Need a little help with the lab?

Alleles�are�corresponding�pairs�of�genes�located�on�an�individual’s�chromosomes.�Together,�alleles�

determine�the�genotype�of�an�individual.�

The�Genotype�describes�the�specific�genetic�make�up�of�an�individual.��A�

person’s�genotype�tells�us�exactly�what�Alleles/genes�they�have.��You�cannot�

see�someone’s�genotype.

Phenotypes�are�the�observable�traits�of�an�individual�which�the�individual’s�genes�(alleles)�have�expressed.

Genotype Phenotype

� A rich couple that died in a traffic accident 10 days ago has one heir to their fortune.

� Five people claim to be the lost heir of the rich couple and they have filed a claim to the

family’s lawyer to receive their rightful inheritance.

� By using genetic evidence and looking at the parent’s Phenotypes, you will help the

family lawyer to determine which individual is the rightful heir.

The Claimants

FirstFirst, let’s look at their , let’s look at their earlobesearlobes. .

Having Having attached or detached earlobes is a trait you inherit from your parents. In attached or detached earlobes is a trait you inherit from your parents. In

this example we are using an Upper case this example we are using an Upper case AA to represent the Dominant Gene and a to represent the Dominant Gene and a

lower case lower case aa to represent the Recessive Gene. to represent the Recessive Gene.

Read the information below and see if you can answer these questions. Read the information below and see if you can answer these questions.

1. Do the parents have attached or detached earlobes?1. Do the parents have attached or detached earlobes?

2. What about the claimants? Attached or detached earlobes?2. What about the claimants? Attached or detached earlobes?

3. If you have detached earlobes, what possible genotypes can you have?3. If you have detached earlobes, what possible genotypes can you have?

4. If you have attached earlobes, what possible genotypes can you have?4. If you have attached earlobes, what possible genotypes can you have?

Both parents have Attached earlobes. Since we know that having attached earlobes is Both parents have Attached earlobes. Since we know that having attached earlobes is

a Recessive trait we can determine that the parents can only have the recessive genes a Recessive trait we can determine that the parents can only have the recessive genes

for this trait. Therefore, the only possible genotype that the parents can have is for this trait. Therefore, the only possible genotype that the parents can have is aaaa. .

If If both parents have the recessive trait then they can only pass on a Lower case both parents have the recessive trait then they can only pass on a Lower case a a

(recessive gene)(recessive gene) to their offspring. Because we know this information, it will be easy to to their offspring. Because we know this information, it will be easy to

rule out one or more claimants by simply looking at their earlobes. If a claimant has rule out one or more claimants by simply looking at their earlobes. If a claimant has

DETACHED Earlobes, they can’t be the offspring of this couple. If a claimant has DETACHED Earlobes, they can’t be the offspring of this couple. If a claimant has

DETACHED earlobes, then they have at least one Dominant gene or Uppercase DETACHED earlobes, then they have at least one Dominant gene or Uppercase A A in in

their Genotype.their Genotype.

aa

aa

aaaaaaaa Aa or AA

a a

Now let’s look at another phenotype, Dimples. Having Dimples is a Dominant Trait.

Look over the information below and see if you can answer the following questions

1. If an individual has dimples, what is their possible Genotype?

(remember, these are letters and you can have more than one possible

genotype)

1. Do the parents have dimples or not? What is there genotype?

2. Can you eliminate any claimants based on this phenotype (dimples or no

dimples?

This is a tough one. Let’s take a closer look

Both the parents have Dimples. This means that they have the Dominant

Trait. This also means that they must have at least one Dominant Gene

in their Genotype. Both Mom and Dad could have a DD or a Dd as their

Genotype. What does this mean for the offspring? Is it possible for these

Parents to have offspring with out dimples? The answer is Yes.

For example if both Mom and Dad have a Genotype of Dd then it is possible

for them to pass on the recessive traits. A Lower case d can come from

Mom and a Lower case d can come from the dad which would produce an

Offspring WITHOUT dimples (dd). Cool huh?

You are doing great! Keep it up! We have a few more phenotypes to look at.

Remember the Widow’s peak?

Take a look at the info below and see if you can answer the following questions.

1. Is having a Widow’s peak a Dominant or Recessive trait?

2. If you have a Widow’s peak, what are your possible Genotypes?

3. If you don’t have a Widow’s peak, what is your possible Genotype?

4. Can you eliminate any claimants based on this Phenotype?

Last Phenotype: Blood Types A, B, AB or O This is a tricky one! Last Phenotype: Blood Types A, B, AB or O This is a tricky one!

For blood types we do not worry about Uppercase or Lowercase letters.

A and B are the Dominant genes for blood type and O is considered the

recessive gene. A and B can be co-dominant.

For example: If a mom has type A blood and the father has type 0 blood then the

offspring of this couple with have type A blood because the A from the mom is

dominant over the dad’s recessive O gene.

Mom has

Blood type

Dad has

Blood type

O

A + O = O

Blood type

AGenotype AA

OGenotype OO

Son gets A from mom

and O from Dad.

A is Dominant so Son

has blood type A

Son’s Genotype is AO

A and B can be co-dominant.

If a mom had type A blood and the dad had type B blood then the

offspring of this couple could have type AB blood because both A and

B are dominant genes and they form a sort of team so that both A and

B are present. They co-dominate.

A + B = AB

Mom has Dad hasMom has

Blood type

A

Genotype AO

Dad has

Blood type

B

Genotype BO

Son get’s A from mom and B from Dad.

Both A and B are Dominant traits so son

has type AB blood.

Blood type:

Now that you know a little bit more about what Alleles determine an individual’s

blood type you should be able to eliminate another claimant based on their blood

type. Take a look at the Mother’s blood type and Father’s Blood type. The Father

is AB and the mother is O. Which one of the 3 claimants below can you eliminate

as the heir?

� The DNA test is final test to determine the true heir to the fortune.

When DNA from the offspring is compared with the DNA of the

Parents, specific chromosomes are compared. If certain

chromosomes match up then there is a very high probability that

the individuals are related.