Meiosis & Sexual Reproduction

Section 11-1: Reproduction asexual reproduction, sexual reproduction -The offspring produced by asexual reproduction is identical to it’s parent while the offspring produced by sexual reproduction is genetically different. binary fission, fragmentation -Binary fission is where a prokaryotic or unicellular eukaryotic cell copies & divides roughly in half whereas fragmentation is where a part of an organism breaks off and grow new parts while developing into complete adults. budding, parthenogenesis -Budding is where a new organism sprouts off of an adult organism while parthenogenesis is where a female can produce an egg which grows into an adult without being fertilized by a male.

Asexual vs Sexual Reproduction What are the advantages and disadvantages of asexual reproduction? -Advantages: simple, fast, efficient, don’t need a mate -Disadvantages: lack of genetic diversity What are the advantages of sexual reproduction? -Increased genetic diversity

Chromosomes Chromosomes that are similar in size, shape, and genetic content are called: -Homologous Why do you have 23 pairs of homologous chromosomes? - You get half from mom & half from dad through sexual reproduction. A cell, such as a somatic cell, that contains two sets of chromosomes is said to be: - Diploid (di = ?) Biologists use the symbol to represent one set of chromosomes. Human somatic cells have chromosomes. 2n = 46 n 46

Autosomes & Sex Chromosomes What is the difference between an autosome and a sex chromosome? -Autosomes do not contain genes that determine the sex (male or female) of the individual. -Sex chromosomes have genes that determine the sex. What are the sex chromosomes in human females and males? What is one major difference between them? -X & Y Males = XY (if you have a Y you’re a guy) Females = XX

Section 11-2: Meiosis What is meiosis? - Cell division that results in daughter cells with half the number of chromosomes. Explain the difference between meiosis I and meiosis II. Meiosis I creates haploid cells, Meiosis II then divides these chromosomes in half. List the stages of meiosis in the order that they occur.

Stages of Meiosis __The centromeres divide, and the chromatids move to opposite poles of the cell. __The homologous chromosomes separate. The chromosomes of each pair are pulled to opposite poles of the cell by the spindle fibers. The chromatids do not separate at their centromeres. __The chromosomes condense, and the nuclear envelope breaks down. Homologous chromosomes pair all along their length and then crossing-over occurs. __After one division of the nucleus, a new spindle forms around each group of chromosomes. __Individual chromosomes line up along the equator, attached at their centromeres to spindle fibers. __A nuclear envelope forms around each set of chromosomes. Two cells undergo cytokinesis, forming haploid offspring cells. __Individual chromosomes gather at each of the two poles. In most organisms, the cytoplasm divides, forming two new cells. __The pairs of homologous chromosomes are moved by the spindle to the equator of the cell. The homologous chromosomes, each made up of two chromatids, remain together Prophase I Metaphase II Telophase II Telophase I Metaphase I Anaphase I Anaphase II Prophase II

Genetic Variation What are 3 ways in which populations increase their genetic variation? 1.Crossing over 2.Independent Assortment 3. Random Fertilization

Crossing Over What is crossing over? -Homologous chromosomes exchanging parts while paired up during Prophase I.

Independent Assortment What is independent assortment? During which phase(s) of meiosis does independent assortment occur and what is the significance of this process? -The random distribution of homologous chromosomes during Metaphase I. -This allows for different combinations of chromosomes in the daughter cells.

Random Fertilization

Animations

Diploid Life Cycle in Humans

Spermatogenesis & Oogenesis

Mitosis vs. Meiosis