Class 10 - Sept 29

Class 10 - Sept 29 - IB35ac Class 10: Genetics Offspring...

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Unformatted text preview: IB35ac Class 10: Genetics Offspring look like their parents because they inherit genetic material from them. I'll introduce the concept of meiosis and recombination, and the definition of "gene". We'll briefly talk about regulatory elements, proteincoding elements, the triplet code, RNA, etc. IB35 Human Biological Variation Class #10 Some important terms Gene = a section of DNA that has an effect on the phenotype Allele = an alternative version of a gene Genotype = the genetic constitution of an organism Phenotype = observable properties of an organism (genotype + environment) Genome = a term used to refer to all of the genes carried by a single gamete (sperm or egg) Topics for today: Genetics Sequence = the specific nucleotide arrangement of a segment of DNA Nucleotide = A, T, C, or G Composed of ->a nitrogenous base ->a five-carbon sugar (either ribose or 2'-deoxyribose) ->one to three phosphate groups Genetics: An overview Statistical Approach Quantitative genetics: how variation is inherited within families (i.e., heritability analyses) Developmental genetics: studies how genes are expressed during development p g p Population genetics: study of the allelic composition within and between populations Genomics: statistical analyses that compare large sequences of DNA (often between different species) Genetics: An overview How genes do what they do Quantitative genetics Developmental genetics Genomics How DNA sequences vary w/in and between populations, species, etc. Population genetics Genomics Heritability = proportion of total variance that is attributable to genes Decomposing the Total Variance Continuously varying trait Terms to know: Zygote Embryo Fetus Ontogeny fertilized egg after implantation until 8 weeks 2 months after embryo v TOTAL = v GENES + v ENVIRONMENT ONTOGENY AND PHYLOGENY ->Individual organisms develop (ontogeny) ->Species evolve (phylogeny) Describes the origin and the development of an organism from the fertilized egg to its mature form 1 Tcre;Fgfr1 skeletal phenotypes and gene expression http://www.news.wisc.edu/newsphotos/fruitfly.html Verheyden, J. M. et al. Development 2005;132:4235-4245 http://www.americanscientist.org/bookshelf/pub/clever-tinkering ->Individual genes are expressed in multiple phenotypes ->NOT 1-1 The Genome The complete DNA sequence of a set of chromosomes. "gene" + "chromosome" ~3,000,000,000 b 3 000 000 000 base pairs i ~32,000 genes 46 human chromosomes... (23 pairs you get one set from each parent) karyotype Most of sex-related characteristics found on ychromosome Chimpanzees, Gorillas & Baboons have 24 pairs of chromosomes Humans have 23 pairs of chromosomes -> derived/primitive? Ans: Derived. Last common ancestor most probably had 24 pairs Gametes are the cells in your body that form sperm or egg cells - the germ lines. Chromosomes Are comprised of DNA and Proteins 1953 discovered that DNA is the material of heredity 23 pairs i h i in humans (24 i chimpanzees) in hi ) One is inherited from mom The other is inherited from dad So... sperm and egg cells are special in having only of a complete set of chromosomes. DNA is comprised of nucleotides. There are four kinds of bases: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) A pairs with T C pairs with G 2 The Double Helix Two important abilities: 1. Faithful replication at cell division y 2. Ability to control cellular function James Watson and Francis Crick (1953) Replication: DNA unwinds -> Free nucleotides (RNA) bind to exposed strands -> Forms 2 new strands of DNA Transcription... Translation... Redundancy built into DNA replication; multiple codes code for the same amino acid Organelles to remember: Nucleus (where transcription occurs) and ribosomes (where translation occurs) DNA nucleus To function or not to function? Functional or coding DNA Genes (code for proteins) Regulatory elements (turn genes on and off) transcription RNA translation 1 5% of th h 1.5% f the human genome consists of i t f protein encoding sequence ribosome Protein 3 The Importance of Gene Regulation Protein coding regions (make proteins) transcription DNA 1 2 3 gene A gene B The Double Helix Two important abilities: 1. Faithful replication at cell division y 2. Ability to control cellular function Regulatory elements (turn genes on and off everything in between) CENTROMERES: Region where 2 sister chromatids come into contact TELOMERES: Region of repetitive DNA at the end of a chromosome, which protects the end of the chromosome from destruction Two types of replication Mitosis Meiosis Recombination Mitosis MITOSIS Eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei MEIOSIS ->Process of reductional division in which the number of chromosomes per cell is cut in half ->Results in the formation of gametes Recombination 1 in 100 million chance of a mutation per nucleotide per generation... estimates range from 1 mutation in 40 to 1 in 600 generations Genetic Mutations How often do mutations occur? Are mutations evenly distributed across the genome? T Types? ? 1 in 100 million chance of a Nonsense mutation per nucleotide per Missense generation... estimates range Silent from 1 mutation in 40 to 1 in 600 generations. Skin is replaced over the course of about a month. This means that your dermis produces a lot of skin cells. What type of cell replication is this? Ans: Mitosis 4 Codons Nonsense mutation Missense mutation cat ran far kat ran far car ran far cat rxn far original sequence silent mutation missense mutation nonsense mutation Silent mutation Insertion or deletion of a number of nucleotides that is not evenly divisible by three from a DNA sequence Silent - New amino acid coded for is the same as intended Missense - New amino acid coded for is different from intended Nonsense - Stops the coding Frameshift mutation Chromosomal Mutations Insertions Deletions Inversions Aneuploidy Monosomy Trisomy C4-Deletion C20-Insertion MONOSOMY ->Chromosome pair has only one chromosome ->Turner Syndrome - Loss of one sex chromosome (only x chromosome left) TRISOMY ->Chromosome pair has three chromosomes ->Down's Syndrome - Trisomy 21 (3 copies of chromosome 21) What should you remember for Exam 1? How many chromosomes do you have? Are all cells the same in terms of # of chromosomes? Does all DNA do the same thing? Are all mutations the same? 46 No No No INVERSION ->Chromosome rearrangement in which a segment of a chromosome is reversed end to end ->Usually do not cause any abnormalities in carriers as long as the rearrangement is balanced with no extra or missing genetic information ->increased production of abnormal chromatids leads to lowered fertility due to production of unbalanced gametes 5 ...
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