Monohybrid Inheritance

Question 1

What is a gene?

Answer 1

A gene is a section of DNA that codes for a specific protein, determining a characteristic.

Question 2

What is an allele?

Answer 2

An allele is a variant form of a gene that can produce different traits or characteristics.

Question 3

How are genes and alleles related?

Answer 3

Genes are the instructions for traits, and alleles are different versions of those instructions that determine the specific traits.

Question 4

What does “homozygous” mean?

Answer 4

Homozygous means having two identical alleles for a particular gene (e.g., AA or aa).

Question 5

What does “heterozygous” mean?

Answer 5

Heterozygous means having two different alleles for a particular gene (e.g., Aa).

Question 6

Give an example of a homozygous genotype.

Answer 6

AA or aa

Question 7

Give an example of a heterozygous genotype.

Answer 7

Aa

Question 8

What is the genotype?

Answer 8

The genotype is the genetic makeup of an organism, represented by the alleles it inherits (e.g., AA, Aa, or aa).

Question 9

What is the phenotype?

Answer 9

The phenotype is the physical expression or characteristics of an organism, determined by its genotype (e.g., having blue eyes or being tall).

Question 10

How do genotype and phenotype differ?

Answer 10

The genotype is the genetic code (alleles), while the phenotype is the observable trait that results from the genotype.

Question 11

What is a Punnett square used for?

Answer 11

A Punnett square is used to predict the possible genetic outcomes of a cross between two parents.

Question 12

How do you set up a Punnett square?

Answer 12

Write the alleles of each parent along the top and left side of the square, then fill in the boxes with all possible allele combinations.

Question 13

What does the term “dominant” mean in inheritance?

Answer 13

A dominant allele is one that expresses its trait even if only one copy is present (e.g., “A” for a dominant allele).

Question 14

What does the term “recessive” mean in inheritance?

Answer 14

A recessive allele only expresses its trait if two copies are present (e.g., “aa”).

Question 15

If a homozygous dominant plant (AA) is crossed with a heterozygous plant (Aa), what are the possible genotypes of the offspring?

Answer 15

The offspring can be either AA or Aa.

Question 16

If a homozygous recessive organism (aa) is crossed with a heterozygous organism (Aa), what are the possible genotypes of the offspring?

Answer 16

The offspring can be either Aa or aa.

Question 17

In a cross between a homozygous dominant (AA) and a homozygous recessive (aa), what is the probability of offspring with the recessive phenotype?

Answer 17

The probability is 0%, because all offspring will be heterozygous (Aa) and express the dominant phenotype.

Question 18

If you cross two heterozygous organisms (Aa x Aa), what is the probability of having a homozygous dominant offspring (AA)?

Answer 18

The probability is 25%, as there is one AA outcome in a Punnett square with four possible combinations (AA, Aa, Aa, aa).

Question 19

What does “dominant allele” mean in monohybrid inheritance?

Answer 19

A dominant allele is one that will express its trait even if only one copy is present (e.g., A for dominant).

Question 20

What does “recessive allele” mean in monohybrid inheritance?

Answer 20

A recessive allele only expresses its trait if both alleles are recessive (e.g., aa).