Name a food that does not have DNA.

If you were talking to your friend on a cell phone how would you describe this person?

If you were talking to your friend on a cell phone how would you describe this person?

•Widow’s peak• Red Hair•Cleft Chin•Freckles•Detached earlobes•Female•Age (20’s)

How would you describe this person? Write down 10 things.

How would you describe this person? Write down 10 things.

•Male•Brown Hair•Blue eyes•Detached Earlobes•Cleft Chin•No Widow’s Peak•Age (20’s)

Phenotype:

In Heredity, when we are talking about a measurable and observable characteristic of an organism, we refer to it as a Phenotype.

Circle the words on your list that can be measured or observed. Those are phenotypes.

Examples of characteristics that can not be measured would include: cute, pretty, handsome, weird or talented.

Gregor Mendel was curious about characteristics and wondered if he could predict what characteristics an offspring would have by looking at the parents. (See biography handout to learn more about his life)

Mendel observed and recorded the characteristics of pea plants that he grew for a number of years. He started to see a pattern.

The pea plants that grew tall for many generations, he called “purebred” tall. The purebred tall pea plant always had tall offsprings.

T = Tall T T

T TT TT

T TT TT

t = short t t

t tt tt

t tt tt

The short pea plants always had short offsprings.

And when Mendel combined the pure tall with the short peas, all the offspring were tall.

Tt = Tall T T

t Tt Tt

t Tt Tt

So Mendel wondered what would happen if these offspring were combined.

Expecting to find all the offspring to be tall like their parents, he discovered some of the offspring were short.

In fact, about a forth were short. He created a theory that each parent passed two factors to each offspring. And that by “crossing” these factors one could predict the probability of the offspring having a certain characteristic. The crossing tool used to calculate the odds of an offspring’s characteristic is called the Punnett Square.

Tt = Tall T t

T(tall)

TT(tall)

Tt

t(tall)

Tt (short)

tt

Mendel called the pea plants that had a tall factor and a short factor a hybrid. Pea plants that were “pure” tall or short were called homozygous.

Mendel called the characteristic that was hidden, the “recessive” factor. And the characteristic that was observed, the “dominant” factor.

What is an offspring called if it has a dominant and a recessive gene?

VOCABULARY sexual reproduction p. 102gene p. 102heredity p. 102allele p. 103phenotype p. 106genotype p. 106dominant p. 107recessive p. 107

During sexual reproduction a cell containing genetic information from the mother and a cell containing genetic information from the father combine into a completely new cell, which becomes the offspring.

A gene is a unit of heredity that occupies a specific location on a chromosome and codes for a particular product.

Heredity is the passing of genes from parents to offspring.

The various forms of the same gene are called alleles (uh-LEELZ).

An organism's phenotype describes the actual characteristics that can be observed.

Genotype is the name for the genes an organism has.

A dominant allele is one that is expressed in the phenotype even if only one copy is present in the genotype—that is, even if the other allele is an alternative form.

A recessive allele is one that is expressed in the phenotype only when two copies of it are present on the homologs.

How would you show the relationship between a hybrid and its purebred parents using a Venn diagram?

1. Explain the difference between acquired and inherited traits.

2. Describe the conclusions that Mendel drew from his experiments with pea plants.

3. What type of alleles are expressed only if two identical copies exist on the homologs of the offspring?

4. Compare and Contrast  What is the difference between a genotype and a phenotype?

5. Analyze  Explain why a person with an allele for a particular trait may not have a phenotype that shows the trait.6. Apply  In guinea pigs, the allele for black fur is dominant over the allele for brown fur. If you had two parent guinea pigs, each with brown fur, what color fur might the offspring have, and why?

VOCABULARY Punnett square p. 110ratio p. 112probability p. 112percentage p. 112

A Punnett square illustrates how the parents' alleles might combine in offspring.

A ratio compares, or shows the relationship between, two quantities. A ratio is usually written 4:4 and read as “four to four.” This can be interpreted as “four out of four.” The Punnett square shows that four out of four offspring will express the dominant gene for regular height.

A ratio compares, or shows the relationship between, two quantities. A ratio is usually written 4:4 and read as “four to four.” This can be interpreted as “four out of four.” The Punnett square shows that four out of four offspring will express the dominant gene for regular height.

Punnett squares and the ratios they show express probability. Probability is the likelihood, or chance, of a specific outcome in relation to the total number of possible outcomes. The ratios derived from a Punnett square tell you the probability that any one offspring will get certain genes and express a certain trait.

Another way of expressing probability is as a percentage. A percentage is a ratio that compares a number to 100.

Homozygous: Both alleles are dominant or recessive. This would be a characteristic of a purebred. An example would be TT, tt, SS, ss, LL or ll.

Heterozygous: The alleles are different. This would be a hybrid. An example would be Tt, Ss or Ll.

1. Explain how Punnett squares predict the outcomes of heredity.

2. How are ratio and percentages related?

3. How can you find a percentage chance from a Punnett square?

4. Predict  Mendel studied the colors of seeds in his experiments with pea plants. Let G stand for green and g stand for yellow. Green is dominant. Make a Punnett square for a cross between two Gg plants. Find the percentage chance for each outcome.

5. Apply  In pea plants, the allele for smooth peas is dominant over the allele for wrinkled peas. Create a Punnett square and calculate the probability that two smooth-pea plants will have an offspring with wrinkled peas if each parent has one smooth and one wrinkled allele.

Identify the following alleles as Homozygous (HO) or Heterozygous (HE):

LL, Ss, EE, ee, Ee, Ll, SS, ss

Mendel’s Law of Dominance: When there is a dominant and recessive allele, the dominant one will be expressed and the recessive one will be hidden.

Example: B is dominant for eye color brown. b is recessive for eye color blue. A person with genotype Bb for eye color will have brown eyes.

Mendel’s Law of Segregation: Allele pairs separate during gamete formation. One of those alleles is passed down randomly to the offspring.

Example: Father has BB genotype for eye color. Mother has Bb genotype for eye color. Father will pass down one B, Mother will pass down either a B or b.

How is it possible for two brown eyed parents to have 3 blue eyed offsprings if brown is dominant over blue for eyes?

ABO blood types are inherited through genes and they do not change as a result of environmental influences during life.  An individual's ABO type is determined by the inheritance of 1 of 3 alleles (A, B, or O) from each parent.  The possible outcomes are shown below:

Parent Alleles A B O

A AA(A)

AB(AB)

AO(A)

B AB(AB)

BB(B)

BO(B)

O AO(A)

BO(B)

OO(O)

GENOTYPE

(PHENOTYPE)

GENOTYPE

GENOTYPE

(PHENOTYPE)

(PHENOTYPE)

Both A and B alleles are dominant over O.  As a result, individuals who have an AO genotype will have an A phenotype.  People who are type O have OO genotypes.  In other words, they inherited a recessive O allele from both parents. The A and B alleles are codominant.  Therefore, if an A is inherited from one parent and a B from the other, the phenotype will be AB.   Agglutination tests will show that these individuals have the characteristics of both type A and type B blood.

Parent Alleles

A B O

A AA(A)

AB(AB)

AO(A)

B AB(AB)

BB(B)

BO(B)

O AO(A)

BO(B)

OO(O)

What is codominance?

Sickle Cell Anemia