Nucleic acidsDNA

LOCATION OF DNA

Nuclear DNA

Chloroplastic DNA

Mitochondrial DNA

FUNCTIONS OF DNA Controls protein synthesis Carries hereditary characteristics

DNA –Position in the cell

Nucleus

DNA double helix

Chromosomes

HISTORY OF DNA

A. Rosalind Franklin and Maurice Wilkins - X-ray photo of DNA. (1952)

B. Watson and Crick - described the DNA molecule from Franklin’s X-ray. (1953)

C. Watson crick and Wilkins – received Nobel price(1962). Franklin passed away

Complete activity textbook pages 16-17

DNA Structure

DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.

A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Each nucleotide consists of:1. Phosphate group2. Pentose sugar3. Nitrogenous base

Nucleotides

Phosphate

PentoseSugar

NitrogenousBase

Nucleotides

The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”.

There are four types of nitrogenous bases.

Nucleotides

A

Adenine

T

Thymine

G

Guanine

C

Cytosine

Remember

DNA T – AG - C

It's hard to believe that an alphabet

with only four letters can make

something as wonderful and complex as a

person

Nucleotides

Each base will only bond with one other specific base.

Adenine (A)Thymine (T)

Cytosine (C)Guanine (G)

Form a base pair.

Form a base pair.

DNA Structure

Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

G

G

A

T

T

A

A

C

T

G

C

A

T

C

DNA Structure

To crack the genetic code found in DNA we need to look at the sequence of bases.

The bases are arranged in triplets called codons.

A G G - C T C - A A G - T C C - T A GT C C - G A G - T T C - A G G - A T C

DNA Structure

A gene is a section of DNA that codes for a protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us a unique phenotype.

THE ROLE OF DNA (pg 23)

• PROTEIN SYNTHESIS- DNA has the code to make all proteins• PASSING ON OF HEREDITARY MATERIAL- Passed on from

parent to offspring.• REPLICATION- DNA can make a copy of itself for cell

division.• CARRYS GENETIC INSTRUCTIONS- Has instructions to make

all components of the cell.• MAINTAINS STRUCTURE AND REGULATION- large sections of

DNA are non-coding and they maintain structure of chromosomes and regulate the functions of genes.

HOMEWORK PG 20 EX 1.

DNA REPLICATIONProcess of making a new DNA molecule from an existing DNA molecule that is identical to the original

WHYSo that genetic code is passed on to each new daughter cell formed during cell division

WHENDuring interphase

DNA REPLICATION PROCESS

• UNWIND• UNZIP• COMPLEMENTARY PAIRING• REZIP • REWIND• CONTROLLED BY ENZYMES

DNA Replication

Unzip into two single strands

New bases attached themselves in the correct place of each strand

Free nucleotides in nucleoplasm

Two identical strands are formed

Each strand now becomes a double helix.

Strand 1 Strand 2

1. Identify the above molecule.2. Give labels for parts numbered 1to 53. Describe how the above molecule replicates itself.4. What is it significance that this molecule can replicate itself?

Questions on the DNA Molecule 1

2

3

4

5

G

T

ANIMATION

H bonds break Two strands seperate

Sugar phosphate backbone is made by joining the adjcent nucleotides ( DNA polymarase enzyme( ) )

Nucleotides with Complementary bases are assembled alongside each strands

Two identical DNA molecules are formed

HOMEWORK pg 20 Ex 1 ANSWERS1 A Deoxyribonucleic acidB Double helixC Adenine, Thymine, Cytosine and GuanineD Weak hydrogenE Pyrimidines2. Nucleotides join with matching bases e.g. A-T and

C-G3. It is made of small molecules called nucleotides4. These are complimentary bases for each C there

will be a G attached on the other strand of DNA

DNA Profiling

Each PERSON’S DNA profile is unique!

What is DNA Profiling?

A technique used by scientists to distinguish between individuals of the same species using

only samples of their DNA

Where do we get DNA

DNA profiling• Technique used to identify sequence of bases

• The nucleotides are separated from each other in

the order that they are found in strand of DNA.

• Nucleotides appear as dark bands

• The sequence in this segment

of DNA reads CTT- AGT

• Use as DNA fingerprint

• Unique for every person

DNA Profiling can solve crimes

• The pattern of the DNA profile is then compared with those of the victim and the suspect.

• If the profile matches the suspect it provides strong evidence that the suspect was present at the crime scene (NB:it does not prove they committed the crime).

• If the profile doesn’t match the suspect then that suspect may be eliminated from the enquiry.

Solving Medical Problems

DNA profiles can be used to determine whether a particular person is the parent of a child.

A childs paternity (father) and maternity(mother) can be determined.

This information can be used in• Paternity suits• Inheritance cases• Immigration cases

• DNA fingerprinting is often used by the police in identifying the suspect of a crime. • A useful but controversial method• A sample of a suspect’s bodily fluid or tissue is to be compared with a sample found at the scene of a crime. • The pattern of lines represents a person’s specific genetic make-up.• DNA fingerprinting use in 11/9 disaster to identify victims

DNA Fingerprinting

1 2 3 4 5 6 7 8 9 X

Problem 1:

X is a DNA sample found at the scene of a murder.

9 suspects were requested to provide DNA samples.

Which person is likely to be the murderer?

Could this be disputed?

HOMEWORK PG 28 CASE STUDY 2

ANSWERS CASE STUDY 2

1 From Chantal T2 Possibly as a result of a tussle with the killer. 3. The victim 4. Chantal T5. The sample might be from the victim themselves and not the killer. 6. No, we can confirm that her skin was under the victims nails, not that she committed the murder.

• Diabetics need insulin to live• Diabetes use insulin from pigs and cattle. This

is not the same as human insulin and sometimes produces side effects. With genetic engineering, bacteria are used to produce some human insulin

Bacterial DNA - Manufacturing of insulin

1. A ring of DNA is taken from a bacterium

2. A piece is cut out using enzymes as ‘chemical scissors’

3. A cell is taken from a human pancreas. The gene for insulin is cut from the chromosome

4. The insulin gene is put into the ring of bacteria DNA

5. The bacteria reproduce, making

clones of themselves

6. The insulin is collected and purified ready for use

Pg 26 Ex 2

Why is there still controversy?

SOLVE CRIMES

PATERNITY SUITS/Inheritance cases

IDENTIFICATION OF DEAD BODIES.

DIAGNOSIS OF INHERITED DISORDERS

DEVELOPING CURES FOR INHERITED DISORDERS

USES OF DNA FINGERPRINTS

•RNA is a small molecule • It has a single strand• It is made up of monomers called nucleotides

STRUCTURE OF RNARIBONUCLEIC ACID

A nucleotide consists of a A sugar molecule = Ribose A PHOSPHATE Portion A NITROGEN base Cytosine Uracil Adenine Guanine

RNAThree types and location

1. Messenger RNA (mRNA) - Nucleus and cytoplasm2. Transfer RNA (tRNA) - cytoplasm3. Ribosomal RNA (rRNA) - ribosome

FUNCTIONS• Messenger RNA (mRNA) – transfers DNA code

to ribosomes for translation. Acts as a template for protein synthesis.

• Transfer RNA (tRNA) – brings amino acids to ribosomes for protein synthesis.

• Ribosomal RNA (rRNA) – Ribosomes are made of rRNA and protein.

QUESTIONS

1. Name the types of RNA, state the location of each and give the function of each.

2. Draw a stick diagram to illustrate the structure of an RNA molecule with bases ACCGUU

3. Tabulate the differences between RNA and DNA.

Differences between DNA and RNADNA RNA

Double strand Single strand

Deoxyribose sugar Ribose sugar

Thymine and Adenine Adenine and Uracil

PROTEIN SYNTHESIS

TRANSCRIPTION• In the nucleus.• DNA unzips during replication.• A DNA strand acts as a template for

transcription.• RNA nucleotides join complimentarily.• mRNA molecule is formed.• Process controlled by enzymes.

The mRNA moves out of the nucleus, through the nuclear pore, into the cytoplasm. It attaches to the ribosome.

TRANSLATION

• mRNA is attached to the ribosome with triplet bases (codons) exposed.

• tRNA with a complimentary RNA code (anticodon) bring specific amino acids (1 of 20) to the ribosome.

• Amino acids from different tRNA are joined by peptide bonds. A protein is made up of 50 or more amino acids.

A U G G G C U U A A A G C A G U G C A C G U U

This is a molecule of messenger RNA.

It was made in the nucleus by transcription from a DNA molecule.

mRNA molecule

codon

A U G G G C U U A A A G C A G U G C A C G U U

A ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule.

ribosome

A U G G G C U U A A A G C A G U G C A C G U U

It brings an amino acid to the first three bases (codon) on the mRNA.

Amino acid

tRNA molecule

anticodon

U A C

A transfer RNA molecule arrives.

The three unpaired bases (anticodon) on the tRNA link up with the codon.

A U G G G C U U A A A G C A G U G C A C G U U

Another tRNA molecule comes into place, bringing a second amino acid.

U A C C C G

Its anticodon links up with the second codon on the mRNA.

A U G G G C U U A A A G C A G U G C A C G U U

A peptide bond forms between the two amino acids.

Peptide bond

C C G U A C

A U G G G C U U A A A G C A G U G C A C G U U

The first tRNA molecule releases its amino acid and moves off into the cytoplasm.

C C G U

A C

A U G G G C U U A A A G C A G U G C A C G U U C C G

The ribosome moves along the mRNA to the next codon.

A U G G G C U U A A A G C A G U G C A C G U U

Another tRNA molecule brings the next amino acid into place.

C C G

A A U

A U G G G C U U A A A G C A G U G C A C G U U

A peptide bond joins the second and third amino acids to form a polypeptide chain.

C C G A A U