Biology Leaving Cert 2 3 Cell continuity Biology

Biology Leaving Cert 2. 3 Cell continuity

Biology Leaving Cert 2. 3 Cell continuity Learning objectives • Today you should learn about 1. What cell continuity is 2. The difference between haploid and diploid cells 3. The two main stages in mitosis 4. What happens during interphase in the cell cycle

Biology Leaving Cert 2. 3 Cell continuity means that new cells can only be produced by the division of existing live cells. This requires: 1. Synthesis of materials needed in the cell, 2. Growth of the cell 3. Cell reproduction

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 1 Chromosomes • Chromosomes are the structures made of DNA and protein which are located in the nucleus of the cell. Nuclear membrane Nuclear pore Chromatin

Biology Leaving Cert 2. 3 Cell continuity Haploid cells A haploid cell has only one of each type of chromosome. • Def Haploid number is the number of chromosomes in a haploid cell • Haploid number is represented by the letter n n = 4 describes a haploid cell that has four chromosomes.

Biology Leaving Cert 2. 3 Cell continuity Diploid cells • A diploid cell has two of each type of chromosome. Def Diploid number is the number of chromosomes in a diploid cell Diploid number is represented by the letter 2 n 2 n = 4 describes a Diploid cell that has four chromosomes.

Biology Leaving Cert 2. 3 Cell continuity Check your learning. . 1. What cell continuity is 2. The difference between haploid and diploid cells

Biology Leaving Cert 2. 3 Cell continuity Learning objectives 1. The two main stages in mitosis 2. What happens during interphase in the cell cycle 3. What mitosis is and how it happens

Biology Leaving Cert 2. 3 Cell continuity The Cell Cycle Dividing stage Mitosis Interphase Non dividing stage The Cell Cycle is the sequence of events in a cell which includes a state of non division and division.

Biology Leaving Cert 2. 3 Cell continuity During Interphase • The chromosomes: 1. Elongate – as chromatin 2. then make copies of themselves! • The cell also produces new organelles and makes chemicals, enzymes and proteins Mitosis Interphase

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 4 Mitosis Interphase • Def Mitosis is the division of the nucleus to produce two daughter nuclei, containing identical sets of chromosomes. Daughter nuclei with chromosomes identical to parent cell

Biology Leaving Cert 2. 3 Cell continuity Learning check… • What does cell continuity mean? • Distinguish between haploid and diploid • Define mitosis

Biology Leaving Cert 2. 3 Cell continuity Today’s objectives • To learn the names of the four stages of mitosis • To learn about what happens in each stage of mitosis

Biology Leaving Cert 2. 3 Cell continuity Mitosis: Stage 1 • The chromatin shortens, thickens and double stranded chromosomes become visible in the nucleus. • The Nuclear membrane breaks down : • Fibres are formed Cell membrane Double stranded chromosomes Fibres Nucleus Nuclear membrane

Biology Leaving Cert 2. 3 Cell continuity Mitosis: Stage 2 • Fibres attach to the chromosomes. • The chromosomes line up along the centre of the cell.

Biology Leaving Cert 2. 3 Cell continuity Mitosis: Stage 3 • Chromosomes are pulled apart to opposite ends of the cell Chromosomes pulled apart

Biology Leaving Cert 2. 3 Cell continuity Mitosis: Stage 4 • A nuclear membrane forms around each set of new chromosomes and the cell divides in two Cell divides in two

Biology Leaving Cert 2. 3 Cell continuity Interphase Mitosis – stage 2 Mitosis – stage 1 Mitosis – stage 4 Mitosis – stage 3 • The end result of mitosis is two new daughter cells – each with the same number of chromosomes as the parent cell

Biology Leaving Cert 2. 3 Cell continuity H 2. 3. 8 Mitosis: Stage 1 - Prophase • The chromatin shortens, thickens and double stranded chromosomes become visible in the nucleus. • The Nuclear membrane breaks down : • Spindle fibres are formed Cell membrane Double stranded chromosomes Spindle Fibres Nucleus Nuclear membrane

Biology Leaving Cert 2. 3 Cell continuity H 2. 3. 8 Mitosis: Stage 2 - Metaphase • Fully formed Spindle fibres attach to the chromosomes pairs at the centromere. • The chromosomes line up along the centre of the cell – the equator line. Centromere Chromosomes line up on the equator line Spindle Fibre

Biology Leaving Cert 2. 3 Cell continuity H 2. 3. 8 Mitosis: Stage 3 - Anaphase • Spindle fibres contract and chromosome pairs are pulled apart at the centromere • Chromosomes are pulled to opposite ends of the cell Chromosomes pulled apart Centromere

Biology Leaving Cert 2. 3 Cell continuity H 2. 3. 8 Mitosis: Stage 4 - Telophase • A nuclear membrane forms around each set of new chromosomes and the cell divides in two Cell divides in two

Biology Leaving Cert 2. 3 Cell continuity Today’s objectives • Difference in Telophase between plant and animal cells • Function of mitosis in unicellular organisms • Function of mitosis in multicellular organisms

Biology Leaving Cert 2. 3 Cell continuity H 2. 3. 8 Mitosis: Stage 4 - Telophase • Cell division in an animal cell involves cleavage furrow formation Chromosomes appear as chromatin again

Biology Leaving Cert 2. 3 Cell continuity Mitosis: Stage 4 - Telophase • Cell division in a plant cell involves cell plate formation

Biology Leaving Cert 2. 3 Cell continuity Interphase Mitosis - PMAT Metaphase Prophase Telophase Anaphase • The end result of mitosis is two new daughter cells – each with the same number of chromosomes as the parent cell

Biology Leaving Cert 2. 3 Cell continuity

Biology Leaving Cert 2. 3 Cell continuity Function of Mitosis 1. A method of reproduction for single celled organisms mitosis allows single celled organisms to multiply and produce offspring identical to themselves. E. g. Amoeba

Biology Leaving Cert 2. 3 Cell continuity If living organisms are composed of cells, what do they need in order to grow bigger? … …MORE CELLS !!

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 5 Function of Mitosis • 2. A method of growth for multicellular organisms.

Biology Leaving Cert 2. 3 Cell continuity The Cell Cycle 2. 3. 4 • Def Cancer is a group of disorders in which cells lose the ability to control the number of times that mitosis happens and how fast it happens. It results in uncontrolled multiplication of cells. Two possible causes of cancer: Cigarette smoke Ultraviolet radiation

Biology Leaving Cert 2. 3 Cell continuity Check your learning • How mitosis happens in haploid and diploid cells • Difference in Telophase between plant and animal cells • Functions of mitosis • Cancer – definition and possible causes

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 6 Meiosis • Def Meiosis is division of the cell to produce daughter cekks which contain half the chromosome number of the parent cell. Diploid cell with 2 n = 4 Haploid cells with n=2

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 7 Function of Meiosis 1. Sexual reproduction in Multicellular organisms Meiosis produces haploid cells with half the number of chromosomes as body cells.

Biology Leaving Cert 2. 3 Cell continuity 2. 3. 7 Function of Meiosis • 2. Meiosis produces variation through the random sorting of genetic material which takes place during meiosis. • The cells resulting from meiosis are not identical to the parent cell