# SAT II Biology M : Inheritance Patterns

## Example Questions

### Example Question #1 : Genetics

According to the law of independent assortment, what is the possible number of combinations that chromosomes can assort to independently in the gamete?

70,368,744,177,664

8,388,608

4,194,304

16,777,216

2,048

8,388,608

Explanation:

According to the law of independent assortment, there are 2n combinations where chromosomes can assort into different gametes. So where n is the haploid number, you get 223=8,388,608. There are 8,388,608 possible combinations of chromosomes when assorting into gametes.

### Example Question #2 : Genetics

What contributes to genetic variation during human reproduction?

Nonrandom mating

Independent assortment

All of these

Random fertilization

Crossing over

All of these

Explanation:

All three contribute to giving rise to genetic variation. Independent assortment allows for the chromosomes to assort in millions of random of combinations during fertilization. Crossing over between chromosomes produces recombinant chromosomes, or the combination of chromosomal DNA from two parents into one chromosome. Random fertilization allows aids with variation because it means any sperm can fertilize any egg. It is sometimes easy to overlook, but humans do not mate randomly. Lots of energy is put into choosing an optimal mate with whom to reproduce.

### Example Question #1 : Inheritance Patterns

Each person can have one of four possible blood types: A, B, AB, or O. Blood type A means that the "A" antigen is present on the red blood cell surface. Blood type B means that the "B" antigen is present on red blood cells' surfaces. Blood type "AB" means that both the "A" antigen and the "B" antigen are present on the red blood cells' surfaces. Blood type "O" means that no antigens are present on the red blood cells' surfaces.

A mother with blood type A and the genotype "A/O" and a father with blood type B and genotype "B/B" have a child with blood type AB. This is an example of what type of inheritance pattern?

Codominance

Incomplete dominance

Complete autosomal dominance

Autosomal recessive

Codominance

Explanation:

The child is blood type AB, meaning that the child has both the "A" antigen and the "B" antigen on his or her red blood cells. The child is able to express the products of both genes simultaneously. The A antigen was inherited from mom, and the B antigen was inherited from dad. The "A" and "B" alleles are codominant because they can both be expressed in the same person at the same time if the person inherits both alleles, as is the case in this example.

### Example Question #2 : Genetics

Each person can have one of four possible blood types: A, B, AB, or O. Blood type A means that the "A" antigen is present on the red blood cell surface. Blood type B means that the "B" antigen is present on red blood cells' surfaces. Blood type "AB" means that both the "A" antigen and the "B" antigen are present on the red blood cells' surfaces. Blood type "O" means that no antigens are present on the red blood cells' surfaces.

Someone with genotype "A/A" or "A/O" will have type A blood. Someone with genotype "B/B" or "B/O" will have type B blood. Someone with genotype "A/B" will have AB blood, and someone with genotype "O/O" will have type O blood.

Assuming that blood type is not a sex-linked trait, what is the probability that a mother with genotype "A/O" and a father with genotype "A/B" will have a child with type B blood?

Explanation:

The easiest way to solve this problem is to draw a punnet square. The genotypes of the parents are "AO" and "AB". The potential genotypes of their children are "AA", "AO", "BA", and "BO". Only genotype "BO" will produce type B blood. "BO" is one out of four results of this punnet square, so the probability of this outcome is .

### Example Question #1 : Inheritance Patterns

In a certain flower, a blue petal phenotype is dominant to a white petal phenotype. If you cross a heterozygous flower with a homozygous recessive flower, what is the probability of inheritance for the white petal phenotype?