Chapter 3

Chapter 3



Mutations: Altered Genes



Point mutations alter a single base.

A chromosomal mutation changes part of a chromosome (deleted/repeated/moved)



Too much genetic change (mutation) can be harmful to the individual. 



However, genetic variation (caused by mutation) is necessary for evolutionary change of the species. 




Chromosomes

Composed of chromatin- a complex of DNA and proteins



Homologous chromosomes: pairs that contain the same genes one from each parent



Karyotype homologous pair



Chromosomes must be replicated before cell division

  • Sister chromatids: 2 copies of the same chromosome

  • Connected at their kinetochores



Mitosis

  • New cells are identical to the old cells

  • Chromosome number is the same in parent and daughter cells(diploid-2N)




Growth, repair, replacement, and asexual reproduction 



Phases of mitosis

  • Interphase

  • Growth and animal call activities 

  • DNA is duplicated





Prophase

  • Chromosomes condense (siter chromaitids)

  • Centrioles move to poles

  • Nuclear membrane dissolves



Metaphase

  • Sister chromatids line up along the equator of the cell

  • Chromosomes attach to spindle fibers



Anaphase 

  • Spindle fibers pull sister chromatids to opposite ends of the cells

  • An identical set of chromosomes moves to each pole




Telophase

  • Chromosomes uncoil 

  • Nucleus reforms

  • Cytokinesis: cell membrane pinches to form 2 separate cells



IPMAT order of names 



Meiosis

  • Parent cell divides twice to produce 4 cells

  • Produces gametes (sex cells)

  • Daughter cells have half the original number of chromosomes (haploid - 1N)



When two gametes join to form a zygote, it will have the normal # of chromosomes.



Daughter cells are not genetically identical

  • homologous chromosomes separate sending one version of each to the new cell

Crossing over: sometimes chromosomal segments are exchanged between homologous chromosomes



Phases of meiosis

  • During meiosis 1 homologous chromosomes are held together by proteins. 



1 interphase

2 prophase 

3 metaphase 

4 anaphase 

5 telophase 



Meiosis 2

1 prophase 2 

2 metaphase 2

3 anaphase 2

4 telophase 2




Membrane Structure 



Fluid mosaic model



Cellular membranes have 4 components

1 phospholipid bilayer

Transmembrane proteins

Interior protein network cell surface marker 



Phospholipid structure consists of

  • Glyvrtol is a 3-carbon polyalcohol acting as a backbone for the phospholipid 

  • 2 fatty acids



Osmosis 

When 2 solutions have different osmotic concentrations 

  • A Hyperonic solution has a higher solute concentration

  • A Hypotonic solution has a lower solute concentration



Osmosis moves water toward the hypertonic solution.



More passive transport

  • Channel proteins have a polar interior allowing polar molecules to pass through.

  • Ex

  • Ion channels allow the passage of ions which are associated with water

  • Gated channels are opened or closed in response to a stimulus (chemical or electrical)

Facilitated diffusion is the movement of molecules from high to low concentration with the help of a carrier protein 

  • Carrier proteins  bind to a specific molecule to facilitate its passage 

  • Is specific 

  • Is passive 

  • Saturates when all carriers are occupied 



Active transport

  • Requires energy- atp is used directly or indirectly to fuel active transport



  • Moves substances from low to high concentration OR 

  • Moves large amounts of material

  • ENFOCYTOSIS movement of substances into the cell

  • Exocytosis material is discharge from the cell