2.1 Structure of RNA and DNA Flashcards
(19 cards)
Describe the basic function of DNA and RNA in all living cells
DNA: Holds genetic information which codes for polypeptides (proteins)
RNA: Transfers genetic information from DNA to ribosomes
Name the types of molecules from which a ribosome is made
RNA and Proteins
What is the monomer that makes up DNA
A nucleotide
What are the 4 nitrogenous bases in DNA
Guanine
Cytosine
Adenine
Thymine
Describe how nucleotides join together to form polynucleotides (3)
- Condensation reactions, removing water molecules
● Between phosphate group of one nucleotide and deoxyribose / ribose of another
● Forming phosphodiester bonds
How is the polynucelotide held together
Strong covalent bonds called phosphodiester bonds
How are the DNA polymer pairs joined together
Hydrogen bonds between the Nitrogenous bases
This is how the double helix strcutre is created as the two chains twist
What is the only condition through which hydrogen bonds form in polynucelotides
They can only form between complimentary base pairs
Cytosine—Guanine 3
Adenosine–Thymine 2
Guanine—Cytosine 3
Thymine–Adenine 2
Number of ‘-‘ represent the number of h bond bwteen the bases
What is RNA (3)
*A polymer of a nucleotide formed of a:
- Ribose
-Nitrogenous base
- Phosphate group
*Relatively short
*Single Stranded
Name the 4 nitrogenous bases in RNA
Adenine
Uracil
Guanine
Cytosine
What are the differences between the DNA and RNA monomers
- DNA contains the base Thymine whereas RNA has Uracil instead of Thymine
- DNA contains the pentose suagr deoxyribose whilst RNA contains Ribose
What are the two differences between the polymers of DNA and RNA
Length
- DNA is much longer as it contains 23,000 genes whereas RNA is shorter as it only contains 1
- DNA is double stranded whilst RNA is single stranded
Which Nitrogenous bases are Purine
Adenine and Guanine
They both have two rings
Guanine has a double bond to O
Which Nitrogenous bases are pyrimidine
Thymine Cytosine and Uracil
Has one ring
Why can Adenine and Cytosine not bond
Adenine would form 2 hydrogen bonds whereas Cytosine would form 3 hydrogen bonds
What is the differnece between Deoxyribose and Ribose
Deoxyribose chemical formula-C5 H10 O4
Ribose has the same but one more oxygen
Strcture of Deoxyribose is more stable so it has a sotrnger covalent bonds as the C3 bond will be bonded directly oto the phosphate group
How are polynucleotides formed
When DNA contains a second antiparallel chain that runs in the opposite direction
E.g. 5’ prime and 3’ prime end
Why is DNA stable
- The phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
- Hydrogen bonds link the organic base pairs forming bridges
Suggest how you can use incomplete information about the frequency of bases on DNA strands to find the frequency of other bases (3)
- % of adenine in strand 1 = % of thymine in strand 2 (and vice versa)
- % of guanine in strand 1 = % of cytosine in strand 2 (and vice versa)
* Because of specific complementary base pairing between 2 strands