Biology 30 Essays

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Chapter 16- Cellular Reproduction

The continuity of life:
-Is based upon the reproduction of cells or cell division
Unicellular organisms – PROYCARYOTIC * Reproduced by cell division Multicellular organism’s- EURKAYOTIC - depend on cell division for: 1. Repair 2. Reproduce (fertilized cells) 3. Growth
The cell cycle * Cell division results in genetically identical daughter cells * Cells duplicate their genetic material * Before they divided, ensuring that each daughter cell receives an exact copy of the genetic material. DNA (found in chromosomes) (23 + 23) * Histones are proteins that the DNA is wrapped around. Organized proteins condense DNA into nucleolus


- Eukaryotic chromosomes * Consist if chromatin
-In animals * Somatic cells have 2 sets of chromosomes * Gametes (sperm, egg) have 1 set of chromosomes
- Each duplicated chromosome * Has two sister chromatids, which separate during cell division
-Eukaryotic call division consists of * Mitosis, is the division if the nucleus * Cytokinesis, the division of the cytoplasm
- In meiosis * Sex cells are produced after a reduction in chromosomal number
- Chromosome number * 46 chromosomes * 22 pairs id homologous chromosomes (known as Autosomes) * 2 sex chromosomes (may not be the same (X or Y)) * Male- XY * Female- XX * 50% chance of boy or girl | X | X | X | XX | XX | Y | XY | XY |

Homologous Chromosomes (somatic cell /2 = gamete cell)
-Homologous chromosomes have the same genes at the same locus, but may have different alleles of the gene
- Diploid- means “Double“
-Humans – 46 chromosomes, 23 pairs, 2n
-Haploid- means, “Single“
- Human gametes- 23 chromosomes, n
-Polyploid- 3 or more (ex. tetraploid, triploid, octoploid)

Karyotype * A particular set if chromosomes that are individual possesses (know diseases and disorder’s for diploma) one X= turners syndrome, 3 chromosome’s on group 21= down syndrome. You can determine sex at 8-9 weeks during pregnancy.

The cell cycle and mitosis

All cells follow that same sequence of mitotic divisions, and this is known as the cell cycle. (roughly 24 hours a cycle)

Stages of the cell cycle * Interphase * Cells carry out regular metabolic functions and prepares fro cell division 1. G1 “growth 1”- rapid growth and metabolic activity. 2. S “DNA synthesis”- DNA synthesis and replication (produce sister chromatids (when DNA joins together by the centromere) 3. G2” growth 2- cell prepares to divide. * Mitosis * Division of genetic material into two complete and separate sets

* Cytokinesis * Division of cytoplasm and organelles into two separate cells

- Mitosis * The process of nuclear division that occurs before a cell physically divides in two. * Key facts: 1. The daughter cells receive that same number of chromosomes as the parent cell. 2. Somatic cells divide by mitosis. 3. Most of our body cells contain identical chromosomal pars 4. Most human diploid cells contain 46 chromosomes or 23 pairs of homologous chromosomes.

Phase Activity

Interphase | * Most time consuming phase * Three parts (G1,S, G2) | Prophase | * Chromosomes of nucleus become visible * In animal cells a centriole moves to opposite poles of the cell * Spindle fibers form * In animal cells we have an aster * Chromosomes structure consists of two chromatids, a centromere holding together chromatids * The centromere attaches to the spindle fibers * Nuclear membrane fades | Metaphase (above each other, at equator) | * Chromosomes composed of sister chromatids move toward the center of the cell. | Anaphase (move apart) | *