Biology 1001A Lecture Notes - Lecture 5: Allosome, Zygosity, Gamete
6 Nov 2016
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Document Summary
Variation in traits is due to different alleles (he called them factors) Alleles segregate randomly into gametes: organisms inherit two alleles for each trait (one from mother and one from father) Appearance of heterozygotes is determined by dominant alleles (the allele that determines the phenotype of the organism is the dominant one) distribution of progeny (offspring), given parental genotypes in monohybrid and sex-linked crosses. For a parent that"s heterozygous for a trait, it makes two different kinds of gametes, one with each different kind of allele, equally frequently. A homozygous parent makes only one kind of gamete. A cross between two monohybrid organisms will result in a 3:1 ratio of a single trait (assuming that both of the organisms are heterozygous) A cross link between two dihybrid organism organisms will result in a 9:3:3:1 ratio of two different traits (like pea shape and colour) Sex chromosome combinations can produce recessive sex linked traits.
