Cell Reproduction Asexual reproduction the cells reproduce on

Cell Reproduction

• Asexual reproduction: the cells reproduce on own, without contact with another. • Sexual reproduction: takes the genetics of two different individual to combine and form a new individual.

• DNA (deoxyribonucleic Acid) : is a long molecule that stores genetic info. It is a double helix of nucleotides. – The pairs are: Adenine with Thymine and Guanine with Cytosine * These are the genetic codes found in chromosomes.

• RNA (Ribonucleic Acid): is a single strand. – Instead of thymine, there is Uracil. • A-U • G-C – -copies code of DNA to direct protein sythesis.

• ATP (adenosine triphosphate) – Energy transfer molecule – Formed when cell respiration releases energy form food molecules. – Used for energy requiring processes.

Chromosomes • Are made up of a single DNA and proteins. Are coiled up in nucleus. • Each half of a chromosome is called a chromatid. – When divide, each new cell will get 1 chromatid from each parent. – Chromatids are held together in the middle by a Centromere.

• Sex Chromosome: determine the sex of the organism. X or Y. • Autosomes: all other chromosomes in the organism. – Human have 46 total chromosomes, or 23 pairs.

• Each cell has 2 copies of each autosome. You receive 1 copy from each parent. • The 2 copies are called Homologous Chromosomes. • Karyotype: a picture of the chromosomes.

• Diploid: have 2 sets of chromosomes (2 N) • Haploid: 1 set of chromosomes (1 N) – sex cells • Homologous Chromosomes: one of a pair of similar chromosomes. Each organism receives one copy from each parent. We have 22 pairs of homologous pairs, and one pair of sex cells.

Cell Divisions • 2 different ways of Cell Division – 1. Mitosis: which is for the body cells. Make new body and tissue cells. 1 cell will divide into 2 identical daughter cells with 46 chromosomes – 2. Meiosis: is the division of the sex cells. The cells divide in half, with only 23 chromosomes and form the Gametes (egg and sperm)

Mitosis • 1. Interphase: chromosomes make a copy

• 2. Prophase: chromatids still attached at centromere. Centrioles move to opposite poles and the spindle fiber start to appear.

• 3. Metaphase: chromtids line up in middle. Center attaches to spindle fibers, and divide.

• Anaphase: have 2 complete sets. The spindle fibers pull toward the poles.

• Telophase: DNA uncoils, membrane forms around chromosomes.

• Cytokinesis: cytoplasm divides, a new cell is formed.

Meiosis • Has 2 stages. The first stage is the same as mitosis. The cell copies and divides. The those cells just divide again, and end with ½ the chromomes. • Result on formation of egg and sperm

Meiosis I • 1. Prophase I: DNA coils up into chromosomes, spindle fibers appear, the chromosomes lime up next to its homologue called Synapsis. Each pair called a tetrad. The chromatids twist around allowing portion to break off and attach to adjacent chromatid, called Crossing-Over, which results in Genetic Recombination, a new mixture of genetic material.

• Metaphase I: tetrads line up in middle. Spindle fibers attach to centromere

• Anaphase I : each homologous chromosome move to opposite pole, then have a random separation. Independent Assortment.

• Telophase I: chromosomes reach opposite ends. • Now have 2 new cells with one chromosome from each homologous pair

Meiosis II • During Meiosis II, the DNA is not copied, the 2 cells go through the phases again and end in 4 cells , each has only ½ the original number of chromosomes.