A1.2 Nucleic Acids SL & HL PDF

Molecules A1.2 Nucleic acids SL Learning goals I can draw a nucleotide I can draw an example of DNA molecule (including hydrogen bonds) I can summarize the main differences between DNA and RNA I can explain that diversity by any length of DNA molecule and any base sequence is possible....

Molecules A1.2 Nucleic acids SL Learning goals I can draw a nucleotide I can draw an example of DNA molecule (including hydrogen bonds) I can summarize the main differences between DNA and RNA I can explain that diversity by any length of DNA molecule and any base sequence is possible. A1.2.1 DNA as the genetic material of all living organisms Nucleic acids are information molecules in cells and viruses. The genetic code in nucleic acids is universal. Two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is genetic material found in the  some viruses use RNA as their genetic material diseases caused by RNA viruses include the common cold, COVID-19, influenza, dengue fever, hepatitis C, rabies, Ebola, polio, mumps and measles. Viruses depend on the cells of living organisms to survive and replicate, and so are not considered to be living  A1.2.2 Components of a nucleotide A nucleotide consists of three substances combined through covalent chemical bonding. These are: a nitrogenous base – the four bases of DNA are cytosine (C), a guanine (G), pentose adenine sugar (A) and – deoxyribose thymine occurs (T) and ribose in RNA in DNA a phosphate group (phosphate diester).  A1.2.2 Components of a nucleotide These components are combined by an enzyme-controlled condensation reaction to form a nucleotide. Condensation reactions occur when two molecules combine, producing water as a by-product. purin pyrimidi DRAW a nucleotide! In diagrams of nucleotides use circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases DRAW a nucleotide! In diagrams of nucleotides use circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases phosphates base pentose sugar A1.2.3 Sugar–phosphate bonding and the sugar– phosphate “backbone” of DNA and RNA Nucleic acids are very long, thread-like (linear) macromolecules with alternating sugar and phosphate molecules forming the ‘backbone’. The sharing of electrons in the covalent bond between sugar and phosphate provides strength to the A1.2.4 Bases in each nucleic acid that form the basis of a code What are the names of the nitrogenous bases again? In the DNA who pairs with who? A1.2.5 RNA as a polymer formed by condensation of nucleotide monomers RNA molecules are relatively short in length, compared with DNA. RNA molecules tend to be from a hundred to thousands of nucleotides long RNA molecule is a polymer with a single strand of polynucleotide in which the sugar monomer is ribose The bases found in RNA are cytosine, guanine, adenine and uracil (which replaces thymine of DNA) There are three functional types of RNA: o messenger RNA (mRNA) DRAW it! In diagrams of nucleotides use circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases. Write R for ribose and DR for deoxyribose inside the pentose sugars. Draw a labelled diagram of: All the possible separate nucleotides of DNA All the possible separate nucleotides of RNA  A1.2.6 DNA as a double helix made of two antiparallel strands of nucleotides with two strands linked by hydrogen bonding between complementary base pairs The DNA molecule consists of two antiparallel polynucleotide strands, paired together, and held by hydrogen bonds. The two strands take the shape of a double helix. The two strands are termed ‘antiparallel’ because one runs from a 5' carbon to a 3' carbon, and the other from a 3' carbon to Phosphate is combined with carbon-3 of one deoxyribose and carbon-5 of the next The carbon atoms in organic molecules such as ribose can be numbered (Figure A1.2.4). The numbering runs from right to left, clockwise. This enables the bonds between adjacent sugars and their phosphate neighbours to be identified, along with the direction in which the polynucleotide is orientated DRAW it!  A1.2.9 Diversity of possible DNA base sequences and the limitless capacity of DNA for storing information The nitrogenous bases A, C, T and G can be combined in a limitless way in a DNA molecule. The diversity of DNA molecule will comprise both length and base sequence. Lets imagine a sequence with 15 base pairs (bp), since we have four bases, the possibilities of sequences will be: A1.2.9 - Google Presentasjoner  A1.2.9 Diversity of possible DNA base sequences and the limitless capacity of DNA for storing information The nitrogenous bases A, C, T and G can be combined in a limitless way in a DNA molecule. The diversity of DNA molecule will comprise both length and base sequence. Lets imagine a sequence with 15 base pairs (bp), since we have four bases, the possibilities of sequences will be: Learning goals I can draw a nucleotide I can draw an example of DNA molecule (including hydrogen bonds) I can summarize the main differences between DNA and RNA I can explain that diversity by any length of DNA molecule and any base sequence is possible. Work on the exercises in OneNote - Exercises A1.2 Nucleic acids SL DNA vs RNA (Updated) - YouTube Extra reading  Lonkov, L & Settlmyer, B. DNA: The Ultimate Data-Storage Solution - Scientific American. Scientific American (2021)  A1.2 Nucleic acids HL Learning goals I know the directionality of DNA and RNA, and why it is important I can identify a nucleosome: DNA molecule wrapped around a core of eight histone proteins held together by an additional histone protein attached to linker DNA using a visualization software I can understand how the Hershey-Chase experiment support the conclusion that DNA is the genetic material I can understand how Chargaff´s rule addresses the A1.2.11 Directionality of RNA and DNA A1.2.12 Purine-to- pyrimidine bonding as a component of DNA helix stability In the DNA molecule there are two strands that run antiparallel to each other. One strand of DNA will run to 5´ to 3´and the other will run 3´ to 5´. Phosphate is combined with Why is directionality important? carbon-3 of one deoxyribose and carbon-5 of the next - Nucleotides are added to the DNA or RNA molecule one at a time. The process is not random. - The first nucleotide is always by the 5´ (five-prime) end - When DNA is copied (replication), the two strands separate from each other, and pairing nucleotides are added at each strand from the 3´end A1.2.13 Structure of a nucleosome (packaging of DNA) DNA is negatively charged and histones are positively charged DNA fun fact The DNA from ONE of our cells is 6 feet, or 1.83 meters long if we uncoil each strand and place them end to end. Molecular visualization software to study the association between the proteins and DNA within a nucleosome. Go to: RCSB PDB: Homepage https://www.rcsb.org/ search for: 6T79 structure of human nucleosome (do not put the search term in quotes) Select the “3D view” to view the protein structure in mol* o The 3-D structure of the nucleosome can be viewed o The DNA double helix can be clearly seen surrounding the histone proteins o Rotate or zoom into the image to visualise the different components o The DNA can be seen to make two loops around the histone octamer core Look carefully - the tails of each histone protein can be seen projected from the nucleosome core A1.2.14 Hershey–Chase experiment for DNA as the genetic material Technological developments can open up new possibilities for experiments. When radioisotopes were made available to scientists as research tools, the Hershey–Chase Work on the exercises A1.2 Nucleic acids HL – ONLY CONCEPT: Hershey– Chase experiment A1.2.15 Chargaff’s experiment  A1.2.15 Chargaff’s experiment In the 1900s it was known that the cell nucleous had both DNA and proteins The hypothesis was that DNA was a tetranucleotide molecule (proposed by Levene) Chargaff in the 1940 showed equal proportions of the nitrogenous bases in various sources of DNA(1:1 A-T, 1:1 C-G), which later became known as Chargaffs rule.  Why is Chargaff’s rule important? It falsified the hypothesis that DNA was a tetranucleotide molecule falsification is an important part of the scientific process because a hypothesis which is confirmed after one or many experiments, may yet for some unknown reason be falsified later. if a hypothesis is shown to be false, then genuine knowledge is gained: the hypothesis is not true deduction induction Work on the exercises A1.2 Nucleic acids HL Learning goals I know the directionality of DNA and RNA, and why it is important I can identify a nucleosome: DNA molecule wrapped around a core of eight histone proteins held together by an additional histone protein attached to linker DNA using a visualization software I can understand how the Hershey-Chase experiment support the conclusion that DNA is the genetic material I can understand how Chargaff´s rule addresses the