Biology - Meiosis and Gamete Formation - Quick Guides | Biology

Preview (3 of 10 Pages)

100%

Biology - Meiosis and Gamete Formation - Page 1 preview image

Loading page ...

Study GuideBiology–Meiosis and Gamete Formation1. MeiosisMost plant and animal cells arediploid.The worddiploidcomes from the Greek worddiplos, meaning “double.” This means diploid cells havepairs of chromosomes.For example, human body cells contain46 chromosomes, arranged into23 pairs. Because thereare two copies of each chromosome, human body cells are diploid.1.1 Diploid vs. Haploid CellsSexual reproduction involves special cells calledgametes(sex cells).•In humans, gametes aresperm cellsandegg cells•Gametes arehaploid, meaning they containonly one set of chromosomesThe wordhaploidcomes from the Greek wordhaplos, meaning “single.”Human gametes contain23 chromosomes, which is half of the usual 46.When a sperm and an egg join during fertilization, they form azygote.This restores thediploid number (46 chromosomes). After that,mitosisallows the zygote to growinto a multicellular organism.1.2 What Is Meiosis?Meiosisis the type of cell division that produces gametes.Its main purpose is to:•Cut the chromosome number in half•Producefour haploid cellsfromone diploid cellIn humans, this means:

Biology - Meiosis and Gamete Formation - Page 2 preview image

Loading page ...

Study Guide•One cell with46 chromosomes•Divides to formfour cells, each with23 chromosomes1.3 The Two Stages of MeiosisMeiosis happens intwo major divisions:1.Meiosis I2.Meiosis IIEach division includes the same basicphases seen in mitosis:•Prophase•Metaphase•Anaphase•TelophaseHowever, meiosis has important differences that make it unique.1.4 Homologous ChromosomesChromosomes exist inpairscalledhomologous chromosomes.•One chromosome comes from eachparent•They are similar butnot identical•They may carry different versions of the same geneFor example, one chromosome may code for blond hair, while its partner codes for black hair.1.5 Preparing for MeiosisBefore meiosis begins, the cell goes through theS phaseof the cell cycle.•Each chromosome is copied•Every chromosome now consists oftwo sister chromatids•These chromatids are joined at a structure called thecentromere

Biology - Meiosis and Gamete Formation - Page 3 preview image

Loading page ...

Study Guide1.6 Meiosis I: The Reduction DivisionAt the start of meiosis I, a human cell has:•46 chromosomes•92 chromatids1.6.1 Prophase IThis stage is very important.•Chromosomes condense and become visible•Synapsisoccurs: homologous chromosomes pair up•Each paired group forms atetrad(four chromatids total)Another key event here iscrossing over:•DNA segments are exchanged between chromatids•This createsnew genetic combinations•Crossing over increasesgenetic variation•It plays a major role in evolutionAfter crossing over, homologous chromosomes are genetically different.1.6.2 Metaphase I•Tetrads line up at theequatorial plate(center of the cell)•Spindle fibers attach to the centromeres•Each centromere attaches toone spindle fiber1.6.3 Anaphase I•Homologous chromosomes separate

Preview Mode

This document has 10 pages. Sign in to access the full document!

Report

Biology - Meiosis and Gamete Formation

Study Now!

Document Details

Related Documents

Biology - Vascular Plants Structure and Function

Biology - The Unity and Diversity of Life

Biology - The Science of Biology

Biology - The Origin and Evolution of Life

Biology - The Chemical Basis of Life

Biology - The Biology of Cells

Biology - Support and Movement in Animals

Biology - Reproduction

Biology - Recombinant DNA and Biotechnology

Biology - Protista

Company

Explore

Study Tools