AP Bio Unit 5

What was the focus of Mendel’s work with pea plants?

To understand heredity.

Why did Mendel choose pea plants for his experiments?

They have a short generation time, many traits with two distinct forms, and allow controlled breeding.

What is a true-breeding plant?

A plant that produces offspring identical to itself when self-pollinated.

What is a gene?

A unit of heredity; a segment of DNA coding for a trait.

Define allele.

Different versions of a gene.

What is the difference between homozygous and heterozygous?

Homozygous has two identical alleles (AA or aa), while heterozygous has two different alleles (Aa).

What is the meaning of genotype?

The genetic makeup of an organism (AA, Aa, or aa).

What does phenotype refer to?

The physical expression of the gene.

State Mendel's Law of Segregation.

Two alleles for a gene separate during gamete formation, so each gamete carries only one allele.

What is demonstrated using a monohybrid cross?

The inheritance of one trait.

What phenotype ratio is displayed in the F2 generation when crossing purple (P) and white (p) flowers?

A 3:1 ratio of purple to white.

What is Mendel's Law of Independent Assortment?

Genes for different traits segregate independently during gamete formation.

How does a dihybrid cross demonstrate inheritance?

By examining two traits at once, producing a 9:3:3:1 ratio in the F2 generation.

What is complete dominance?

When one allele completely masks the expression of another.

What is incomplete dominance?

When the heterozygous phenotype is a blend of both alleles.

What is codominance?

When both alleles are fully expressed in a heterozygous individual.

What is pleiotropy?

When one gene influences multiple traits.

What does epistasis refer to in genetics?

When one gene affects the expression of another gene.

Explain polygenic inheritance.

When multiple genes contribute to a single trait, showing continuous variation.

What is the impact of environment on phenotypes?

The environment can affect gene expression.

What does the Multiplication Rule in genetics state?

The probability of independent events occurring together is the product of their probabilities.

What is the probability described by the Addition Rule?

The probability of either of two mutually exclusive events occurring is the sum of their probabilities.

What is the expected phenotypic ratio in a monohybrid cross?

3:1 ratio.

What ratio do you expect in a dihybrid cross?

9:3:3:1 ratio.

What is the expected ratio for incomplete dominance?

1:2:1 ratio.

What is a test cross expected to show?

1:1 ratio.

What is a common pattern of inheritance for recessive disorders in humans?

They require two copies of the allele (aa) to express the disorder.

What is characterized by an autosomal pattern of inheritance?

The inheritance of genes found on autosomes (non-sex chromosomes), which can be dominant or recessive.

What is true about dominant inheritance?

Only one copy of the dominant allele is needed for the trait to be expressed and does not skip generations.

Examples of dominant inheritance disorders include what?

Huntington’s, Marfan Syndrome, Dwarfism.

What is required for a recessive inheritance trait to be expressed?

Two copies of a recessive allele are needed (aa).

How can recessive traits skip generations?

If two carriers (Aa) have children, the trait can skip generations.

What are the characteristics of autosomal dominant inheritance in pedigrees?

Appears in every generation, affecting both males and females equally, and affected individuals have at least one affected parent.

In autosomal recessive inheritance, how can affected individuals appear?

They may have unaffected carrier parents, and this trait can skip generations.

What is sex-linked inheritance?

It refers to genes located on a sex chromosome.

Explain why X-linked recessive traits are more common in males.

Males have only one X chromosome, so one recessive allele will express the trait.

How do affected males inherit X-linked traits?

They inherit the trait from their mother, who may be a carrier.

What is characteristic of X-linked dominant inheritance?

Only one copy of the dominant allele is needed to express the trait, affecting both males and females, but more commonly females.