13.4-20.3

13.4-20.3 - When making the squares, there are 5 steps. do...

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When making the squares, there are 5 steps. .. do the key, the squares, the genotype, the phenotype, the crossing 13.4 Chromosomes are composed of Mendel’s hereditary determinants, or genes. Locus - location of a gene Principle of segregation - separation of alleles during anaphase causes it. If the alleles are different (not sister-chromatids) then they aren’t going to join together Chromosome theory of inheritance - Mendel’s is from the independent alignment and separation of homologous chromosomes at meiosis I Wild type - most common phenotype for each trate Mutation - change in gene Fruit flies with white eyes where mutants He way trying to figure out why white eyes when to males A female produces half y chromosome gametes and half x He figured the X chromosome carried the white eye trait Sex linkages - traits that go with specifically x or y chromosome Autosomal inheritance - genes that aren’t linked to x or y chromosome 13.5 So genes shouldn’t go through independent assortment if they’re on the some chromosome. If they are on the same chromosome then they have a linkage. Morgan also discovered that the fruit fly body color gene is located on the X chromosome along with the eye color, so he thought that the linked genes would always be transmitted together. He tested this with an experiment, but the results showed that genes would be switched around because of genetic recombination and crossing over. A genetic map can be made if you know how often crossing over takes place. It tells the relative position of genes along a chromosome. Then they tested four-o’clock flowers. They saw that the first generation of purple and white flowers made lavender flowers, but then the generation after that made half lavender, one fourth white, and one fourth purple. A 1:2:1 ratio So the flowers didn’t have a dominant phenotype. Instead, they have incomplete dominance. solve like a normal cross, but like black and white, the phenotype will be gray. They’re looking to see if you know how to blend. Codominance is when heterozygotes have the phenotype for both alleles. With blood, if you have the a and the b phenotype they you’ll have type AB blood. AO would be A thought How many alleles and phenotypes exist?
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If there are more than 2 alleles for the same gene then it is called multiple allelism. If there are more than 2 phenotype then it’s called polymorphic hair color,etc Because there are so many, there will be tons of genetic combinations, so you can’t really get a good ratio. Genes can affect more than one trait. If this happens then the gene is pleiotropic. Marfan syndrome affects tons of genes at the same time. Phenotypes aren’t always controlled by genes.
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This note was uploaded on 02/12/2012 for the course SCI 2341 taught by Professor Yates during the Spring '11 term at Alabama.

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13.4-20.3 - When making the squares, there are 5 steps. do...

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