DNA Replication And The Genetic Code Flashcards
why do cells divide?
produce more cells needed for growth or repair of tissues.
what is DNA replication?
two strands of DNA double helix seperate and each strand serves as a template for the creation of a new double stranded DNA molecule. complementary base pairing rules ensure that the two new strands are identical to the original.
what must happen before DNA can replicate?
the double helix structure has to unwind and seperate into two strands, so the hydrogen bonds holding the complementary bases together must be broken.
what happens during semi conservative DNA replication?
- free DNA nucleotides will then pair with their complementary bases, which have been exposed as the strands seperate.
- hydrogen bonds are formed between them.
- new nucleotides join to their adjacent nucleotides with phosphodiester bonds.
what is semi conservative DNA replication?
two near DNA molecules of DNA are produced, each one consisting of one old strand of DNA and one new strand.
what controls DNA replication?
enzymes.
which enzyme unwinds and seperates the two strands of the DNA double helix?
DNA helicase.
how does DNA helicase work?
it travels along the DNA backbone, catalysing reactions that break the hydrogen bonds between complementary base pairs as it reaches them.
which enzyme catalyses the formation of phosphodiester bonds between these nucleotides?
DNA polymerase.
what are the steps of semi conservative replication of DNA?
- a representative portion of DNA, which is about to undergo replication.
- DNA helicase causes the two strands of DNa to seperate.
- DNA helicase completes the seperation of the strand. meanwhile, free nucleotides that have been activated are attracted to their complementary bases.
- once the activated nucleotides are lined up, thehy are joined together by DNA polymerase. the remaining unpaired bases continue to attract their complementary nucleotides.
5.all the nucleotides are joined to form a complete polynucleotide chain using DNA polymerase. In this way, two identical molecules of DNA are formed. Each new molecule of DNA is composed of one original strand and one newly formed molecule.
what is a mutation?
random and spontaneous error which can lead to a change in the sequence of bases.
what is the genetic code?
the idea that DNA must code for a sequence of amino acids.
how was the genetic code determined?
scientists understood that DNA must carry the blueprint needed to synthesise the many different proteins needed by organisms.
what is the code in the base sequences?
a simple triplet code. a sequence of three bases, called a codon.
what does a codon code for?
an amino acid
