Meiosis Guided Notes

Interphase… Prior to prophase I, the cell goes through cell growth and DNA replication during ________________. interphase

Prophase I (chapter 10) condensed homologue homologous pairing DNA coils into ___________ chromosomes, spindle fibers appear, nucleus disappears. Every chromosome is paired up next to its ______________ (the chromosome that is the same size and shape). This is called _____________ and does not occur in mitosis. homologue homologous pairing

Prophase I (cont.) synapse crossing over homologous Each pair of homologous chromosomes is called a ______________. When chromosomes line up next to each other, “__________________” occurs and they exchange pieces of DNA. This is called _________ recombination. synapse Crossing over crossing over homologous

So why is Crossing Over SO important????? Reasons why: crossing over is important because it results in new combinations of genes the that are different from either parent, contributing to genetic diversity.

Review of Key Terms Homologue (Homologous Chromosomes): Synapsis Tetrad Crossing Over

Metaphase I Homologous chromosomes Homologous chromosomes __________________________ line up in the center of the cell next to each other. Spindle fibers from one centriole attach to the centromere of one _____________ chromosome then spindle fibers from the opposite centriole attach to the other homologous ____________________. Homologous chromosomes Homologous chromosomes

Anaphase I opposite equal independent genes Each homologous chromosome moves to the _____________ pole. This __________ separation of homologous chromosomes is called ________________ assortment. It separates the chromosomes you inherited from your mom and dad and creates new combinations of ________ on each chromosome! opposite equal independent genes

Telophase I Chromosomes reach the opposite ends of the ___________, new nuclei form in each new cell, and spindle fibers ________________. These new cells are called daughter cells. cell disappear

To review… What are the major events in Meiosis I?… Prophase I: Metaphase I: Anaphase I: Telophase I:

NO INTERPHASE HERE There is no interphase between _____________ 1 and ____________ 2. This is very important because there is no S phase!!! (no doubling of the __________________!!!) Meiosis Meiosis chromosomes

Start of Meiosis II Prophase II poles disappears Centrioles form and move toward the __________ The nuclear membrane ________________ poles disappears

Metaphase II __________ fibers attach from the centrioles to the centromeres The __________ chromatids line up along the cell equator Spindle sister

Anaphase II chromatids The sister ___________ separate. The cell starts to __________ apart separate

Telophase II – Cytokinesis The cell pulls _____________ apart – forming new nuclei, one in each cell Cytokinesis reaches completion, creating ___ haploid ____________ cells fully 4 daughter

These 4 haploid cells then create: ______________! If the organism going through meiosis is a female, only ___ of the cells becomes the egg, the others become “_______ Bodies” and are dissolved by the body. This process of making an egg is called __________________. If the organism going through meiosis is a male, _______ cells become spermatids which mature in to sperm. This is called _______________________. gametes 1 polar oogenesis 4 spermatogenesis

Major events in Meiosis! The cell starts out by doubling the DNA in Interphase: After S1 phase (Sister chromatids) Copy of Chromosome (doubling the DNA) A chromosome before the S1 phase Original Chromosome

Meiosis Is related to sexual reproduction. Is a biological process that creates a new organism by combining the genetic material of two organisms in a process that starts with meiosis. The union of cells produced by meiosis (gametes) is called fertilization which creates a zygote.