Homework from last class:• Complete the Introduction to Meiosis and

Reproductive Systems worksheet

• Study for your Genetics and Reproductive Systems quiz

Quiz Time!

You have about 10 minutes to write the quiz.

Good luck!

2

Chapter 6 pp. 191-197

Ch. 6.1 Meiosis

MeiosisMeiosis: the form of cell division that produces

gametes (sex cells) with half the number of chromosomes as body cells

Diploid (2n) Haploid (n) parent cell sex cells

Meiosis only occurs in gonads (testes or ovaries)

Meiosis is similar to mitosis, but there are several differences:• Involves 2 cell divisions•Results in 4 cells with ½ the genetic information (n instead of 2n)

Meiosis occurs in 2 phases:

Meiosis I (1st cell division)

Meiosis II (2nd cell division)

Meiosis I

Meiosis II

Meiosis I• Prior to meiosis I, DNA replicates once, in

interphase

Fig 6.4 p. 191

Meiosis I• In meiosis I, a pair of matching homologous

chromosomes, one from each parent, lines up at the equator

Homologous chromosomes: a pair of matching chromosomes

Fig 6.5 p. 191

Meiosis I• Homologous

chromosomes line up at the equator

• The homologous chromosome pair separates and moves to opposite poles of the cell

• 2 daughter cells result

Fig 6.5 p. 191

Crossing Over

Crossing over: event in meiosis I where non-sister chromatids exchange segments of DNA; results in variation in gametes

• As a result of crossing over, each chromosome picks up new genetic information from the other

Independent Assortment

Independent assortment: an event in meiosis I where homologous pairs of chromosomes separate and sort themselves into daughter cells

• Genes are shuffled leads to genetic diversity

Crossing Over and Independent Assortment

Fig 6.6A p. 192

Meiosis II

• DNA not replicated again before meiosis II begins

• Meiosis II is like mitosis the chromatids of each chromosome are pulled to opposite poles

• Each daughter cell inherits 1 chromatid from each chromosome

• 4 haploid (n) daughter cells result

Fig 6.4 p. 191

Outcome of Meiosis II Fig 6.6B p. 193

Summary of Meiosis

Meiosis Animationhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/

animation__how_meiosis_works.html

Homework for next class:

It was fun teaching you during my

practicum! Best of luck to you

all!

Works CitedImages taken from the following sources:http://biologydiva.pbworks.com/w/page/14796955/Chapter-22http://chsweb.lr.k12.nj.us/mstanley/outlines/meiosis/APMeiosis.htmhttp://www.bcscience.com/bc9/index.htmlhttp://geneticssuite.net/node/21http://www.sflorg.com/sciencenews/scn100608_01.html