Notes - Life Science

7/28/2019 Notes - Life Science

1/6

Done by Goh Zuo Min

Notes Life Sciences(Raffles Institution Year 4 Biology)

Cloning

Cloning is creating an organism that is an exact genetic copy of another.Every bit of DNA is same between the two.

Types of Cloning

1. Artificial Embryo Twinning2. Somatic Cellular Nuclear Transfer

a. Therapeutic Cloning

b.

Reproductive Cloning3. Vegetative Propagation (descendants of single plant)4. DNA/Molecular Cloning Recombinant DNA Technology

Artificial Embryo Twinning

1. Zygote divides into two-celled embryo, and the two cells separate.2. Each cell continues dividing on its own, developing into separate

individuals.

1. Manually separates early embryo into individual cells.2. Plated in Petri dishes.3. Resulting embryos placed in surrogate mother, where they are

carried to term and delivered.4. All the embryos came from the same zygote, and hence they are

genetically identical.

Somatic Cellular Nuclear Transfer

1. Nucleus of somatic cell (diploids) removed2. Inserted into unfertilisted and enucleated egg cell (nucleus removed)3. Egg with donated nucleus divides, to form an embryo4. Embryo placed inside surrogate and develops

Reproductive CloningThe blastocyst is placed into a surrogate mother.

Therapeutic CloningThe embryonic stem cells are separated for tissue culture.

Dolly the SheepCreated by Somatic Cellular Nuclear Transfer


2/6

Done by Goh Zuo Min

Not truly an identical clone of donor animal because only chromosomal ornuclear DNA is the same as the donorSome genetic materials come from mitochondria in the cytoplasm of theenucleated egg

DNA/Molecular Cloning Recombinant DNA Technology

1. Identify and isolate a gene associated with a phenotype (location,DNA sequence)

2. Replicate to form many copies of the gene, using restriction enzymesto remove sections of DNA at a target sequence

3. Gene inserted into plasmids, which are structures that form frombacterial DNA, using DNA ligase to seal the DNA fragments

4. Plasmids are inserted into bacterial cells and then cultured

Cloning an Organism vs. Gene

Cloning an organism is making an exact genetic copy of that organism.

Cloning a gene is isolating an exact copy of a single gene from the entiregenome of an organism. Used to study the function of the individual gene inthe laboratory.

Risks of Cloning 1. High failure rate

a. Success rate 0.1 3.0%b. Enucleated egg and transferred nucleus may not be compatiblec. Egg with newly transferred nucleus may not begin to divide or

develop properlyd. Implantation of the embryo into the surrogate mother might

faile. The pregnancy itself might fail

2. Problems during later developmenta. Large Offspring Syndrome (LOS) b. Cloned animals that survive tend to be much bigger at birth

than their natural counterparts, and have abnormally largeorgans

c. Lead to breathing, blood flow and other problemsd. LOS doesnt always occur; scientists cannot reliably predict its

occurrencee. Some clones without LOS have developed kidney or brain

malformations and impaired immune systems

3. Abnormal gene expression patternsa. Clones may not express the right genes at the right time


3/6

Done by Goh Zuo Min

b. Re-programming the transferred nucleus to behave like in anearly embryonic cell, and for subsequent differentiation, isdifficult

4. Telomeric differencesa. As cells divide, their chromosomes get shorter. DNA sequences

at both ends of a chromosome, called telomeres, shrink inlength every time the DNA is copied.

b. The older the animal, the shorter its telomeres.c. Transferred nucleus is already old shortened telomeres may

affect its development or lifespan]

Frozen Ark

1. Scientists take small tissue samples from animals, so life is notendangered

2. Tissue may be frozen for safe-keeping3. DNA extracted from tissue sample straight after it was obtained or

after freezing4. DNA can be used for research, which may one day lead to

resurrection of extinct species5. Some DNA samples are sent to other labs as an insurance against

damage or loss6. Unused DNA can be frozen, potentially for thousands of years

Ethical Considerations

1. What is the moral status of the organisms created by cloning?2. Is it permissible to create a developing human entity only to destroy

it?3. Is it right to seek human eggs for scientific research?4. What are the ethical issues relating to the person whose cells are

being cloned?5. Will therapeutic cloning facilitate reproductive cloning, the birth of a

cloned baby?


4/6

Done by Goh Zuo Min

Stem Cells

The body is made up of over 200 different types of cells.

All these cell types come from a pool of cells, named the embryonic stem

cells (ESCs), totipotent stem cells, in the early embryo from the inner cellmass in the blastocyst.

Stem cell is a single cell that can replicate itself and has the potential todifferentiate into many cell types.

Properties of Stem Cells

1. Unspecialised2. Capable of dividing themselves for long periods to produce more stem

cells3. Can differentiate into specialized cell types under appropriate

conditions

Unspecialised stem cells Long term self-proliferation (underappropriate conditions) Differentiate into many cell types

Types of Stem Cells

1.

Early Embryonic Stem Cells (Totipotent)2. Blastocyst Embryonic Stem Cells (Pluripotent)3. Fetal Stem Cells (Pluripotent)4. Umbilical Cord Stem Cells (Multipotent)5. Adult Stem Cells (Unipotent)

Stem Cell Potency

Totipotent means that it can differentiate into all cell types.

Pluripotent means that it can differentiate into cells derived from any of the three germ layers.

Multipotent means that it can differentiate into a number of cells, but onlythose of a closely related family of cells.

Unipotent means that it can produce only one cell type, their own.

Uses of Stem Cells

1. Human Development (how cells differentiate and function)2. Drug Development (test for effects of drugs)


5/6

Done by Goh Zuo Min

3. Stem Cell Therapy (replace damaged tissue, e.g. heart failure,diabetes, Parkinsons)

Stem Cell Therapy

1. Define the Problem2. Finding the Right Type of Stem Cell3. Match Stem Cells with Recipient

a. Immune system attacks foreign material including stem cellsand tissues

b. Transplanted stem cells must match recipient closelyc. Tissue typing test performed using blood samples from both

individualsd. However, immune responses are typically muted in the brain

compared to other areas of the bodye. Fetal tissues should not trigger an intense immune response in

recipient4. Put Stem Cells in Right Place5. Make the Transplanted Stem Cells Perform

Control

1. Receive treatment2. Do not receive treatment

3.

Receive surgical procedure, and pre- and post- surgical care with nofetal tissue implant (placebo effect)


6/6

Done by Goh Zuo Min

Model Organisms

Apotiosis

Importance

microRNA

Role

Process of RNA interference in modulating the expression of DNA

Revolutionize personalized disease therapy

Bacterial Transformation

GFP gene carried on a plasmid

Notes - Life Science

Documents

Transcript of Notes - Life Science