genetika-2 (minggu 6)

Summary

This educational video on animal genetics explores deviations from Mendel's laws, focusing on gene interactions such as atavism, polygenic inheritance, epistasis, and complementary genes. The instructor explains polygenic traits through examples like red wheat and discusses epistasis using dog coat color inheritance. The concept of complementary genes is illustrated with the inheritance of flower color in *Lathyrus odoratus*. The video emphasizes the need for careful analysis of genotype and phenotype relationships and encourages viewers to practice and deepen their understanding of genetic principles through examples and exercises.

Takeaways

• 😀 Mendel's laws can be affected by gene interactions such as atavism, polymerism, and epistasis.
• 😀 Polymerism involves multiple genes interacting cumulatively to influence a single trait, exemplified by the color of wheat seeds.
• 😀 In a specific wheat cross, the presence of dominant alleles results in a stronger red color in seeds, illustrating the concept of polymerism.
• 😀 Epistasis occurs when one dominant gene masks the effect of another gene, as seen in the color inheritance of dog fur.
• 😀 An example of epistasis is the inheritance of coat color in dogs, where a dominant gene can hide the expression of another.
• 😀 The cross between a white dog and a brown dog demonstrates the principles of epistasis and hypostasis in gene interactions.
• 😀 Complementary gene interactions occur when two different dominant alleles are required together to express a specific phenotype.
• 😀 The interaction of alleles in pea flowers can lead to purple flowers only when both required dominant alleles are present.
• 😀 A clear understanding of these genetic interactions is essential for predicting phenotypic outcomes in breeding.
• 😀 Practical application and repetition are crucial for mastering complex genetic concepts, particularly through problem-solving exercises.

Q & A

What is the primary focus of the video lecture?

The video lecture focuses on discussing deviations from Mendel's laws of inheritance, specifically through gene interactions, including atavism, polygenic inheritance, cryptomery, hypostasis, epistasis, and complementary interactions.

What is polygenic inheritance?

Polygenic inheritance refers to the cumulative interaction of multiple genes, which influence the same trait, resulting in a range of phenotypic expressions. An example provided is red wheat, which is influenced by two genes (M1 and M2) that together strengthen the expression of the red color.

How does epistasis function in gene interactions?

Epistasis occurs when the effect of one gene (epistatic gene) suppresses or masks the effect of another gene (hypostatic gene). For instance, in the color of dog fur, the dominant gene 'B' can mask the effects of another gene responsible for color.

What is the phenotypic ratio expected in the F2 generation of the polygenic inheritance example given?

In the polygenic inheritance example of red wheat, the expected phenotypic ratio in the F2 generation is 15 red to 1 white, highlighting the dominance of the red trait due to the presence of dominant alleles.

Can you explain the concept of complementary genes?

Complementary genes are genes that work together to produce a specific phenotype. If either gene is absent, the trait may not be expressed. An example discussed involves the flower color of Lathyrus odoratus, where both genes must be present for the purple color to appear.

What is the significance of gene interactions in plant and animal breeding?

Understanding gene interactions is crucial in breeding because it helps predict phenotypes based on genetic crosses, allowing for more effective selection of traits in both plants and animals.

What role does dominance play in the examples provided?

Dominance plays a key role as it determines which allele's trait is expressed in the phenotype. In cases of epistasis and polygenic inheritance, the presence of dominant alleles can significantly alter the expected traits in offspring.

What is the outcome when F1 individuals are crossed in the epistatic example with dogs?

When F1 individuals from the dog example are crossed, the phenotypic ratio observed in the F2 generation is 12 white, 3 black, and 1 brown, demonstrating the dominance of the white phenotype due to the epistatic gene.

How is atavism related to genetic expression?

Atavism refers to the re-emergence of ancestral traits in offspring, which can occur when certain alleles that were not expressed in recent generations reappear, potentially influenced by environmental factors or genetic recombination.

What approach should students take to grasp the complexities of genetic interactions?

Students are encouraged to study independently and repeatedly, practice problem-solving related to genetic crosses, and create comparison tables for phenotypic outcomes to enhance their understanding of genetic interactions and Mendelian deviations.