Chapter 17

Question 1

What is the Law of Segregation?

Answer 1

Each organism has two alleles for each gene, which separate during gamete formation so each gamete gets only one allele.

This law explains how alleles are distributed to gametes.

Question 2

What is the Law of Independent Assortment?

Answer 2

Alleles for different genes assort independently of one another during gamete formation.

Traits are inherited separately if on different chromosomes.

Question 3

What is the Chromosome Theory of Inheritance?

Answer 3

Genes are located on chromosomes, and the behavior of chromosomes during meiosis explains Mendel’s laws.

This theory links genetics to the physical structure of chromosomes.

Question 4

How does the Law of Segregation relate to chromosomes?

Answer 4

It reflects the separation of homologous chromosomes during anaphase I of meiosis.

This process ensures that each gamete receives only one allele for each gene.

Question 5

How does the Law of Independent Assortment relate to chromosomes?

Answer 5

It reflects the random alignment of homologous chromosome pairs during metaphase I of meiosis.

This random alignment leads to genetic variation.

Question 6

What’s the difference between segregation and independent assortment?

Answer 6

• Segregation: one gene → alleles separate
• Independent assortment: two or more genes → alleles sort independently

These concepts describe different mechanisms of genetic inheritance.

Question 7

Define homozygous.

Answer 7

Having two identical alleles for a gene (e.g., TT or tt).

Homozygous individuals can be either dominant or recessive.

Question 8

Define heterozygous.

Answer 8

Having two different alleles for a gene (e.g., Tt).

Heterozygous individuals express the dominant trait.

Question 9

Define character.

Answer 9

A heritable feature of an organism (e.g., flower color).

Characters are the broad categories of traits.

Question 10

Define trait.

Answer 10

A variant of a character (e.g., purple or white flowers).

Traits are specific expressions of characters.

Question 11

Define allele.

Answer 11

Different versions of the same gene that produce variations in a trait.

Alleles can be dominant or recessive.

Question 12

Define dominant allele.

Answer 12

Expressed trait that masks the recessive allele in a heterozygote (uppercase letter).

Dominant alleles determine the phenotype when present.

Question 13

Define recessive allele.

Answer 13

Trait that is masked in the presence of a dominant allele (lowercase letter).

Recessive alleles only express their traits when homozygous.

Question 14

Define true breeding.

Answer 14

Organisms that always produce offspring with the same trait when self-fertilized (homozygous).

True breeding lines are essential for genetic studies.

Question 15

What is a monohybrid cross?

Answer 15

A cross examining one gene or character (e.g., Tt × Tt).

This type of cross helps to study inheritance patterns of a single trait.

Question 16

What is a dihybrid cross?

Answer 16

A cross involving two genes or characters (e.g., YyRr × YyRr).

This cross examines the inheritance of two traits simultaneously.

Question 17

What is the typical monohybrid F2 phenotypic ratio?

Answer 17

3:1 (dominant:recessive).

This ratio reflects the expected outcomes of a monohybrid cross.

Question 18

What is the typical dihybrid F2 phenotypic ratio?

Answer 18

9:3:3:1 (double dominant : dominant/recessive : recessive/dominant : double recessive).

This ratio illustrates the inheritance of two traits.

Question 19

What is a testcross?

Answer 19

A cross between an individual showing a dominant trait and a homozygous recessive individual to determine the unknown genotype.

Testcrosses are used to reveal the genotype of dominant phenotypes.

Question 20

What is a Punnett Square?

Answer 20

A diagram used to predict the genotypes and phenotypes of offspring from genetic crosses.

This tool simplifies the calculation of genetic probabilities.

Question 21

How to use a Punnett Square (steps)?

Answer 21

• Write parent genotypes
• Determine possible gametes
• Fill in the grid
• Count genotype & phenotype ratios

Following these steps helps visualize genetic crosses.

Question 22

What is incomplete dominance?

Answer 22

Neither allele is fully dominant; heterozygotes show a blended intermediate phenotype (e.g., red × white → pink).

This phenomenon results in a mix of traits.

Question 23

What is codominance?

Answer 23

Both alleles are expressed equally in the heterozygote (e.g., AB blood type).

Codominance results in distinct expression of both traits.

Question 24

What are multiple alleles?

Answer 24

A gene that has more than two possible alleles in the population (e.g., ABO blood group).

Multiple alleles increase genetic diversity within a population.

Question 25

How do **incomplete dominance** and **codominance** differ?

Answer 25

Incomplete dominance: blended phenotype. Codominance: both traits appear distinctly. ## Footnote These terms describe different patterns of inheritance.