What cloning is? Can we clone human?

What is cloning?

• It is a highly artificial form of asexual reproduction based on mitosis to form new individuals.


• The new individuals are called CLONES, which have the same genetic material as the parent.

How is animal cloning carried out?

• An animal is cloned using a nucleus obtained from an adult tissue.


• The clone is genetically identical to the somatic cell donor.


• In 1996, Scotland , Dolly became the first cloned sheep done through a technique called Somatic Cell Nuclear Transplant (SCNT). She was produced after 270 attempts & has many deformities. She died of lung disease in 2003 at the age of 6, while a normal life span of a sheep is around 10-16 years.

To know more about cloning, watch the video below or click here.

Human embryo cloning – 3 minutes


FIRST HUMAN EMBRYO-CLONE CREATED
Uploaded by neverknwo. - Explore more science and tech videos.

You can watch Dolly, the clone sheep, go to 5-7 minutes of the 2nd video below.
To watch the full documentary, click the video below or click here

Panayiotis Zavos is a controversial fertility doctor. He said to “The Independent” that he had already cloned human embryos and transferred 11 of them into the wombs of four women who had been prepared to give birth to cloned babies.
Since cloning embryos into the human womb is a criminal offense in most countries, Dr. Panayiotis Zavos is said to have worked at a secret laboratory in the Middle East where there is no cloning ban.
Dr. Zavos also revealed that he has produced cloned embryos of three dead people, including a 10-year-old child called Cady, who died in a car crash. He did so after being asked by grieving relatives if he could create biological clones of their loved one.>

Human cloning – 45 minutes






Do you think we should be cloning human?

Nucleic Acid - DNA & RNA

Nucleic Acid are complex macromolecules which store genetic information in the form of a code.


There are 2 types of nucleic acid: DNA (Deoxyribonucleic acid) & RNA (Ribonucleic acid).

• basic units of nucleic acids are nucleotides


• A nucleotide is made up of:
  
  1. a pentose sugar (deoxyribose for DNA, ribose for RNA)
  2. a nitrogenous base


• 3. a phosphate group
  

What is DNA molecule?

• DNA molecules can be found inside the nucleus, the mitochondria & chloroplast organelles.


• The sequence of nitrogenous base in a DNA molecule is called gene.
  
• A DNA molecule contains thousand of genes which code for the synthesis of specific proteins. (eg: enzyme)
  
• A DNA molecule consists of two polynucleotide strands coiled together/twisted around each other to form a DOUBLE HELIX. (above diagram)
  
  
  
  
  
  How are the nucleotides linked?
  Each nucleotide is joined to the next nucleotide through the phosphate group to form a long polynucleotide strand.
  Diagram shows 2 polynucleotide strands arranged in anti-parallel.
  
  
  




• 
  
  
  
  
  
  
  In 1953 James D. Watson and Francis Crick suggested what is now accepted as the first correct double-helix model of DNA structure.
  
  
  
  
  
  

What is RNA?

• can be found in the nucleus, ribosomes & cytoplasm.


• there are 3 types of RNA (mRNA, rRNA, tRNA) - this is not covered under spm syllabus.


• messenger RNA (mRNA) carries DNA's genetic code into the cytoplasm & direct the synthesis of proteins.

What are the differences between DNA & RNA?

1. DNA consists of 2 strands of polynucleotide (that coiled together to form a double helix) while RNA consists of only one strand of polynucleotide.

2. The pentose sugar in DNA is deoxyribose while in RNA it is ribose.

3. types of nitrogenous bases - you will learn in form 5.

Spinal Cord & Neurones

Human Nervous System is made up of the Central Nervous System (CNS) & the Peripheral Nervous System (PNS).

• PNS consists of the cranial nerves (12 pairs) & the spinal nerves (31 pairs).
• CNS is the control centre of the body.
  
• Spinal Cord (SC) link between the brain & the PNS.

*note: in the above diagram, an Interneurone should be drawn to connect the Sensory neurone to motor neurone via synapse.


• In a cross section, SC consists of :
  1) grey//gray matter which consists mainly of cell bodies of neurones (nerve cells).
  2) white matter (surrounding the grey matter), which consists of myelin-coated axons of neurones.
  
• Spinal nerves arise from the SC & has a dorsal root & a ventral root.
  
• Dorsal root ganglion - contains cell bodies of afferent neurone.
  
  
  

• Neurones (nerve cells):
  1) a typical neurone has a cell body, dendrites & usually one axon.
  2) neurones transmit nerve impulses (NI)/electrical signal to other nerve cells, glands or muscles.
  
  
• There are 3 types of neurones.
  1) Afferent neurone (AN) / sensory neurone
  2) Interneurone (IN) / (relay neurone, association neurone)
  3) Efferent neurone (EN) / motor neurone

*note: EN (neurone P), IN (neurone Q), AN (neurone R).
** unipolar, bipolar, multipolar neurones are not part of spm syllabus.

• State the differences between neurones:
  1) AN has cell body located at one side, EN has cell body located at one end while IN has cell body located at the centre.
  2) AN transmits/sends NI from the sensory receptor to the CNS, EN transmits NI from the CNS to the effectors while IN transmits NI from the AN to the EN.
  3)
• State the function of dendrite, axon, myelin sheath, node of Ranvier. (refer yr notes.)
• draw a labelled diagram of EN. (refer yr notes for drawing)