Nuclei acids Flashcards
What is dna made up of
2 polynucleotide chains which twist to form a double helix
Describe a dna nucleotide
How are the components of dna joined
As a result of a condensation reaction
How are nucleotides joined together
Through condensation reaction between deoxyribose of 1 mono nucleotide and phosphate group of next by a phosphodiester bond
What are the base pairs on DNA?
Adenine pairs with thymine
Guanine pairs with cytosine
What is key information from the mark scheme about DNA and RNA
DNA and RNA are polymers of nucleotides
What do histones do
Organise and condense DNA tightly so it fits into nucleus
What does DNA stand for
Deoxyribonucleic acid
What does RNA stand for
Ribonucleic acid
What are the bases in RNA?
Adenine to uracil
Cytosine to guanine
Is RNA single or double stranded
Single
Is it a short or long, polynucleotide chain
Relatively short
Who worked out structure of DNA
Watson and Crick
What is phosphodiester made of
2 ester bonds and a phosphate group
How is DNA adapted to carry out its function
Large molecule- carries lots of genetic material
Why have many scientists doubted dna carried genetic code
Because of its simplicity
How is dna adapted to carry out function (2 strands..)
2 strands joined by hydrogen bonds allow to separate during dna replication
How is DNA adapted to carry out its functions( base pairing)
Base pairing- dna can replicate and transfer information mRNA
How id DNA adapted to carry out it’s function(generations)
Can pass genetic information from generation to generation without signifant change. Mutations are repaired
How do you package DNA
DNA wrapped around histones, which are protein beads to form a structure called a nucleosome. Chain of nucleosome is called chromatin. chromatin is woundup to form a single chromosome.
What is the function of R.N. A
to transfer genetic code found in DNA to ribosomes
What is each DNA polynucleotide strands said to have
A 3’ end and a 5’ end
What does three end and a five end do
They run in opposite directions they are antiparallel
Are ribosomes bigger in eukaryotic cells or prokaryotic cells
Eukaryotic (80S)
Are ribosomes surrounded by membranes
No
What is the purpose of semiconservative replication?
Before cell divides, it needs to copy DNA within so that to new daughter cells will both receive for copies of parental DNA
Why is it called semiconservative replication?
In each new DNA molecule one DNA strand is from original DNA molecule and one is new
Why is it important to retain one original DNA strand?
It insures genetic continuity between generations of cells
What does semiconservative replication need?
Free Nucleotides
Both strands of DNA to act as a template, enzyme DNA polymerase, DNA helicase and a source of chemical energy
Describe semiconservative replication
Enzyme DNA Heli case breaks hydrogen bonds between complimentary base pairs
Double helix, then unwinds
Each exposed polynucleotide strands then acts as a template to which complimentary three nucleotides bind by specific base pairing
Nucleotides joined in a condensation reaction by enzyme DNA polymerise to adjacent ones
What were the three possible ways, scientist, believed DNA could replicate
Fragmented, semi, conservative or conservative
Who was Watson and Criks theory proved by
Meselson and Stahl
How did Meselson and Stahl prove it was semi conservative replication
Heavy 15 and culture bacteria was spun in centrifuge. DNA containing heavy nitrogen settled in a bottom of tube. This was added to only lighter 14 and nitrogen it was left long enough for one round of DNA replication, then centrifuged
What would Meselson and Stahl findings have been if it was conservative replication
The original DNA, which was the only heavy nitrogen what is settle at the bottom and the new DNA, which was only lighter nitrogen would be at the top
What did the test tube show to prove it was semiconservative replication
DNA containing mixture of light and heavy nitrogen settled in middle of test tube
