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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.

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Presentation on theme: "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."— Presentation transcript:

1 Unit 4 – Lecture 4

2 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

3 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 mRNA  problem in protein synthesis

4 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]

5 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 = yrs old]

6 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

7 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

8 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

9 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 –

10 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 – AUA – A Met – Leu – [stop]  Met – Leu – Ile –

11 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)

12 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.

13 DNA Mutations 4 classifications (4) nonsense forms premature “stop” codon UAC (tyrosine)  UAG (stop)

14 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.

15 Chromosomal Mutations Occur during meiosis 4 types: (1) deletion – piece of chromosome is lost may be lethal depending on which gene is lost

16 Chromosomal Mutations Occur during meiosis 4 types: (2) duplication – piece of chromosome is duplicated often harmless

17 Chromosomal Mutations Occur during meiosis 4 types: (3) inversion – piece of chromosome is inverted/flipped typically lethal, but in rare cases is advantageous

18 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

19 Non-Disjunction Non-disjunction – pairs of chromosomes don’t separate properly during meiosis [metaphase] Metaphase I – ALL gametes affected

20 Non-Disjunction Non-disjunction – pairs of chromosomes don’t separate properly during meiosis [metaphase] Metaphase II – only half of gametes affected

21 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

22 Polyploidy Polyploidy – multiples of entire chromosome set. lethal in humans, common in plants plants: causes larger cells, larger plants Examples: peanuts = 4n sugar cane = 8n coffee = 2n, 4n, 6n, 8n wheat = 6n

23 Polyploidy


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