Lecture 2 Flashcards
Genetic Material
- information contained in genes that gets passed onto new generation
- source of variability among organisms
- originally thought to be protein since it is much more visible and abundant
Darwin’s Postulate
To serve as genetic material, molecule must be able to:
- replicate
- store information
- express information
- allow variation by mutation
Tetranucleotide hypothesis
- DNA contains equal amounts of four nucleotides
- postulated identical groups and repeats of four components was basis of DNA structure
- Lack of chemical diversity in DNA suggested it could not store extensive genetic information
- proteins favored as genetic material
Griffith’s Transformation Experiment
- provided foundation for Avery, MacLeod, and McCarty’s research
- showed avirulent strains of Diplococcus pneumoniae could be transformed to virulence
- speculated transforming principle could be part of polysaccharide capsule or compound required for capsule synthesis
Avery, MacLeod, and McCarty’s research
DNase utilized to destroy transforming activity, demonstrated transforming principle was DNA, not protein
Work of Hershey and Chase
- used Escherichia coli and bacteriophage T2
- demonstrated that DNA, not protein is the genetic material
- used radioisotopes 32P and 35S
- demonstrated DNA enters bacterial cell during infection an directs viral reproduction
Transfection
- infection by only viral nucleic acid
- proves conclusively that viral DNA alone contains all necessary information for production of mature viruses
Nucleotides
- DNA is a nucleic acid
- nucleotides: building blocks of nucleic acid
- building blocks of DNA
- nucleoside with a phosphate group added
What are nucleotides made of
- nitrogenous base (two kinds)
- pentose sugar
- phosphate group
Purines
9 member rings
- adenine
- guanine
Pure as gold
Pyrimidines
6 member rings
- cytosine
- thymine
- uracil
Cut the pye
Nucleoside
- contains nitrogenous base and pentose sugar
- molecule is composed of purine or pyrimidine base and ribose or deoxyribose sugar
Nucleoside monophosphates
a nucleotide
Nucleoside diphosphate
nucleotide with addition of two phosphate groups
Nucleoside triphosphate
nucleotide addition of three phosphate group
energy storage unit
triphosphate
serves as precursor molecule during nucleic acid synthesis
ATP and GTP
- adenosine triphosphate and guanine triphosphate
- large amount of energy involved in adding/removing terminal phosphate group
Phosphodiester bonds
nucleotides are linked by phosphodiester bonds between phosphate group at C-5’ position and OH group on C-3’ position
What is the exception for double stranded RNA
animal viruses have double-stranded helices
three classes of cellular RNAs
originate as complementary copies of one of two DNA strands during transcription
rRNA
ribosomal RNA
- structural components of ribosomes for protein synthesis
- most abundant type
mRNA
messanger RNA
- template for protein synthesis
- carry genetic information from gene to ribosome
- middle abundance
tRNA
transfer RNA
- carry amino acids for protein synthesis
- least abundant
telomerase RNA and RNA primers
involved in DNA replication at chromosome ends
SnRNA
small nuclear RNA, processes mRNAs
Antisense RNA, microRNA, siRNA
involved in gene regulation
