biology key area 2, replication of DNA

when does DNA replication occur

DNA replication occurs prior to cell divison (mitosis)

name the enzyme that replicates DNA

DNA polymerase

what is a primer

a short strand of nucleotides

what does a primer do in DNA replication

binds to the 3’ end of the parent strand of DNA, which allows DNA polymerase to add new nucleotides

what is the first stage of DNA replication

DNA unwinds and hydrogen bonds are broken, this forms two template strands

what is the second stage of DNA replication

a primer is added to the 3’ end of the parent DNA strand

what is the third stage of DNA replication

DNA polymerase joins complementary nucleotides to the leading strand of DNA.

how is the leading strand replicated

the leading strand is replicated continuously

how is the lagging strand replicated

in fragments joined by DNA ligase

why is the lagging strand replicated in fragments

as DNA polymerase can only add nucleotides onto the 3’ end of the strand.

what does the polymerase chain reaction do

amplifies DNA using complementary primers for specific target sequences

describe the first stage of PCR

DNA is heated to between 92°C and 98°C to break the hydrogen bonds between bases and separate the two strands

describe the second stage of PCR

the DNA is then cooled to between 50°C and 65°C to allow primers to bind to target sequences

describe the third stage of PCR

DNA is then heated to between 70°C and 80°C for heat tolerant DNA polymerase to replicate the region of DNA.

describe practical applications of PCR

settle paternity suits, solve crimes, diagnose genetic disorders