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Lani Chung

Mr. Nakamura

Biology Period 2B

14 April 2012

The Genetics of Parenthood Analysis Questions

1. What percentages does each parent contribute to a child’s genotype?

50%

2. Explain how/what part of your procedures represent the process of meiosis.

The flipping of the coins is the part of the procedure that represent the process of mitosis because

when organisms produce gametes, genes are separated and there is a 50:50 chance whether any

one particular egg/sperm contains a certain allele which is a bit like tossing a coin for heads or

tails.

3. Using examples from this activity, explain your understanding of the following inheritance

patterns:

a) Dominant: If an allele is dominant, it will be expressed in the phenotype whether it is

heterozygous or homozygous. For example in the case of face shape, because the mother

gave a dominant allele coding for round face shape while the father gave a recessive

allele coding for square face shape, the child ended up with a round face.

b) Recessive: If an allele is recessive, it will only be expressed in the phenotype if it is

homozygous, otherwise it will be unexpressed due to a dominant allele if it is in

heterozygous form. For example, in the case of cleft chin, both the mother and the father

gave recessive alleles coding for an absent cleft chin which caused the absent cleft chin to

be expressed in the child’s phenotype.

c) Incomplete Dominance: When a heterozygous allele pair expresses a mixture of both

the dominant and recessive alleles, thus creating an intermediate trait in the phenotype.

For example in the case of red tints, because the mother gave a L1 allele coding for dark

red tints while the father gave a L2 allele coding for no red tints, the phenotype created an

intermediate expression of light red hair tinting.

d) Polygenic: When a phenotype is determined by the combination of several gene pairs.

For example in the case of skin color, a coin had to be flipped three times for each of the

three gene pairs that are involved in determining the skin color of the offspring. The skin

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color that was determined turned out to be a very dark brown skin phenotype which is a

result of alleles from multiple genes.

e) Epistasis: When a trait is supposed to be expressed but is covered up by another trait

which masks the expression of that particular phenotype. For example, in the case of hair

color and red tints, although the red tints were supposed to be lightly expressed, the

brown hair mixed with blond caused it to be very difficult to see.

4. Compare the predicted phenotype ratio (punnett squares) to the actual ratio (class data) for

the following traits:

a) Trait #2 (Chin Size): The predicted phenotype ratio for very prominent chin to less

prominent chin was 3:1. However, the actual ratio turned out to be 7:4 which is not

equivalent to the predicted ratio.

b) Trait #8 (Hair Type): The predicted phenotype ratio for curly hair to wavy hair to

straight hair was 1:2:1. However the actual ratio turned out to be 2:6:5 which is not

equivalent to the predicted ratio.

5. All the children had 2 heterozygous parents. Use the law of independent assortment to explain

why there were no identical twins produced.

No identical twins were produced because of how slim the chances are for two offspring to end

up having all the same traits as each other. This is due to the way you have to flip the coin for

each trait which is similar to the law of independent assortment which states that alleles for a

trait randomly separate when gametes are formed. These allele pairs are then randomly united at

fertilization. What this basically means is that genes are determined separately instead of

together. Just because one offspring receives one particular gene, it doesn’t necessarily mean that

they will also receive any other particular gene.