Image: ABCDE Answer the questions using the cell images shown below. 1. What type of cell is shown in the pictures above? Plant or Animal 2. Which cell is in the first phase of cell division? _____ 3. Which cell is in anaphase? _____ 4. What stage is shown in cell A? ______________ 5. Which stage is shown in cell B? _______________ 6. List the cells in the order they occur in cell division. ___  ___  ___  ___  ____

ABCDE 1. What type of cell is shown in the pictures above? Plant or Animal 2. Which cell is in the first phase of cell division? _____ 3. Which cell is in anaphase? _____ 4. What stage is shown in cell A? ______________ 5. Which stage is shown in cell B? _______________ 6. List the cells in the order they occur in cell division. ___  ___  ___  ___  ____ The answers are … PROPHASE C D E EADCB TELOPHASE

Can you think of 3 reasons why mitosis is important? Answer question on pg9 CGP biology – Protein synthesis

DNA replication Aims: What happens during DNA replication? How is a new polynucleotide strand formed? Why is the process of DNA replication called semi-conservative? Why do we need to know? Nfv1jKuA

Replication of DNA Cells that make up organisms are always derived from existing cells by the process of cell division. Cell division occurs in 2 main stages: –Nuclear division (mitosis and meiosis) –Cell division

Replication of DNA Before a nucleus divides its DNA must replicate. All daughter cells need to have the same genetic information to produce all the enzymes and other proteins they need. DNA replication is very precise. How do you think it happens? Make a model to show me

Task: Make a model of DNA replication How do you think it happens? What enzymes are involved? Record it on audio boo Challenge: Explain the evidence for your model

Two possible mechanisms of DNA replication.

Meseleson and Stahl’s experiment to test the semiconservative hypothesis of DNA replication.

10 DNA Replication How does DNA replicate? Evidence for Semi- conservative replication Meselson & Stahl’s experiment

11 DNA Replication How does DNA replicate? Semi-conservative replication Enzymes are the key to the process, they: Split helix; Prime replication; Add nucleotides (DNA polymerase).

Semiconservative replication. Each parental chain of DNA acts as a template for the synthesis of a new chain, which forms by complimentary base pairing.

The stages of the cell cycle.

An outline of mitosis: sister chromatids are separated and two genetically identical daughter nuclei are formed.

15 MITOSIS – cell division Need to be able to describe and recognise stages of mitosis. 1.INTERPHASE; 2.PROPHASE; 3.METAPHASE; 4.ANAPHASE; 5.TELOPHASE.

Interphase and prophase, the first stage of mitosis. Chromatin = diffuse DNA associated with histone proteins Centromere

Mitosis continued: metaphase, anaphase, telophase, and cytokinesis in an animal cell. CENTROMERE Each chromosome now consists of two CHROMATIDS Joined at the CENTROMERE ANAPHASE: chromatids separate pulled to the “poles” by spindle fibers TELOPHASE: Nuclear envelope reforming, cytokinesis begins METAPHASE: Chromosomes lined up on the equator

Human Life Cycle

Meiosis What does meiosis achieve? –Shuffles chromosomes; –Increases variety; –Cross over exchanges genes; –Halves chromosome number. Your genome is down to how the chromosomes were dealt!

Outline of meiosis.

CROSSING OVER

Photomicrographs of the different stages of mitosis, (i).

Week 22: Images Photomicrographs of the different stages of mitosis, (ii).

Week 22: Images Photomicrographs of the different stages of mitosis (iii).

25 Mitosis Quiz

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30 1. = anaphase 2. = telophase3 = interphase 4. = prophase 5. = metaphase

31 1. = anaphase 2. = telophase3 = interphase4. = prophase 5. = metaphase

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DNA replication Aims: What happens during DNA replication? How is a new polynucleotide strand formed? Why is the process of DNA replication called semi-conservative? Why do we need to know? Nfv1jKuA