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THE HUMAN GENOME AND HEREDITY Nutrition and Gene Expression Jan 23, 2014

THE HUMAN GENOME AND HEREDITY Nutrition and Gene Expression Jan 23, 2014. This graphic is a simple cartoon the genome (46 chromosomes). Most of your cells contain this complete set of chromosomes. (note FEMALE/MALE difference). If your progeny got exactly these genes,

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THE HUMAN GENOME AND HEREDITY Nutrition and Gene Expression Jan 23, 2014

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  1. THE HUMAN GENOME AND HEREDITY Nutrition and Gene Expression Jan 23, 2014

  2. This graphic is a simple cartoon the genome (46 chromosomes). Most of your cells contain this complete set of chromosomes. (note FEMALE/MALE difference). If your progeny got exactly these genes, Then your progeny would be essentially your twin (except of course, much younger than you!). But that’s NOT what happens. Your children will have 46 chromosomes, but 23 of those chromosomes will be from the maternal set, and 23 of those will be from the paternal set.

  3. MATERNAL SET PATERNAL SET 23 are selected for the ovum 23 are selected for the sperm The new embryo has a full set of 46 chromosomes

  4. SIMPLE MITOSIS: Duplication of Chromosome 2. This happens as a regular part of each cell division, since each cell needs a complete copy of all the DNA in the cell. For a homework assignment, you will need to fill in the missing steps. SEVERAL STEPS

  5. MEIOSIS The duplication of the chromosomes during formation of gametes (eggs and sperm) is called MEIOSIS. This is different in fundamental ways from mitosis. The mechanism of meiosis explains major features of the way genes are passed on to the offspring.

  6. THESE SLIDES HAVE COMPLEX NOTATION. FURTHER EXLANATION WILL BE PROVIDED DURING LECTURE. We use different codes, for example: #1 = chromosome 1 (forms a pair, in most cells) M = maternal chromosomes, P = paternal a,b = each of the two maternal chromosomes that can be provided to the gamete

  7. DURING MEIOSIS, GAMETES ARE FORMED THAT ONLY HAVE ONE COPY OF EACH CHROMOSOME. THE EMBRYO OF COURSE HAS TWO COPIES. Ovum DNA Sperm DNA BOTH ARE HAPLOID DIPLOID EMBRYO THE PROCESS IS VERY COMPLEX, AND IS OFTEN MISUNDERSTOOD. I WILL SHOW YOU GRAPHICALLY, IN THE FOLLOWING SLIDES, THE STEPS THAT ACTUALLY OCCUR IN THE FORMATION OF GAMETES.

  8. a a a b b b MEIOSIS: The process is shown only for the process in the ovum, it’s in the same in the sperm. We will illustrate this only for chromosome 1. When the DNA is duplicated for the ova, the female has a chromosome from her mother (a) and her father (b) that can be used. CHROMOSOMES, SET 1 1 STEP 1: Each copy of chromosome 1 is duplicated.

  9. a a a a b b b b The chromosomes have been duplicated. Two of them MOVE within the cell, so the are directly adjacent. STEP 2: One of the copies from maternal, and one from paternal, pair up!

  10. a a b b STEP 3 Part of the DNA sequence is exchanged between the two that are paired. (this is called: CROSSING OVER). RESULT: For 2 of the 4 chromosomes, there has been PARTIAL DNA exchange. This shows one exchange, there may be 2-3 crossovers ror each meiotic pair. a a/b b/a b

  11. a/b b/a b POSSIBLE DNA STRUCTURES FOR CHROMOSOME 1 IN THE OVUM a From mother: no changes From father: no changes Mixture/maternal and paternal Mixture/paternal and maternal IN THIS DIAGRAM, MOTHER and FATHER REFER TO THE CHROMOSOME YOU GOT FROM EACH PARENT. NOTE: THE OVA AND SPERM ARE HAPLOID, AND HAVE ONLY 1 COPY OF EACH CHROMOSOME.

  12. a a/b a/b b/a b/a b b WHEN THE OVA ARE FORMED, ONE COPY GOES TO EACH OVUM. a

  13. WHAT DOES THIS MEAN? It means that 50% of the time, the chromosome #1 that you provide your child has been REARRANGED so it has a mixture of your PATERNAL #1 DNA and your MATERNAL#1 DNA. You could also provide a chromosome #1 that is identical, to what you got from your father or from your mother.

  14. The subject of genetic recombination is complicated, and often is misunderstood. We will revisit this topic for additional discussion in further lectures. THE NEXT TOPIC: Since you get 2 copies of most genes (one from each parent), what consequences can occur?

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