Chapter 16&17

transcription- occurs in the nucleus; done by RNA polymerase; is the creation of a RNA strand from DNA; part of replication

Transformation- named by Fredrick Griffith, means a change in genotype and phenotype due to the addition of external DNA.

Hershey and Chase used phages to prove that phage DNA entered the cell but not phage protein.

Bacteriophages were huge in the research of DNA. They infect cells and change take control of their metabolic processes

DNA has three key components: a nitrogenous base, a phosphate group and a pentose sugar. The base could be adenine or thymine (which group together) or guanine or cytosine (which group together).

Chargaffs rules:

  1. DNA base composition varies between species
  2. Each species the percentage of A&T are roughly the same and so are C&G.

DNA's moleculafr structure was discovered by Watson and Crick.

DNA's shape is a double helix with two-sugar antiparallel back bones meaning their subunits run . in opposite directions.

There are 10 layers of base pairs in every turn of the helix.

Watson and Crick also came up with the idea of the semiconservative model of DNA replication which is that each daughter molecule's DNA is made of a strand of each parents DNA.

Replication of chromosomal DNA begins at certain spots called origins of replication

A replication fork is a y shaped region where the parental strands of DNA are being broken apart. This unwinding is caused by many proteins.

These proteins are helicases , single-strand binding proteins and topoisomerase.

The initial nucleotide chain produced is actually an RNA strand called a primer which is synthesized using an enzyme called primase.

DNA polymerase catalyzes the synthesis of new DNA.

A new DNA strand can only elongate in the 5 to 3 direction.The DNA strand is made by this mechanism called the leading strand.

To elongate the second new DNA strand it must elongate away from the replication fork and this is called the lagging strand. The lagging strand is synthesized in fragments known as Okazaki fragments which are joined together by DNA ligase.

Mismatch repair- enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors.

Nucleotide excision repair- when enzymes (DNA polymerase and DNA ligase) fill in the gaps made by nuclease which takes out damaged DNA

Telomeres are sections of repeating nucleotides that protect from the shortening of DNA strands and prevents the cell from carrying out a cells monitoring for DNA damage.

Translation is when the Codons (three base pair set) are read and turned into amino acids; part of replication ; there are 20 amino acids

MUTATIONS

point v frameshift- one spot changes the nitrogen base v insertion or deletion causing the frame to shift

missense v silent- causes change of amino acid through change of base v change of base doesnt affect the amino acid produced

nonsense- any mutation causing change

Covalent bonds hold nucleotides together

hydrogen bonds hold nitrogenous bases together

Types of RNA

mRNA-messanger

tRNA- transportation/translation

rRNA- structural

Codon- 3 bases on mRNA, codes for amino acids

anticodon- 3 bases on tRNA

triplet- 3 bases on DNA

A promoter is the part of the strand that starts the production also known as the codon AUG or amino acid, methionine

The coding strand is the4 one that has a promoter on it

During this process introns (unimportant pieces of DNA) are cut off and the remaining exons are put together using spliceosomes.

Ribosome's are responsible for translation

translation occurs in the cytoplasm or rough E.R

tRNA and start codons help ribosome's "know" what to do

aminoacyl tRNA synthase- the enzyme that gives each tRNA the appropriate amino acid

three active sites of translation: 1. A- assemble 2. P- puts the peptide together 3. E- tRNA exits

Amino acids are held together by peptide covalent bonds in a dehydration reaction; gives primary structure

a short chain of amino acids is known as a polypeptide chain

secondary and tertiary shape are determined by hydrogen bonds and disulfide bonds which both give 3-D shape; these are affected by temperature and pH

stop codon stops the peptide chain because there is no amino acid on the tRNA

the peptide chain then moves into the Golgi to put the final touches onto protein.