Lab Manual - eScience Labs

Lab 14: Mendelian Genecs
The law of segregaon states that during
meiosis, homologous (paired) chromosomes
split (Figure 1). The law of independent
assortment states that during
meiosis, each homologous chromosome
has an equal chance of ending up in either
gamete, and alleles for individual
genes segregate with the chromosomes
on which they are located (Figure 2).
Using corn as an example (Figure 2):
Figure 2: Law of Independent Assortment
• The large chromosome has the gene for kernel color (Y = yellow, y = blue).
• The small chromosome has the gene for kernel texture (S = smooth (green); s = wrinkled (red)).
When a dominant allele is present, that characterisc is expressed, regardless of the second allele. In
this case both the Yy and YY offspring will be yellow.
A recessive allele is only expressed when both alleles are recessive. In this case only the yy combina-
on is blue. The dominant allele is always represented by capital leers, while the recessive is represented
by lower case leers.
Genotype refers to the combinaon of alleles for a parcular trait. Phenotype refers to the appearance
of that combinaon of alleles. In our example, the genotype of the diploid cell is Yy, Ss, while the
phenotype is Yellow and Smooth.
Figure 3: Monohybrid Cross
Punne Square F 1
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