Kriptomeri Kelas 12 | Penyimpangan Hukum Mendel

Summary

The video discusses the concept of cryptomery, a phenomenon where dominant genes appear hidden when standing alone, but their effects become evident when two dominant genes are present together. Using the example of Linaria maroccana flowers, the lesson explains how flower color (red, purple, or white) is influenced by dominant genes for pigment (anthocyanin) and pH levels. A genetic cross is analyzed, illustrating the inheritance patterns and resulting phenotypes in offspring. The video concludes with a focus on mastering the ratios for phenotypic outcomes in cryptomery genetics.

Takeaways

• 📘 Cryptomery refers to a condition where a dominant gene appears hidden unless two dominant genes are present together.
• 🌸 Cryptomery is observed in flowers such as Linaria maroccana, which have red, purple, and white colors influenced by genetic interactions.
• 🧬 The color formation in Linaria is determined by the presence of anthocyanin pigment and genes that control pH levels.
• 🔬 The dominant gene for anthocyanin produces pigment, while the gene controlling pH (basic or acidic) also influences the final color.
• 🌿 If both dominant genes (pigment and basic pH) are present, the flower appears purple, while a lack of pigment results in a white flower.
• 🔍 When crossing red and white Linaria flowers, F1 generation shows a 100% purple phenotype due to cryptomery.
• 🔄 Self-crossing of F1 purple flowers results in a 9:3:4 phenotypic ratio for purple, red, and white flowers in the F2 generation.
• 💡 The ratio can be explained by considering the combination of genes for anthocyanin and pH control in the offspring.
• 📊 The expected phenotypes in the F2 generation include 9 purple, 3 red, and 4 white flowers based on genetic inheritance patterns.
• 📝 Cryptomery requires careful analysis of dihybrid crosses, and understanding the role of dominant and recessive alleles in producing visible traits.

Q & A

What is cryptomery as explained in the transcript?

Cryptomery refers to a condition where a dominant gene seems hidden when present alone and only shows its effect when combined with another dominant gene.

How does cryptomery differ from Mendel’s classical law?

Cryptomery is a deviation from Mendel's classical law because it involves hidden gene effects, whereas Mendel’s law typically suggests that dominant genes express themselves when present.

What example is used to explain cryptomery in the transcript?

The example of the Linaria maroccana flower is used, which can exhibit different colors (red, purple, or white) based on the combination of pigment genes and pH levels.

What determines the color of Linaria maroccana flowers?

The color is determined by the pigment anthocyanin and the pH level. A dominant gene for anthocyanin and a base pH results in purple, while an acidic pH results in red, and the absence of anthocyanin produces white flowers.

Why does the purple color appear in the flowers?

The purple color appears when the flower has both the dominant gene for anthocyanin and a base pH level, which allows the pigment to express fully.

What happens when the flower has anthocyanin but an acidic pH?

If the flower has anthocyanin but an acidic pH, it will exhibit a red color.

What is the phenotype of flowers with no anthocyanin and a base pH?

Flowers without anthocyanin and a base pH will appear white, as there is no pigment to show color.

How are the parental flowers in the crossing experiment described?

The parental flowers are described as one with a red color (due to the presence of anthocyanin and acidic pH) and the other as white (due to the absence of anthocyanin and base pH).

What are the phenotypic results of the F1 generation in the experiment?

In the F1 generation, all the offspring exhibit a purple color due to the presence of both dominant genes for anthocyanin and base pH.

What is the phenotypic ratio of the F2 generation in the cryptomery example?

The F2 generation shows a phenotypic ratio of 9 purple, 3 red, and 4 white, following a typical 9:3:4 ratio in a dihybrid cross exhibiting cryptomery.