Genetics - 10

Genetic material characteristics

replication, storage of information, expression of information, and variation by mutation

transcription

Transfer of genetic information from DNA by the synthesis of a complementary RNA molecule using one strand of the DNA as a template

Types of RNA

messenger RNA, transfer RNA, ribosomal RNA

translation

derivation of the amino acid sequence of a polypeptide from the base sequence of an mRNA molecule in association with a ribosome and tRNAs

Central dogma of molecular genetics

DNA transcribed to make mRNA, rRNA, and tRNA. mRNA translated with assistance of rRNA and tRNA into protein

nuclein

found by Friedrich Miescher, now known to contain DNA

tetranucleotide hypothesis founder

Phoebus A. Levene

Levene’s discovery

DNA contained equal amounts of four similar molecules called nucleotides

tetranucleotide hypothesis

DNA is composed of identical groups of four nucleotides repeated over and over

Fredrick Griffith

performed experiments with virulent bacteria and showed transformation

Fredrick Griffith’s experiment

Injected heat killed virulent and non virulent cells in mice. The mice died and analysis showed virulent cells in their blood. This showed bacteria’s ability to convert or transform.

transformation

heritable change in a cell or an organism brought by exogenous DNA.

What question did the Avery, Macleod, McCarty expirament seek to answer?

What is genetic information?

Avery, Macleod, McCarty experiment

heat killed virulent cells were treated with protease, RNase, and DNase. Only DNase destroyed the active factor involved in transformation. This showed DNA was the transforming principle

Hershey and Chase experiments existing information

T2 phages consist of approximately 50 percent protein and 50 percent DNA, infection is initiated by adsorption of the phage by its tail fibers to the bacterial cell, production of new viruses occurs within the bacterial cell

What question did the Hershey and Chase experiment seek to answer

What enters bacteria from T2 to direct viral reproduction

Hershey and Chase experiment

used radioisotopes 32P and 35S to mark DNA and protein respectively. Using this marking, they showed that most of the DNA had entered bacteria following adsorption. After lysing, the new phages formed by bacteria were shown to be marked as well. This showed that in T2 DNA is the genetic material

protoplasts

bacterial or plant cell with the cell wall removed

Indirect evidence for DNA as genetic material in eukaryotes

distribution of DNA, mutagenesis

Direct evidence for DNA as genetic material in eukaryotes

recombinant DNA studies

tobacco mosaic virus experiment

showed that RNA is genetic material for virus

retroviruses

type of virus that uses RNA as its genetic material and employs the enzyme reverse transcriptase during its life cycle

reverse transcriptase

facilitates reverse transcription using RNA as a template to transcribe a single stranded DNA molecule

DNA components

nitrogenous base, pentose sugar, phosphate

purines

guanine and adenine

pyrimidines

cytosine, thymine, uracil

RNA pentose sugar

ribose

DNA pentose sugar

deoxyribose

nucleoside

nitogenous base and pentose sugar

nucleotide

nitrogenous base, pentose sugar, phosphate

phosphodiester bond

covalent bonds by which a phosphate group links adjacent nucleotides, extending from 5’ carbon to 3’ carbon

oligonucleotides

short chains of nucleotides

polynucleotides

long chains of nucleotides

Watson and Crick model for DNA

1.two chains in a right hand double helix 2. chains are antiparallel 3. bases lie flat perpendicular 4. nitrogenous bases are paired through hydrogen bonding 5. each turn of helix is 10 bases or 34 A long 6. major and minor grooves alternate 7. diameter is 20 A wide

Chargaff’s rule 1

adenine proportional to thymine, guanine proportional to cytosine

Chargaff’s rule 2

A+G = C+T

Chargaff’s rule 3

G+C does not necessarily equal A+T

complementarity

chemical affinity between nitrogenous bases of nucleic acid strands as a result of hydrogen bonding

hydrogen bond

weak attraction between a H atom covalently bonded to an O or N and an atom that contains an unshared electron pair

A DNA

more compact DNA

B DNA

regular DNA

C DNA, D DNA, E DNA

less compact DNA

Z DNA

left handed DNA

Svedberg coefficient

indicates size and shape

ribosomes

protein composed of two subunits, involved in translation

small nuclear RNA

processing mRNAs

microRNA

involved in gene regulation

mid point of graph

melting temp, 50% of strands have denatured