Chapter 8 DNA Replication

DNA Replication

1. Two helical strands unravel and separate from each other at a replication fork.
2. Synthesis of new strand begins.
3. Complementary base pairing yields a complementary copy of the original DNA. (AT, CG)
4. Segments of new nucleotides are joined to form short strands of DNA by DNA polymerase enzymes.
5. Short strands are joined into continuous DNA by action of DNA ligase enzymes.
(skipped some enzyme steps here)
6. Called semi conservative replication because each new double stranded DNA molecule has one original strand and one new strand.

Protein Synthesis

1. DNA gets a signal we need more proteins. Sends a message to mRNA.
2. mRNA carries the message DNA to protein transcriber.
1. mRNA is translated in codons. (three mRNA nucleotides = one amino acid)
2. codons “encode” for each amino acid in a protein (see degeneracy, sense, nonsense)
3. codes until it gets a stop codon because there is no tRNA to stop it. Has a start and an end because they don’t want the entire DNA transcribed.

DNA Polymerase reads it in:
E: placing (empty site)
P: reading (where the peptide bond happens. Peptide bond joins two amino acids)
A: attachment

(another way to look at it)
Transcription: In transcription, a strand of messenger RNA (mRNA) is synthesized from the genetic information in DNA. The region where RNA polymerase (needed for synthesis) binds to DNA and transcription begins is known as the promoter site. The terminator site is whereENA polymerase and newly formed mRNA are released from the DNA, signaling the endpoint for transcription of the gene.
Translation: Protein synthesis is called translation because it translates the language of nucleic acids into the language of proteins. The language of mRNA is in codons, groups of three nucleotides such as AUG. Each codon “codes” for a particular amino acid. The sites of translation are ribosomes that move along mRNA. The amino acids are transported to the ribosome by transfer RNA (tRNA). Each tRNA molecule is made specifice for an amino acid by an anticodon that is complementary to a codon. The codon AUG would be complementary to the anticodon UAC. (see 8.9 fig)







Various facts

mRNA is the transcriber
rRNA on ribosomes
tRNA translator

RNA polymerase is in transcription.

The “ladder” sides of DNA are made up of phosphate and carbon.

Most bacteria have only one chromosome.
Circular molecule

DNA polymerase: enzyme that replicates DNA

There are two major steps for expressing any enzyme:
1. transcription
2. translation

Proteins are composed of amino acids. (GCAT)
DNA is made up of nucleotides

Reproduction = DNA replication
Regulation = protein synthesis

Ribosome carry out protein synthesis. 50s and 30s = 70s

Protein synthesis starts at AUG.
AUG may be the start of a new amino acid or the middle of another.
Protein synthesis ends at UAA, UAG, UGA. (nonsense codons)

You do not need a live cell for recombination, only a piece of DNA is transferred. Host may take 2 genes and leave 8. The rest will degrade. That is why it is so scary, bacteria dies, but the DNA lives. (I think in this case she was talking about TRANSFORMATION)

Definitions

RNA primer: a short strand of RNA used to start synthesis of the lagging strand of DNA, and to start the polymerase chain reaction.

mRNA: (messenger RNA) the type of RNA molecule that directs the incorporation of amino acids into proteins.

tRNA: (transfer RNA) the type of RNA molecule that brings amino acid to the ribosomal site where they are incorporated into proteins.

Anticodon: the three nucleotides by which a tRNA recognizes an mRNA codon.

Bacteriocin: An antimicrobial peptide produced by bacteria that kills other bacteria.

Chromosomes: The structure that carries hereditary information; chromosomes contain genes.

Codon: a sequence of three nucleotides in mRNA that specifies the insertion of an amino acid into a polypeptide.

Degeneracy: Redundancy of the genetic code; that is, most of the amino acids are encoded by several codons.

Genetic code: the mRNA codons and the amino acids they encode.

Genetic recombination: the process of joining pieces of DNA from different sources.

Genome: One complete copy of the genetic information in a cell.

Genotype: The genetic makeup of an organism.

Lagging strand: During DNA replication, the daughter strand that is synthesized discontinuously.

Leading strand: During DNA replication, the daughter strand that is synthesized continuously.

Nonsense codon: a condon that does not encode any amino acid.

Phenotype: the external manifestations of an organism’s genotype (genetic makeup)

Replication fork: The point where DNA strands separate and new strands will be synthesized.

Semiconservative replication: The process of DNA replication in which each double-stranded DNA molecule contains one original strand and one new one.

Spontaneous mutation: a mutation that occurs without a mutagen.

Transcription: The process of synthesizing RNA from a DNA template.

Translation: the mRNA as a template in the synthesis of protein.