Structure and replication of DNA Flashcards
What information in inherited
Genetic information is inherited
DNA is a substance that does what
DNA is a substance which encodes the genetic information of inheritance in a chemical language
How to describe DNA
DNA is a very long, double - stranded molecule in the shape of a double helix
What is each strand of DNA made up from
Each strand of DNA is made up of chemical units called nucleotides
What three parts make up a DNA nucleotide
DNA nucleotide is made up from deoxyribose, phosphate, and a base
what do deoxyribose molecules have
Deoxyribose molecules have five carbon atoms numbered 1 to 5
What happens between nucleotide phosphates and the carbon molecules
The phosphate of one nucleotide joins to the carbon 5’5 and is linked to the carbon 3’3 of the next nucleotide in the strand
This produces a 3’-5’ sugar-phosphate-backbone
What are the four different DNA bases called
A - adenine
C - cytosine
T - thymine
G - guanine
How are the strands joined together
The nucleotides of one strand of DNA are linked to the nucleotides on the next strand of DNA through their complementary base pairs
What are the pairs
Adenine - Thymine
(Adenine - Uracil)
Guanine - Cytosine
How are base pairs held together
Base pairs are held together by weak hydrogen bonds
What does each strand have
Each strand has a sugar-phosphate backbone which has a 3’ end that starts with a deoxyribose molecule and a 5’ end that finishes with a phosphate molecule
What way do the two strands of a DNA molecule run
The two strands of a DNA molecule run in opposite directions and are antiparallel to each other
What forms the genetic code
The base sequence of DNA forms the genetic code
When do DNA molecules replicate
DNA molecules replicate before cell division
What is replication
Replication is the process by which DNA molecules can direct the synthesis of identical copies of themselves
What does DNA replication require
DNA replication requires the original DNA strands to act as template strands, a supply of DNA nucleotides, primers, enzymes DNA polymerase and ligase, ATP
What is DNA replicated by
DNA is replicated by the enzyme DNA polymerase before cell division
What is needed to start replication
DNA polymerase requires primers to start replication
Describe a primer strand
A primer is a very short complementary strand of nucleotides which bind to the 3’ end of the template
(DNA strand allowing polymerase to add DNA nucleotides
How does DNA polymerase add DNA nucleotides to the new strand of DNA being formed
DNA polymerase adds DNA nucleotides, using complementary base pairing, to the deoxyribose 3’ end of the new DNA strand which is forming
How are two template strands created
DNA is unwound and hydrogen bonds between complementary bases are broken to form two template strands
What happens to the leading strand and lagging strand
DNA polymerase can only add nucleotides in one direction from it 3’ end to it’s 5’ end and as a result, the leading strand is replicated continuously and lagging strand is replicated in fragments
How are the fragments joined together
Fragments are joined together by the enzyme ligase
