Download Mendelian Genetics Coin Toss Lab

Mendelian Genetics Coin Toss Lab
PRE-LAB DISCUSSION:
In heredity, we are concerned with the occurrence, every time an egg is fertilized, of the
probability that a particular gene or chromosome will be passed on through the egg, or
through the sperm, to the offspring. As you know, genes and chromosomes are present in
pairs in each individual, and segregate as they go into the gametes (egg and sperm).
There are two possible genes that the egg or sperm might obtain from each pair, but it
actually receives only one of them. If the probability of getting either one is equal, this
probability can be expressed as 1/2, like the probability of getting heads or tails when you
flip a penny. But one cannot examine the genes in a sperm or egg. One must wait until
fertilization has occurred and a new individual has been produced, and some
characteristic controlled by the genes has had time to develop. Thus, we are faced with
the probability that it will go into the sperm, together with the probability that these will
combine at fertilization. The following model will help you to see this.
PURPOSE:
To determine the genotypes and phenotypes of an offspring based on two parents.
PROCEDURE:
Record all your work on attached data sheet!
1. Determine your baby’s gender. Remember, this is determined entirely by the
father. The mother always contributes an X chromosome to the child.
Heads= X chromosome, so the child is a girl (X, X)
Tails= Y chromosome, so the child is a boy (X, Y)
2. Name the child
3. Determine the child’s facial characteristics by having each parent flip a coin.
Heads will equal the dominant trail while Tails will equal the recessive trait.
Record your child’s genotype in the chart and than draw your child.
Skin Color: To determine the color or skin or any other trait controlled by more than 1
gene, you will to flip the coin for each gene pair. Since skin color is determined by three
gene pairs, each parent will flip their coin three times.
6 dominant alleles= black
2 dominant alleles= light brown
5 dominant alleles= very dark brown 1 dominant allele= light tan
4 dominant alleles= dark brown
0 dominant allele= white
3 dominant alleles= medium brown
Hair Color: Hair color is determined by four pairs of genes. Each parent flips their coin
4 times.
8 dominant=black
3 dominant= brown
7 dominant= very dark brown
2 dominant= blond
6 dominant= dark brown
1 dominant= light blonde
5 dominant= brown
0 dominant= white
4 dominant= light brown
Eye color: Is determined by two pairs of genes so each parent flips their coin and matches
the genotype to the chart below.
PPQQ- black
PpQq-Brown
ppQQ-green
PPQq- dark brown
PPqq-violet
ppQq- dark blue
PpQQ- brown with green Ppqq-gray blue
ppqq- light blue
Genotype
Face Shape
Hair Type
Widow's Peak
Eye Shape
Eye Slantedness
Eye Lashes
Eyebrow Length
Lip Thickness
Dimples
Nose Size
Earlobe Attachment
Hair Ears
Freckles
Skin Color
Hair Color
Eye Color
Draw your child on the next page.
Phenotype
Post-Lab Questions
1. What is a genotype of a homozygous recessive trait?
2. What is a genotype of a homozygous dominant trait?
3. What is a genotype of a heterozygous trait?
4. Can two parents with round eyes have a child with almond shaped eyes? Explain.
5. If two parents with almond eyes, had a child with round eyes, what must the
genotypes of the parents be?
6. What is the difference between genotypes and phenotypes? Provide an example.
7. Why do we have two alleles per trait, instead of just one?
8. Explain why your there is greater variation in skin pigment among siblings, versus a
common trait, such as face shape with only two alleles.