BIOL 202 textbook notes

BIOL 202 textbook notes - BIOL 2 0 2 : Te xt b o o k No t e...

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BIOL 202: Te xtbook Note s Le cture 2: Single Ge ne Inhe rita nce I pgs. 37-57 ble nding inhe rita nce : offspring typica lly show som e cha ra cte ristics tha t a re sim ila r to both of the ir pa re nts (pre -Me nde lia n, proble m s with this the ory) pa rticula te inhe rita nce : cha ra cte rs a re de te rm ine d by discre te units tha t a re inhe rite d inta ct down through ge ne ra tions Mendel's Law of Equal Segregation Mendel used peas—came in wide variety of colours, shapes etc., peas can cross pollinate character: specific property of an organism pure line: population that breed true for or shows no variation from a particular character being studied (all offspring from selfing or crossing within the population show the same form of the character) character difference: a contrasting difference between 2 lines of organisms in one particular character (eg.flower colour) pure line organisms—parental generation (P) progeny generation resulting from the cross of 2 pure lines—first filial generation (F 1 ) reciprocal crosses: for plants, any cross can be made in 2 ways: 1) female from yellow line x male from green line = F 1 peas all yellow 2)female from green line x male from yellow line = F 1 peas all yellow in all cases of Mendel's experiment one parental phenotype disappeared in the F 1 and reappeared in the one fourth of the F 2 , creating 3:1 ratio dominant and recessive phenotypes are present in F 2 generation of a selfed cross there was a fundamental 1:2:1 ratio ¾ yellow, ¼ green phenotypes resulted but their genotypes had a 1:2:1 ratio ½ Y ½ y ½ Y ¼ Y/Y ¼ Y/y ½ y ¼ Y/y ¼ y/y Mendel's Explanation for the 1:2:1 ratio: 1. hereditary factor, a gene, is necessary for producing pea colour 2. each plant has a pair of this type of gene 3. this gene comes in two forms called alleles 4. a plant can either be Y/Y, y/y, or Y/y (/ shows the alleles are a pair) 5. Y/y plant, Y allele dominates, phenotype = yellow, Y allele is dominant, y is recessive 6. in meiosis, the members of a gene pair separate equally into the eggs and the sperm (Mendel's First Law, or Law of Equal Segregation) 7. a single gamete contains only one member of a gene pair 8. at fertilization, gametes fuse randomly regardless of which of the alleles they bear zygote: the first cell that develops into a progeny individual homozygote vs.heterozygote monohybrid vs. dihybrid homozygous dominant (AA) vs. Homozygous recessive (aa) or heterozygous recessive 1:1 ratio is produced by a cross of Y/y x y/y
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The Chromosomal Basis of Single Gene inheritance Patterns gene pairs located on chromosome pairs, members of the chromosome pair segregate somatic cells divide by mitosis mitosis can take place in either diploid or haploid cells—one progenitor cell becomes 2 2n--> 2n +2n or n--> n+n meiocytes: specialized diploid cells produce sex cells such as sperm and eggs (plants and
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BIOL 202 textbook notes - BIOL 2 0 2 : Te xt b o o k No t e...

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