13th Lecture : 11/11/14

Topic: Structure and Function of Genetic Material

Notes:
1) Genes are the segment of DNA codes for genetic material.

2) Genome are the genetic information in a cell.

3) Nucleic acid : DNA ( Deoxyribonucleic acid) and RNA ( Ribonucleic acid)

4) Nucleotise is made up of pentose sugar ( ribose and deoxyribose ) , nitrogenous base and phosphoric acid.

5) The structure of Deoxyribose and Ribose:

• The formula for Deoxyribose is C5H10O4 while the formula for ribose is C5H10O5.
• Deoxyribose lack of one oxygen atom.
• Ribose have an OH attach to carbon number 2 instead of H atom.

5) Nitrogenous bases are divided into pyrimidine (Cytosine, Thymine and Uracil ) and purines ( Adenine and Guanine )

6) The structure of nucleotide :

• Nitrogenous base always attach to carbon 1 while phospheric acid attach to carbon 5 and carbon 3 of next pentose sugar.
• Nucleoside composed of pentose sugar and base while nucleotise composed of nucleoside and phospheric acid.
• Polynucleotide is bonded by phosphodiester bond. (between phosphate group and the sugar of adjecent molecules.

• The DNA molecules consist of 2 polynucleotide chain which are antiparallel, joined by pairs of bases to form a double helix.
• The pairings are always C and G, A and T . 3 hydrogen bonds formed between C and G. 2 hydrogen bonds between A and T.
• One strand run from 5 prime end to 3 prime end and the other strand run from 3 prime end to 5 prime end.

6) The 4 nitrogenous base found in RNA are U, A, C and G. U will pairs with A while C pairs with G.

7) There are 3 types of RNA : nRNA, tRNA, rRNA.

8) mRNa synthesized in nucleus from one part of DNA and associates with ribosomes and acts as template for protein synthesis.

9) Codon is a series of 3 adjacent bases in one polynucleotise chain which codes for a specific amino acid.

10) tRNA attach amino acid to its head according to the codon that is complementary to its anticodon.

11) Anticodon is a sequence of 3 adjacent nucleotides in tRNA that binds to a corresponding codon in nRNA during protein synthesis.

12) rRNA contains 3 bingding sites for protein synthesis ( P site, A site and E site).

13) A site hold the tRNA that carrying the next amino acid to be added to the polypeptide chain, P site hold the tRNA that carrying the growing polypeptide chain, E site discharged tRNa to leave the ribosome.

14) Short overview of DNA replication:

The two stands of DNA will separated and the free nucleotides attached to their complementary bases. DNA polymerase will fit the nucleotide to the single polynucleotide chain according to their complementary bases. The free DNA nucleosides add in in the 5 prime ro 3 prime direction.The new polycucleotide strand that formed continuously towards the replication fork is leading strand. The new polynucleotide chain that formed away from the replication fork is lagging strand. Okazaki fragments formed along the lagging strand. The okazaki fragments are then joined by the DNA ligase. When replication is completed, the 2 double-stranded daugther DNA molecules are formed.

15) DNA replication was accepted as semiconservative model because the replicated DNA will contain a parental strand and new strand.

16) The characteristics of genetic code:

• The code for almost all organisms is the same
• The code is degenerate.
• The code is non-overlapping.

17) Short overview of DNA transcription:

The DNA double strands unwind and RNa polymerase attaches to the transcribing DNA strand at the promoter site. As the RNA polymerase move along to the 3 prime end of DNA, complimentary nucleotides are added to it.When the enzyme move to another region of transcribing DNA strand, the double helix of DNA reforms behind it. Once reaching terminator, the enzyme deattached and the nRNA molecules moves away from DNA.

18) Translation is the process by which information encoded within mRNA is used to make specific polypeptide chain.

19) Start codon is the first codon in mRNA that translated by ribosome. The common start codon is AUG.

20) Stop codon is the codon in mRNA that signals the termination of translation. The common stop codon is UAA, UGA and UAG.

21) Wobble hypothesis states that the bases in first position of anticodon on tRNa is usually an abnormal base, like inosine. These abnormal bases able to pair with more than one type of nitrogenous base in the third position of the codon on mRNA. For example, inosine can pair with A, C and U. That's means only 32 tRNA are needed.

Activities: No other activities carried out except for teaching...^^

My own explorace:

1) Why pyrimidine must match with purines?

It is to ensure the center of DNA always contain 3 rings, ( Pyrimidine has one ring and purine has two rings)

2) Why introns need to remove?

It is because introns didn't carry any information for amino acid. If introns are not remove, wrong proteins will be translate or made.

3) The degenerate characteristics of genetic code means that some of the amino acids are coded for more than one codon.

4) James Watson and Francis Crick are the scientists that identified and discovered the double helix structure of DNA. 

Reflection:

Prof Khatijah was a cute and friendly lecturer. She kept told us about her story and experience because she doesn't want us to feel boring in her lecture. This lecture makes me recall back the genetics that I have learnt in from 6. Genetics is an interesting topic and I like this topic very much.