Reproduction

Cell Cycle / Mitosis The cell cycle is the cycle of growth, DNA replication and cell division in eukaryotic cells. Cell Cycle Animation Interphase – Normal cell processes and growth of cell, DNA replication, and more growth. Cells spend most of their time in interphase.

Mitosis Mitosis is the part of the cell cycle where the replicated DNA (sister chromatids) separates equally to both sides of the cell. Mitosis produces two identical nuclei within the cell usually in preparation for cell division (cytokinesis). There are 4 steps to mitosis: Prophase – Nuclear membrane disappears Metaphase – Sister chromatids line up in the center of the cell. Anaphase – Sister chromatids split into chromosomes and migrate to opposite sides of the cell Telophase – Nuclear membranes form around the two sets of chromosomes forming two nuclei.

Cytokinesis Cytokinesis is the part of the cell cycle where the cytoplasm and cellular organelles are divided and the cell divides into two separate cells. In animal cells the cell membrane pinches in (forms a cleavage furrow) to separate the cells. In plant cells, a cell plate forms to divide the cell into two separate cells. Mitosis & Cytokinesis Animation

Homework Monday, October 30, 2006 6A. Read the section of the textbook Write the definitions, understand and memorize the following terms Asexual Reproduction Binary Fission – not in text. Budding Spore Regeneration Sexual Reproduction

Asexual reproduction involves only one parent and produces offspring genetically identical to that parent. It is most common in single celled or simple organisms and in plants. Asexual reproduction involves mitosis. Sexual reproduction involves combining the genetic material from two parent organisms to produce genetically unique offspring. Meiosis is the process by which the gametes are formed in the parents and fertilization is the process by which a gamete from each parent combines to produce the offspring.

Asexual Reproduction Examples Binary Fission occurs in bacteria (prokaryotes) and in most single celled eukaryotes (protists). The cell divides in half to form two identical (or almost identical) daughter cells. Budding occurs in eukaryotes (such as yeast) through mitosis (to create two identical nuclei) and the formation of a bud (a small protrusion of the cell membrane). The new cell formed is smaller than the parent cell. Multicellular organisms (such as plants and hydra) also bud to produce offspring genetically identical to the parent. Spores are specialized cells that act similar to seeds but are produced asexually. Spores have protective coats that allow them to endure hot, dry, or cold conditions. When conditions are good for growth, the spore grows into a new organism genetically identical to the parent. Ferns, bread mold, and mushrooms produce spores. Regeneration occurs through mitotic cell division to reproduce parts of an organism which are damaged, lost, or injured. Many organisms display varying degrees of regenerative ability. Some organisms such as planaria and certain starfish can produce multiple offspring by regeneration.

Binary Fission

Budding Yeast

Budding Hydra

Homework Write the definitions, understand and memorize the following terms (p93, 208, 298) Gamete Egg Sperm Fertilization Zygote Haploid Diploid Conjugation (Read Page 173)

Bacterial Conjugation

Sexual Reproduction Gametes are the specialized sex cells formed by meiosis in each parent which combine during fertilization to form the offspring. Egg (Ovum) cells are female gametes Sperm cells are male gametes Gametes are haploid because they only have one copy of each chromosome Parents are diploid if they have two copies of each chromosome Meiosis is the process that makes haploid gametes from diploid cells. During fertilization, two haploid gametes combine to form a diploid zygote. A zygote is a fertilized cell – the offspring

Karyotype

Meiosis

Meiosis I

Meiosis II

Fertilization

Homework Draw and label a color diagram of an eukaryotic cell cycle on white unlined paper with no holes. Include: Interphase Prophase Metaphase Anaphase Telophase Cytokinesis State what happens at each phase. Label the parts that are mitosis.

Homework Draw and label a color diagram of meiosis on white unlined paper with no holes. Include: Interphase Prophase I Metaphase I Anaphase I Telophase I Cytokinesis I Prophase II Metaphase II Anaphase II Telophase II Cytokinesis II State what happens at each phase. Due Wednesday

NYS Core Curriculum 2.1a Hereditary information is contained in genes. Genes are composed of DNA that makes up the chromosomes of cells. 2.1b Each gene carries a single unit of information. A single inherited trait of an individual can be determined by one pair or by many pairs of genes. A human cell contains thousands of different genes. 2.1c Each human cell contains a copy of all the genes needed to produce a human being. 2.1d In asexual reproduction, all the genes come from a single parent. Asexually produced offspring are genetically identical to the parent. 2.1e In sexual reproduction typically half of the genes come from each parent. Sexually produced offspring are not identical to either parent.

NYS Core Curriculum 4.1a Some organisms reproduce asexually. Other organisms reproduce sexually. Some organisms can reproduce both sexually and asexually. 4.1b There are many methods of asexual reproduction, including division of a cell into two cells (binary fission), or separation of part of an animal or plant from the parent (budding), resulting in the growth of another individual. 4.1c Methods of sexual reproduction depend upon the species. All methods involve the merging of sex cells (gametes) to begin the development of a new individual. In many species, including plants and humans, eggs and sperm are produced. 4.1d Fertilization and/or development in organisms may be internal or external.

NYS Core Curriculum 4.2a The male sex cell is the sperm. The female sex cell is the egg. The fertilization of an egg by a sperm results in a fertilized egg (zygote). 4.2b In sexual reproduction, sperm and egg each carry one-half of the genetic information for the new individual (haploid). Therefore, the fertilized egg contains genetic information from each parent (diploid).

NYS Core Curriculum 4.4a In multicellular organisms, cell division is responsible for growth, maintenance, and repair. In some one-celled organisms, cell division is a method of asexual reproduction. 4.4b In one type of cell division (mitosis), chromosomes are duplicated and then separated into two identical and complete sets to be passed to each of the two resulting cells. In this type of cell division, the hereditary information is identical in all the cells that result. 4.4c Another type of cell division (meiosis) accounts for the production of egg and sperm cells in sexually reproducing organisms. The eggs and sperm resulting from this type of cell division contain one-half of the hereditary information. 4.4d Cancers are a result of abnormal cell division.