Presentation on theme: "Chapter A-2 Reproduction and Change. Cells – Cells are the basic units of living things."— Presentation transcript:
Chapter A-2 Reproduction and Change
Cells – Cells are the basic units of living things.
Cells divide and form new cells.
Chromosomes Structures in the nucleus of a cell that control the cell’s activities.
Mitosis Through mitosis the two new cells have sets of chromosomes that are identical to the parent cell and each other. The parent cell ceases to exist.
Mitosis Step 1. Chromosomes are copied.
Mitosis Step 2. Chromosomes line up
Mitosis Step 3. Chromosomes separate
Mitosis Step 4. Cells Divide Telophase: Daughter chromosomes arrive at the poles and the microtubules disappear. The condensed chromatin expands and the nuclear envelope reappears. Cytokinesis: The cytoplasm divides, the cell membrane pinches inward ultimately producing two daughter cells. Cytokinesis
Reproduction Reproduction is the process by which offspring are created
Asexual Reproduction Only one parent cell - Organisms that reproduce by cell division often reproduce quickly.
Sexual Reproduction Two parent cells – an egg cell and a sperm cell
Meiosis Cell division that makes the reproductive cells in most many-celled organisms. Each egg or sperm cell contains only half as many chromosomes as the other cells in an organism’s body.
Meiosis How many cells will the reproductive cells have if the organisms has …? PictureOrganismNumber of Chromosomes Mosquito6 Toad22 Wheat42 Horse64 Carp104
Fertilization Fertilization is the joining of the sperm cell and the egg cell. These conifers produce eggs in the seed cone and sperm in the pollen cone.
Fertilized egg cell The fertilized egg has the same number of chromosomes as the cells in the parent organism’s body, can grow and develop into a new organism. Each has split into 4 cells within 2 hours – (hot- crossed bun stage)
Reproduction in Flowering Plants The female section of the flowering plant is the pistil. The male section of the flowering plant is the stamen.
Inherited Traits Traits that are passed to offspring from parents. Are you right or left handed, footed, sighted?
Chapter A2 Lessons 2 & 3
Inherited Traits Cross arms right/left on top DimplesNo Dimples Cleft or smooth chin Right/Left Thumb on Top Longer Second ToeShort Second ToeBent Little fingerHitchhiker's Thumb
Genes A gene is the part of a chromosome that carries information that controls the train.
Dominant Gene A dominant gene is a controlling gene that can hide or prevent the expression of a another gene (a recessive gene). A dominant gene is always represented by an upper case (capital) letter. In this picture the Tall (upper case T) dominates over the Short (lower case T)
Recessive Gene A recessive gene is a gene whose expression can be hidden by a dominant gene. A recessive gene is always represented by a lowercase (small) letter. In this picture the Short (lower case T) is hidden by the Tall (upper case T)
Hybrids A hybrid is an individual that has a dominant and a recessive gene for a trait. In the first example the dominant Tall hides the Short gene but all the offspring are hybrids (Tt). In the second example when two hybrids reproduce there is a one in four chance that the recessive trait may appear (tt).
Punnett Square A Punnett Square is a diagram that shows the various possibilities of the offspring of two parents with specific forms (alleles) for that trait. The example below shows the possibilities of the offspring with two hybrid parents. 25% purebred dominant, 50% hybrid, 25% purebred recessive. Statistically 3 out of 4 of the offspring would show the dominant trait Male is Bb Female is Bb Offspring BB, Bb, Bb, bb
Mutations A mutation is a permanent change in the structure of a gene or chromosome. Nectarine Albino squirrel Sickle Cell Anemia
Gregor Mendel Mendel studied the traits of the pea plant and learned about dominant and recessive genes. He also discovered that the way one trait is inherited does not usually affect the way other traits are inherited.
Rosalind Franklin Rosalind Franklin was a British scientist who produced the first pictures of DNA molecules
James Watson and Francis Crick Watson and Crick used Franklin’s pictures and other information to make a model of DNA’s structure as a double helix. They received a Nobel Prize in 1962 for their discoveries.
Selective Breeding Selective breeding is the breeding of plants or animals with certain traits to produce offspring with those traits. Corn through the years Dairy cows through the years