Unit 1.2 Higher Human Biology

what is DNA?

Each molecule of DNA consists of 2 strands, where each strand is made up of repeating units called NUCLEOTIDES. The nucleotide is made of : Deoxyribose sugar, Phosphate, Organic Base

What are Nucleotides?

There are 4 different types of nucleotides.

This is because there are 4 different bases: Cytosine, Thymine, Adenine, Guanine The base sequence of DNA forms the genetic code.

what are strong chemical bonds?

STRONG CHEMICAL BOND links the nucleotides between the phosphate and sugar. They are not easily broken and join nucleotides together into a permanent strand

what is the double stranded helix?

Weak hydrogen bond The 2 strands are arranged in a twisted coil called a "DOUBLE HELIX". It is often likened to a spiral ladder, where the sugar-phosphate backbone is the railing and the base are the steps

Stages of DNA Replication?

Full replication is complete in 6 stages:

1.DNA double helix unwinds

2.Weak hydrogen bonds break to form 2 template strands.

3.DNA Polymerase adds FREE nucleotides to join up complimentary pairs on the

open strand

4.Weak hydrogen bonds reform between base pairs

5.Strong chemical bond forms between both nucleotides (controlled by enzyme

called DNA POLYMERASE)

6. Newly formed daughter DNA (identical to original) begins to wind into double

helix

This process can only take

place if the nucleus contains:?

DNA (acts as template or new molecule)

Supply of DNA

nucleotides Appropriate enzymes

Supply of ATP Primers

what is enzyme control?

The important thing to learn is that DNA can only build in the direction 5' - 3' . This means that nucleotides can only be added to the 3' end by an enzyme polymerase.

What is the leading strand?

This leading strand can build continuously in the

correct direction 5' - 3' TOWARDS the point where the

unzipping point

What is the lagging strand?

This lagging strand Can only be built 5' - 3' AWAY from

the unzipping point so must be built in sections

which are 'glued' together

what is PCR?

PCR amplifies DNA using complementary primers for specific target sequences.

what are the requirements for PCR?

The requirements:

DNA Template

Nucleotides

Primers

Heat tolerant DNA polymerase

Stages of PCR?

1. heat to 92-98'C, meaning complementary strands separate.

2. Cool to 50-65'C, primers anneal to their complementary base sequence on the DNA

3. Heat to 70-80'C, DNA polymerase extends the primers completing the new DNA strand and original DNA has been replicated.

4. Heat to 92-98'C, DNA separates into single strands now there are 4 templates available for the polymerase to copy.

what does using PCR do?

Help solve crimes

Settle paternity suits

Diagnose genetic disorders

DNA Fingerprinting

DNA Profiling