Topic Biomolecule Essay - Main Points!

Describe the differences between amino acids and nucleotides

Main points
Key idea:	Components
(each) Amino acid: · Has an amino (NH) gp, a carboxyl (COOH) gp, a H atom & a R gp attached to a central α carbon atom (each) Nucleotide: · Made up of a pentose sugar, a nitrogenous base & a phosphate gp · Ref to 3 phosphate gps in each ‘free’ nucleotide
Key idea:	Ionization
Amino acids: · In H2O, COOH & NH gps ionize, form –ve charged & +ve charged gp, respectively · Ref to amphoteric property (i.e. –ve charged COOH accepting a H+, -ve charged NH donating H+); i.e. aa act as pH buffer Nucleotides: · In H2O, the phosphate gp is -ve charged, hence nucleotide is soluble in H2O · Also result in net -ve charges of RNA & DNA polynucleotides (DNA migrate toward +ve electrode during gel electrophoresis due to -ve charges along sugar phosphate backbone)
Key idea:	Types
Amino acids: · 20 (naturally occurring) aa distinguished by identity of R gp · Ref to aa categorized into polar uncharged, non-polar uncharged & charged (basic or acidic) aa Nucleotides: · 4 diff types of nucleotides in DNA distinguished by base - cytosine, guanine, thymine & adenine · In RNA, bases are same except for uracil replacing thymine
Key idea:	Formation of bonds
Amino acids: · Diff R gps allow for formation of ionic, H, disulfide bonds or hydrophobic interactions b/w aa; result - sec, tertiary & quarternary struc of a protein Nucleotides: · H bonds b/w complementary bases (C and G, A and T), result - formation of double helix struc of DNA
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) For this type of essay question, you could answer in a table format too (v) If time permits, draw and label a general amino acid and nucleotide

Topic DNA/Genomics Essay - Main Points!

Q) Use a named example of a genetic disease to explain the effect of substitution mutation

Main points
Key idea:	Named example : Sickle cell anaemia – substitution mutation
· Thymine nucleotide in the β-globin gene is substituted by adenine nucleotide. · After transcription, original codon (GAG) of mRNA coding for hydrophilic aa glutamic acid is changed to a new codon (GUG) coding for hydrophobic valine
Key idea:	Effect on specific conformation and function of polypeptide chain
· After translation, the new aa seq (i.e. pri struc) alters folding of polypep chain into its specific conformation · Abnormal haemoglobin interact with each other - form fibre-like struc at low O2 level
Key idea:	Effect on red blood cells (rbc) + health of patient
· RBC form sickle shapes instead of usual biconcave shapes · Blockage of bl capillaries, tissue damage, pain · Destruction of deformed rbc leads to anaemia
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Discuss the effect of base substitution mutation at the mRNA and protein level (v) Do not mix up the effect of changed DNA seq on (1) mRNA seq, (2) aa seq of β subunit of Hb, (3) specific shape of protein, and (4) shape of rbc (vi) Anaemia refers to the decrease in number of red blood cells or less than the normal quantity of haemoglobin in the blood.

Topic DNA/Genomics Essay - Main Points!

Q) Discuss the significance of mRNA in the formation of protein

Main points
Key idea:	What is messenger RNA (mRNA), how is it formed and its role
· Product of transcription in which template strand of gene is used for syn of mRNA · Via complementary base pairing b/w exposed DNA nucleotides on template and free RNA nucleotides ·  Ref to RNA polymerase catalyzes formation of phosphodiester bonds b/w adj RNA nucleotides · After its syn, mRNA exits nucleus, via nuclear pore, to cytoplasm · Binds to ribo for translation · Coding seq of single-stranded mRNA consists of triplets of bases (codons), each codon codes for 1 aa
Key idea:	Initiation of translation
· Initiation of translation - 1st codon + 2nd codon of mRNA occupy peptidyl-tRNA binding site (P site) + aminoacyl-tRNA binding site (A site) of ribo, respectively · Ref to codons - complementary to anti-codons of transfer RNA (tRNA) carrying specific aa · Ref to 1st codon (AUG) codes for methionine
Key idea:	Elongation and termination of translation
· Syn of peptide bond b/w methionine + 2nd aa · Ribo translocate 3 base downstream of mRNA, 2nd & 3rd codons now occupy P & A sites, respectively · Another tRNA carrying correct aa will bp to 3rd codon where another peptide bond join 3rd aa to carboxyl end of dipeptide before ribo translocate downstream · Process repeats itself until a stop codon (e.g. UAA, UGA and UAG) occupies A site · Stop codon does not code for any aa, but signal termination of translation · Ref to newly syn polypep, ribo dissociate fr mRNA · Throu this process, mRNA codon seq codes for a single polypep
Key idea:	Processing of eukaryotic mRNA
· Alternative splicing that occur during mRNA processing - diff mature mRNAs each coding for a different polypep
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Alternative splicing refers to a process by which the exons of the RNA produced by transcription of a gene are joined in multiple ways during RNA splicing. The resulting different mRNAs may be translated into different polypeptides. Thus, a single gene may code for multiple proteins.