Key words to know

DNA - deoxyribonucleic acid; the main storage system for genetic information in living cells; double-helix structure made of nucleotide monomers that use deoxyribose sugar

RNA - ribonucleic acid; used for various purposes within the cell - copied in shorter segments from DNA -- there are many types (mRNA, rRNA, tRNA for example, but there are lots of other types); single-helix structure, made of nucleotide monomers that use ribose sugar

nucleotides (3 parts of a nucleotide) - phosphate, sugar, nitrogenous base

Complementary base pairing (how bases pair) - bases pair by forming hydrogen bonds between complementary bases → in DNA, adenine (A) always bonds with thymine (T), and guanine (G) always bonds with cytosine (C) 

nitrogen bases (adenine, thymine, guanine, cytosine, uracil) - form a sequence that is interpreted as the genetic code that leads to the formation of specific proteins -- these are found in 2 types: purines (larger, consist of 2 carbon-nitrogen ring structures), and pyrimidines (smaller, consist of just 1 carbon-nitrogen ring); adenine and guanine are purines, and cytosine, thymine, and uracil are pyrimidines

Genes - a short stretch of DNA that codes for the formation of a specific protein according to the sequence of nitrogenous bases within that gene

Chromosomes - formed during cell division (mitosis); this is when the looser chromatin form of DNA condenses into rod-shaped or x-shaped structures that organize the DNA so it can move around the cell to prepare for cell division

double helix - the characteristic structure of DNA, discovered by scientist Rosalind Franklin and published together with scientists James Watson and Francis Crick; DNA is formed like a twisted ladder shape, with the nitrogenous base pairs in the center and the sugar and phosphate groups forming the backbone for both sides of the DNA molecule

Leading strand v. Lagging strand - in DNA replication, the leading strand is replicated continuously all in one stretch, and the lagging strand is replicated in shorter fragments; this is due to the directionality of DNA -- all new DNA must be synthesized starting with the 5’ end and going to the 3’ end

Replication - the process of making an identical copy of a cell’s DNA by splitting the double helix and building a new strand of DNA onto each old strand using complementary base pairing. The replication process is considered semiconservative, because each daughter strand is composed of one complete original strand and one complete new strand. 

Helicase - the enzyme responsible for “unzipping” the DNA double helix by breaking the hydrogen bonds between base pairs -- this is in preparation for replication

Primase - the enzyme that creates short stretches of RNA nucleotides (called “RNA primers”) that signal to the DNA polymerase to attach at that location to begin replication

DNA polymerase - the enzyme that assembles the new strand of DNA by attaching complementary nucleotides to each nucleotide base on the original strand

Ligase - the enzyme that connects fragments of newly-synthesized DNA strands by completing bonds in the sugar-phosphate backbone

Transcription - 

RNA polymerase - the enzyme that builds mRNA transcripts for a gene using one strand of the gene’s DNA as a template

mRNA - messenger RNA, made as a short “copy” of the sequence of bases in DNA (replacing T with U) by RNA polymerase enzyme, then transported out of the nucleus to a ribosome

Translation - 

Codon - a sequence of 3 bases on mRNA that is associated with a specific amino acid (by matching anticodons on tRNA)

Anticodon - a sequence of 3 bases on tRNA that is complementary to the codon on mRNA -- used to match amino acids to each codon being translated by the ribosome

tRNA - transfer RNA, brings each amino acid to the ribosome for assembly into polypeptide chain

amino acids - building blocks of polypeptide chains, which are then folded into proteins

Ribosome - a large enzyme/rRNA complex that forms the organelle responsible for translating mRNA into polypeptide chains

Polypeptide chain, protein - a sequence of amino acids assembled by a ribosome that will them fold into a 3-d structure called a protein 

Mutations - 

frameshift mutations (insertion, deletion) - A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is grouped into codons for translation.

point mutations / substitution mutations (nonsense, missense, silent) - A point mutation affects a single base pair. A point mutation may cause a silent mutation if the mRNA codon codes for the same amino acid, a missense mutation if the mRNA codon codes for a different amino acid, or a nonsense mutation if the mRNA codon becomes a stop codon.