Honors Biology Unit 5 Final Exam

Purpose of meiosis

To reduce the chromosome number from diploid to haploid and to generate genetic diversity among the producers.

How many haploid cells are produced in meiosis?

4 genetically distinct haploid cells.

Which stages of meiosis are diploid?

Prophase I and Metaphase I, whereas Anaphase I through Meiosis II are haploid.

Major events in meiosis

Crossing over and synapse occur in Prophase I; Independent Assortment occurs in Metaphase I; Nondisjunction can occur in Anaphase I and Anaphase II.

Genetic variability in meiosis

Independent assortment, crossing over/synapse, and random fertilization.

Homologous chromosomes

Paired chromosomes with identical gene sequences, one from each parent.

Non-homologous chromosomes

Chromosomes that have different genes and are not paired.

Tetrad

A group of 4 chromatids.

Chiasma

The point where homologous chromosomes are paired during crossing over.

Centromere

The region that shapes the number of chromosomes and is where sister chromatids join.

Karyotype

A visual representation of an organism’s complete set of chromosomes, including their number, size, and shape.

Nondisjunction

The failure of chromosomes to separate, occurring in Anaphase I and II.

Effects of chromosome alterations

Chromosome deletion, duplication, inversion, or translocation can disrupt normal gene function and lead to various genetic disorders.

True-breeder

A homozygous recessive individual.

Hybrid

The offspring of two different parents.

P generation

Two individuals that are mated to foresee or analyze the genotypes of their offspring.

F1 Generation

The resulting offspring from the P0 generation.

F2 Generation

The result of two F1 plants that were crossed or self-pollinated.

Difference between incomplete dominance and codominance

Incomplete dominance involves blending of alleles to create a new phenotype, whereas codominance shows both alleles present in the heterozygote.

Test-Cross

The mating between an individual of unknown genotype and a true-breeding individual.

Law of Independent Assortment

Alleles of different genes assort independently during gamete formation.

Pedigree rules for genetic disorders

A 50/50 ratio of affected men and women suggests autosomal disorders; affected males predominantly suggest X-linked disorders; a disorder not skipping generations suggests it is dominant.

Pleiotropy

When one gene influences many characteristics or symptoms.

Polygenic inheritance

A single phenotypic character results from the additive effects of two or more genes.

Linked genes

Genes that are close together on a chromosome, reducing the chance of crossing over; failure to follow Mendelian outcomes suggests linkage.