DNA, genes and chromosomes

• Name the fixed position occupied by a gene on a DNA molecule.

  Locus
•  Describe how a gene is a code for the production of a polypeptide. Do not include information about transcription or translation in your answer. 

  A gene is a sequence of DNA bases that code for a polypeptide.

  This contains the bases of DNA which each code for a polypeptide when counted in 3.

  A polypeptide is a sequence of amino acids.
• Describe how mRNA is produced from an exposed template strand of DNA. 

  Do not include DNA helicase or splicing in your answer. 

  Free floating RNA nucleotides. These line across the complimentary base pairs.  

  RNA polymerase and ATP will form the bond between one set of complimentary bases.

  Forming phosphodiester bonds.
• Define the term exon. 

  Base sequences that code for the sequence of amino acid / DNA.
• A student concluded that the mutation involved the addition of one nucleotide within the sequence. Does information in this question support the student’s conclusion? Give reasons for your answer. 

  No, amino acids are coded in triplets and due to the code being degenerate a frame shift must have happened.

  Affecting all subsequent amino acids.
• Eukyarotic cells contain linear DNA, within their nucleus. This DNA contains chromosomes, which are thread like structures made of DNA wrapped around histones.
• Mitochondria and chloroplasts have their own DNA. Like prokaryotic DNA their DNA is circular and is not bound to histones. By having their own DNA, mitochondria can easily synthesize ATP.
• Prokaryotes DNA may also exist in central nucleotides and have accessory plasmids within the cytoplasm.
• Introns: Make up 98% of DNA, but do not code for anything. Their role is still unknown.

  Extrons: Make up 2% of DNA, these are the coding parts of DNA and contain polypeptide bonds.
• Genes: Small section of genetic material of DNA. These are located in a specific place, called a locus. These code for an amino acid sequence of a polypeptide / functional RNA such as tRNA and rRNA.
• Alleles: Different forms of a gene, each inherited from the parents. Any changes in a base sequence of a gene produces a mutation of that gene, resulting in a new allele.
• A full chromosome is made through long and linear DNA strands. These are wrapped around a histone protein to form nucleosomes. These nucleosomes coil tightly to create a chromatin loop, making chromosomes.
• Chromosomes are only visable as distinct structures during the certain points of the cell cycle. They appear as chromatids and are joined by a centromere. Each containing long arms (q arms) and short arms (p arms).
• Genome: The entire series of genes
• Proteome: The entire collection of an organism proteins
• A gene of DNA codes for a protein:

  • The order of bases in the gene determines the order of an amino acid in a protein
  • Each protein is ordered by a sequence of a 3 bases codes for glycine.
• The 3 bases which code for the amino acid are called codons.
• Plasmid DNA is circular and contain functional genes which code for a protein.
• Prokaryotic DNA contains no introns and eukaryotic contains a repeating sections of DNA
• Karyotyping: The full chromosome component of a cell or whole organism and illustrates the number, size and shape of the chromosome.
• The human genome project has 5 fundamentals:

  • None - overlapping (each triplet code is only read once + doesn't share bases)
  • Genes are seperated by introns
  • DNA code is degenerate
  • Code is universal
  • A triplet is always read in one direction.
• Define 'non-coding bases' and describe where they are placed within the genome

  Non-coding bases are called introns

  Positioned in between genes