DNA Flashcards
nucleic acid composition
long polymer of individual molecules called nucleotides
nucleotide composition
nitrogenous base, sugar molecule, phosphate molecule
types of nitrogenous base
purines (adenine and guanine) and pyrimidines (cytosine, thymine and uracil)
types of nucleic acid
ribonucleic acid and deoxyribonucleic acid - hydroxyl group at 2 position of ribose sugar is replaced by a hydrogen
thymine only in DNA, uracil only in RNA
where are RNA and DNA found?
RNA in cytoplasm and nucleolus, DNA in chromosomes
DNA structure
2 chains of nucleotides arranged in a double helix
backbone of each chain is formed by phosphodiester bonds between 3’ and 5’ carbons of adjacent sugars
two chains held together by hydrogen bonds between nitrogenous bases - point toward centre of helix
polarity of DNA chain
determined by orientation of sugar-phosphate backbone
pairing of nitrogenous bases
guanine-cytosine
thymine-adenine
forms complementary strands
nuclear division
two strands of DNA double helix separate through DNA helicase (enzyme)
each strand directs synthesis of complementary strand through base pairing
2 daughter DNA duplexes identical to parent molecule
what separates DNA strands?
DNA helicase (enzyme)
semiconservative DNA replication
only one strand of each daughter cell has been newly synthesised
what enzyme is involved in DNA replication?
DNA polymerase
where does DNA replication occur?
origins of replication, forming bifurcated Y-shaped structures - replication forks
replication forks
bifurcated y shaped structures in DNA strands during replication
direction of synthesis
5’ to 3’ direction
