Cellular Division

Chromosomes Chromosome In a eukaryotic cell, a condensed structure in the nucleus that is made up of DNA In a prokaryotic cell, the main ring of DNA

Chromosomes Chromatin – genetic material that’s in string-like form when cells grow

Chromosomes Chromatid – one of the two strands of a chromosome that become visible during mitosis and meiosis Sister chromatids form chromosomes Chromatid Sister Chromatids

Chromosomes Centromere – the region of the chromosome that holds the two sister chromatids together Chromatid Sister Chromatids

Chromosomes Chromosomes can be unduplicated or duplicated

Chromosomes Karyotype – A chart depicting the arrangement of chromosomes of autosomes and sex chromosomes Autosomes – chromosomes from somatic (body) cells In each pair, one chromosome comes from each parent Karyotype is organized by size In humans, sex chromosomes are the last (23rd) pair

Chromosomes Humans have a total of 46 chromosomes Sex chromosomes 44 autosomes and 2 sex chromosomes Sex chromosomes X – female Y – male

Male or female karyotype?

Cell Cycle The longest phase of the cell cycle

Mitosis Acronym to learn order of mitotic division (or the M phase) P Prophase M Metaphase A Anaphase T Telophase Mitosis – the division of the nucleus

Interphase Interphase is NOT a part of mitosis The cell grows in this phase

Interphase Centrioles becomes visible DNA present in chromatin form Nucleus becomes visible

1. Prophase Centrioles begin traveling to opposite ends of the cell Chromatin wind up to form chromosomes Centromeres hold chromatids together Nuclear membrane and nucleolus start to disappear Centrioles make spindle fibers in late prophase (or prometaphase)

2. Metaphase “Meta” – middle Chromosomes line up in the middle of the cell Spindle fiber production concludes Spindle fibers attach to centromeres

3. Anaphase Spindle fibers pull daughter chromosomes to opposite ends Cell starts to pull away from itself

4. Telophase and Cytokinesis Cleavage forms Pinching in the middle of the two cells Nuclear membrane reappears Cytokinesis occurs The division of cytoplasm

4. Telophase and Cytokinesis Cell goes back to interphase after telophase and cytokinesis In plant cells, cell plates form during cytokinesis

Mitosis and cytokinesis video http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

Cancer Apoptosis – A form of cell death in which a programmed sequence of events leads to the elimination of cells Cancer – uncontrollable cell growth and division Tumor – a growth that arises from normal tissue but that grows abnormally in rate and structure and lacks a function

Cancer A tumor can be benign or malignant Benign – does not spread to other parts of the body Malignant – invades nearby healthy tissues and organs

Cellular Reproduction Asexual reproduction – requires only one parent Ex. – bacteria Sexual reproduction – requires two parents Asexual Sexual Internal fertilization External fertilization

Cellular Reproduction Two types of asexual reproduction Conjugation – occurs when two bacteria exchange genetic material Binary fission – reproduce by asexual reproduction A single cell divides into two identical cells Conjugation

Binary Fission

Cellular Reproduction Internal fertilization – sperm and egg unite inside the body External fertilization – sperm and egg unite outside the body Asexual Sexual Internal fertilization External fertilization

Mitosis vs. Meiosis Meiosis Mitosis One cell divides into four genetically different cells Gametes – sex cells Haploid chromosome number – One set of chromosomes Haploid symbol – n 23 chromosomes in humans Mitosis One cell divides into two genetically identical cells Somatic cells – body cells Diploid chromosome number – Two sets of chromosomes Diploid symbol – 2n 46 chromosomes in humans

Meiosis

Meiosis I Several events occur during prophase I Homologous chromosomes pair up forming tetrads Crossing over occurs Spindle fibers are produced

Meiosis I Homologous chromosome – two chromosomes (one of paternal origin, the other of maternal origin) that are identical in appearance and pair during meiosis

Meiosis I Tetrad (or synapse) – coupled homologous chromosomes form during prophase I Crossing over – the exchange of genetic material between homologous chromosomes

Meiosis I

Meiosis II

Meiosis video http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_works.html

Spermatogenesis The formation of sperm Spermatocyte – mature sperm cell Spermatid – immature sperm cell

Oogenesis The formation of eggs Oocyte – mature egg Ovum - egg

Cloning A cell, cell product, or organism that is genetically identical to the unit or individual from which it was derived The first cloned mammal was Dolly the sheep She lived for six years. Normal sheep live for 11 -12 years.

Cloning