Transcript chromosomes
Ch. 8 Cell Reproduction Ch 8.1 Chromosomes How is DNA organized? Usually in a cell, DNA is wrapped histone proteins in long around ________ strands called chromatin. During cell division, the chromatin condenses into chromosomes. __________ The chromosome is made of two identical DNA structures, called chromatids, that are joined together at the _____________. centromere Chromatin and Condensed Chromosome Structure chromatid nucleus centromere chromosome chromatin DNA helix histones Each species has a specific number of chromosomes. _______ Each different chromosome contains information for different traits ________. Types of Chromosomes Sex chromosomes: In humans, X and __, Y chromosome __ determine the sex of a person. –Females have two X, and males have X and Y. All other chromosomes are autosomes called _____________. How many chromosomes are in a cell? Most human cells normally two sets of each contain ____ chromosome. diploid cells These are called _______ and is abbreviated as ____. 2n Reproductive cells, sperm and haploid egg cells, are _______. one Haploid cells contain only ___ set of chromosomes. This is n . abbreviated as ___ Karyotype An organized profile of an organism’s complete set of chromosomes. Scientist pair together homologous chromosomes based on their size, banding pattern, and position of their centromere. Then they arrange them by size from largest to smallest. Human male karyotype Cell Division Asexual vs. Sexual Reproduction Asexual Reproduction Requires only one parent. Resulting offspring are genetically identical. The only source of genetic variation comes from mutations. Budding Parent produces an outgrowth that pinches off, forming a new organism Occurs in yeast, hydra, sponges. http://www.waycross.edu/faculty/bmajdi/hydra%20budding.jpg Spore formation Single or multi-celled spores are produced and grow into a new organism. Occurs in algae, fungi, protists, and plants Binary Fission DNA replicates and one cell divides into two Occurs in bacteria, protozoa, and algae. Sexual reproduction Requires two gametes (sex cells) : egg and sperm. The egg and sperm join to form an entirely new organism The offspring is genetically different from the parent organism Why do cells reproduce? Produce more offspring (new organisms). Organism needs to grow or repair Prokaryotes Prokaryotic cells divide by binary fission ________ ___________. They have circular chromosomes without any proteins and cell division occurs very quickly. Eukaryotes Eukaryotes divide by mitosis Cells spend only a small percentage of their time dividing. The set of events in the life of a cell is called the cell cycle. A cell spends most of its life in interphase. G1 Phase Cell size grows to mature S Phase DNA replicates. G2 Cell grows and prepares to divide. What is cancer? Cancer occurs when cells do not stop growing. Healthy cells regulate when and how often they continue in the cell cycle. Cancer cells continuously go through the cell cycle without stopping, which leads to a tumor.