Flashcards in Chapter 10 - Molecular Biology of a Gene Deck (28):
what is molecular biology?
the study of DNA, its properties, and its role within the cell at the molecular level.
primary structure of DNA
4 types of nitrogenous bases:
single ring pyrimidines: cytosine and thymine
double ring purines: guanine and adenine
primary structures of polynucleotides
includes a nucleotide monomer which consists of a phosphate group, sugar, and nitrogenous base.
what is the sugar phosphate backbone?
same basic structure in all polynucleotides. it is read from 3' (sugar) end to 5' (phosphate) end.
sugars are either ribose (RNA) or deoxyribose (DNA).
primary structure of RNA
almost the same as DNA, sugar is a ribose, thymine is replaced by uracil and it does not form a double helix.
what are base pairing rules?
A to T and C to G. with these rules, each strand of DNA can serve as a template for synthesis of new copy of its compliment.
what is DNA polymerase?
enzyme which forms new chain of nucleotides against template, adding monomers at 3' end. can synthesis smoothly against one strand, must rely upon DNA ligase joining up interrupted new segments against other strand.
what is the central dogma?
the genotype (DNA) encodes instructions for the primary structures of proteins = sequence of amino acids.
RNA transmits genetic information (translation & transcription) to protein ~ synthesis mechanism.
proteins produce phenotype.
gene and protein relationship
one gene = one protein (poly peptide).
What is DNA?
linear sequence of DNA bases; in a gene, exact sequence very important as it specifies order of amino acids in primary structure of a protein.
what is RNA?
linear sequence of RNA nucleotides synthesized upon the plate of DNA bases; complementary RNA bases = transcription of a gene.
what is a polypeptide?
sequence of amino acids corresponding to linear sequence of bases in RNA molecule - translation of RNA codons to specific amino acid.
triplet codon of bases
codes for each of 20 amino acids in amino acid pool used by terrestrial organisms, with abundant redundancy = room for mistakes.
what are substitution mutations?
one nucleotide replaces another (one way of forming alleles). may make a little or great difference.
what are deletions and insertions?
generally distort reading frame. sequence of poly peptide changes from that point on.
What are the 3 types of RNA?
mRNA: transcribed from DNA, carries codons for linear sequence of amino acids. codons are a series of 3 RNA bases, compliments to DNA triplet code.
rRNA: makes up bulk of ribosome
tRNA: attaches to ribosome, carries anticodon (compliment to specific codon on mRNA) at one end and appropriate amino acid at the other.
what is transcription initiation?
promoter DNA sequence on chromosome. RNA polymerase attaches to promoter on "unzipped" sequence of DNA. RNA monomers line up against corresponding DNA monomers, held by hydrogen bonds. RNA polymerase joins RNA monomers into polypeptide mRNA.
what is transcription elongation?
mRNA strand elongates and peels away?
what is transcription termination?
terminator DNA sequence on chromosome. RNA polymerase attaches to terminator on "unzipped" sequence of DNA. mRNA detaches from RNA polymerase = transcription complete.
takes place in nucleus: mRNA must pass through nuclear membrane to ribosomes in cytoplasm or rough ER = translation. various transcript factors involved.
processing in nucleus: cap and tail added to promote translation.
what is splicing?
intron sequences clipped out from between exons (coding sequences), exons joined together to form continuous coding mRNA. Allows for regulation.
what are the two meanings of translation?
1. rendering a message from one language to another.
2. moving an object from one place to another.
what happens during translation?
the mRNA moves from the transcription site to the site where the codons will be read and amino acids polymerized. the information encoded down the length of the mRNA is rendered into a sequence of amino acids.
what is the role of tRNA?
the interface between amino acid pool in cytoplasm and RNA sequence along length of mRNA. one end carries anticodon = bases complementary to the codon for a particular amino acid on mRNA. other end: sites for attachment of amino acid specified by codon/anticodon by specific enzymes. enzyme recognizes anticodon and binds correct amino acid to tRNA.
what is the role of ribosomes?
function: protein synthesis site. composed of rRNA and proteins. holds mRNA and complementary tRNA close together, allows peptide bonds to form between adjacent amino acids.
when not in use, two separate subunits, large and small.
assembled, there are two tRNA binding sites, with one mRNA binding site.
what is translation initiation?
isolated ribosomal small subunits bind with mRNA poly nucleotide. start codon of mRNA binds with initiator tRNA in P site. large ribosomal subunit binds with complex.
what is translation elongation?
sequential attachment of appropriate tRNAs to complementary sections of mRNA as it moves along mRNA binding site. peptide bonds formed between successive amino acids as they are brought to the ribosomes.