Molecular genetics grade 12

• The DNA double helix is held together by hydrogen bonds between complementary base pairs.
• Replication begins at specific sites called origins of replication.
• Leading strand is continuously synthesized from one end towards the other
• RNA primers are synthesized on both strands using RNA polymerase III.
• DNA polymerase adds nucleotides to the growing strand, following the template strand.
• Each parental strand serves as a template for synthesis of a daughter strand.
• DNA replication occurs through semiconservative replication, where the two strands separate and serve as templates for new nucleotides to be added.
• Topoisomerases relieve tension caused by uncoiling of the DNA molecule during replication
• Lagging strand has gaps where Okazaki fragments were joined together.
• Okazaki fragments are short pieces of DNA that form during lagging strand replication.
• Okazaki fragments are short sections of newly synthesized DNA that are joined together during lagging strand synthesis.
• Ligase joins Okazaki fragments into continuous strands.
• During transcription, mRNA is transcribed from DNA in the nucleus.
• During replication, leading and lagging strands are separated by an enzyme called helicase.
• The leading strand is synthesized continuously while the lagging strand is synthesized discontinuously.
• Lagging strand has many Okazaki fragments joined together by ligases.
• Lagging strand moves away from origin of replication at variable speeds due to formation of RNA primers.
• Replication fork is where two daughter strands separate.
• In prokaryotes, there is only one type of RNA polymerase.
• The enzyme RNA polymerase reads the base sequence of one DNA strand (template) and assembles complementary bases to make an antisense RNA copy.
• Replication occurs at multiple origins on both chromosomes simultaneously.
• In eukaryotes, RNA polymerases bind to specific promoter sequences on DNA and initiate transcription.
• Leading strand is synthesized continuously towards the replication fork.
• Lagging strand is synthesized discontinuously away from the replication fork.
• Transcription begins with initiation phase, followed by elongation and termination phases.
• Ribosomes are made up of proteins and rRNAs.
• Transcription occurs when mRNA is transcribed into protein.
• Translation involves ribosome binding sites on mRNA.
• Initiation involves binding of RNA polymerase to promoter region, unwinding of double-stranded DNA, and separation of template strands.
• Elongation involves addition of nucleotides to growing chain through phosphodiester bonds between adjacent ribonucleotide triphosphates.
• What are Watson and Crick commonly referred to as?


  Fathers of DNA
• What is added to the 5’ and 3’ end of an mRNA strand before leaving the nucleus?

  5' cap and 3’ poly-A tail.
• Molecular Genetics is the study of the molecular structure of DNA, its cellular activities and its influence on the overall makeup of an organism.
• Genetic research and biotechnology have social, legal and ethical implications.
• DNA, or Deoxyribonucleic acid, is a molecule that carries genetic information for the development and functioning of an organism.
• DNA is the 'instruction manual' for the synthesis of proteins.
• Proteins control a huge variety of cellular processes.
• DNA is tightly arranged into structures called chromosomes that are located in the nucleus of the cell.
• Our current understanding of DNA is the result of the work of countless scientists over the span of a century.
• Frederick Griffith made a breakthrough discovery in 1928 while researching Streptococcus pneumonia.