sex cells carry genetic information.

HeredityHeredity : the passing of traits from parent to parent to offspringoffspring

Traits are controlled by genesgenes, SO what is GENETICS?

Genetics: The study of how traits are inheritedinherited.

oFirst known geneticist and “father father of genetics”

oWas an Austrian monk and was born in 18221822

oDid most of his genetic studies on peapea plants

GREGOR MENDELGREGOR MENDEL

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

o Some traits Mendel worked with were shapeshape of pea pea and it’s pod, colorcolor and shape of seedsseeds, plant heightheight, flower positionposition and flower color.

oAre ONE FORM FORM of a gene (there can be more than one form)

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

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

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

WHAT ARE ALLELES?WHAT ARE ALLELES?

o A Dominant trait: will always be expressed and will “maskmask” a recessive trait

o A recessive trait can only be expressed if there

are no dominant dominant alleles present.

DOMINANT AND RECESSIVEDOMINANT AND RECESSIVE

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.

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

Example:RR= dominant rr = recessive

Each organism

is represented by TWOTWO letters, one for each

allele.

o“Purebred” species have two alleles of the same same traito Represented by two of the same letters. This is called homozygoushomozygous. For For instance: BB or bb.instance: BB or bb.

oSpecies with two different alleles or two different forms of the gene would be “hybrid”o Represented by two different “lettersletters” and by called “heterozygous”. For For instance: Bbinstance: Bb

oThe alleles present in the organism are referred to as its genotypegenotype. For instance, BB, Bb, or bb.BB, Bb, or bb.

o The PHYSICALPHYSICAL trait that shows, regardless of genotype is called a PHENOTYPEPHENOTYPE.

o For instance, BlueBlue or BrownBrown 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

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!

PROBABILITYPROBABILITY

o Used to help predict Mendelian genetics

Using a Punnett Square…Using a 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.

Steps for using the Punnett square:

B b

B

b

BB

bbBb

Bb

Let’s say the parents are Bb and Bb (the same genotype).

What would be their phenotype?

Brown EyesBrown Eyes

Steps for using the Punnett square:Steps for using the Punnett square:

B 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

So, if Miss Hemphill had children with her husband to be …what color eyes would they have?

Mr. Ellinger

Blue eyes (bb)

Miss Hemphill

Blue eyes (bb)

All of their kids would have blue eyes!

bb bb

bb bb

b b

b

b

Using a Punnett Square Clip

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

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 #1Practice Problem #1

Bb bbBb bb

Practice Problem #1Practice Problem #1

B bb

b

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

Use any letter you like.

Practice Problem #2Practice Problem #2

bb bbbb bb

Practice Problem #2Practice Problem #2

b bb

b

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 GgGg gg

Practice Problem #3Practice Problem #3

G gG

g

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 rrRr rr

Practice Problem #4Practice Problem #4

R rr

r

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

How would you solve this one?

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

XX XYXX XY

Practice Problem #5Practice Problem #5

X YX

X

Heredity by Brainpop

Heredity by Brainpop

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

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

3Which kind of trait can’t be passed from parent to child?

a)Eye color b) height c) broken arm