Gbio 106 1st EditionFinal Exam Study GuideLECTURE 17:Cell Division and Genetics: -Eukaryotic Chromosomes: DNA winds around proteins to form chromosomes. Only visible during cell division, and otherwise remain in chromatin form. There are 23 pairs of chromosomes, 46 single, in human cells. -Homologous chromosomes are pairs of chromosomes that contain genes of the same traits. Cells that contain pairs of each chromosomes are diploid. -Sex cells are haploid cells and only contain one of each chromosome. -Binary fission occurs in bacteria. DNA occurs in one loop, and the loop copies itself. Cell splits with one loop in each new cell. Bacterial growth starts slow and then by the time the cells multiply enough, it spreads quickly. -Eukaryotic Cell Reproduction: Occurs in protists, fungi and animals. Cells have a nucleus and store DNA.Two types of nuclear division:-Mitosis: Happens in body cells (somatic cells). Mitosis occurs when a parent cell divides to make an identical cell. Responsible for growth and maintenance. -Meiosis:-The Cell Cycle: Interphase and Mitosis. In order for a cell to divide it must replicate its DNA and divide its nucleus and cytoplasm. -Interphase: Takes up 90% of the cell cycle. Can’t be seen, pretty boring. DNA is invisible. But in G1, the cell is growing. In synthesis (s-phase), DNA is replicated. Then in G2, the cell prepares for mitosis (PMAT). -DNA is our genetic code. It is the molecule responsible for coding for the traits we have as well as what species we are. All of our cells contain the same DNA. -Adenine and Thymine bond, as well as Guanine with Cytosine. -DNA Replication: -2 original strands of DNA unwind and separate to expose their n-bases. -Each parental strand is used as a template. -Eventually, each DNA strand and its newly formed strand wind together to form 2 new DNA molecules. -Copies are wrapped around protein and make chromosomes. All 23 pairs. -Centromere holds pairs of chromosomes together. -Mitosis: Prophase is where we first see chromosomes. Microtubules form spindle fibers. Nucleus starts to dissolve, freeing the chromosomes. The fibers attach to the centromere and grab sister chromatids. LECTURE 18:-Mitosis Continued: Copying of body cells. Growing, maintenance and repair. Nuclear division in which the chromosome number is maintained from one generation to the next. Consists of four phases. -Interphase first. See last lecture.-Prophase: Chromatin condenses into visible chromosomes called sister chromatids. Microtubules form spindle fibers, and the nuclear membrane dissolves. This frees the duplicated chromosomes. This is when chromosomes first appear. -Metaphase: Sister chromatids line up in the middle of the cell alone the metaphase plate. -Anaphase: Chromosomes migrate toward opposite poles of the cell. -Telophase: Individual chromosomes reach opposite ends of the cells. The spindle apparatus begins to break down, unravelling the chromosomes. The nuclear membranes reform. Chromosomes decidedness (unwind) back into chromatin form. Two separate nuclei are formed, with identical genetic information. Actin filaments contract and pinch the cell in half. Cytokinesis. -Cytokinesis: Occurs in telophase and after telophase. The cell pinches and forms a cleavage furrow eventually dividing in half. -Meiosis is a two-staged form of cell division that occurs in reproductive organs that produce haploid daughter cells (sex cells) and contain one copy of each chromosome. -Spermatogenesis: Production of sperm.-Oogenesis: Production of egg (ovum). -Gametes: Sex cells. Female egg holds the organelles and cytoplasm. -Don't want pairs in sex cells!!!!!!!!! Meiosis 1 separates the pairs. Meiosis then splits the sister chromatids apart so nothing results in pairs. -Meiosis 1 - Prophase 1: Chromatin condenses into visible chromosomes. Spindle fibers form. The nuclear membrane dissolves. Synapsis occurs; the pairing of homologous chromosomes. This forms a tetrad. Crossing over may occur, where segments of DNA are exchanged between non-sister chromatids. This crossing over creates unique combinations of genetic material. Creates genetic variation. -Meiosis 1 - Metaphase 1: Tetrads line up along the metaphase plate. The positioning of each homologous pair of chromosomes during Metaphase 1 is a matter of chance. The arrangement of chromosomes at Metaphase 1 will dictate which chromosomes will be packaged together in the sex cells. Adds another level of variation. -Meiosis 1 - Anaphase: No pairs allowed.-Meiosis 1 - Telophase: Two cells with half of what we started with. Still have sister chromatids though. Meiosis 1 is just the reduction of chromosome number. So begins Meiosis 2. -Meiosis 2: Everything basically happens again. Boring. Not being tested on this process. LECTURE 19: -Random Fertilization: Creates genetic variation, randomly combined sperm and egg. -Non-disjunction: The failure of 1 or more chromosomes to separate during cell division. -Down’s Syndrome: 3 copies of the 21st chromosome. -Turner’s Syndrome: Monosomy, missing female chromosome. -Genetics: Study of patterns of inheritance. -Heredity: The study of the passage of traits from parents to offspring. -Monohybrid cross: Inheritance of one trait. -Alleles: Alternate forms of one gene. -Dominant: highest probability of being expressed. NOT most commonly expressed. -Recessive: Masked by dominant. -Locus: Location of a gene on a chromosome. -Law of Segregation: For every trait there are 2 alleles and these separate and recombine randomly through inheritance.LECTURE 20: -Dihybrid cross: Study of two traits at one time. For example, using pea color and pea shape. -Independent assortment: Chromosomes independently arrange themselves during Metaphase 1. -Why do gens separate independently? Because the genes for the two traits are on different chromosomes. -Gene linkage: Tendency for genes to be located on the same chromosome and therefore to be inheritedtogether. Linked genes do not follow Mendel’s law so they cannot independently assort. -Incomplete dominance: Blending. A pure red and a pure white snapdragon create a pink flower. -Pleiotropy: One gene effects many traits. PKU causing brain damage and mental retardation. -Epistasis: Genes for two different traits, that will mask the expression of the alleles of another gene. LECTURE 21: SEX LINKED TRAITS: Usually skip a