Describe the behavior of chromosomes through prophase I
- Chromosomes coil tighter and become visible (condense)
o Each chromosome is composed of 2 sister chromatids - Homologous chromosomes/nonsister chromatids exchange chromosomal material
Describe the behavior of chromosomes through metaphase I
Homologues are aligned @ metaphase plate side by side & are attached to microtubules from opposite poles
Describe the behavior of chromosomes through anaphase I
- Homologues are separated from each other & move to opposite poles
o Sister chromatids remain attached @ centromeres
Describe the behavior of chromosomes through telophase I
- Homologous chromosomes are separated
- New nuclear envelopes form
Describe the behavior of chromosomes through metaphase II
- Chromosomes consisting of sister chromatids are joined @ the centromere and align along metaphase plate
- Microtubules attach to kinetochores of sister chromatids
Describe the behavior of chromosomes through anaphase II
Sister chromatids are pulled to opposite poles
Describe the process of crossing over during prophase I
o Genetic recombination between NONsister chromatids (homologous chromosomes)
Homologues can exchange chromosomal material
Meiosis I is different from Meiosis II because
Homologous chromosomes separate
Meiosis II is different from Meiosis I because
Sister chromatids separate
Explain the consequence of errors in meiosis
- nondisjunction
- aneuploid gametes
nondisjunction
Failure of chromosomes to move to opposite poles during either meiotic division
Nondisjunction during meiosis I results in 4 abnormal gametes (two n+1 and two n-1)
Nondisjunction during meiosis II results in 2 normal and 2 abnormal gametes (two n gametes, one n+1 gamete, and one n-1 gamete)
aneuploid gametes
Gametes with missing or extra chromosomes
