nucleic acids sl Flashcards
Components of a nucleotide
- In diagrams of nucleotides use circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases.
DNA and RNA is made up of nucleotides to form a polymer. A nucleotide consists of three parts:
- A sugar with 5 carbon atoms (pentose sugar)
- An acidic phosphate group, negatively charged.
- One of 4 - 5 different bases that contains nitrogen
The building blocks of DNA and RNA, the nucleotides, are very similar. Both have a sugar, phosphate and base. However, RNA has a ribose sugar, while DNA has a deoxyribose.
Difference in nitrogenous base for RNA and DNA?
- also difference in sugar
- RNA has all the ones found in DNA except Thymine, which is replaced by Uracil
- RNA - ribose / DNA - deoxyribose
DNA as the genetic material of all living organisms
- Some viruses use RNA as their genetic material but viruses are not considered to be living.
- DNA (deoxyribose nucleic acid) is the genetic material of of life, and is used as the blueprint for the production of building blocks. Viruses can have RNA (ribose nucleic acid) or DNA as genetic material.
Sugar–phosphate bonding and the sugar–phosphate “backbone” of DNA and RNA
- Sugar–phosphate bonding makes a continuous chain of covalently bonded atoms in each strand of DNA or RNA nucleotides, which forms a strong “backbone” in the molecule.
- The individual nucleotides of a DNA or RNA strand are linked together to polymers in long chains through a condensation reaction (releasing water) forming covalent bonds with a characteristic sugar-phosphate backbone.
Bases in each nucleic acid that form the basis of a code
- Students should know the names of the nitrogenous bases.
- Name purine (2 rings) and pyrimidine bases (1 ring ). - PURE AS GOLD
- Purines (adenine and guanine) are two-carbon nitrogen ring bases while pyrimidines (cytosine and thymine) are one-carbon nitrogen ring bases.
NOTE:
- Chargaff had also demonstrated that DNA is composed of an equal number of purines (A + G) and pyrimidines (C + T)
- This indicates that these nitrogenous bases are paired (purine + pyrimidine) within the double helix
- In order for this pairing between purines and pyrimidines to occur, the two strands must run in antiparallel directions
- Adenine and thymine paired via two hydrogen bonds, whereas guanine and cytosine paired via three hydrogen bonds (ALWAYS TOGETHER / GREAT COUPLE)
RNA as a polymer formed by condensation of nucleotide monomers
- Students should be able to draw and recognize diagrams of the structure of single nucleotides and RNA polymers.
- just draw one line/half of DNA
DNA as a double helix made of two antiparallel strands of nucleotides with two strands linked by hydrogen bonding between complementary base pairs
- In diagrams of DNA structure, students should draw the two strands antiparallel, but are not required to draw the helical shape.
- Students should show adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). (COMPLIMENTARY BASE PAIRING)
- Students are not required to memorize the relative lengths of the purine and pyrimidine bases, or the numbers of hydrogen bonds.
- DNA is a double helix: It has two strands that twist around each other in an antiparallel way. Each strand is made of single units called nucleotides. It has a sugar-phosphate backbone. The bases join the two strands by hydrogen bonds.
- see slide 12!
Differences between DNA and RNA
- Include the number of strands present, the types of nitrogenous bases and the type of pentose sugar.
- Students should be able to sketch the distinction between ribose and deoxyribose.
- Students should be familiar with examples of nucleic acids. (in table)
- see slide 21!
- Ribose sugar has a hydroxyl (OH) group at position 2, whereas deoxyribose sugar has a hydrogen (H) atom at position 2. Due to this, deoxyribose sugar is more stable than ribose sugar.
Role of complementary base pairing in allowing genetic information to be replicated and expressed
- Students should understand that complementarity is based on hydrogen bonding.
- describes the manner in which the nitrogenous bases of the DNA molecules align with each other. Adenine always pairs with Thymine, Guanine always pairs with Cytosine.
- ensures regular arrangement and geometry within the double helix and allows an exact copy to be made in a process called replication.
- Complementary base pairing of nucleotides is dependent on hydrogen bonding between matching bases.
Diversity of possible DNA base sequences and the limitless capacity of DNA for storing information
- Explain that diversity by any length of DNA molecule and any base sequence is possible.
- Emphasize the enormous capacity of DNA for storing data with great economy.
- Genetic information is stored in the base sequence of one of the two strands of a DNA molecule. Any sequence of bases is possible. There are 4 different bases which can be arranged in any order: A, C, G, T
- 4^n = amount of possible base sequences
- Capable of storing 215 petabytes (215 million gigabytes) in a single gram of DNA
- the diameter of a DNA molecule is very small, so lots of
DNA can be stored in it, making DNA very economical in terms of the space it takes up/amount of material used to make it - the amount of DNA in your body could store every movie made in the 21st century 3 BILLION TIMES OVER
Conservation of the genetic code across all life forms as evidence of universal common ancestry
- Students are not required to memorize any specific examples of variations.
- The sequence of bases in DNA or RNA contains information in a coded form. The information is decoded during protein synthesis.
- Groups of three bases are called codons and code for one specific amino acid. Because nearly all organism (bacteria, plants, animals, fungi…) have the same genetic code, it is said to be universal and most like the basis of common ancestry.
- Scientists have genetically engineered plants which can glow by transferring genes from a firefly, which are subsequently expressed by the plant.
