DNA, genes and chromosomes

• prokaryotic chromosomes coil around themselves by supercoiling
• supercoiling condenses the circular chromosomes so they can fit inside the cell
• where is DNA found in prokaryotes?


  cytoplasm
• diploid eukaryotes have homologous pairs of chromosomes. this is where 1 chromosome is from the dad and 1 chromosome from mom and have the same gene and loci but different alleles
• DNA in eukaryotes are tightly wrapped around protein to form histones
• endosymbiotic theory explains the presence of DNA in mitochondria and cytoplasm
• endosymbiotic theory - bacterial cells were engulfed by a larger cell during evolution. the bacteria and host cell form a symbiotic relationship
• roles of DNA: 1. DNA in mitochondria encodes enzymes for respiration 2. DNA in chloroplasts encodes enzymes for photosynthesis
• what are the 4 bases of DNA?

  1. adenine 2. thymine 3. cyotine 4.
• locus - the specific spot of gene in the DNA that codes for a particular amino acid. the shape is a fixed condition
• codon - 3 bases of a gene. a specific codon codes a specific amino acid
• the codons present in a sequence in translated into a sequence of amino acids
• the sequences of bases is made into a polypeptide by copying DNA into messenger RNA (mRNA)
• functional RNA's are necessary for protein synthesis
• the coding regions in genes are called exons. exons interrupt at regular intervals in the sequence of bases
• the non-coding regions are called introns. introns are removed from the sequence if the gene has been translated through protein synthesis
• when a genetic code in non-overlapping, the tripled codon is separate from the other codon sets in the chromosome
• a genetic code is degenerate when amino acids are encoded by more than 1 codon
• complementalisation in eukaryotic cells enables the building of more complex proteins and RNA products. in prokaryotes, complementalisation has DNA and protein synthesis occurs more quickly