Transcript 06.Genetics
Genetics Inheritance of Traits Gregor Mendel 1822 – 1884 Born to peasant parents Ordained a priest in 1847 Studied physics and natural science 18511853 1857(?) began pea experiments http://www.jic.ac.uk/germplas/pisum/zgs4f1.gif Inheritance Children resemble their parents because they directly inherit traits from them Parts of DNA are expressed, and these are called genes (note that geneticists also refer to sequences not expressed as genes) Genes are not always identical – and each is referred to as an allele One gene may have many alleles – or variations of that gene’s ultimate function Mendel’s Peas Began with plants that only produced each of these – only spherical or dented seeds, only yellow or green seeds, only purple or white flowers (etc.) http://mac122.icu.ac.jp/gen-ed/mendel-gifs/03-mendel-characters2.JPG Mendel’s Peas Crossed a wrinkled with a spherical seed plant Crossed a yellow with a green seed plant Results? Dominant and recessive genes http://www.wwnorton.com/college/anthro/evolve4/ch/02/2_1.jpg Punnett Squares Remember during meiosis that 1 cell replicates DNA, the pairs separate, then the original and copy of DNA separates to 4 cells The Punnett reflects a single mother and single father germ cell’s possibilities http://www.biologie.uni-hamburg.de/b-online/library/onlinebio/mono2.gif Punnett Squres Help to determine chance of inheriting a specific allele Genes are randomly assorted http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial4_files/fig_14_8.gif Human Genetic Conditions Use of Mendelian genetics can determine the likelihood of inheriting or carrying a dangerous allele – like Huntington's disease http://www.daviddarling.info/images/autosomal_dominant.jpg Genetic Disorders – Single Gene Cystic Fibrosis defective gene 7 protein produced normally helps salt (sodium chloride) move in and out of cells if protein doesn't work correctly movement is blocked and an abnormally thick sticky mucous is produced on the outside of the cell cells most seriously affected by this are the lung cells mucous clogs the airways in the lungs, and increases the risk of infection by bacteria http://www.sjsu.edu/faculty/gerstman/StatPrimer/autorecessive.jpg Genetic Disorders – Single Gene Sickle Cell Anemia single nucleotide substitution 11 prevents oxygen from reaching the spleen, liver, kidneys, lungs, heart, or other organs, causing a lot of damage Without oxygen, the cells that make up these organs will begin to die As a result, these patients often experience frequent infections Many others http://library.thinkquest.org/06aug/00440/images/sicklecell.jpg Genetic Disorders - Chromosomal Down Syndrome Turner Syndrome Klinefelter Syndrome Cri du chat Syndrome Williams Syndrome Many others Down Syndrome triploidy 21 Distinctive features: flat face small broad nose abnormally shaped ears large tongue upward slanting eyes with small folds of skin in the corners respiratory infections gastrointestinal tract obstruction (blocked digestive tract) Leukemia heart defects hearing loss hypothyroidism various eye abnormalities moderate to severe mental retardation http://www.ucl.ac.uk/~ucbhjow/bmsi/lec7_images/47_xx_21.gif http://www.faqs.org/health/images/uchr_07_img0706.jpg Turner Syndrome missing X Distinctive features: shorter than normal may fail to start puberty when they should because ovaries (which produce eggs, as well as the sex hormones estrogen and progesterone) fail to develop properly. have a stocky appearance arms that turn out slightly at the elbow receding lower jaw short webbed neck low hairline at the back of the neck lymphedema (swelling of hands and feet) heart and/or kidney defects high blood pressure infertility https://images1.clinicaltools.com/images/gene/karyotypes/turnersyndromexnoy.jpg http://learn.genetics.utah.edu/content/disorders/whataregd/turner/images/turner_person.jpg Klinefelter Syndrome - XXY Distinctive features: develop as males often tall don't develop secondary sex characteristics, such as facial hair or underarm and pubic hair extra X chromosome primarily affects the testes, which produce sperm and the male hormone testosterone http://images2.clinicaltools.com/images/gene/trisomyxxy.jpg http://learn.genetics.utah.edu/content/disorders/whataregd/klinefelter/images/kleinfelter_person.jpg Cri du chat Syndrome deletion 5 Distinctive features: small head (microcephaly) an unusually round face a small chin widely set eyes folds of skin over their eyes a small bridge of the nose. heart defects muscular or skeletal problems hearing or sight problems http://www.biology.iupui.edu/biocourses/N100/2K2humancsomaldisorders.html http://www.findhealer.com/glossary/images/criduchat.gif Williams Syndrome missing part 7 Distinctive features: mental retardation heart defects unusual facial features (small upturned nose, wide mouth, full lips, small chin, widely spaced teeth) low birth weight failure to gain weight appropriately kidney abnormalities, and low muscle tone behaviors, such as hypersensitivity to loud noises and an overly outgoing personality. http://medgen.genetics.utah.edu/photographs/diseases/high/williams_syndrome_original1.gif Multifactoral Genetic Disorders Alzheimer’s Disease People who have the disorder slowly lose their ability to think clearly. At first, they may forget words or names, or have trouble finding things. As the disorder worsens, they may forget how to do simple tasks (such as walking to a friend's house or brushing their hair). Some people with Alzheimer's also feel nervous or sad http://2.bp.blogspot.com/_kQrramY7bs4/RvB6HmEZFCI/AAAAAAAACQU/b6sysujyPKU/S420/alzheimer.normal.brain.jpg More Mendel Besides dominance/recessive, there is: incomplete dominance co-dominance multiple alleles polygenic inheritance pleiotrophy Definitions Phenotype – the expression of the genes – what the organism looks like and how it functions Genotype – genes inherited – the alleles of the genes whether expressed or not For example, if an organism inherits both the dominant and recessive alleles, it would have the phenotype of the dominant allele, but the genotype would be both dominant and recessive Incomplete Dominance Organism receives both alleles, in this case, red flower and white flower. The phenotype is intermediate to red and white - pink http://dwb4.unl.edu/Chem/CHEM869N/CHEM869NLinks/www.rrz.uni-hamburg.de/biologie/b_online/ge08/01.gif Co-dominance When alleles share fully in the expression of the gene. For example, our blood types A, B, AB and O. http://www.agen.ufl.edu/~chyn/age2062/lect/lect_10/bloodtyp.gif Multiple Alleles Follows same “rules” as other inheritance Frequency of the allele can change with the population http://static.icr.org/i/articles/imp/imp-3647-Allele%20freq.jpg http://1.bp.blogspot.com/_DZH2cmCoois/Rdyly-4z72I/AAAAAAAABAg/Z8LaotoW8s4/s400/ABO_antigens.jpg Polygenic Inheritance But we don’t inherit one gene… Estimates range from 20,000 to 40,000 coding genes http://porpax.bio.miami.edu/~cmallery/150/mendel/c8.14x13.polygenic.jpg http://www.diversitycourses.co.uk/diversity3.jpg Pleiotrophy Hemophilia – single gene influence multiple phenotypic traits Lacking protein in blood Excessive bruising Pain and swelling in the joints Vision loss Anemia Fatigue Neurological problems if bleeding occurs in brain http://www.friesian.com/history/impfamil.jpg http://upload.wikimedia.org/wikipedia/commons/a/a3/XlinkRecessive.jpg Gender Is it a boy or girl? Mom always has XX Dad has XY Dad’s sperm cells – two X and two Y (remember, DNA replicates first) Mom’s egg cells – four X cells http://www.csupomona.edu/~biology/bio110/inherit/fig10.gif Not true for all species Some species, the female has different chromosomes and the male has the identical chromosomes. In this system, the chromosomes are referred to as W and Z Some species gender is determined by temperature Some species can change from male to female or vice versa Some species, only queens and drones reproduce Some species are both male and female – hermaphrodite The term "hermaphrodite" derives from Hermaphroditus, the son of Hermes and Aphrodite, who fused with the nymph Salmacis, and thus possessing physical traits of both sexes. Questions? BJ Shaw Panochthus frenzelianus American Museum of Natural History 2004