genetics

• 22 pairs of autosomes. 2 sex chromosomes.
• a genetic locus is the location of a particular gene on a chromosome. at each genetic locus, an individual has an allele on each homologous chromosome. AA homozygous dominant. aa homozygous recessive. Aa heterozygous. A = phenotype, Aa = genotype
• the phenotype is the presentation of that gene
• chromsomes have a short arm, p, and a long arm, q
• the centromere is where spindle fibres attach during cell division. It is the centre of the chromosome and where the two halves are attache.d
• The bands that can be seen upon g staining are numbered. CHROMSOME,arm,region,band.sub-band eg 13p12.2
• chromosomal rearrangements are an alteration in the copy number of a complete set of chromosomes or in their structure eg trisomy 21
• A triploid cell has a full additional set of each chromsome (3N)
• polyploid means more than two sets of chromosomes. common in plants, cancer cells, adult liver cells, and megakaryocytes
• aneuploid = variation in individual chromosome number, seen in humans eg trisomy 21
• 'somy' suffix is the number of an individual chromosomes in aneuploids
• rearrangements: duplications, inversions, deletions, translocations > affect gene expression.
• paracentric inversions flip genes, not inc centromere. pericentric inversion flips across the centromere.
• inversion doesn't change gene dosage, unless the breakpoint disrupts genes. makes meiosis during gamete production tricky. post-meiosis deletion product chromosomes can be non-viable due to extreme loss of genetic information, leading to infertility and early miscarriages
• REMEMBER

  
• translocations are the exchange of genetic material between non-homologous chromosomes. can be balanced - no loss. unbalanced - loss. robertsonian - loss, since close to centromere
• promotor mutations affect the way enzymes for gene expression bind for starting transcription
• splice site mutations affect how exons and introns stick together
• within exon mutations change the reading sequence of the amino acid produced
• mutations of STOP codons affect the reading frame of the gene, causing extra translation and this extra amino acids that aren't the target product
• extragenic mutations in support and regulatory elements affect how transcription starts at the start site
• whole exon/whole intron mutations affect what type of sequences we get and how we regulate gene expression of those sequences
• mutations can be substitutions, insertion (of a base pair) or deletion (of a base pair)
• specific classification refers to what happens to the dna sequence as a whole - missense, nonsense, inframe, frameshift and splicing
• missense mutations change one amino acid (substitute a single nucleotide to create a new codon)
• Nonsense mutations substitute a single nucleotide (can be insertion/deletion too) to create a STOP codon. translation is stopped, truncating protein
• inframe mutations and/delete a codon which produces extra/less protein products
• frameshift mutations add/delete part of a codon to change the reading frame. This changes the amino acid sequence from the site of mutation. usually have a big effect on phenotype.
• splice site mutations mean the intron is either not removed remains in processed mRNA transcript - alters amino acid sequence - OR the exon is spliced out - truncated mRNA sequence = truncated amino acid sequence
• a pedigree is a diagrammatic representation of the genetic history of a family. can be used to infer inheritance patterns and map disease links
• basic inheritance patterns inc. autosomal vs sex linked, dominant/recessive
• pedigrees are used to find other at-risk family members and potential risks for offspring when someone is diagnosed with a genetic disorder
• female = circle
• male = square
• coloured = affected individual
• a line connecting the sides of 2 people indicates a marriage/relationship
• generations are labelled with roman numerals
• vertical lines show connections to families and siblings
• unknown sex = diamond
• top right to bottom left cross = deceased individual