Chromosomes and Cell Reproduction: Prokaryotic and Eukaryotic Cell Division

1. Chapter 6 Chromosomes & Cell Reproduction

2. Prokaryotic (bacterium) CellDivision • Binary fission is form of asexual reproduction. • Binary fission produces identical offspring • Binary fission is the process by which bacteria reproduce

3. Eukaryotic cellreproduction • Gametes– sex cells • Male – Human sperm cell (23 chromosomes) • Female – Human egg cell (23 chromosomes) • Gametes – haploid cells (n number) • Haploid number is ½ the organism’s body cell chromosome number. • Human sperm and egg have 23 chromosomes. • Humans the haploid number is 23 • The symbol used to designate the haploid number is n

4. In humans gametes contain 22 autosomes and 1 sex chromosomes • Males – sperm with either an x or y chromosome • In human males determine the sex of child b/c males have one x and one y chromosome. • The X and Y chromosome are called the sex chromosomes • Female : XX :: male : XY

5. Chromosomes/Genes • Chromosomes are made up of DNA, Genes and Protein. • The DNA in Eukaryotic cells is packaged into structures called chromosomes. • Chromatids – two exact copies of chromosome • Genes on chromosomes are the units of inheritance • A Gene is a segment of DNA that direct the production of a specific protein • A gene is a segment of DNA that carries the instructions for producing a specific trait • There are 1,000’s of genes on a DNA molecule

6. The point at which two chromatids are attached to each other in a chromosome is called a centromere • A picture of a cell’s chromosome is called a Karyotype • Karyotypes can be studied to lean about the number and structure of a chromosome in a somatic cell

7. Sets of chromosomes • Homologous chromosomes – chromosomes that are similar to each other • Somatic chromosomes are calledbody cell chromosomes • Somatic cells – contain the diploid or 2n number of chromosomes • In humans the diploid number is 46 • Gametes – sex chromosomes

8. Egg cell has 23 chromosomes and a sperm cell has 23 chromosomes. • A Zygote has 46 chromosomes. • A zygote is a fertilized egg cell. • A diploid cell is one that • has two homologues of each chromosome • is designated by the symbol 2n • Has chromosomes found in pairs

9. Change in chromosome number • Each of an individual’s 46 chromosomes has thousands of genes. • Sometimes an individual can have an extra copy or be missing one or more chromosomes. • The failure of replicated chromosomes to separate is called nondisjunction • A mutation in which a piece of a chromosome is lost during meiosis is called deletion

10. Abnormal syndromes • Down’s syndrome – In humans, this is a specific condition caused by an extra chromosome 21 • Down’s syndrome is also called trisomy 21 because it is a mutation that results in a cell having an extrachromosome • People with Down’s syndrome have 47 chromosomes instead of 46

11. Human chromosomes • Exist in 23 pairs in all cells but gametes • Each contain thousands of genes • Form right before cells divide • In order to fit within a cell , DNA becomes more compact by wrapping tightly around associated proteins. • The shape of a bacterium’s chromosome is circular

12. 1. How many chromosomes are in the body cell of an organism with the haploid number of 8? ____ • 2. Diploid number is 46 then what is the number of chromosomes found is a human ovum ? ___ • 3. Diploid : somatic :: haploid : ______

13. 1. 16 If the haploid or sex chromosome number was 8 then Diploid (2n) would be 2(8)=16 • 2. 23 If the diploid number was 46 then the haploid number would be ½ which is 46/2 = 23 • 3. Gamete Diploid cell and somatic cell are the same. • Therefore what word means the same as haploid? Gamete is the same as haploid

14. The Cell CycleSection 2 • CELL CYCLE – sequence of events that occurs in a cell from one mitotic division to the next. • Normal cell growth and cell division are stimulated by PROTEINS • The information needed by a cell to direct its activities and to determine its characteristics is contained in molecules of DNA • After cell division, each new cell will contain the same genetic information as the original cell. • Asexual reproduction can occur by mitosis

15. Cell Cycle • Cell cycle (G1 – S – G2 – M – C) • Interphase • G1 – first growth phase • S phase – Synthesis phase • G2 – 2nd growth phase • Mitosis • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis • Cytoplasm divides

16. Interphase • Interphase is the phase that the cell cycle occupies most of the cell’s life • Cell spends 90% of its time in this phase • The first three phases of the cell cycle are collectively known as Interphase

17. Section 3 • Mitosis – is a process by which the nucleus is divides into two nuclei • Mitosis – is a process by which a cell’s nucleus divides • Spindles – structures that will move chromosomes during cell division A spindle fiber is a specialized from of microtubule • Stages of Mitosis Prophase Metaphase Anaphase Telophase

18. Prophase • Prophase – 1st stage of mitosis - Chromosomes coil up into short, fat rods - Chromosomes coil up and become visible - The nuclear membrane dissolves

19. Metaphase/Anaphase/Telophase • Metaphase - The arrangement of all chromosomes along the equator of the cell • Anaphase– • The stage in which the centromeres divide. • Chromosomes move toward opposite poles • Telophase- • Spindle dissolves • Nuclear membrane forms around each set of new chromosomes • Chromosomes uncoil • Cell membrane begins to pinch inward • In plant cells = a cell wall begins to form

20. Cytokinesis • Cytokinesis – last stage of the cell cycle • Mitosis ends and Cytokinesis begins • Cytokinesis -Cytoplasm of the cell is divided into half, and the cell membrane grows to enclose each cell. • After mitosis and cytokinesis, each new cell has a complete set of the parent’s chromosomes

21. Plant and Animal cells both undergo cell division • Plant and animal cells have different strategies for cytokinesis • Animal cell - cell division • No cell wall • Cell membranes form • Plant cell – cell division • Cell membrane forms • Cell Wall Forms • Cytokinesis in plant cells involves the formation of a cell plate

22. CANCER • Cancer is a disease characterized by uncontrolled cell growth • Normal cells become cancerous when • Regulation of cell growth and division is lost • Cell’s do not respond normally to control mechanisms • Cells continue to divide without passing through G1

23. Pg 130 • Be able to place sketches in correct order for mitosis • Prophase • Metaphase • Anaphase • Telophase