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Bio - Unit 3
3.4-3.6
| Question | Answer |
|---|---|
| histones | positively charged spool proteins that negatively charged dna is attracted to |
| nucleosomes | -basic unit of dna storage -cluster of 8 histones with dna wrapped around it |
| solenoid | strings of nucleosomes are coiled into a cylindrical fibre -most dna is in this form during interphase |
| metaphase chromosome | solenoids are further supercoiled to form x-shaped chromosomes during cell division |
| chromosome in prokaryotes | single, curlcuar chromosome -not enclosed by nuclear membrane |
| supercoiling in prokaryotes | continously twisting the circular dna -used instead of histones |
| plasmids | small, circluar peices of dna seperate from main chromosome |
| conjugation in porkaryotes | plasmids can be transferred from a donor to a recipeient bacterium through a bridge |
| solution to end replication problem | telomeres - repatitive useless sequences |
| the central dogma | flor of genetic information in a cell |
| transcription | process of copying the info from a dna gene into a complementary rna copy - occurs in nucleus |
| translation | assembly of amino acids into a polypeptide chain -happens on ribosomes in the cytosol |
| messenger rna | acts as the message between dna and the ribosomes |
| transfer rna | transfers the correct amino acid to the ribosome to build the protein |
| ribosomal rna | structural component of the ribosome - binds with proteins to formt he ribosome itself |
| process of transcription | 1. initiation 2. elongation 3. termination 4. post transcription madifications |
| initiation in transcription | rna pol. binds to the promoter -rna pol. unwinds dna double helix |
| TATA box | a sequence high in A and T -A and T only share two H bonds - weaker bonding requires less E for rna pol. to break open dna helix |
| elongation in transcription | new rna strand is synthesized 5'-3' -rna pol. doesn't require a primer to start synthesis -rna pol. moves along dna and adds complementary nucleotides |
| template strand | rna pol. reads the dna strand to builf the new rna |
| coding strand | other dna strand that is not being copied |
| termination in transcription (prokaryotic) | 1. protein binds to the new rna and stops transcription 2. rna folds into a hairpin loop that stops the process |
| termination in transcription (eukaryotic) | termination sequence includes string of uracils - nuclear protiens binds to uracils, stopping trancription |
| post-transcription modifications | 5' capping 3' polyadenylation mrna splicing |
| 5' capping | 7 G is added to the 5' end of the pre mrna -cap acts as inital attachment site for ribosomes |
| 3' polyadenylation | long chain of A added to 3' end -protects the mrna from being broken down by enzymes in the cytosol |
| mrna splicing | if introns are left in the mrna code, the aminoacid sequence with be altered |
| splicing process | carried out by spliceosome ( made out of snRNP's) -snurps bind to the coundaries between inrons and exons -spliceosome loops intron out and cleaves it at both ends -exons are joined together |
Created by:
gracie.elisabeth