DNA, meiosis & protein synthesis

• A gene is a section of dna that codes for the synthesis of a specific polypeptide
• a chromosome is a linear dna molecule wrapped around histone proteins
• eukaryotes have long, linear dna molecules that are associated with histone proteins
• prokaryotes have circular, short dna molecules that are not associated with histone proteins
• Degenerate code= a genetic code in which some amino acids may be encoded by more than one codon
• Many eukaryotes have non-coding dna that does not code for polypeptides
• introns are non coding sections of dna that separate exons, normally cut out before protein synthesis
• exons are the coding sections of dna that lead to the formation of polypeptides
• mRNA is a short polynucleotide that is single stranded
• tRNA is a single stranded clover shaped molecule it’s an amino acid binding site
• transcription:

  1.) at gene locus, hydrogen bonds broke, template is exposed for mRNA

  2.)free floating nucleotides complementary base pair to template

  3.) rna polymerase moves down template to form phosphodiester bonds

  4.) rna polymerase moves down gene to the stop codon and trna polymerase releases itself

  5.) mRNA exits nucleus
• homologous chromosome= pairs of chromosomes, one maternal, one paternal that have the same gene loci and determine the same features
• prophase 1: chromosomes condense and become visible and homologous chromosomes pair up with each other, crossing over occurs ( chromosomes exchange dna)
• metaphase 1: homologous chromosomes line up on equator at random orientations, creations random combinations (independent segregation) and spindle fibres attach
• anaphase 1: homologous chromosomes move apart from each other to opposite parts of cell
• telophase 1: 2 cells created that are haploid
• metaphase 2: chromosome line up along equator
• anaphase 2: sister chromatids serrated and pulled to opposite poles of cell
• telophase 2: the formation of 4 genetically different haploid cells
• chromosomal mutations involve a change in chromosome structure or number whereas gene mutations involves a change in the base sequence of dna
• types of gene mutation: substitution, deletion,inversion, insertion
• Proteome= The full range of proteins a cell is able to produce
• genome= the entire genetic material of an organism, including all genes and dna (coding and noncoding)
• In protein synthesis, what is produced by transcription?

  mRNA
• translation: ribosome attaches to mRNA, Ribosome moves to find the start codon, tRNA carries specific amino acid, complementary Anticodon on tRNA binds to codon on mRNA, Ribosome moves along to next codon, amino acids join by peptide bonds.
• universal genetic code: same triplet always codes for the same amino acids
• non-overlapping: each base is only part of one triple codon
• what is an allele?

  different forms of a particular gene found at the same locus
• what is substitution mutation?


  A mutation where one nucleotide is replaced by another in the dna sequence
• what is deletion mutation?

  A mutation that removes a nucleotide from the DNA sequence, leading to a frame shift
• what is the role of RNA?

  transfers genetic info from dna to ribosomes for protein synthesis