4.1 CELL DIVISION AND GENETIC MATERIAL

Transcription

1 4.1 CELL DIVISION AND GENETIC MATERIAL

2 GENETICS Field of biology Study how genetic information is passed from one generation of organism/cells to the next

3 THE CELL THEORY developed in mid-1800s 1. All living things are composed of one or more cells. 2. Cells are the smallest units of living organisms. 3. New cells come only from pre-existing cells by cell division. Thus, traits must be passed from a parent cell to new daughter cells

4 SOMATIC CELL a plant/animal body cell go through cell cycles: 1 cell 2 cells cell cycle duration depends on: 1. the cell type 2. the organism Most healthy, actively dividing cells: hrs

5 THE CELL CYCLE 3 main stages 1. interphase: growth and intense cell activity 2. mitosis: nucleus and genetic material divide 3. cytokinesis: division of the cell cytoplasm and creation of new cells

6 THE CELL CYCLE 3 functions 1. growth of the organism 2. repair of tissues and organs 3. maintenance to replace dead cells Specific checkpoints 1. monitor growth 2. ensure the cycle continues or stops appropriately. Regulation is the key to preventing uncontrolled and rapid growth, such as cancerous growth.

7 INTERPHASE the cell carries out its normal functions: 1. grows 2. makes copies of its genetic material. 3 phases: Growth 1 (G1), Synthesis (S), and Growth 2 (G2). Growth 1 (G1): major period of growth. Synthesis (S): DNA (also called chromatin) is replicated. Growth 2 (G2): further growth and molecule synthesis.

8 MITOSIS separation of the cell s replicated genetic material. chromosome: a structure in the nucleus that contains DNA sister chromatid: one of two chromosomes that are genetically identical and held together at the centromere centromere: the region where two sister chromatids are held together in a chromosome spindle fibre: a microtubule structure that facilitates the movement of chromosomes within a cell centrosome: a structure that helps to form the spindle fibres

9 MITOSIS (VIDEO 3:08)

10 CYTOKINESIS different in different cell types. animal cells: microfilaments constrict Furrow forms in cell membrane along the equator of the cell. deepens and pinches off into two cells. This transmission electron micrograph shows two identical kidney cells forming. Magnification: 1700x

11 CYTOKINESIS plant cells: rigid cell wall does not pinch inward a cell plate forms between the daughter nuclei A cell wall forms on each side of the cell plate.

12 PROKARYOTIC CELLS no nucleus complete cell division with binary fission DNA is pulled apart cell separates into two prokaryotic cells.

13 THE STRUCTURES OF GENETIC MATERIAL DNA Made of nucleotides long, spiraling double helix Nucleotide: a sugar (deoxyribose), a phosphate group, a base. 4 bases: adenine (A), guanine (G), cytosine (C), thymine (T). A - T and C - G

14 DNA REPLICATION during interphase double helix unwinds each strand of DNA serves as a template Each new double helix contains one original strand and one new strand and one new strand Semi-conservative

15 CHROMOSOMES NO relationship between # of chromosomes and complexity of organism.

16 HUMAN CHROMOSOMES Each somatic cell has 2 sets of 23 chromosomes one set from father and one set from mother. The 2 sets are homologous same sequence of genes (traits) same length, location of the centromere, and stain banding pattern. However, they can contain different alleles (forms) of a gene.

17 CHROMOSOMES 22 pairs are called autosomes true homologous pair 1 pair is the sex chromosomes determine the sex of the individual The two chromosomes (X and Y) are not homologous. XX = female XY = male

18 KARYOTYPES a person s particular set of chromosomes chromosomes are collected and stained when a cell is in metaphase so they appear as sister chromatid Xs. This is a human karyotype. The chromosome pairs are arranged and numbered in order of their length, from longest to shortest. The sex chromosomes are placed last in a karyotype. Note that the banding patterns between homologous chromosomes are different in this image because of the type of dye that was used.

19 HOMEWORK p. 168 #1,3-6, 8, 9, 11,13,14,16, 17