Lecture 7 Flashcards
parents pass on to their offspring – later known as genes that are responsible for inherited traits
discrete heritable factors
Mendel’s first law of inheritance explains
3:1 F2 phenotype ratio
threadlike structures in the nucleus of a eukaryotic cell that become visible when cell begins to divide
chromosome
entire genetic info for flies are on –
4 pairs of chromosomes
Thomas Morgan 1908
eye color gene in Drosophila on the X chromosome
1860s: Mendel presents studies on – in peas
heredity
1869: Miescher isolated large substance in nucleus of white cells in pus from surgical bandages
slightly acidic, sugar, and rich in phosphorous; called it “nuclein”
genetic materials are in chromosomes, which are in –
nucleus
chromosomes contain a variety of – in addition to DNA
proteins
– made using killed microorganisms which could be injected into patients to elicit the immune response of live cells without the risk of disease
vaccines
1928: Griffith stumbled on a demonstration of the transmission of genetic instructions by a process we now call the
“transformation principle”
1929: Levene determined the chemical composition and structure of the
DNA building blocks
Avery’s lab discovered how to transform R strain into S strain –
in vitro
Avery’s two conclusions
1) molecules that can carry heritable info are in S strain
2) molecule that carries the heritable info is DNA
When extracts of heat killed S strain + R stain were treated with DNase –>
no cells transformed to infective form
1944: Avery, Macleod, and McCarty concluded that DNA was the
“S substance” but there were still doubters
people finally accepted that DNA is the genetic material after whose experiment
1952: Hershey and Chase
How can the info to specify an organism be carried in chemical form?
DNA is a linear polymer of 4 different monomers, strung out in a defined sequence like the letters of a document written in an alphabetic script
How can DNA be duplicated and copied from generation to generation?
each strand of the double helix can serve as a template
– are the building blocks of DNA
nucleotides
to maximize the efficiency of base-pair packing, the 2 sugar-phosphate backbones wind around each other to form a right handed double helix, with one complete turn every –
10 base pairs
DNA is negatively charged because of
phosphate
DNA strands are complementary and run in – direction
antiparallel
the chain of nucleotides in a DNA strand, being both – and –, can be read as letters on a page
directional and linear
most stable form of DNA
double helix
purines (A, G) have – rings
2 rings
pyrimidine –, –, –, have 1 ring each
cytosine, thymine, uracil
base pairing between – and –
purines and pyrimidines
2 H bonds between
A and T
3 H bonds between
C and G
each base pair is of similar width and thus hold the – at a constant distance apart along the DNA molecule
sugar-phosphate backbones
the – and – of the bases allow hydrogen bonds to form efficiently only between A and T and between C and G
shapes and chemical structures
bases can only pair if the two polynucleotide chains that contain them are – to each other
antiparallel
the coiling of the two DNA strands around each other creates two – in the double helix
grooves
5’ end usually shown carrying the
phosphate group
Chargaff’s Rule
% A = %T
%G = % C
purines = pyrimidines
usually, only the – strand is presented in the 5’ to 3’ direction
top
only one strand can serve as a template for one particular gene during –
transcription
for transcription, usually given – which has the exact sequence of mRNA (except for U)
non-template strand
DNA is often measured in
bp or kb
1 bp (base pair) = – Daltons
660
only – code for proteins
exons
exons are – % of DNA
1.5%
Franklin and Wilkins showed that DNA is helical from –
x-ray diffraction
Franklin’s data showed
1) backbone on the outside
2) provided insight that allowed Watson and Crick to determine that the strands were antiparallel
3) provided the best evidence of the helical nature of DNA
each turn of DNA is about
10.5 base pairs
bases of DNA are stabilized by
hydrogen bonds
the double helix is stabilized by
base pairing and base stacking
the – groove is rich in chemical information
major
minor groove has same arrangement of
hydrogen acceptors and donors
major groove provides –
specificity
DNA has many –
forms
most common form of DNA (and was discovered by Watson and Crick)
B DNA
double helix goes to the – depending on environment
lowest energy state
protein alpha helices have h bonds that are – to the axis of the helix
parallel
proteins are rigid, –, and –
short, and connected by turns
double-stranded DNA helix have H bonds that are – to the axis
perpendicular
DNA can be – by protein
bent
DNA can be – around proteins to fit in nucleus
tightly packed
DNA bases point
IN
Protein R groups point
OUT
protein turns =
3.6 amino acids
DNA backbone
phosphodiester bond
protein backbone
peptide bond
