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Summary Genetics (NWI-BB091)
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Summary of the lectures, lecture slides and tutorials of genetics, with diagrams and pictures.
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Genetics summaryL1 mutations
Genetic variation = during meiosis
• Crossover = mix of chromosomes
• Independent assortment = splitting chromosomes differently due to arrangements in meiosis
• Mutations = new allele added/allele deleted
o Somatic mutation = in non-reproductive cell, not much influence
o Germline mutation = in gametes, all cells of descendants have mutations
o Gene mutations vs chromosome mutations (= visible under microscope)
Crossover + independent assortment = recombination
Most mutations gets fixed by DNA repair systems, but can lead to evolution so some tolerance
Genetic mutations:
Point mutations = one base/small number
• Base substitution = same amount replaced
o Transition = purine-purine or pyrimidine-pyrimidine; same chemical category
o Transversion = purine-pyrimidine; different chemical category
▪ Synonymous = silent = aa sequence doesn’t change, code for same aa, no effect
▪ Conservative missense = = unlikely to affect protein structure/function
▪ Nonconservative missense = likely to affect protein structure/function
▪ Nonsense mutation = makes stop codon -> early termination
• Indel = insertion
o Frameshift = not in 3-fold -> amino acid sequence changes completely
• Deletion
Expanding nucleotide repeats = repeats get bigger because hairpins form during replication
Forward mutation = alters phenotype
Reverse mutation = reversion = changes mutated phenotype back to wildtype
,Loss-of-function mutation = causes complete/partial absence of normal protein function
• Coding region -> structure of protein is altered -> doesn’t work properly
• Regulatory region: disturb gene expression -> amount of protein changes, not function
• Splicing region = splice-site mutation -> extra part spliced out/left in
Recessive -> other allele to mask
Gain-of-function mutation = causes protein/gene product with function that’s normally not present
• Entirely new product
• In inappropriate tissue
• At wrong time of development
Dominant -> no other allele to mask
Suppressor mutation = hides effect of another mutation
• Intragenic = in the same gene as the mutation it suppresses
• Intergenic = in a different gene as the mutation is suppresses -> gene interactions
Mutation rate = frequency of which wild type alleles change into mutant at said locus
Spontaneous rate in gametes = 10E-6 to 10E-5 -> low
-> can be induced by researchers
with mutagens = environmental agent that increases mutation rate
transposon = transposable element = jumping gene = can insert themselves at locations in genome
can cause mutation
deletion, inversion or deletion + insertion
-> can promote chromosomal rearrangements
, Karyotype = complete set of chromosomes in metaphase lined up in size
Chromosome mutations = can be seen with microscope
• Chromosome structure = chromosome rearangements
Caused by: breakage + rejoining or crossing overs
o Duplication/deletion
▪ problem with chromosome pairing -> form loop in one chromosome
▪ centromere too much/little
▪ unbalanced gene dosage -> too much/little gene product
▪ lose essential genes
o inversion
▪ paracentric = without centromere
▪ pericentric = incl centromere
▪ balanced = total amount of genetic material stays the same
▪ form loops in meiosis but with 2 chromosomes
▪ gene disruption -> weird phenotype/lethal/gene fusion
o translocation
▪ reciprocal = balanced = switch of genes btwn 2 non-homologous genes
heterozygous -> problem in chromosome pairing
▪ non-reciprocal = unbalanced = one way transfer btwn non homologous gene
-> abnormal phenotype/lethal
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