Co dominance I n genetics an instance in which two different but equally

Co dominance i n genetics an instance in which two

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Co-dominance: I n genetics, an instance in which two different but equally powerful genes produce a phenotype in which both genes are expressed. Carrier: In genetics, individuals who possesses a recessive gene associated with a disease and who, although they do not have the disease, can transmit the gene for it to offspring. Sex-linked gene: An attribute determined by a gene that appears on one of the two types of sex chromosomes, usually the X chromosome; ex. Hemophilia, Fragile X Poly-genetic characteristics: Traits affected by several genes and environmental factors at once; ex. intelligence, height, weight, etc. Single-gene [pair inheritance]: The genetic mechanism through which a characteristic is influenced by only one pair of genes, one gene from the mother and its partner from the father. Chromosomal abnormalities: Conditions in which a child has too few, too many, or  incomplete chromosomes because of errors in the formation of sperm or ova. Turner syndrome (X0) Klinefelter’s syndrome (XXY) Fragile X  Know about Huntington (p. 73) , sickle cell anemia  (p. 72) , PKU, muscular dystrophy,  hemophillia  (p. 70) , Down (p. 70)  Turner s & Klinefelter (p. 71) , etc.  
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Huntington’s is a dominant single gene defect that affects the nervous system.  Sickle cell is recessive sex-linked  PKU is recessive and affects the body’s ability to break down phenylalanine, leading to  build up that interferes with cognitive development; a diet low in phenylalanine can  prevent symptoms.   Know percent of genetic relatedness among parent/child, sibs, grandparents, etc.  (lecture).  Child to parent – 50% Sibling – 50% Grandchild to grandparent – 25% Identical twin – 100% Fraternal twins – 50% What exactly did the Human Genome Project map  (p. 66) The Human Genome Project  mapped the sequence of the chemical units that make up the strands of DNA in a full set  of 46 human chromosomes (Weiss, 2003).   Know Gotlieb s Epigenetic Theory (lecture, also  Ch. 3, p. 86 ).  Genes do not dictate  development; rather, they interact with each other, leading to epigenetic effects where  cell expression is turned on or off according to the enviroments’ interaction with the  given genes.   Define epigenetics.  Epigenetics:   Ways in which the environment influences or alters the expression of genes.  Know the two mechanisms discussed in class: histone acetylation and DNA methylation  (lecture & p. 86).  Histone acetylation adds an acetyl tail to a clump of proteins (genes) that make it unwind and easier to read – turning it ON.  DNA methylation does the opposite, by adding a  methyl group to the cytosine base, it represses transcription and turns it OFF.  See also  fetal programming  on p. 100. 
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