DNA, genes and protein synthesis Flashcards
what is a gene?
a section of DNA that contains the coded information for making polypeptides and functional RNA
the gene is a base sequence of DNA that codes for:
– the amino acid sequence of a polypeptide
– functional RNA, including ribosomal RNA and transfer RNAs
what are some features of the genetic code?
– a few amino acids are coded for by a single triplet
– remaining amino acids are coded for by between two and six triplets each
– the code is known as a ‘degenerate code’ because most amino acids are coded for by more than one triplet
– a triplet is always read in one direction
– non-overlapping
what is the structure of a chromosome?
– DNA helix
– histone
what is a homologous chromosome?
one of each pair is found from mother and other is from farther.
diploid.
what is an allele
one of a number of alternative forms of a gene
what is a codon?
the sequence of thee bases on mRNA that codes for a single amino acid
what is a genome?
the complete set of genes in a cell, including those in mitochondria or chloroplasts
what is a proteome?
full range of proteins produced by the genome
what is the structure of RNA?
– pentose sugar (ribose)
– A, G, C, U
– phosphate group
what is the process of splicing?
– DNA provides the instructions in the form of a long sequence of bases
– a complementary section of part of this sequence is made in the form of a molecule called pre-mRNA - transcription
– the pre-mRNA is spliced to form mRNA
– the mRNA is used as a template to which complementary tRNA molecules attach and the amino acids they carry are linked to form a polypeptide - translation
describe the process of transcription
– an enzyme acts on a specific region of the DNA causing the 2 strands to separate the nucleotide bases in that region
– the nucleotide bases on one of the 2 DNA strands, known as the template strand pair with the complementary nucleotides from the pool which is present in the nucleus.
– in this way and exposed guanine base on the DNA binds to the cytosine base of a free nucleotide
– as the RNA polymerase adds the nucleotides one at a time to build a strand of pre-mRNA
what is splicing of pre-mRNA
– get rid of introns to only leave exons
describe the synthesis of polypeptides?
– a ribosome becomes attached to the starting codon at one end of the mRNA molecule
– the tRNA molecule with the complementary anticodon sequence moves to the ribosome and pairs up with the codon on the mRNA
– a tRNA molecule with a complementary anticodon pairs with the next codon on the mRNA
– the ribosome
what does assembling a protein involve?
– the polypeptide is coiled or folded, producing its secondary structure
– the secondary structure is folded, producing the tertiary structure
– different polypeptide chains, along with any non-protein groups, are linked to form the quatenery structure
