Biology quiz
9 Meiosis
CHAPTER OUTLINe
Meiosis (p. 172)
9.1 Discovery of Meiosis (p. 172; Figs. 9.1, 9.2)
A. In 1882, Belgian cytologist Pierre-Joseph van Beneden discovered that the gametes of the roundworm Ascaris contained two chromosomes while somatic cells contained four.
B. Fertilization
1. van Beneden proposed in 1887 that an egg and sperm could fuse to form a zygote.
2. The fusion of gametes is called fertilization or syngamy.
C. Meiosis
1. A reduction division is required to reduce the number of chromosomes to half so sexual reproduction can occur.
2. This reduction division is known as meiosis.
D. The Sexual Life Cycle
1. Adult cells are diploid, and gametes are haploid.
2. Sexual reproduction joins haploid gametes to produce a new diploid individual.
9.2 The Sexual Life Cycle (p. 173; Figs. 9.3, 9.4)
A. Somatic Tissues
1. In the sexual life cycle, there is an alternation of diploid and haploid generations.
2. Normal diploid body cells are called somatic cells.
3. Somatic cells arise from the zygote and are genetically identical to the zygote.
B. Germ-Line Tissues
1. Cells that produce gametes are called germ-line tissues.
2. Germ-line cells will undergo meiosis to produce haploid gametes.
9.3 The Stages of Meiosis (p. 174; Figs. 9.5, 9.6, 9.7)
A. Meiosis has two divisions: meiosis I serves to divide the two versions of each chromosome; and meiosis II separates the two replicas of each chromosome.
B. Meiosis I
1. Meiosis is similar to mitosis, except that it involves two divisions, meiosis I and meiosis II, and the resulting cells are haploid, rather than diploid like those produced by mitosis.
2. Also, a phenomenon called crossing over occurs during prophase I of meiosis I when pieces of nonsister chromatids exchange places to promote new genetic combinations in the offspring.
3. Prior to meiosis I, during interphase, the DNA replicates and the cell readies itself for cell division.
4. Meiosis I consists of four stages: prophase I
CHAPTER OUTLINe
Meiosis (p. 172)
9.1 Discovery of Meiosis (p. 172; Figs. 9.1, 9.2)
A. In 1882, Belgian cytologist Pierre-Joseph van Beneden discovered that the gametes of the roundworm Ascaris contained two chromosomes while somatic cells contained four.
B. Fertilization
1. van Beneden proposed in 1887 that an egg and sperm could fuse to form a zygote.
2. The fusion of gametes is called fertilization or syngamy.
C. Meiosis
1. A reduction division is required to reduce the number of chromosomes to half so sexual reproduction can occur.
2. This reduction division is known as meiosis.
D. The Sexual Life Cycle
1. Adult cells are diploid, and gametes are haploid.
2. Sexual reproduction joins haploid gametes to produce a new diploid individual.
9.2 The Sexual Life Cycle (p. 173; Figs. 9.3, 9.4)
A. Somatic Tissues
1. In the sexual life cycle, there is an alternation of diploid and haploid generations.
2. Normal diploid body cells are called somatic cells.
3. Somatic cells arise from the zygote and are genetically identical to the zygote.
B. Germ-Line Tissues
1. Cells that produce gametes are called germ-line tissues.
2. Germ-line cells will undergo meiosis to produce haploid gametes.
9.3 The Stages of Meiosis (p. 174; Figs. 9.5, 9.6, 9.7)
A. Meiosis has two divisions: meiosis I serves to divide the two versions of each chromosome; and meiosis II separates the two replicas of each chromosome.
B. Meiosis I
1. Meiosis is similar to mitosis, except that it involves two divisions, meiosis I and meiosis II, and the resulting cells are haploid, rather than diploid like those produced by mitosis.
2. Also, a phenomenon called crossing over occurs during prophase I of meiosis I when pieces of nonsister chromatids exchange places to promote new genetic combinations in the offspring.
3. Prior to meiosis I, during interphase, the DNA replicates and the cell readies itself for cell division.
4. Meiosis I consists of four stages: prophase I