AP Biology Unit 2: Chapter 13 - Meiosis

Locus

Location where a specific gene is located on a chromosome

Tetrads

Structure formed by two homologous chromosomes (made up of two sister chromatids each) that come together during Prophase I

Sister chromatid

Identical copies of a chromosome that are created during the S phase (DNA replication) of Interphase I

Recombinant chromosomes

Chromosomes that result from homologous chromosomes “crossing over” during Prophase I

S phase

Happens during Interphase I; when DNA replication occurs creating sister chromatids

Gametes

Sex cells; sperm in males and eggs in females

Parental chromosomes

Chromosomes in gametes that didn’t “cross over”

When are parental chromosomes identified?

After meiosis II

Chromosomes vs. DNA

Chromosomes are made up of tightly packed DNA; DNA is the molecule that stores genetic info

Independent assortment

During Anaphase I, tetrads separate independently of one another (the way one tetrad separates doesn’t affect the others) and it’s random which chromosome goes to each gamete

Haploid

A cell containing one set of chromosomes (23 for ova/sperm); “n”

Diploid

A cell containing two sets of chromosomes (46 for humans); 2n

Random Alignment

The way tetrads align at the metaphase plate during Metaphase I is random

Who came up w/ Random Alignment?

Mendel