A1.2 Nucleic Acids Flashcards
Genetic material
The material that carries all of the hereditary information specific to an organism. It is made up of DNA or RNA.
Genes
The “instructions” to build an organism out of molecules. Genes are units of heredity that are passed down to offspring to determine their characteristics.
Polymer
A molecule made up of repeating subunits called monomers. Both DNA and RNA are considered polymers.
Monomers
The subunits or building blocks that make up polymers. Nucleotides are the monomers of DNA and RNA.
DNA
Deoxyribonucleic acid (DNA) is one of the two nucleic acids that makes up genetic material. They are polymers made up of monomers known as nucleotides.
1. Double helix / double stranded
2. Deoxyribose sugar
3. Contains nitrogenous base of thymine (T)
RNA
Ribonucleic acid (RNA) is one of the two nucleic acids that makes up genetic material. They are polymers made up of monomers known as nucleotides.
1. Single-stranded
2. Ribose sugar
3. Contains nitrogenous base of Uracil (U)
Viruses
Viruses consist of a nucleic acid molecule inside of a protein coat. They are only able to multiply when in a living host, and they aren’t typically considered to be living organisms. Some viruses like Covid use RNA for their genetic material.
Nucleotide
The subunits, or building blocks, of DNA and RNA. Each is made up of a pentose sugar, phosphate, and nitrogenous base. They are typically represented with a pentagon, circle, and rectangle respectively.
Condensation reaction
Both DNA and RNA nucleotides must undergo condensation reactions, where water is released, in order to form the phosphate-sugar bonds with each other.
Review: What are the three major structural differences between DNA and RNA?
DNA
1. Deoxyribose pentose sugar
2. Double-stranded
3. Contains nitrogenous base Thymine (T)
RNA
1. Ribose pentose sugar
2. Single-stranded
3. Contains nitrogenous base Uracil (U)
Sugar-phosphate backbone
The continuous covalent bonds between the phosphate of one nucleotide and the pentose sugar of another in a DNA or RNA sequence. The “backbone” is strong and allows for more reliable and long-lasting storage of information.
Nitrogenous Bases
Each nucleotide in DNA or RNA contains one of the five nitrogenous bases. They can either be pyrimidines, which have one ring, or purines, which have two rings. A pyrimidine always matches with a purine and this helps to establishes the double helix form of DNA. These are called complementary bonds and they occur between Adenine (A) and Thymine (T) and Cytosine (C) and Guanine (G) in DNA, whereas RNA has the same bonds except Uracil (U) replaces T.
Purine
The two-ringed nitrogenous bases in nucleotides. They are Adenine (A) and Guanine (G).
Pyrimidine
The one-ringed nitrogenous bases in nucleotides. They are Cytosine (C) and Thymine (T) in DNA, but T is replaced with Uracil (U) in RNA.
Complementary Base pairs
The pairing of nitrogenous bases between nucleotides. Adenine (A) pairs with Thymine (T only in DNA) or Uracil (U only in RNA), and Cytosine (C) pairs with Guanine (G). These pairs are complementary because they have one purine and one pyrimidine base.
Double Helix
The shape of a DNA molecule, which is created by two spiraling strands of nucleotides. The uneven rings between the nitrogenous bases in the complementary base pairs creates the spiral when the strands are linked together.
Antiparallel
The two strands of DNA run antiparallel. They are parallel to each other but run in the opposite direction. This means the terminal phosphate group of one strand is on the opposite end of the DNA than the phosphate group of the other.
DNA Replication
Complementary base pairing allows DNA strands and genes to be accurately replicated and passed down to offspring.
Transcription
Complementary base pairing allows for the base sequence of a single DNA strand to be copied and transported in messenger RNA (mRNA) form to complete protein-coding.
Translation
Complementary base pairing allows for Ribosomes to identify the sequence of three-base codons and build polypeptide chains with the help of transfer RNA (tRNA) anticodons.
Codon
A sequence of three nitrogenous bases in messenger RNA (mRNA) that codes for a specific amino acid. These are essentially the instructions to building polypeptide chains (the things that make up proteins).
Anticodon
Each three-base codon of messenger RNA (mRNA) is complemented by the three-base anticodon of a transfer RNA (tRNA), which carries the amino acid specific to the codon. Each of the bases of the anticodon forms base pairs with those of the codon, and this links the amino acid of the tRNA to the polypeptide chain being coded by the mRNA.
Review: What do the complementary base pairs contribute to genetic material?
The complementary base pairs allow for DNA replication, transcription, and translation. All of these make inherited genes and protein-coding possible.
DNA base diversity
The almost limitless diversity within DNA because of the bases. Although there are only four nitrogenous bases within DNA, genes often have over one thousand bases. If the number of possible sequences is 4^n, where n is the number of bases, then there are almost an infinite number of base sequences possible. This contributes to the diversity of organisms.
LUCA
The Last Universal Common Ancestor (LUCA) is the hypothesized single-cellular organism which all life evolved from. The universality of genetic coding suggests the existence of LUCA. There are only 64 codons and 20 amino acids that all living organisms use.
(AHL) 3’ terminal end
Also known as “3 prime.” Where a DNA or RNA strand ends with the free hydroxyl group of a pentose sugar. When constructing a strand, free-floating nucleotides are added to this end.
(AHL) 5’ terminal end
Also known as “5 prime.” Where a DNA or RNA strand ends with a phosphate group. This is considered the beginning of a strand because strands are built from 5’ to 3.’
Review: Where are the 5’ and 3’ terminal ends of DNA located?
The 5’ end is located at the end of a DNA strand that ends in a phosphate. The 3’ group is located at the end of a DNA strand that ends in a free hydroxyl group of a pentose sugar.
(AHL) Nucleosomes
Disc-like structures used by eukaryotes to package DNA into condensed chromosomes and help control replication and transcription. Each nucleosome core is made up of eight histone proteins and DNA is wound around the core twice. Another histone binds the DNA to the nucleosome. This makes DNA look like a string of beads under an electron microscope.
(AHL) Histone
The proteins that make up nucleosome cores.
(AHL) The Hershey-Chase experiment
A 1950s experiment that provides strong evidence that genetic material is composed of DNA rather than proteins. Hershey and Chase radioactively marked the DNA within T2 viruses in one fluid supernatant and then marked proteins in another fluid supernatant. Then they mixed each T2 fluid with E. Coli, a bacterium that is infected by the T2 virus. They centrifuged the mixture and tested each solid pellet of infected E. Coli bacterium for radioactivity. The results showed that the majority of the radioactivity was in the pellet when the DNA was radioactively marked.
(AHL) Chargaff’s Data
Erwin Chargaff’s data on the amount of each nitrogenous base in different tissues and species. He found that Adenine (A) and Thymine (T) and Cytosine (C) and Guanine (G) always had similar values to each other. This provided evidence that there were complementary base pairs in DNA. He also found that the amount of purines and pyrimidines each consistently made up about 50% of DNA. This provided evidence that purines pair with pyrimidines.
(NOS) The tetranucleotide hypothesis
A hypothesis proposed in the early 20th century that proposed DNA molecules are a chain of alternating sugar and phosphate groups, with a base attached to each sugar in a repeating sequence of the four bases. This would mean that all nitrogenous bases make up 25% of DNA. However, this was proved to be wrong by Chargaff’s data on the amounts of each base in DNA.
(NOS) What are the two possible outcomes of a well-designed experiment?
- results that fit the hypothesis, which could therefore be true
- results that prove the hypothesis to be false
