VIDEO UKIN PPG BIOLOGI ANGKATAN IV Tahun 2021. Materi Pewarisan Sifat Berdasarkan Hukum Mendel II

Introduction

This tutorial will guide you through the principles of inheritance based on Mendel's laws, specifically focusing on the second law of inheritance. Understanding these foundational concepts in biology is crucial for students and anyone interested in genetics, as they explain how traits are passed from one generation to the next.

Step 1: Understand Mendel's Laws of Inheritance

• First Law (Law of Segregation): Each individual has two alleles for each trait, which segregate during gamete formation, resulting in each gamete carrying only one allele.
• Second Law (Law of Independent Assortment): Alleles for different traits assort independently of one another during gamete formation. This means the inheritance of one trait does not affect the inheritance of another.

Practical Tip

• To visualize these laws, use Punnett squares to predict the genotypes of offspring from parental crosses.

Step 2: Explore Monohybrid Crosses

• Definition: A monohybrid cross involves a single trait with two alleles.
• Example: Crossing a homozygous dominant pea plant (TT) with a homozygous recessive pea plant (tt).

Steps for Monohybrid Cross

1. Identify the parent genotypes.
2. Set up a Punnett square with the alleles from each parent.
3. Fill in the Punnett square to determine possible genotypes of the offspring.
4. Analyze the phenotypic ratio in the offspring.

Common Pitfall

• Ensure that you accurately represent dominant and recessive traits. Dominant traits mask the expression of recessive traits.

Step 3: Conduct Dihybrid Crosses

• Definition: A dihybrid cross examines two traits simultaneously.
• Example: Crossing pea plants that are heterozygous for two traits (TtRr x TtRr).

Steps for Dihybrid Cross

1. Identify the alleles for both traits in the parents.
2. Create a 16-box Punnett square to represent all combinations of alleles.
3. Fill in the Punnett square with the gametes from each parent.
4. Calculate the phenotypic ratios for each trait combination.

Practical Tip

• Use color coding for different traits in your Punnett square to better visualize the combinations.

Step 4: Analyze Genetic Ratios

• After completing your Punnett squares, determine the ratios of genotypes and phenotypes.
• Example: In a monohybrid cross, you may find a 3:1 phenotypic ratio for dominant to recessive traits.

Real-World Application

• These genetic ratios are essential for predicting traits in agriculture, animal breeding, and understanding genetic diseases in humans.

Conclusion

Understanding Mendel's laws of inheritance provides a foundation for studying genetics. By mastering monohybrid and dihybrid crosses, you can predict how traits are inherited in various organisms. Next steps could include exploring more complex genetic concepts, such as polygenic inheritance or gene linkage, to deepen your understanding of genetics.