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Lecture 4

Lecture 4.doc

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BIOL 1010
James Cheetham

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Lecture 3,4 Tuesday, October 5, 2010 - single gene disorder- mutation in single gene (cystic fibrosis, Huntington’s, etc.) - a lot of human diseases are polygenic o heart disease o cancer o stroke o hypertension - Effects of different alleles- many genotypes - Height, skin colour, eye colour, etc- controlled by many genes - A lot of mutation are lethal (in utero- die before birth) - Can have them generation to generation or spontaneous - Incomplete penetrance- mutation could be masked by other alleles interacting - Expressivity- two people with Parkinson’s could exhibit different symptoms - Pleiotropy- gene influences several aspects of the phenotype - DARP- gene that was turned off for mice- brain gene that also affected kidneys, females wouldn’t do ordosis (stick butt up when in heat) - Triple chromosomes- non-disjunction in meiosis - X-linked diseases (hemophilia, colour-blindness) usually worse in males because they only need one copy of the recessive gene o If mother carries one x-chromosome with non-functional red-green allele and father passes on his y-chromosome, the son (xy) will inevitably be colour-blind- doesn’t have another x-chromosome to balance it out like girls do - Lots of important traits on x-chromosome, lots of x-linked diseases - Linkage- genes on same chromosome- genes tend to move together- can see inheritance patterns very clearly - Regular female and hemophiliac male o Xx (normal) and xy (the x has the nonfunctional allele) o Xx (carrier), xx (carrier), xy (normal), xy (normal)- because father’s x- chromosome doesn’t get passed on to sons o Because girls are carriers, once they mate with normal male, girl’s bad x- chromosome matches with guy’s y-chromosome and ¼ of children (1/2 the sons) will be hemophilic o SKIPS A GENERATION- X-LINKED TRAIT - This is how conventional breeding works - Alzheimer’s called the Swedish mutation because of particular Swedish family - Attached earlobe is recessive trait o If you have two heterozygote parents (carriers), you can still have attached earlobes - Widow’s peak appears in every generation- half of heterozygote will get it - Forensic DNA- take this into account when doing calculations- probability of his DNA matching crime scene DNA- based on allele frequencies of different populations- there can be millions of different alleles - Louise Brown in England- “test tube baby”- in vitro fertilization - Aneuploidy (odd number of chromosomes) from chromosome non-disjunction o Don’t come apart properly o Could have both chromosomes stuck in one egg in first step of meiosis, so you wind up having 2 out of the 4 gametes with no chromosomes (they’re all on other side) o Or could have them initially divide fine- one chromosome on one side, one on the other. But in second step when those divide, you could wind up having one of those chromosomes split unevenly.  Extra copy of chromosome- Down’s syndrome - Polyploidy- made corn, strawberries bigger - Initially thought all disease was environmental (70s)- DDT, chemicals in environment, etc. - Now we think all disease is genetic- Human Genome Project - But there’s an interaction between the two - Pre-implantation genetic diagnosis o Blastocyst (embryo developed a bit) o Take one cell out of it, screen for genetic diseases before it’s injected into mother o Controversial- making sure child isn’t undesirable- could extend to picking whether child will be tall, blond, smart, etc. Review - the reason G goes with C is because guanine has oxygen, hydrogen and hydrogen on one side o cytosine has hydrogen, nitrogen, and oxygen on one side o they form three hydrogen bonds (O-H, H-N, H-O) o *Hydrogen is donor, oxygen is acceptor - A and T go together because adenine has hydrogen and nitrogen on one side o Thymine has oxygen and hydrogen on one side o They form two hydrogen bonds (H-O, N-H) - A and T are easier to separate because they have less bonds - For G-C, have to go to higher temperature to separate - RNA could make enzyme - siRNA- RNA used for receptors - miRNA - etc. - genes- regulatory region, coding region, etc. - bacteria are more functional because they don’t have introns - Every cell has all genes (except for gametes) but just don’t express them o Stem cells- can fiddle with gene expression to make them into different types of cells - Big genes- higher chance of mutation - Could change splicing patterns (as baby cut out intron 1, as adult cut out 1 and 2) - Epigenetic regulation- environmentally determined- modify the DNA (not a problem of DNA sequence) o Inheritance of acquired characteristics o Refuted- called Lamarcianism- if giraffe stretches its head longer, children will have long necks- environment can affect sperm o Doesn’t make sense o Darwin said those who compete well have lots of offspring o Lamarck is partially correct, although he was a quack - Folate (b-vitamin for women)- important for methylation reaction o Methylation of DNA in developing embryo - E. coli would methylate its DNA (to protect its own DNA), when foreign DNA came in it would cut it - pSC101 and pSC102- plasmids o codes for protein- antibacterial resistance
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