Coin Sex Lab and Unit 4 Reflection

        In the coin sex lab, we simulated the inheritance of traits on different genes through crosses. This effectively models genetic concepts, as the flipping of coins represents the random recombination of alleles, and thus creates plausible results that conform to the combinations found in a punnett square. We tested a cross with sex chromosomes, autosomal inheritance, x-linked inheritance, monohybrid crosses, and a dihybrid cross. Across the board, though our results and ratios did not always completely match the expected results, such a discrepancy can easily be explained by the small sample sizes (10-16 flips), and our results all fit within the possible genotypes from meiosis. Using probability to predict offsprings' traits is limited in that in the real world, as the results often vary from both randomness and environmental traits (here factors that affect the flip result).

Data for dihybrid cross

        As expected, the X-linked colorblindness cross yielded mostly affected males, and the dihybrid cross yielded different genotypes with more double heterozygous and few double homozygous. In the dihybrid cross, BbEe brown haired, brown eyed individuals were crossed, which is expected to produce 9:3:3:1 phenotypic ratio. Our results produced a 14:1:1:0 ratio, which is close to expected, and this high brown-brown expected value is due to there being more combinations that result in it. Dominant alleles dominate others, so the double dominant genotype would be much more common. This understanding can be directly related to life, as dominant traits are observed much more in the phenotypes than recessive ones, and this can be used to understand how recessive traits such as blue eyes or blond hair are passed down through generations even if masked. This can explain where people around you attained such unique characteristics as the ones they have.

        In this unit, we explored concepts like these, such as the cell cycle (interphase, mitosis, cytokinesis), the process of meiosis, how asexual and sexual reproduction each have their costs and benefits, the difference between haploid and diploid cells, Mendel's experiments with pea plants, the principle of inheritance, Mendel's Laws of Segregation and Independent Assortment, genotypes and phenotypes of traits, how dominant alleles mask recessive alleles, the usage of Punnett squares, incomplete dominance and codominance, how genes affect one another through epistasis, and the multiple genes that contribute to polygenic traits.

Diagram and punnett square of a dihybrid cross

        Some of this material was a bit challenging and confusing to understand, such as the complex probabilities of X-linked traits. However, after practicing and learning about how these alleles are passed along differently in males and females that guarantee certain things, I have grasped a better understanding of it. After lectures and completing the labs and infographic, I could make more connections between the different aspects of genetics, and understood better how Mendel's laws make the principles and complications possible. In addition, I would like to explore some of the more convoluted processes a bit more. For example, how do the spindle fibers in meiosis work? How are they produced and how do they extend and latch onto chromosomes to pull them apart? Also, in DNA replication, how exactly are the strands replicated? Are the leading and lagging strands copied differently due to their direction?