DNA Replication

• means the “copying of DNA’• It happens during

Interphase• semi-conservative:

each new DNA helix formed is made of one old strand and one new strand.

STEP 1:

• Original DNA strand is pulled apart by the enzyme DNA helicase. It breaks the hydrogen bonds.

STEP 2:

• Another enzyme, DNA polymerase, adds new nucleotides to each strand which produces two new, identical DNA strands.

STEP 3:

• The strands wrap back up and the cell is ready to divide (mitosis!!!)

DNA Replication

• http://www.youtube.com/watch?v=yqESR7E4b_8

Cloning

• The production of identical copies of molecules, genes, cells or even entire organisms.

• Dolly the sheep was cloned by Ian Wilmut (Scottish scientist) in 1997.

WILMUT’S EXPERIMENT

• He took an egg cell from one adult female sheep and removed its nucleus. • He replaced the nucleus

with one from a mammary gland cell from a different adult female sheep.• The egg cell with the new

nucleus was implanted into the uterus of a surrogate mother sheep. • It began to divide and form

an embryo.

WILMUT’S RESULTS

• 5 months later Dolly was born. (She lived for 8 years)• She was an exact copy of her “mother” –

the cell that provided the nucleus.• It took many failed attempts and

experiments before this technique of cloning finally succeeded.

Dolly the Sheep

• http://www.youtube.com/watch?v=YoEWYJHf0kU

Useful application of Cloning

• Cloning is used in agriculture to produce many copies of high-quality crop plants.• In medicine • to produce identical strands of bacteria

for research.• to try to replace damaged cells, tissues,

and possibly organs.• GENE cloning is more common than

cloning of whole organisms.

Gene Cloning

• Scientists cut out a gene of interest.• Insert gene into bacterial cell genome.• As the bacteria cells divide and replicate,

the new gene is copied along with their own DNA.• The bacteria start to make the protein that

the gene codes for. Ex. Insulin• Similar process also used in GMO’s.

Issues with cloning

• Read the assigned case study

• Write down the ethical problem specific to the scenario

• Brainstorm 3-5 possible solutions or alternative actions to the problem

• Be prepared to discuss your opinions with the class