Key Points of DNA Translation Process

ACT 1 - Initiation 

• The smaller Subunit of Ribosome charged with tRNA and the amino acid Methionine encounters mRNA
• They attach and start to scan for the start signal 
• The small subunit ribosome finds the starting sequence (AUG), the codon (triplet) for amino acid Methionine
• The large subunit of ribosome joins the small subunit to form the complete ribosome 
• Ribosomal subunit for Prokaryotic cells - 50 S and 30 S
• Ribosomal subunit for Eukaryotic cells - 60 S and 40 S

Act 2 - Elongation 

• A new tRNA + amino acid enter the A site of the ribosome 
• Anti-codon matches with mRNA codon basepairs, ribosome can link the 2nd amino acid together 
• tRNA shifts from A site to P site, P site to E site and leaves the ribosome without any amino acid
• The ribosome itself moves one triplet forward and a new tRNA + amino acid will enter the ribosome
• Procedure is repeated 

Act 3 - Termination 

• When ribosome reaches 1 of the 3 stop codons (UGA, UAG and UAA), there are no corresponding tRNAs
• Termination proteins bind to the ribosome and stimulate the release of the amino acid chain (polypeptide chain) 
• Large and small subunit dissociate as ribosome released from mRNA 

Key Points of DNA Transcription

ACT 1 - Initiation 

• Transcription factors (TFs) recognize and locates the promoter region (TA-TA Box)
• RNA Polymerase II binds the TFs and creates a transcription initiation complex
• DNA begins to unwind and then stabilized 
• RNA Transcription takes place in the complimentary strand of DNA
• RNA Polymerase II begins to transcribe 

ACT 2 - Elongation 

• RNA grows from 5' to 3'
• RNA Polymerase II adds nucleotides to the 3' end of the growing pre-mRNA
• Pre-mRNA is anti parallel with the Template DNA Strand (Antisense), and it's similar with the Coding DNA strand (Sense)
• Uracil replaces thymine within the pre-mRNA
• The direction of the Transcription goes from upstream towards downstream of the DNA strands

ACT 3 - Termination  

• RNA Transcription stops when it reaches the terminating region (AAAUAAAA) 
• Pre-mRNA turns into mRNA (messenger RNA) by applying a G-cap and poly-A tail 
• Introns of the pre-mRNA are cut by Spliceosome and exon parts are bind together

An Amazing Journey through DNA Replication

Prologue: 

In this prologue, the cell replicates it's DNA inside the nucleolus. As the cell grows bigger, it needs more nutrients and space in order to survive. Before undergoing mitosis, DNA replication has to happen first.

ACT 1: Initiation 

An enzyme called Helicase, unwinds the double helix DNA molecule and separates the strands; this also breaks the hydrogen bonding between nitrogenous bases. SSBP (Single-strand binding proteins) stabilize the DNA strands and this creates replication bubbles. As tension builds up during the unwinding, DNA Gyrase enzymes cuts the DNA in order to release the tension. RNA Primase enzymes place RNA Primers to signal Polymerase III to begin replicating the strands.

ACT 2: Elongation 

DNA Polymerase III synthesizes the new DNA from a 5' to 3' direction and adds free nucleotides to the 3' direction. Since DNA is an anti parallel structure, the two new strands will have to grow in an opposite direction. A new strand of DNA called "the leading strand" replicates continuously using a 3' to 5' so that it will become 5' to 3' with the template. Another new strand of DNA is called "the lagging strand" replicates discontinuously as RNA Primase comes in and synthesizes a short RNA Primer, which will be extended by DNA polymerase III to form sections called Okazaki Fragments; the leading strand replicates in an opposite direction with the lagging strand.

Act 3: Termination

DNA Lygase enzyme acts as a glue and joins each Okazaki fragment together. Phosphodiester bonds are created between DNA Lygase and Okazaki fragments. DNA Polymerase I comes in and proofreads the newly synthesized strands and replaces the RNA Primer with DNA. At last the two new DNA molecules separate from each other.
DNA Replication is now complete!

The Relationships between Catabolism, Anabolism and Metabolism

The Definition of Catabolism:

The metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy. 

Examples of Catabolism:

Glycolysis

Kreb's Cycle

Electron Transport Chain

The Definition of Anabolism:

The phase of metabolism in which simple substances are synthesized into the complex materials of living tissue

Examples of Anabolism:

Calvin Cycle

Cyclic Photosynthesis

Non-Cyclic Photosynthesis
















The Definition of Metabolism:

The total chemical reaction processes that occur within a living organism in order to maintain life

Catabolism + Anabolism = Metabolism

STORY TIME - The Extinction of Passenger Pigeons

             Pigeons, they are everywhere. If you take a walk in downtown Toronto you will most likely see a couple within the block, these animals live wherever they want. There are several species of these pigeons, and today we shall talk about the passenger pigeon.
     
             The name of "passenger" pigeons is refereed as a French word "passager" which means passing by. During the 19th century, these birds were THE MOST abundant bird in North America, possibly even the world. They migrate in huge flocks that have over 3.5 billion birds, it could even blacken the sky! If accurate, that number would be representing a large faction of the entire population at it's time.

             The Government at that period of time had decided to hunt down these birds and pigeon meat were used as cheat food for slaves and the poor. There had been ZERO worries concerning the population of the passenger pigeon as you could literally shoot one down if you randomly aim at the sky. These birds are one of the most sociable birds of all times, without a large flock, they wouldn't be able to communicate with each other. Their diet consists of all kinds of nuts such as acorn and chestnuts, sometimes even berries.

             As the years go on with the constant hunting and commercial exploitation of passenger pigeon meat at a massive scale, the population of these birds start to decline; moreover, deforestation increased rapidly during the 1900s, the bird's habitat had reached to a certain size where there is not enough space for the passenger birds to migrate and reproduce. Conversationalists set up bills that it became illegal to net pigeons within two miles, but this was weakly enforced.

             By the mid-1990s, the passenger pigeon total population almost completely disappeared. At last there were only 1 passenger pigeon left in the entire world, it's name was Martha. She was kept in Cincinnati Zoo and was named as the loneliest bird ever; she died in September 1st, 1914. This was the end of the most abundant bird in the world. This year - 2014 is the 100th anniversary of remembrance of the passenger bird.

             After hearing this story told by our tour-guide, I felt extremely depressed as to know that humans have the power to wipe out a species that was abundant. Who knows which abundant species would go extinct next with all these global warming and loss of animal habitat from deforestation. This story needs to be heard by a lot more people, as far as i know; most people don't even know about the passenger bird's legacy.

The Journey within Photosynthesis (10 Key Points)

• It all begins with two hydrogen molecules covalent bonding with a oxygen molecule
• When an electron is lost in an element, it is called oxidization 
• When an electron is gained in an element, it is called reduction 
• In order for PSII and PSI to gain electrons, it needs sunlight to get excited and oxidized
•  The action of getting the electron from water molecule is called photolysis
• As NADP becomes oxidized, it takes 1 hydrogen molecule and becomes NADPH, the other H+ is released into the environment
• Adenine bonds with two phosphate molecules to form the adenine diphosphate (ADP)
• ADP synapse and ADP spins fast for the hydrogen to pass through the filter to exit the leaf
• The transformation of hydrogen slows down the spinning
• A 3rd phosphorus molecule comes in and takes the diphosphate, forming (ATP)
  

Fetal Pig Dissection

Right before we start a new unit in grade 12 biology, we had a fetal pig dissection in this homeostasis unit.
The purpose of this dissection is to know and closely examine different body systems - Nervous system, Endocrine system and Urinary system.

This is how the lab began.
The first task was to determine the gender of our fetal pig.

We counted the number of toes and examined the inside of the mouth.

We located the taste buds on the side of the tongue 

Our second task was to cut open the abdominal and thoracic cavity of the fetal pig and identify structures.

We start to see different organs after we cut open the abdomen

The third task was to isolate organs inside the abdominal cavity and observe them.

 The isolation of the stomach 

 Here we have the biggest organ in the fetal pig - the Liver

 The Spleen is a long tongue-like organ

 The pancreas can be easily damaged 

 The small intestine consists of - duodenum, ileum, cecum

 The kidneys are located in the dorsal point of the fetal pig

 This is the cross-section of the kidney

 Ovary

- This concludes the first day of the dissection-

Second day of fetal dissection begins

Task four, dissection of the thoracic cavity.

 The diaphragm can be seen right below the chest cavity

 

We started cutting open the chest cavity and discovered the pair of lungs and the heart under it.

         The Heart

   

The Cross-Section of the heart

 

The Thyroid gland looks like a V-shaped structure and it lies atop of the trachea

After the dissection of the Thoracic Cavity, Mr Chung gave us another task, isolate the brain off the skull.

Task five, dissection of the brain.

 The skull is really hard and tough to cut open

           Success!

Final task, dissection of the eye.

                                   

We had to cut away the skin and obtain the eye ball from its socket

 The retina can be clearly seen after the cross-section 

The fetal pig has a biconvex lens 

Woah that was a long post, overall the dissection was a success and it is really interesting to see different organs up-close and examine them.