10 2 Meiosis Diploid Haploid Cells Chromosomes in
- Slides: 14
10. 2 Meiosis
Diploid & Haploid Cells • Chromosomes in body cells occur in pairs. • Diploid – a cell with two of each kind of chromosome (2 N) • Gametes have single chromosomes. • Haploid – a cell with one of each kind of chromosome (N)
Homologous Chromosomes • Paired chromosomes with genes for the same traits are called homologous. • Genes are arranged in the same order on homologous chromosomes.
Why Meiosis? • Human somatic cells (body cells) are diploid. • Gametes (sperm and egg) are haploid • Meiosis – a type of cell division that produces four gametes, each with half the number of chromosomes as a body cell.
Meiosis • Meiosis occurs in two separate divisions, meiosis I and meiosis II. • Meiosis starts with one 2 N cell and ends with four N cells. • Meiosis is necessary for sexual reproduction.
Meiosis cont.
Whiteboards • • What are homologous chromosomes? What does diploid mean? What does haploid mean? What is the difference between gametes and somatic cells? • What would happen if gametes were diploid instead of haploid?
Meiosis I • Crossing Over – nonsister chromatids of homologous chromosomes exchange genetic material. • Homologous chromosomes are separated into two new cells.
Meiosis II • Sister chromatids are separated • Results in four cells, each with one copy of each chromosome.
Meiosis Provides Variation • Meiosis makes cells that are not identical. • Meiosis results in a variety of different gametes. • Gametes are randomly fertilized, producing very large numbers of possible unique offspring. • Crossing over in Meiosis I adds more variation.
Mistakes in Meiosis • Nondisjunction – failure of homologous chromosomes to separate. • Results in gametes that are missing chromosomes or that have extra chromosomes.
Mistakes in Meiosis cont. • Trisomy – organism has three chromosomes instead of a pair.
Mistakes in Meiosis cont. • Monosomy – one chromosome instead of a pair. • Triploidy – three copies of ALL chromosomes, resulting from complete nondisjunction.
Whiteboards • What is crossing over? • How does crossing over generate variation? • At the end of Meiosis how many cells are produced, and are they identical or different? • What is non disjunction?
- Diploid to haploid meiosis
- Homologous chromosome vs sister chromatid
- Two haploid cells
- Diploid vs haploid
- Primary oocyte haploid or diploid
- Crossing-over occurs during
- Introduction of embryology
- Is mitosis asexual
- Haploid vs diploid venn diagram
- Meiosis
- Haploid vs diploid
- Bit.ly/2m8prtt
- Homologous pairs vs sister chromatids
- Salamander
- Dna structure and replication pogil