3.1.5 - DNA & RNA Flashcards
describe the structure of DNA (5)
- polymer of nucleotides (polynucleotide)
- each nucleotide formed from deoxyribose, a phosphate group and a nitrogenous base
- phosphodiester bonds between the nucleotides
- double helix (two strands held together by hydrogen bonds)
- hydrogen bonds/pairing between adenine, thymine and cytosine, guanine
describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule (2)
- condensation reaction/loss of water
- between phosphate and deoxyribose
- catalysed by DNA polymerase
name the protein associated with DNA in a chromosome (1)
histone
in the process of semi-conservative DNA replication, the two strands within a DNA molecule are separated.
describe how the separation of strands occurs (2)
- DNA helicase
- breaks hydrogen bonds between complementary base pairs
describe the role of DNA polymerase in the semi-conservative replication of DNA (2)
- joins adjacent DNA nucleotides
- DNA polymerase catalyses condensation reaction
- catalyses formation of phosphodiester bonds between adjacent nucleotides
name the two scientists who proposed models of the chemical structure of DNA and of DNA replication (1)
Watson and Crick
give two features of DNA and explain how each one is important in the semi-conservative replication of DNA (2)
- weak hydrogen bonds between bases allow two strands to easily separate
- two strands, so both can act as templates
- complementary base pairing allows accurate replication
describe the role of two named enzymes in the process of semi-conservative replication of DNA (3)
- DNA helicase catalyses breaking of hydrogen bonds between DNA strands, unwinding the helix
- DNA polymerase joins the DNA nucleotides
- forming phosphodiester bonds (forms sugar-phosphate backbone)
ATP is a nucleotide derivative.
contrast the structures of ATP and a nucleotide found in DNA to give two differences (2)
- ATP has ribose and DNA nucleotide has deoxyribose
- ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group
- ATP base is always adenine and in DNA the nitrogenous base can vary
describe the structure of DNA and how it relates to its functions (6)
- sugar - phosphate backbone gives strength;
- (coiling gives) compact shape;
- sequence of bases allows information to be stored;
- long molecule stores large amount of information;
- information can be replicated / complementary base pairing;
- (double helix protects) weak hydrogen bonds / double helix makes
- molecule stable prevents code being corrupted;
- chains held together by weak hydrogen bonds; chains can split for replication / transcription
give two features of DNA and explain how each one is important in the semi-conservative replication of DNA (2)
- weak hydrogen bonds - allows helix to be unzipped
- two strands - both can act as template
- complementary base pairing allows accurate replication
scientists concluded that an increase in phosphate in the embryo was linked to growth of embryo
suggest two reasons why these can be linked (2)
- phosphate required to make DNA
- required to make RNA
- required to make ATP
- required for membranes
- required for phosphorylation
use your knowledge of semi-conservative replication of DNA to suggest 1. the role of the single-stranded DNA fragments 2. the role of DNA nucleotides (3)
- template, determines order of nucleotides (2)
- forms complementary base pairs (1)
describe the process of semi-conservative replication (5)
- DNA helicase unwinds the double helix OR breaks hydrogen bonda
- both strands act as templates
- free DNA nucleotides line up in complementary base pairs
- DNA polymerase joins nucleotides
- forming phosphodiester bonds
- each new DNA molecule consists of one original strand and one new strand
name two enzymes that are involved in replicating DNA and describe their roles in the replication process (3)
- DNA helicase and DNA polymerase
- helicase breaks hydrogen bonds to unwind DNA
- polymerase forms phosphodiester bonds between adjacent nucleotides
