Life Science Chapter Four Cell Reproduction DNA RNA Mitosis Meiosis

Cell Cycle Page 93 for Diagram Interphase Growth and development stage for a cell Phase between cell divisions Nucleus is clearly seen Rapid growth DNA synthesis Production of organelles Growth and preparation for division Chromosomes can’t be seen

Cell Division Mitosis Nucleus divides and cytoplasm divides Two new cells are formed Nerve and muscle cells—no longer divide—they are always in interphase Skin cells divide a lot

Cell Division Mitosis Defined Is the process in which the nucleus divides to form two identical nuclei, each has the same number of chromosomes

Cell Division Chromosomes Structures in the nucleus that contain DNA Double stranded Held together by a centromere

Cell Division Prophase First stage Chromosomes become visible Nucleolus and nuclear membrane disappear Centrioles move to opposite sides of the cell Threadlike spindle fibers stretch to attach to chromosomes

Cell Division Metaphase Second stage Double stranded chromosomes line up in the center of the cell Spindle fibers attaches to centromere

Cell Division Anaphase Third stage Centromere divides and chromosomes separate Separate strands begin to move to opposite poles of cell

Cell Division Telophase Fourth stage Spindle fibers and centrioles disappear Nuclear membrane forms around the chromosomes Cells pinch apart and nucleolus appears

Cell Division Plant Differences Cell walls So they don’t pinch apart Instead cell wall forms between the two nuclei Do not have centrioles

Cell Division Mitosis is important because Division of the nucleus Produces two nuclei with the same number of chromosomes

Asexual Reproduction Defined A new organism is produced from one parent Plants have asexual reproduction Runners, potato eyes, cuts of stems and leaves Animals have asexual reproduction Budding, fission and regeneration

Asexual Reproduction Bacteria Reproduce asexually Binary fission Division of an organism into two equal part Budding Asexual reproduction New organism grows off the side of its parent Regeneration Asexual reproduction The ability to replace body parts An animal can replace a lost part or two organisms can result from one

Sexual Reproduction Defined A new organism is produced by combining sex cells from two parents Egg—female parent Sperm—male parent Ovule—plant female Pollen—plant male

Meiosis Defined Division of the cell nucleus to produce sex cells Sex cells are important because you get a new genetic makeup of new genes Diagram page

Fertilization Defined The fusion of an egg and sperm sexual

Humans Babies get 23 chromosomes from mom and 23 chromosomes from dad resulting in 46 chromosomes total

Humans Diploid cells have 46 chromosomes Body cells Haploid cells have 23 chromosomes Sex cells

DNA Deoxyribonucleic acid Master copy of an organisms information or code Controls your traits Controls cell activities Dr. Franklin X-ray technique to show that DNA is double stranded

DNA Watson and Crick First model of DNA Nitrogen bases (rungs) are adenine (A), thymine (T), quanine (G), cytosine (C) Hand rails are sugar and phosphate alternating

DNA Adenine (A) always combines with Thymine (T) Guanine (G) always combines with Cytosine (C)

DNA Copies DNA copies Enzyme untwists/separates DNA strand between nitrogen bases Bases on original strand match up with a new base A-T and G-C only New strands of DNA are produced and retwists

DNA DNA contains Genes

Proteins Proteins are made of units called amino acids Amino Acids Basic building blocks of life Genes directs the making and order of amino acids which makes a protein

RNA Ribonucleic acid T is replaced with Uracil (U) Does its work outside of the nucleus Single stranded Carries the code from DNA to make proteins

RNA Defined Carries code for making proteins Two types of RNA Messenger RNA mRNA Transfer RNA tRNA Diagram page 108