3.1.5 Nucleic Acids 3.1.5.1 Structure Of DNA and RNA Flashcards
Full names for DNA and RNA
DNA - deoxyrubonucleic acid
RNA - ribonucleic acid
2 scientists who helped us understand DNA structure (1953)
James Watson
Francis crick
Who made their work for DNA structure possible and how
Rosalind franklin
She discovered DNA using X-ray imaging
What did DNA discovery open up
Major scientific breakthroughs and medical research
What does DNA carry
Genetic code
Where is DNA stored
In nucleus of eukaryotic cells
What’s DNA stored as in nucleus’
Chromosomes (x shaped)
What’s DNA and what’s it made up of
A polymer made of of nucleotide monomers
3 parts of DNA structure
Phosphate group
Deoxyribose sugar
Organic base (1 of 4)
How many sides does deoxyribose sugar have
5
4 possible DNA bases
Adenine
Thymine
Cytosine
Guanine
How are the base , sugar and phosphate group joined together in DNA
Whats released
Condensation reaction
Water
Another word for 1 nucleotide
Mononucleotide
Another word for 2 nucleotides
What would they be joined by
Dinucleotide
Condensation reaction
What’s the bond between mononucleotides called
Phosphodiester bond
What parts of mononuclotides does the phosphodiester bond form between
The sugar of 1
Phosphate group of another
What’s the phosphate backbone made up of
Alternating deoxyribose sugar and phosphate
What polymer is made by joining many mononucleotides in condensation reactions
Polynucleotide
What do organic bases form
What do they contain
Complementary base pairs
Nitrogen
What does adenine pair with always
Thymine
What does cytosine pair with always
Guanine
What must the quantities of A + T and C + G be like In a DNA molecule
Equal
How many hydrogen bonds do A + T have joining to each other
2
How many hydrogen bonds do C + G have joining to each other
3
Is A + T or C + G stronger
Why
C + G
An extra hydrogen bond
They’re weak but stronger the more that there are
What does the DNA backbone have
Whats formed
2 strands that coil around each other
Forming a double helix
How are the 2 strands held in a twist in DNA
By hydrogen bonds that form between base pairs
What’s DNA the more stable with
The more cytosine + guanine base pairs there are as they have 3 hydrogen bonds
How many carbon-nitrogen rings do thymine and cytosine have
Just 1
How many carbon-nitrogen rings do adenine and guanine have
2
What 2 bases are the biggest
What are they called
Adenine
Guanine
Purines (longer bases)
What are thymine and cytosine also know as
Pyrimidines (shorter bases)
Whys a DNA molecule the same width throughout
Why is the good
As a purine base always bonds with a pyrimidine base
So it can coil neatly
Whys stability in DNA important
As DNA is used to pass on genetic information through generations so it must be copied without any changes
3 ways DNA is stable
Hydrogen bonds between bases
Coiling of DNA keeps chemically reactive bases protected in helix
Further forces between bases help (base stacking) bonds form between adjacent bases
Whats the bond process called that forms between adjacent bases for stability
Base stacking
What arrangement is DNA in
Antiparralel arrangement
What’s antiparallel arrangement
When 1 strand of nucleotide is the right way up with other is upside down
What sugar do nucleotides have with carbons numbered 1-5
Pentose
What group is on carbon 3 in a nucleotide
Hydroxyl group (OH)
What is carbon 5 on a nucleotide attached to
The phosphate group of another nucleotide
What are the 3 and 5 carbons often called
3-prime
5-prime
3 points about the left side of the antiparallel arrangement diagram
Top strand is NOT upside down
5-prime at top, 3-prime at bottom
Strand runs in direction of 5’ -> 3’
3 points about the right side of the antiparallel arrangement diagram
Top strand is upside down
3-prime carbon at top, 5-prime at bottom
Strand runs in 3’ -> 5’ direction
3 other DNA adaptions
Huge - carries lots of information to each generation
Base pairing rules allow DNA to be copied each time accurately and allows information to be transferred (e.g during protein synthesis)
DNA coiling into a helix protects the code from chemicals/physical forces outside
Why did people used to not think DNA could be the code for life
As it only had 4 bases so was said to be too simple
What’s RNA made up of like DNA
Nucleotides
3 differences between rna and DNA
Its single stranded and quite short
Pentose sugar is ribose (not deoxyribose)
4 bases are a, g, c and uracil (not thymine)
2 most important types of RNA
mRNA
tRNA
What’s mRNA
What does it do
Messenger rna
Transfers genetic information from DNA in the nucleus to the ribosomes
What’s tRNA
What’s it involved in
Transfer rna
Protein synthesis
What does tRNA look like
1 single strand folded to form a clover leaf shape structure
What’s rRna
what does it make up
Ribosomal rna
Makes up ribosomes with protein
What’s the point in DNA (3)
Designed to control :
Protein synthesis
Cell division (mitosis and meiosis)
Passing on genetic information (inheritance)
