RA # 3.1

 What else can RNA do besides deliver molecular information?  Act as an enzyme  When it acts as an enzyme, what is it called?  A ribozyme

 Why is DNA more stable and longer lasting than RNA?  Because it is double-sided, so one side protects and stabalizes the other side

 What has to occur in order for life to continue on the earth?  Organisms must reproduce

 1) Replication of DNA ◦ Occurs during “s” phase ◦ “s” = synthesis  2) Replication of organelles  3) Division of the cytoplasm & cell membrane- “cytokinesis”  Movement of cytoplasm

 Binary Fission

 What is theta replication?  Discovered by John Cairns in the 1960’s. He referred to it as Circular or Theta replication. The Greek symbol for the letter Theta is: Θ.  This type of replication  occurs in organisms  that have circular  chromosomes  (prokaryotes – bacteria)

 Replication starts at “origin”  Replication continues around entire single, circular chromosome creating two identical circular chromosomes in the nucleoid region

 What is the nucleoid region?  The area where you would expect to see the nucleus of a cell

 A cleavage furrow is produced using actin & myosin microfilaments of the cytoskeleton  Produces two identical daughter cells (clones)  100% identical DNA

 Binary fission came first  Mitosis would have evolved from binary fission as as DNA increased in cells & as organelles began  What two major steps are the same in both processes? ◦ Synthesis ◦ Division

 1. Cell division ◦ Results in two genetically identical daughter cells  2. Maturation (includes growth & repair)

 The entire genetic material for an organism or cell.  Human genome = 2 m or 7 ft per cell  DNA is our “Million Dollar Blueprint”  Genomes vary from species to species

 Chromatin = loose state  Chromosomes = tightly coiled state

 Loose allows easier access to the DNA for replication and transcription  Tightly coiled allows easier and more accurate division of the DNA

 Somatic cells = body cells ◦ 2n or diploid ◦ 46 chromosomes in humans  Germ cells = sex cells or gametes ◦ 1n or haploid (by meiosis) ◦ 23 chromosomes in humans beginning

 protein that helps DNA coil up “condense” to form the chromosomes needed for division.

 DNA coiled up around histones to form chromosomes.

 Half of a duplicated chromosome held together by a centromere  The centromere  is a group of  proteins in a  constricted  portion of the  chromosome

Ordinary cell division Parent and daughter cells identical One division Cell division to form gametes Gametes are NOT identical to parents or each other Involves two divisions