2.6 Structure of DNA and RNA Flashcards
Who determined the double-stranded structure of DNA? How did Rosalind Franklin contribute to the discovery of DNA is helical structure?
James Watson and Francis Crick stole Rosalinds research and was given all the credit and was awarded a nobel peace price. Her X-ray diffraction studies gave them the idea of DNA’s structure
What methods did Watson and Crick use to test their ideas on possible structures of DNA?
Why was their first model, triple helix, rejected?
What did they realize from their setbacks?
What else was suggested from the correct model?
They used stick and ball models to visualize the molecules and see how well it fitted the available evidence.
- It was rejected because the ratio of adenine to thymine was not 1:1. It also required too much magnesium.
- they realize DNA must be double helix, the relationship between the base and base pairing, the strands must be anti-parallel to allow base pairing to happen
Because of the visual nature of their work the second and the correct model suggested:
* possible mechanisms for replication
* information was included in triplets of bases
What are nucleic acids?
How important is it? Important in where? What can it do?
- the most fundamental and important constitute of a living cell
- Carry the potential for self duplication
- act as a repository and transmitters of genetic information for every cell, tissue an organism
- encodes blueprint for an organism
- nucleic acids are the VIP of biological molecules.
What are the two types of nucleic acid? What are the differences between the two? Strands? Bases?
DNA and RNA
DNA (double stranded) - deoxyribonucleic acid
RNA (single stranded) - ribonucleic acid
They are both made out of pentose sugar
RNA - ribo sugar (AUCG)
DNA - deoxy sugar (1 less oxygen) (ATCG)
Both are polynucleotides/nucleic acids made of many similar molecules. The monomers are called nucleotide.
What are the 3 components that make up a nucleotide? What reaction joins the components together?
A phosphate group, a sugar and an organic base
Condensation joins the phosphate group and the nitrogenous organic base to the sugar with covalent bonds.
What elements do nucleotides contain? What differentiates the nucleotides?
O, C, H, N and P
The bases differentiates the nucleotides
What are the different bases of nucleotides? DNA vs RNA? Purine vs pyrimidine?
5 bases: Cytosine (C) Guanine (G) Thymine (T) Adenine (A) Uracil (U)
DNA: ATCG (thymine is only found in DNA)
RNA: UTCG (uracil is only found in RNA)
Pyrimidine: C, T, U - 1 ring in their structure
Purine: A, G - 2 rings in their structure
What are the pentose sugars found in DNA and RNA? How do they differ from each other and to glucose? What are they both represent it by?
Ribose is a sugar, glucose, but with only five carbon atoms and it’s molecule - found in RNA only
Deoxyribose is almost the same but lacks one oxygen atom - found in DNA only
Both molecules are represented by a pentagon
How are nucleotides joined together? What is the bond called? Where is the bond between?
Nucleotides joined together in a condensation reaction. The phosphate group of one joins to the sugar group of the next. A phosphodiester bonds form.
How is a molecule of nucleic acid formed? How does DNA usually consists of? How is it held together?
A molecule of nucleic acid is formed by millions of nucleotides joined together in a long chain.
DNA usually consist of a double strand of nucleotides – the double helix
The sugar phosphate chains are on the outside and the strands are held together by hydrogen bonds between the bases
What is complementary base pairing?
What holds two bases together, in return the structure?
What are the complementary base pairing of A,T, C and G?
The base is a nuclear acid always pair up in the same way – this feature is called complementary base pairing
It is hydrogen bonds that hold the structure together
Adenine always pairs up with thymine
Cytosine always paris up with guanine
What does it mean that the two strands of nucleotides are antiparallel?
It means they run in opposite directions. One strand is from 3’ to 5’ prime and the other is 5’ to 3’ prime.
Why is complementary base pairing important?
Make sure that each base is part in the most preferable way. There’s also ensures that when mRNA is synthesized by reading the strand from the 3’ to 5’, it attaches complementary base pairing so that when transcription occurs, it duplicates a copy identical to the original.
What is the importance of hydrogen bonds?
Hydrogen bonds holds the nitrogenous base together They are individually weak but collectively strong, which provides great stability for the double helix structure.
How is DNA organized in cells in eukaryotic cells?
What is a nucleosome? What does it consist of? How is one nucleosome connect it to the next? How protein is used to bind DNA to the core particle?
In eukaryotic cells DNA molecule is wrapped around histones to form nucleosomes, which eventually coil together to form chromosomes.
- A nucleosome consists of a central core of eight histone proteins DNA coiled around proteins.
- The eight proteins consist of two copies of four different types of histones. A short section of the link her DNA connects one nucleosome to the next.
- An additional histone protein molecule called H1, serves to bind the DNA to the core particle
