Year 10

Li

To understand the process of Meiosis.

I can

- Accurately define what meiosis is

-Accurately list the phases of meiosis and what occurs in each stage

-Create an accurate poster that outlines all the phases of meiosis as well as provide a description of each stage with a picture.

Meiosis

Revision

Chromosomes are made up of long coiled molecules of DNA.

This chemical is divided into regions called genes.

The DNA molecule contains four different molecules called bases. There are four different bases.

Each gene is made up of a pattern of these four bases.

What is a chromosome?

Complete the complementary base pairs

AAATCCTGGTTCAA

TTTAGGACCAAGTT

What are the four bases?

Cytosine

Adenine

Thymine

Guanine

Check your understanding

There are four parts to a chromosome

Parts of the chromosome

• Centromere - the central region of the chromosomal structure. It's where the two sister chromatids are joined to each other.

• Short Arm - all human chromosomes possess two arms - a short arm and a long arm. It is termed the 'p' arm.

• Long Arm - is termed the 'q' arm.

• Telomere - The ends of the chromosome

Short arm or ‘p’ arm

Long arm or ‘q’ arm

Telomere

Introduction videoMeiosis square dance Meiosis rap video

Video of meiosis

Haploid cell = for example egg or sperm cell they have one of each chromosomes. Diploid cell = all other cells in the body they contain two of each chromosome. Gametes = another name for haploid cells (e.g. sperm and egg cells) when these two cells fuse together they form a zygote cellParent/mother cell = cell that is replicatedDaughter cell = cells that are made from the parent/mother cellTetrads = A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.

Terms you need to know

-Meiosis is a two-part cell division process in organisms that sexually reproduce that results in new cells. Each new cell contains half the number of chromosomes of the original cell.

-The new cells produced in meiosis are referred to as gametes as they only have half the number of chromosomes that the parent cell (the original cell that was divided) .

- There are two stages of meiosis: meiosis I and meiosis II. At the end of the process, four daughter cells are produced.

What is meiosis

Phase 1

Interphase

Prophase IMetaphase IAnaphase ITelophase I/Cytokinesis

Interkinesis - break periodPhase 2

Prophase IIMetaphase IIAnaphase IITelophase II

Cytokinesis- End result of meiosis is 4 haploid daughter cells

The different stages

Phase 1

-the cell replicates its chromosomes

-each chromosome has two sister chromatids held together by a centromere

Interphase

-chromosomes coil up and a spindle forms

-homologous chromosomes come together.

-Crossing Over may occur when chromatids exchange genetic material

-Crossing Over results in new combinations on a chromosomes

Prophase 1

-the centromere of each chromosome becomes attached to a spindle fibre

-the spindle fibres pull the tetrads to the equator of the spindle

-homologous chromosomes are lined up side by side as tetrads

Metaphase 1

-homologous chromosomes separate and move to opposite ends of the cell

-centromeres do not split

-this ensures that each new cell will receive only one chromosome from each homologous pair

Anaphase 1

-the spindle breaks down and the chromosomes uncoil

-the cytoplasm divides to yield two new cells

-each cell has half the genetic information of the original cell because it has only one homologous

chromosome from each pair

Telophase 1

Phase 2

-a spindle forms in each of the two new cells and the fibres attach to the chromosomes

Prophase II

-the chromosomes are pulled to the centre of the cell and line up randomly at the equator

Metaphase II

-the centromere of each chromosome splits

-the sister chromatids separate and move to opposite poles

Anaphase II

-nuclei re-form

-the spindles break down

-the cytoplasm divides

Telophase II

-four haploid sex cells from one original diploid cell

-each haploid cell contains one chromosome from each homologous pair

-haploid cells will become gametes transmitting genes to offspring

What Meiosis produces (cytokinesis)

What is meiosisWhat are the stages of meiosis What does meiosis produce

Key concepts