HAPPY THURSDAY

BELL WORK:In 33 words, explain how a girl with blue eyes could have two parents with brown

eyes.

**Turn in your HW – The 2 handouts**

Standard: B6F - Predict possible outcomes of genetic combinations

such as monohybrid crosses.

Essential Question: How can I predict genetic outcomes?

Genetics is the scientific study

of heredity.

Gregor Mendel is the Austrian monk who was

particularly important to

understanding biological

inheritance.

A trait is a specific characteristic that varies from one individual to another.

From his experiments, Mendel concluded that biological inheritance is

determined by factors that are passed from one

generation to the next.

The chemical factors that determine traits are called

genes.

The different forms of a gene are called alleles.

When mating two organisms, the original pair of organisms is known as the P

generation.

The “P” in P generation stands for parental.

The offspring of the P generation is the F1 generation.

“F1” in F1 generation stands for first filial.

Filius and filia are the Latin words for son and daughter.

The offspring of crosses between parents with different traits are

called hybrids.

The principle of dominance states that

some alleles are dominant while others

are recessive.

The dominant allele will always be expressed.

A capital letter is used to represent a dominant

allele.

Y = Dominanty = Recessive

When Mendel crossed the F1 generation with itself,

one fourth of the F2 plants showed the trait controlled

by the recessive allele.

The recessive allele will only be expressed when the

dominant allele for the trait is not present.

A lower case letter is used to represent a recessive

allele.

Y = Dominanty = Recessive

The way in which alleles separate during meiosis does not follow a pattern. It is completely random.

The results of genetic crosses can be

explained by the principles of probability.

Probability is the likelihood that a

particular event will occur.

Probabilities predict the average outcome of a large number of events.

Probabilities cannot predict the exact outcome of an individual event.

In probability, sample size eventually determines how close resulting numbers get to the expected values.

In probability, past outcomes do not affect future ones.

The gene combinations that might result from a genetic cross can be determined by

drawing a diagram known as a Punnett square.

The types of gametes produced by each F1 parent are shown

along the top and left sides of a Punnett square.

The possible gene combinations for the F2

offspring appear in the 4 boxes that make up the square.

The letters in the Punnett square

represent alleles.

Punnett squares are used to predict and

compare the genetic variations

that will result from a cross.

Organisms that have two of

the same alleles for a trait are homozygous

Organisms that have two

different alleles for a trait are heterozygous.

Homozygous organisms are true-breeding/purebred for a trait.

Heterozygous organisms are hybrid for a trait.

BB Bb bb

BB Bb bb

A phenotype is an organism’s physical

characteristics.

A genotype is an organism’s genetic

makeup.

Two organisms can have the same phenotype but

different genotypes.

BB Bb bb

Brown Eyes vs Blue eyes

Mendel’s assumptions

about segregation predicted a

phenotypic ratio of 3:1.

Mendel’s assumptions

about segregation predicted a

genotypic ratio of 1:2:1.

The fact that genes that segregate independently

do not influence each other’s inheritance is

known as independent assortment.

The principle of independent assortment

states that genes for different traits can

segregate independently during the formation of

gametes.

Independent assortment helps account for the many

genetic variations observed in many

organisms.

Punnett Square Steps1st Step = Identify what letter is being

usedWhat would be the possible outcomes for the

offspring of a cross between pink flower (PP) and a white flower (pp)?

“P” and “p”

Punnett Square Steps2nd Step = Assign the trait for each letter.

What would be the possible outcomes for the offspring of a cross between pink flower (PP) and a white flower (pp)?

P= PINK p = WHITE

Punnett Square Steps3RD Step = Match what letters are being

used for each parent/gender.What would be the possible outcomes for the

offspring of a cross between pink flower (PP) and a white flower (pp)?

= PP = ppMOMDAD

Let’s sum it up…..1st = Identify what letters are being used.

2nd = Assign the trait for each letter.

3rd = Match what letters are being used for each parent/gender.

4th = Now fill in your Punnett Square.

Punnett Square practice…1. What would be the possible outcomes for the offspring of a cross between pink flower (PP) and a white flower (pp)?

P P

p

p

Pp Pp

Pp Pp

P = Pink p = White

DAD = PPMOM = pp

**When using the letters like “P and p” OR “C and c”, draw the lowercase letter in cursive or just make sure you make them look different. Otherwise, you might

confuse the dominant for the recessive **

2. Long fingers are dominant (F) to short fingers (f). Complete the Punnett square for a homozygous

recessive mom and a heterozygous dominant dad.

F f

f

f

Ff ff

Ff ff

F = Longf = Short

DAD = FfMOM = ff

3. In a plant, long stems are dominant (L) to short stems (l). If a homozygous dominant flower and a homozygous recessive

plant are crossed, what would be the phenotypic ratio of their offspring?

L L

l

l

Ll Ll

Ll Ll

L = LongL = Short

DAD = LLMOM = ll

4. Straight hair (C) is dominant to curly hair (c). What would be the probability that a child would have curly

hair if both parents are heterozygous dominant?

C c

C

c

CC Cc

Cc cc

C = Straightc = Curly

DAD = CcMOM = Cc

5. Having a hitchhiker's thumb is a dominant trait (T). If a woman with a straight thumb has a child with a man who is heterozygous for the trait, what are the chances

their child will have a hitchhiker's thumb?

T t

t

t

Tt tt

Tt tt

T = Hitchhikert = Straight

DAD = TtMOM = tt

6. What would the phenotypic and genotypic ratios be for two purple (Pp) flowers that were bred together?

P p

P

p

PP Pp

Pp pp

P = Purplep = White

DAD = PpMOM = Pp

Can you identify your own genotypes and phenotypes?

Hairline:

Widow’s peak is dominant tostraight hairline

Eye Shape:

Almond eyes is dominant to round eyes

Tongue Rolling:

CAN roll the tongueis dominant to cannot

Eyelash Length:

Long eyelashes is dominant toshort eyelashes

Lip Thickness:

Thick lipsare dominant to thin lips

Hitchhiker’s Thumb:

Hitchhiker’s thumb is dominant tostraight thumb