Nucleotides and nuclei acids Flashcards
What are nucleic acids?
Large molecules contained in the nucleus of cells
What are the monomers that make up DNA?
Nucleotides
What does DNA stand for?
Deoxyribonucleic acid
What are the two types of nucleotide chains?
- RNA= Ribonucleic acid
- DNA= Deoxyribonucleic acid
What are the 3 components that make up nucleotides?
- A phosphate group
- A penthouse sugar
- Nitrogenous base
What elements are found in nucleic acids?
- carbon
- hydrogen
- oxygen
- nitrogen
- phosphorus
Describe how 2 nucleotides are joined together
A phosphodiester bond will form between the phosphate group of one nucleotide, and the pentose sugar of the adjacent nucleotide. This bond is formed through a condensation reaction, producing water as a product, and is catalysed by DNA polymerase
What is meant by the sugar-phosphate backbone?
The part of the nucleotide (phosphate group and pentose sugar) which the base attaches to. The 2 backbones are what coil to create the double helix structure of DNA.
What is a chain of nucleotides called?
Polynucleotide
What is a purine?
- A larger, 2 carbon-nitrogen ring structured base
- Examples= Adenine / Guanine
What is a pyrimidine?
- A smaller, single carbon-nitrogen ring structured base
- Examples: Cytosine/ Thymine / Uracil
Why must a purine bind with a pyrimidine?
Their relative sizes means that they must pair with each other to keep the 2 strands the same distance apart. (Small with big = same distance but big with big= strands aren’t kept same distance)
How many hydrogen bonds are there between Adenine and Thymine, and Cytosine and Guanine?
A and T= 2
C and G=3
Why is it important that the hydrogen bonds between complementary bases can be broken?
-Both strands are used in DNA replication
What is meant by the DNA strands being anti-parallel?
- The 2 strands run in opposite directions
- 5 prime to 3 prime down on left, but 5 prime to 3 prime up on right
What Purines and Pyrimidines are found in DNA?
Purine:
Adenine
Guanine
Pyrimidine:
Cytosine
Thymine
What Purines and Pyrimidines are found in RNA?
Purine:
Adenine
Guanine
Pyrimidine:
Cytosine
Uracil
What is the function of DNA and how is it adapted to carry out this function?
-DNA controls the sequence of amino acids in proteins + heredity material responsible for passing genetic information from cell to cell
- it’s stable= (2 strands with specific base pairings, large numbers of H bonds, and helix shape reduces chance of molecular damage)
- 2 strands can separate so it can self-replicate
- Base pairings prevent corruption from outside chemicals or physical forces
- Large molecule so can carry lots of information
What are the 5 steps of semi-conservative DNA replication?
1) Original DNA molecule is about to undergo replication
2) The enzyme DNA helicase causes the 2 strands of DNA to separate (unzip) by breaking the hydrogen bonds to form 2 single strands
3) DNA helicase completes the splitting of the strand. Meanwhile the free nucleotides are attracted to the exposed complementary bases on the original strand (which acts as a template)
4) Once the activated nucleotides are lined up, they are joined together through hydrogen bonds, by the enzyme DNA polymerase, forming the sugar phosphate backbone
5) All the nucleotides are joined to form a complete polynucleotide chain using DNA polymerase, this creates two identical strands of DNA. Each new molecule of DNA is composed of one original strand and one newly formed strand= semi-conservative replication
