AP Bio - Unit 5: Heredity

What is a gene?

A DNA segment that codes for a specific protein influencing traits.

What are alleles?

Different forms of the same gene (e.g., purple vs. white flower color).

What are chromosomes?

DNA protein structures carrying genes; exist in homologous pairs in diploid cells.

Who developed the Chromosomal Theory?

Walter Sutton and Theodor Boveri.

What does the Chromosomal Theory state?

Genes are located on chromosomes, and inheritance mirrors chromosome behavior during meiosis.

What happens during nondisjunction?

Chromosomes fail to separate properly, causing disorders like Down, Turner, or Klinefelter Syndrome.

What’s an example of a single gene disorder?

Cystic Fibrosis (CTFR gene) or Sickle Cell Disease (HBB gene)

What’s the purpose of meiosis?

To create four haploid gametes and introduce genetic variation.

How many divisions occur in meiosis?

Two (Meiosis I and Meiosis II).

What happens in Prophase I?

Homologous chromosomes pair and exchange DNA (crossing over).

What is independent assortment?

Random alignment of chromosome pairs during Metaphase I; increases variation.

What are the final products of meiosis?

Four unique haploid cells.

How does meiosis generate variation?

Through segregation, independent assortment, crossing over, and random fertilization.

Formula for possible gamete combinations?

2^n (n = number of chromosome pairs).

Who discovered the basic laws of inheritance?

Gregor Mendel.

What is the Law of Segregation?

Each gamete receives only one allele per gene.

What is the Law of Independent Assortment?

Genes for different traits assort independently (unless linked).

What’s the monohybrid phenotypic ratio?

3:1.

What’s the dihybrid phenotypic ratio?

9:3:3:1.

What is simple dominance?

One dominant allele masks a recessive one.

What is incomplete dominance?

The heterozygous phenotype is a blend (red + white = pink).

What is co-dominance?

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

What are polygenic traits?

Traits controlled by multiple genes (e.g., height, skin color).

What are sex linked traits?

Traits on sex chromosomes, often seen in males (e.g., color blindness).

What is gene linkage?

Genes close together on the same chromosome inherited together.

What is non-nuclear inheritance?

Traits passed via mitochondrial or chloroplast DNA (material line)

What is phenotypic plasticity?

One genotype producing multiple phenotypes under different environments.

What factors influence plasticity?

Abiotic (temperature, light) and biotic (predators, competition) factors.

Give an example of plasticity.

Temperature determining reptile sex; dandelions changing leaf shape by crowding.

How does the environment affect gene expression?

It turns genes “on” or “off” via epigenetic changes or hormones.

Why is phenotypic plasticity important evolutionarily?

It boosts survival and reproduction during environmental change.

How is plasticity relevant to conservation?

It predicts how species respond to rapid changes like climate shifts.