Genetic Mutations Unit 4 Lecture 4 Mutations Genetic
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Genetic Mutations Unit 4 – Lecture 4
Mutations �Genetic Mutation – a change in the amount or structure of genetic material of an organism �Mutations can be in DNA or can be chromosomal �Mutations can happen more than once in a sequence [and typically do] �Causes: �mutagens – radiation or chemical substances that increase the rate of mutations
Mutations �[Causes: ] �problem during interphase when DNA is being replicated � problems are typically noticed and repaired by enzymes during growth � typically mismatch in base pairing � problem in DNA problem in m. RNA problem in protein synthesis
Effects of Mutations �ALL known mutations are harmful overall �some are beneficial under certain circumstances � antibiotic resistance: bacteria are immune to harm from antibiotics [good], but causes them to be less efficient at many other cellular processes [competing for resources, rate of reproduction]
Effects of Mutations �ALL known mutations are harmful overall �some are beneficial under certain circumstances � sickle-cell anemia: humans with this disease are less likely to get malaria [good], but cell shape obstructs capillaries & blood flow leading to pain or organ damage [typical life span = 42 -48 yrs old]
Effects of Mutations �Small changes: �may cause no change in the a. as formed �may cause a change in the a. as formed �may cause MASSIVE change in the a. asformed �Large changes…are of course, typically worse than small changes
Effects of Mutations �Can cause cancers, genetic disorders �Mutations in cells: �in gametes – passed to the next generation �in somatic cells – not passed on to next generation
DNA Mutations � 3 types (1) �substitution – change of a single base from one kind to another [aka point mutation] � ex: THE DOG RAN OUT THE FOG RAN OUT � may or may not alter the amino acid formed: �CAU & CAC both code for Histidine �CAA & CAG both code for Glutamine
DNA Mutations � 3 types (2) �deletion – a single base is deleted from the sequence �THE DOG RAN OUT THE OGR ANO UT � changes the sequence of codons – usually quite a bit; but may not change sequence if next letters code for same thing [like near end] � TAC – UUA – UAA TAC – UUU – AA � Met – Leu – [stop] Met – Phe –
DNA Mutations � 3 types (3) �insertion – a single base is added to the sequence � THE DOG RAN OUT THE DOG RAF NOU T � changes the sequence of codons – usually quite a bit; but may not change sequence if next letters code for same thing [like near end] � TAC – UUA – UAA TAC – UUA – A � Met – Leu – [stop] Met – Leu – Ile –
DNA Mutations � 4 classifications (1 -2) �silent – has no effect on amino acid sequence � AGU (serine) AGC (serine) �missense – codes for a different amino acid � AGU (serine) AGA (arginine)
DNA Mutations � 4 classifications (3 -4) �frameshift – changes the “reading frame” � caused by insertion/deletion THE DOG RAN OUT THE OGR ANO UT THE DOG RAN OUT THE DOG RAF NOU T � insertions/deletions in groups of three may not change reading frame, but can change amino acids formed causing protein to not function properly.
DNA Mutations � 4 classifications (4) �nonsense � forms premature “stop” codon � UAC (tyrosine) UAG (stop)
Chromosomal Mutations �Recall: Chromosomes are wound DNA – when chromosomes are altered, we are altering large portions of the DNA message, even if there is only a small change to the chromosome.
Chromosomal Mutations �Occur during meiosis � 4 types: (1) �deletion – piece of chromosome is lost � may be lethal depending on which gene is lost
Chromosomal Mutations �Occur during meiosis � 4 types: (2) �duplication – piece of chromosome is duplicated � often harmless
Chromosomal Mutations �Occur during meiosis � 4 types: (3) �inversion – piece of chromosome is inverted/flipped � typically lethal, but in rare cases is advantageous
Chromosomal Mutations �Occur during meiosis � 4 types: (4) �translocation – piece of chromosome is moved to another part of the same chromosome or moved to its homologue � typically lethal
Non-Disjunction �Non-disjunction – pairs of chromosomes don’t separate properly during meiosis [metaphase] �Metaphase I – ALL gametes affected
Non-Disjunction �Non-disjunction – pairs of chromosomes don’t separate properly during meiosis [metaphase] �Metaphase II – only half of gametes affected
Non-Disjunction �Non-disjunction – pairs of chromosomes don’t separate properly during meiosis [metaphase] �causes types of “monosomy” or “trisomy” �ex: Trisomy-21, Trisomy-X, Monosomy-X, Showing Trisomy
Polyploidy �Polyploidy – multiples of entire chromosome set. �lethal in humans, common in plants � plants: causes larger cells, larger plants � Examples: �peanuts = 4 n �sugar cane = 8 n �coffee = 2 n, 4 n, 6 n, 8 n �wheat = 6 n
Polyploidy
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