Cell continuity Biology Leaving Cert 2.3 Cell continuity

Learning objectives Today you should learn about Biology Leaving Cert 2.3 Cell continuity Learning objectives Today you should learn about What cell continuity is The difference between haploid and diploid cells The two main stages in mitosis What happens during interphase in the cell cycle

Cell continuity This requires: Biology Leaving Cert 2.3 Cell continuity Cell continuity 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 Exist as chromatin during Interphase – stage of non division At end of interphase they contract and can be seen as shorter strands, each is made up of a duplicated strand. Single stranded to double stranded Each chromosome will contain hundreds or thousands of genes. Genes are short sections of DNA which contain coding information for the production of proteins in a cell. Chromatin

Haploid cells A haploid cell has only one of each type of chromosome. 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. Every cell contains chromosomes. A human has a n = 23 Human sex cells are haploid.

Diploid cells A diploid cell has two of each type of chromosome. 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 2n 2n = 4 describes a Diploid cell that has four chromosomes. A pair of homologous chromosomes that are found in diploid cells are called homologous pairs. Each pair has two chromosomes that contain similar genes One of these chromosomes would have came from the mother and one form the father during reproduction. Human cells are all diploid, except for the sex cells

Check your learning.. What cell continuity is Biology Leaving Cert 2.3 Cell continuity Check your learning.. What cell continuity is The difference between haploid and diploid cells

Learning objectives The two main stages in mitosis Biology Leaving Cert 2.3 Cell continuity Learning objectives The two main stages in mitosis What happens during interphase in the cell cycle What mitosis is and how it happens

The Cell Cycle Dividing stage Non dividing stage Biology Leaving Cert 2.3 Cell continuity The Cell Cycle Dividing stage Mitosis Interphase Non dividing stage The cell is usually in a state of non division – called Interphase During Interphase the chromosomes are elongates – as chromatin It is producing new organelles, making chemicals, enzymes and proteins Later the chromosomes make copies of themselves! During mitosis the genetic material divides and the cytoplasm, the organelles and the biomolecules are partitioned into two cells. The Cell Cycle is the sequence of events in a cell which includes a state of non division and division.

During Interphase The chromosomes: Biology Leaving Cert 2.3 Cell continuity During Interphase Mitosis Interphase The chromosomes: Elongate – as chromatin then make copies of themselves! The cell also produces new organelles and makes chemicals, enzymes and proteins

Biology Leaving Cert 2.3 Cell continuity 2.3.4 Mitosis 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

Learning check… What does cell continuity mean? Biology Leaving Cert 2.3 Cell continuity Learning check… What does cell continuity mean? Distinguish between haploid and diploid Define mitosis

Today’s objectives To learn the names of the four stages of 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 : Fibres Cell membrane Double stranded chromosomes There are four main stages in Mitosis Nucleus Nuclear membrane

Mitosis: Stage 2 Fibres attach to the chromosomes. 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 Mitosis Mitosis – stage 4 Mitosis – stage 2 Interphase Mitosis – stage 3 Mitosis – stage 1 The end result of mitosis is two new daughter cells – each with the same number of chromosomes as the parent cell

Mitosis: Stage 1 - Prophase Biology Leaving Cert 2.3 Cell continuity Mitosis: Stage 1 - Prophase H 2.3.8 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 There are four main stages in Mitosis Spindle Fibres Nucleus Nuclear membrane

Mitosis: Stage 2 - Metaphase Biology Leaving Cert 2.3 Cell continuity Mitosis: Stage 2 - Metaphase H 2.3.8 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

Mitosis: Stage 3 - Anaphase Biology Leaving Cert 2.3 Cell continuity Mitosis: Stage 3 - Anaphase H 2.3.8 Spindle fibres contract and chromosome pairs are pulled apart at the centromere Chromosomes are pulled to opposite ends of the cell Centromere Chromosomes pulled apart

Mitosis: Stage 4 - Telophase Biology Leaving Cert 2.3 Cell continuity Mitosis: Stage 4 - Telophase H 2.3.8 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

Mitosis: Stage 4 - Telophase Biology Leaving Cert 2.3 Cell continuity Mitosis: Stage 4 - Telophase H 2.3.8 Cell division in an animal cell involves cleavage furrow formation Chromosomes appear as chromatin again

Mitosis: Stage 4 - Telophase 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 Mitosis - PMAT Telophase Metaphase Interphase Anaphase Prophase 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. The cell cycle is normally carefully controlled so that just enough new cells are formed. Sometimes cells lose the ability to control cell division. Picture a mouse with a breast tumour removed. Carcinogen- a cancer causing chemical Oncogenes – normal genes turned onto cancer causing genes Tumours can be benign or malignant – invade other cancer cells Two possible causes of cancer: Cigarette smoke Ultraviolet radiation

Check your learning How mitosis happens in haploid and diploid cells 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 2n = 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.

2.3.7 Function of Meiosis 2. Meiosis produces variation 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 NEW GENE COMBINATIONS ARE PRODUCED IN THE GAMETE VARIATION PRODCUED DIFFERENCES IN ORGANISMS RESULTING FROM SEXUAL REPRODUCTION.#BASIS FOR EVOLUTION – ALLOWS ANIAMSL TO ADAPT TO THEIR ENVIRONEMNT.