Bio 2

1. Stable source of information 2. Ability to replicate accurately 3. Capable of change (evolution)

Griffith’s Transformation Experiment

Avery’s Transformation Experiment

Chargaff’s Nucleotide Ratio Observations

1) Hershey-Chase Bacteriophage Experiment 2) Franklin and Wilkins X-ray crystallography of DNA

Watson & Crick propose double-helix model of DNA

1) “transforming principle” demonstrated with Streptococcus pneumoniae 2)R-straincarries a mutation and it is not virulent

heritable change in genetic material

Concluded that IIR bacteria has somehow been transformed into smooth, virulent IIIS bacteria by interacting with IIIS strain

proposed this was due to proteins

Also worked with S.P type IIIS. Separated nucleic acids (DNA,RNA) from remaining cell components

Concluded that “IIIS” DNA was the transforming agent responsible for Griffith’s results (not RNA).

Virus that atacks bacteria and replicates by invading a living cell and using the host cell’s molecular machinery

parasitoids

Phage attches to E.coli and injects phage chromosome

Enzymes encoded by phage break down the bacterial chromosome

Phage chromosome replicates, using bacterial materials and phage-encoded enzymes

Phage genes are expressed to produce structural components of the phage particle

Progeny Phage particles assemble

Progeny phage particles are released as bacterial cell wall lyses

DNA and proteins

In one, labeled DNA with isotope^32 P In another, labeled protein with isotope^35 S

Infected E. coli bacteria with two types of labeled T2

32P is discovered within the bacteria and T2 phage progeny, whereas 35S is not found within the bacteria but released with phage ghosts.

One genetic strain can transform another to have a new trait. (He incorrectly concluded the transforming agent is a protein)

DNA (not RNA) is transforming agent

DNA (not protein) is the genetic material

monomers and subunits that make up DNA and RNA

1) Pentose (5-carbon) sugar 2) Nitrogenous base 3) Phosphate group aUached to 5‘carbon of the sugar and 3’ of another

DNA = deoxyribose and RNA = ribose (compare 2’ carbons)

attached to 1’ carbon, Include heterocyclic rings, Purines and Pyrimidines

Adenine and Guanine

Cytosine, Thymine (DNA) and Uracil (RNA)

phosphodiester bonds and polynucleotides

Covalent bond between the phosphate group (attached to 5’ carbon) of one nucleotide and the 3’ carbon of the sugar of another nucleotide

Yes and it is very stable. Can be autocleved without degrading and Forensic science is an obvious application of its durability

One end of the chain has a 5’ carbon (with a phosphate group on it) and the other end has a 3‘ carbon (hydroxyl group on it)

polarity

polynucleotides chain

The phosphate that is not involved in a phosphodiester bond is attached to the 5’ carbon of thedeoxyribose

The 3’ carbon of the deoxyribose is free.

non-covalent hydrogen bonds

a pyrimidine and a purine base (A binds T, G binds C)

thymine is replaced with Uracil

two antiparallel strands

right to leg and from 5’ to 3’. If you write both strands the top strand Is in that orientation

The information is present in TWO copies. If you know the sequence of one strand, you can deduce the sequence of the other.

In the late 1950s, three different mechanisms were proposed for the replication of DNA: 1) Semiconservative 2) Conservative 3) Dispersive

The double-stranded DNA contains one parental and one daughter strand following replication

Both parental strands remain together after DNA replication

Parental and daughter DNA are interspersed in both strands following replication

Grow E. coli in the presence of ^15N (a heavy isotope of Nitrogen) for many generations

heavy-labeled DNA

Transfer labeled E. coli to medium containing only ^14N (a light isotope of Nitrogen) and Collect sample of cells after various times

Analyze the density of the DNA by centrifugation using a cesium chloride (CsCl) gradient

DNA replication is semi-conservative, as proposed by Watson and Crick

Isotope-centrifugation experiments by Meselson and Stahl confirm this hypothesis (and refute alternatives)

E. coli and the mechanisms of DNA synthesis with "in vitro" experiments

An extract of proteins from E. coli, Template DNA and Radiolabeled nucleotides (dNTPs)

1)dNTPs: dATP, dTTP, dGTP, dCTP 2)DNA template 3) DNA polymerase I 4) Mg 2+ ion

DNA polymerase I catalyzes formation of phosphodiester bond between 3’-OH of the deoxyribose and the 5’-phosphate of the dNTP

DNA polymerase I “finds” the correct complementary dNTP at each step in the lengthening process.

Direction of synthesis is 5’ to 3’

synthesized 5’ to 3’ in the direction of the replication fork movement. continuous: requires a single RNA primer

synthesized 5’ to 3’ in the opposite direction (DNA strands are antiparallel). semi-discontinuous: requires many RNA primers.

Polymerase synthesizing short RNA primer from DNA template

Highly progressive 5'-3' polymerase

Procressive 5'-3' polymerase with 5'3' exonuclease activity

seals the gaps between Okazaki fragments with a phosphodiester bond

1) RNA primer added by primase DNA Pol III synthesize DNA until it reaches the previous primer.

DNA Pol I takes over because it has a 5’ exonuclease activity which allows it to chew away the 5’ end of the RNA primer

the final bond between the Okasaki fragments is ligated by a ligase to make a continuous strand

Segments of single-stranded DNA

relaxes the supercoiled DNA

binds to the DNA at the replication fork and untwist the DNA using energy derived from ATP

binds to helicase producing a complex called a primosome (primase is required for synthesis)

synthesizes a short RNA primer of 10-12 nucleotides, to which DNA polymerase III adds nucleotides

adds nucleotides 5’ to 3’ on both strands beginning at the RNA primer.

ability to remove nucleotides from the 3’ end of the chain and Important proofreading ability

Function, structure, development and reproduction of a organism

the genetic code for the amino acid must be read from the DNA and the protein is made

Consist of one or more chains of amino acids. Each chain is a polypep and the sequence is coded by a gene.

Genes are transcribed to mRNA. The transcription product is translated to protein.

is an explanation of the flow of genetic information within a biological system

DNA ->transcription->mRNA->Translation-> Protein

Transcription and Translation

synthesis of single-stranded messenger RNA (mRNA) using the DNA template (1 strand of DNA template is transcribed)

conversion of messenger RNA sequence into the amino acid sequence of a polypeptide (i.e., protein synthesis)

encodes the amino acid sequence of a polypeptide; product of transcription

transports amino acids to ribosomes during translation

forms complexes called ribosomes with protein, the structure on which mRNA is translated

forms complexes with proteins used in eukaryotic RNA processing (e.g., exon splicing and intron removal)

only mRNA is involved in transcription

other types of RNA contribute to translation

1) Regulated by gene regulatory elements within each gene. 2) DNA unwinds next to a gene. 3) RNAis transcribed 5ʼ to 3ʼ from the template

1) NTPs instead of dNTPs 2) RNA polymerase 3) No primer 4) No proofreading 5) Adds Uracil (U)instead of Thymine (T)

1) Binds to the promoter sequence on the DNA template 2)Forma of phosphodiester bond between exis RNA and NTP 3) 5’ to 3’ synthesis

Initiation, Elongation and Termination

1) 5ʼ Promoter, recognized by RNA polymerase, but not transcribed 9-35bp to -10bp) 2) RNA coding sequence 3) 3ʼ Terminator, stops RNA polym.

e combines with sigma factor (a polypep ) to create RNA polymerase holoenzyme. Recognizes promoters and initiates transcription

required for efficient binding and starting of transcription. Different sigma factors recognize different promoter sequences.

binds promoters of template DNA. Binds loosely to -35 promoter (DNA is double stranded). Binds tightly to -10 promoter and untwist DNA

the variation of gene expression (how much and efficiency). Selective control of gene expression is a result

are usually made up of 13 to 25 nucleotides and are designed to hybridize specifically to DNA or RNA sequences

combining two complementary single-stranded DNA or RNA molecules and allowing them to form asingle double-stranded molecule through bping

joining of single strands of DNA

extending the DNA side of the specific gene