SG #2 - BIO EXAM #2 Structure of DNA o Molecules are...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: BIO EXAM #2 Structure of DNA o Molecules are polynucleotides Each has purine (A/G) or pyrimidine (C/T), a sugar, and a phosphate Before cell divides, amt of DNA is doubled, Then divided equally between 2 daughter cells o Double helix of two polynucleotide strands Hydrophilic sugar phosphates outside, less hydrophilic nucleotide bases inside Only uniform if purine paired w/ pyrimidine A & T paired w/ 2 hydrogren bonds, C & G with three Replication of DNA o Due to pairing of specific nucleotides, DNA can be unwound Each strand can be used for replication of new complementary strand o DNA polymerase Responsible for replication Complex of several proteins Separates the 2 strands of DNA & unwinds a portion of the molecule Adds complementary nucleotide to the template strand, verifying it as it goes During this proofreading, if mistake is found, its replaced w/ correct nucleotide Example of molecular motor Moves along DNA template Uses deoxyribonucleoside triphosphates as energy to drive the motor and monomer to be polymerized Mutations o Changes in DNA sequence in gene/chromosome o Range from point to large-scale Point Changes that occur in one/several nucleotides of a gene Can be substitutions, deletions, insertions In each case, DNA code is altered, sometimes producing change in phenotype Large-scale Long sequences of DNA or even entire chromosomes are altered o Errors in replication are responsible for low rate of mutation, but there are external causes too Mutagens Physical/chemical agents that interact w/ DNA to cause mutations Include x-rays, UV light, products of metabolism of oxygen (like free radicals), and other chemicals o Most mutations are caught by cells DNA replication machinery Transcription o Transfer of info from DNA into RNA form o RNA transcript is created from DNA template by enzyme RNA polymerase Structure allows to recognize & bind specific region of a gene, the promoter Once bound, unwinds portion of DNA helix, producing RNA copy of template strand (mRNA) o RNA polymerase is molecular motor Uses ribonucleoside triphosphates as energy for motor & monomers for new strand of mRNA When transcribed to end of gene, encounters terminator region & ends transcription o In prokaryotes, occurs in cytoplasm Transcribed mRNA goes to ribosomes o In eukaryotes, occurs in nucleus RNA transcript must be processed before exiting the nucleus towards ribosomes Original RNA transcript is called precursor mRNA (pre-mRNA) Contains regions of non-coding nucleic acid, introns Introns are interspersed with exons o Coding regions Spliceosomes cut out introns & rejoin the introns to form final, edited mRNA Translation o Genetic info in mRNA is interpreted by ribosomes Produce polypeptides according to sequence originally prescribed by DNA o Process of going from mRNA transcript to polypeptide of prescribed sequence...
View Full Document

Page1 / 6

SG #2 - BIO EXAM #2 Structure of DNA o Molecules are...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online