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Biology Unit 3
Nucleic Acid, Transcription, Translation, DNA Replication, DNA Structure
| Term | Definition |
|---|---|
| Nucleotide | the monomer of a nucleic acid; made up of three basic components: pentose sugar, phosphate group, and a nitrogenous base |
| Five nitrogenous bases | Adenine, Guanine, Cytosine, Thymine, Uracil |
| Purines | Adenine and Guanine |
| Pyrimidine | Cytosine, Thymine, Uracil |
| DNA vs RNA | DNA: deoxyribose sugar, thymine, and double stranded helix RNA: ribose sugar, uracil, single stranded |
| Who came up with the DNA structure? | The structure of DNA was elucidated by Watson and Crick in 1953. Watson and Crick developed a DNA model that demonstrated a double helix structure composed of antiparallel DNA strands and internally facing bases with complementary pairing. |
| Transcription | the synthesis of an RNA sequence from a DNA template; located in the nucleus of the cell |
| What does RNA polymerase do? | separates the DNA strands (breaks hydrogen bonds between base pairs) and covalently joins free complementary RNA nucleotides together |
| What happens after transcription? | the RNA is released to the cytoplasm and the DNA remains within the nucle |
| Three types of RNA | mRNA, tRNA, rRNA |
| mRNA | messenger RNA, transcript used to make protein |
| tRNA | transfer RNA, transfers amino acids to ribosome |
| rRNA | ribosomal RNA, catalytic component of ribosome/protein synthesis |
| Genetic code | the set of rules by which information encoded in mRNA sequences is converted into a polypeptide sequence |
| Codons | triplets of bases which correspond to a particular amino acid |
| Universality | all organisms use the same genetic code |
| Degeneracy | multiple codons may code for the same amino acid |
| Translation | the process of polypeptide synthesis by the ribosome |
| Step 1 of Translation | messenger RNA is transported to the ribosome |
| Step 2 of Translation | a ribosome reads an mRNA sequence in base triplets called codons |
| Step 3 of Translation | each codon codes for a specific amino acid |
| Step 4 of Translation | amino acids are transported to ribosomes by transfer RNA |
| Step 5 of Translation | each tRNA aligns opposite a codon via a complementary anticodon |
| Step 6 of Translation | the ribosome moves along the mRNA sequence and joins amino acids together with peptide bonds |
| Step 7 of Translation | the synthesis of a polypeptide is initiated at a start codon and is completed when the ribosome reaches a stop codon |
| Gene | a sequence of DNA which encodes a polypeptide sequence; one gene = one polypeptide |
| Exceptions to the fundamental relationship of Gene --> Protein | genes may be alternatively spliced (one gene = many polypeptide) genes encoding tRNA or rRNA are transcribed not translated genes may be mutated to alter the original polypeptide product |
| Gene sequence sections | promotor (transcription initiation site) coding sequence (the region transcribed) terminator (transcription termination site) |
| Antisense | strand transcribed into RNA |
| Sense | strand not transcribed into RNA |
| Step 1 of Transcription | RNA polymerase binds to a promoter and unwinds DNA and breaks the hydrogen bonds between the complementary bases |
| Step 2 of Transcription | Nucleoside triophosphates bind to complementary bases |
| Step 3 of Transcription | RNA polymerase covalently joins the nucleotides together and the two extra phosphates are released to provde energy |
| Step 4 of Transcription | At the terminator site, RNA polymerase is detached and the RNA sequence is released and the DNA rewinds |
| Splicing | non-coding regions within genes are removed |
| Introns | non-coding regions in genes; sections of mRNA that not code for proteins; removed from the strand of pre-RNA; eventually broken down and recycled |
| Exons | the coding regions of genes; sections of mRNA which become "expressed" or translated into a protein; spliced with other exons into a long chain of mature mRNA; mature RNA moves to a ribsome where the instructions are translated into a protein |
| Alternative splicing | exons are selectively removed to form different proteins from the same gene |
| Ribosomes | site of polypeptide synthesis; composed of ribosomal RNA and protein; two subunits: small subunit contains an mRNA binding site and large subunit contains three tRNA binding sides |
| Polysome | multiple ribosomes that can translate a single mRNA sequence simultaneously |
| 1* structure | sequence and number of amino acids |
| 2* structure | folding into a helix or pleated sheet |
| 3* structure | three-dimensional shape of a polypeptide |
| 4* structure | presence of multiple polypeptide chains |
| What did Hershey and Chase do? | conducted experiments in 1952 to determine if DNA or proteins were the genetic material of a cell; inserted viruses into DNA and proteins to draw the conclusion that DNA is the genetic material and proteins are not. |
| What did Franklin and Wilkin do? | used X-ray diffraction to elucidate DNA structure; deduced the composition, orientation, and shape of DNA |
| Nucleosomes | help supercoil the DNA, make DNA compact (better storage), prevents DNA damage (less exposed), assists in cell division (more mobility), and involved in transcriptional regulation |
| DNA that does not code for protein | Satellite DNA (tandem repeats), telomeres (chromosome ends), introns (non-coding sequences), non-coding RNA genes, and gene regulatory sequences |
| Helicase | separates the DNA strands to form a replication fork; single stranded binding proteins prevent strands re-annealing |
| DNA Gyrase | reduces the torsional strain created by helicase; prevents the DNA from supercoiling as it is being unwound |
| DNA Primase | generates a short RNA primer on each strand; provide an initiation point for DNA polymerase III |
| DNA Polymerase III | free nucleotides line up opposite complementary bases; covalently joins free nucleotides together |
| Okazaki Fragments | discontinuous segments of DNA strands |
| DNA Polymerase I | removes RNA primers and replaces them with DNA |
| DNA Ligase | covalently joins the Okazaki fragments together |
| Semi-conservative | one strand is from an original template molecule and one strand is newly synthesised |
| Meselson-Stahl Experiment | supported the theory that DNA replication occurred via a semi-conservative process; incorporated radioactive nitrogen isotopes into DNA; DNA was then separated via centrifugation in order to determine its composition of radioisotopes |
| Step 1 of Polymerase Chain Reaction | Denaturation: DNA heated in order to separate strands |
| Step 2 of Polymerase Chain Reaction | Annealing: Primers attach to ends of a target sequence |
| Step 3 of Polymerase Chain Reaction | Elongation: a heat tolerant polymerase copies strands |
Created by:
bennettph101
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