3.1.5 nucleic acids Flashcards
how has DNA adapted to its function?
stable passed from generation to generation = RARELY MUTATATES
Two strands can separate during DNA replication as only joined with H bonds
large molecules can carry huge amounts of information
Base pairs are inside helix, protected from corruption by sugar, phosphate backbone
Base pairing leads to DNA being able to replicate and transfer information as MRNA
what is the function of DNA?
hereditary material response for passing genetic information from cell to cell generation
Averaged, 3.2 million base pairs of DNA in a typical mammal cell
Infinite variety of sequence of bases along the length of the DNA molecule PROVIDING GENETIC DIVERSITY
what is specific base pairing?
have a complimentary shape
double standard helix = double helix
Anti parallel
Bases are A,G,C, T and never U
chains are held together by H bonds between base pairs
10 base pairs per turn off the helix
specific base pairing are A with T and G with C
what feature does a DNA polynucleotidehave?
anti parallel = two strands of DNA, lie strand by strand, but run in opposite directions
what is nucleic acid?
both DNA and RNA
found in all cells = DNA in nucleus and RNA in cytoplasm
building blocks = nucleotides
mononucleotide = form by condensation reaction of phosphate, pentose sugar, and organic base
nucleic acids = poly nucleotide (long chain of mononucleotide type, joined by condensation reaction, with phosphodiester bond between nucleotides)
organic bases
purines = double ring bases
guanine = g
adenine = a
pyrimidines = single ring base
cytosine = c
thymine = t
uracil = u (rna)
what organic bases are in DNA + RNA?
DNA = deoxyribose
RNA = ribose
what is the structure of rna/dna:
phosphate
pentose sugar
organic base
Meselsohn and Stahl
They grew populations of bacteria in a food source of ammonium chloride containing only heavy nitrogen
Bacteria used N15 to make DNA
They left it long enough, so nearly all DNA was N15 not N14
DNA was extracted from the cells and relative mass was determined using centrifugation
DNA IN THE FIRST GENERATION WAS FOUND TO BE INTERMEDIATE BETWEEN HEAVY AND LIGHT TYPES, CONFIRM DNA TO BE MADE OF ONE HEAVY STRAND AND ONE LIGHT
isotopes of nitrogen:
all nitrogen atoms contain seven protons, but the number of neutrons varies
DNA replication theories:
- conservative replication = completely new double helix made from old one
- Semiconservative replication = each new monocle would contain one old Strand and one new strand
1958: Meselsohn and stahl America carried out an experiment to prove DNA replicated semi conservatively, they used equally bacteria, and experimented, relying on variation of N atoms
what is semiconservative replication?
each new DNA molecule consist of one strand from the original DNA double helix and one newly synthesise strand
what is a phosphodiester bond?
Phosphodiester bond is the linkage between the third carbon atom in one sugar molecule and the fifth carbon of another
There’s deoxyribose in DNA and ribose in RNA
what is the mechanism of DNA replication?
- A portion of DNA double helix is about to be replicated
- Replication starts before cell division DNA HELI CASE cause the DNA strand to unwind
- DNA Helicase moves along the DNA double helix, unwinding, and then unzipping it = it, breaks down hydrogen bonds between the nitrogenous bases
- The free nucleotides in the nucleoplasm bind (through hydrogen bonds) to the complimentary bases on each separated strand of DNA
- What’s these new nucleotides are in place the enzyme DNA POLYMERASE links to sugar and phosphate groups of adjacent nucleotides together with PHOSPHODIESTER BONDS
Replication is finished and two new strands of DNA are produced THESE ARE TWO IDENTICAL MOLECULES OF DNA WHICH ARE EXACT COPIES OF THE ORIGINAL MOLECULE
how does cell division occur?
- nuclear division = process by which the nucleus divides MITOSIS AND MEIOSIS
2.cell division = follows nuclear division, and is the process by which the whole cell divides OCCURS WITHIN THE NUCLEUS, AND THE DNA MUST BE REPLICATED
