Higher Human Biology Unit 1.2

How many strands does DNA contain?

DNA is made up of structures called what?

DNA contains 2 strands (double helix)

Made up of structures called nucleotides.

What is each nucleotide made up of?

Each nucleotide is made up of:

Deoxyribose sugar

Phosphate group

Base

What does the deoxyribose sugar molecule and phosphate molecule make up?

The deoxyribose sugar molecule and the phosphate molecule toghether form the sugar phosphate backbone to which a base is attached.

Toghether this forms one nucleotide of DNA

What structure do nucleotides join toghether in and what does it form?

Nucleotides join toghether in an anti parallel structure to form a double stranded helix.

What does the base sequence of DNA form?

The base sequence of DNA forms the genetic code

Adenine = Thymine

Cytosine = Guanine

What are the complementary base pairs held together by?

What is the sugar phosphate backbone held together by?

The complementary base pairs are held together by weak hydrogen bonds.

The sugar phosphate backbone is held together by strong sugar phosphate bonds.

What strands do nucleotides bond together between?

Nucleotides bond together between the 3' carbon position of one sugar and the 5' phosphate position of the next sugar.

What strand are phosphate located at?

New nucleotides can only be added to what stand?

Phosphates are at the 5' end.

New nucleotides can only be added at the 3' end

What is DNA replication?

The process by which a double helix of DNA makes an exact copy of itself.

DNA is replicated prior to what?

What does this ensure?

DNA is replicated prior to mitosis by a DNA polymerase enzyme.

This ensures that new cells have the same number of chromosomes and to ensure that all cells have the same genes.

For DNA replication to occur what are the requirements?

For DNA replication to occur, five things are required:

DNA template (double helix)

DNA free nucleotides

Energy (ATP)

DNA Polymerase & DNA Ligase (enzymes)

Primers

Why does DNA polymerase primers?

What is a primer?

DNA polymerase needs primers in order to start the process of DNA replication?

A primer is a short strand of nucleotides that binds to the 3' end of the template DNA strand allowing polymerase to add DNA nucleotides.

What are the first 3 stages of DNA Replication?

1.The DNA double helix is unwound at the weak hydrogen bonds between the bases are broken to form 2 template strands.

2.A DNA primer binds to the 3' end of the template DNA

3.DNA polymerase adds DNA nucleotides using complementary base pairing, to the deoxyribose 3' end of the new DNA strand which is forming.

DNA polymerase can only add ___ nucleotides in one direction to the what?

DNA polymerase can only add DNA nucleotides in one direction to the 3' end of the new strand.

What is the leading strand (3' end)?

What is the lagging strand (5' end)?

Complementary DNA nucleotides are added continuously to make one new strand.

Complementary DNA nucleotides make DNA fragments which must be joined together to make a new strand.

What are the last 3 stages of DNA replication?

4.Replication is continuous on the leading strand.

5.The primer is positioned at points along the length of the lagging. The lagging strand is replicated in fragments.

6. DNA Ligase joins all the fragments of the lagging strand together.

What is the polymerase chain reaction?

The polymerase chain reaction is a technique used to amplify specific target sequences of DNA.

What are the primers used in PCR (Polymerase Chain Reaction)?

The primers used in PCR:

Are short strand of nucleotides

Are complementary to specific target sequences at the two ends of the region of DNA to be amplified.

What is DNA polymerase?

A special heat target DNA polymerase is used in PCR to replicate target sequences of DNA.

What are the 4 steps in PCR?

1.DNA is heated to between 92 and 98*C to separate the strands.

2.It is then cooled to between 50 and 65*C to allow primers to bind to target sequences.

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

4.At the end of the 1st cycle, two identical molecules of DNA are produced.

DNA is used by scientists to amplify DNA in a number of fields such as:

Solving crimes

Settling paternity suits

Diagnosing genetic disorders