Genes & Dominance

Genes & Dominance Law of Segregation Independent Assortment Probability

Vocabulary          

Trait Hybrids probability Alleles Filial generation (f1,f2,f3) Segregation Homozygous Heterozygous Phenotype genotype

Alleles   

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Alleles: Different forms of a gene Some alleles are dominant and some recessive An example is the gene for blossom color in a flower: a single gene controls the color of the flower, but there may be several different versions (or alleles) of the gene. One version might result in red petals, while another might result in white petals. The resulting color of an individual flower will depend on which two alleles it possesses for the gene and how the two interact.

Chromosome Segregation 

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During Meiosis, alleles separate during gamete formation. Parents (P) pass on genes to offspring. ½ of DNA comes from one parent and ½ from the other parent. Offspring (Filial) generations f1,f2,.. Offspring will carry traits from both parents.

Zygosity  

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Genetic condition of a zygote Used to simplify the description of the genotype of a diploid organism at a single genetic locus. At a given gene or position along a chromosome (a locus), the DNA sequence can vary among individuals in the population. The variable DNA segments are referred to as alleles, and diploid organisms generally have two alleles at each locus, one allele for each of the two homologous chromosomes. Homozygous or Heterozygous

Homozygous    

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Same alleles are present Either dominant or recessive Example: TT or tt Basically meaning “of the same alleles” at a specific locus The two identical copies of the gene affecting a given trait on the two corresponding chromosomes

Heterozygous 

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Gene when it has different alleles occupying the gene's position in each of the homologous chromosomes. In other words, it describes an individual that has 2 different alleles for a trait. Example: Tt Dominant trait will be expressed in phenotype

Dominant and Recessive 

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Dominant trait will mask a recessive trait Recessive trait will only express itself if there is not a dominant trait Types of traits Look at your neighbors and determine which traits are represented.

Probability 

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Monohybrid cross: is a cross between parents who are heterozygous at one locus Represented by Punnett squares Used to predict phenotypes based upon the genotype

Dihybrid cross 

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A dihybrid cross is a cross between two F1 offspring of two individuals that differ in two traits. example: RRyy/rrYY or RRYY/rryy parents result in F1 offspring that are heterozygous for both R & Y.

Online Resources   

Mendelian Genetics Monohybrid cross problem set Dihybrid cross problem set