DNA + RNA Flashcards
What type of structure does DNA have?
A double stranded helix structure
What does a nucleotide of DNA contain?
A pentose sugar (deoxyribose), phosphate group and an organic base
What makes up the backbone of a nucleotide of DNA?
A phosphate group and a pentose sugar
What are the organic base pairs?
Adenine + thymine
Guanine + cytosine
What is RNA?
Ribonucleic acid
What organic base does RNA have?
Adenine + Uracil
Cytosine + guanine
What does a nucleotide of RNA contain?
A phosphate group, a pentose sugar (ribose), and an organic base
What are the differences between the structure of DNA and RNA?
- DNA has deoxyribose as pentose sugar but RNA has ribose
- DNA has thymine as a organic base but RNA has uracil instead
- DNA doesn’t contain oxygen on the second carbon but ribose does
- RNA strands were shorter than DNA polynucleotides
- in RNA nucleotides form a single polynucleotide strand
What bond does the phosphate make with the organic base ?
A phosphodiester bond
What does a phosphodiester bond do?
It holds adjacent DNA together
What is the function of DNA?
To store genetic information. It has all the instructions needed to grow and develop from a fertilised egg to a fully grown adult.
What is the function of RNA?
RNA transfers genetic information from the DNA to the ribosomes. Ribosomes are made from proteins and RNA
How do two DNA poly nucleotide strands join together?
They join together by hydrogen bonds between the bases.
Describe how a DNA double helix is formed from two polynucleotide strands.
Two DNA polynucleotide strands join together by hydrogen bonds between the complementary base pairing. Adenine and thymine had cytosine and Guanine. 2 h bonds form between A and T and 3 for C and G. The antiparallel strands then twist round each other to form the DNA double helix.
What are mutagers?
Mutagers are chemical that cause mutations and damages DNA. This can lead to cancer
What does the phosphodiester backbone do?
It protects the more chemically reactive bases inside the double helix
What is the benefit of cytosine and guanine having 3 hydrogen bonds instead of 2 ?
It makes the bonds stronger which means it makes it more stable.
What is base stacking?
Additional force between opposite base pairs that holds the molecule together.
How does DNA structure aid it’s function?
It has a phosphodiester backbone- prevents organic bases reacting with environment
Long/large molecule- stored alot of information
Double helix structure - makes DNA compact
Weak hydrogen bonds join base pairs- easily broken for DNA replication
Double stranded - allows replication from template strands
Base sequence- allows info to be stored
Base stacking - makes DNA stable
What is needed during interphase ?
- DNA molecule needs to be replicated
- free DNA nucleotides
- DNA helicase enzyme
- DNA polymerase enzyme
Describe how DNA is replicated
- DNA helicase breaks the hydrogen bonds which separates the strands
-both strands now act as templates - the free nucleotides are attracted to their complementary bases
- hydrogen bonds reform
-complementary base paring - the DNA polymerase joins the nucleotides of the new strand
- creates a phosphodiester bond
- this results in a semi- conservative replication as new DNA molecules contain on old strand and one new strand
The Meselson and stall’s experiment
They showed that DNA is replicated using semi-conservative method:
1) two samples of E-coil bacteria were grown for generation on in a nutrient broth containing N15 nutrient agar (heavy) and one in N14 nutrient agar (light)
2) DNA was extracted from both nutrient broth and then spun in a centrifuge. N15 was lower because it was heavier and N14
