BIOLOGI SMA Kelas 12 - Pewarisan Sifat PART 2 (Penyimpangan Semu Hukum Mendel) | GIA Academy

Summary

This video from Kia Academy explores the deviations from Mendel's Laws, known as 'pseudo-Mendelian' inheritance. It explains how certain genetic crosses result in phenotype ratios that deviate from Mendel's expected outcomes. The video covers five types of deviations: epistasis, hypostasis, cryptomerism, complementary genes, and atavism, using examples like flower color in linaria maroccana and chicken comb shapes. It also includes a problem-solving segment to help viewers understand these concepts.

Takeaways

• 🧬 Mendel's Laws have exceptions in nature, known as 'pseudo-Mendelian' deviations.
• 🌱 Pseudo-Mendelian deviations still follow Mendel's basic patterns but result in altered phenotypic ratios.
• 🔍 Epistasis and hypostasis are types of deviations where one gene masks or is overridden by another.
• 🌼 Examples of pseudo-Mendelian crosses include epistasis, hypostasis, cryptic coloration in flowers, gene interaction in wheat kernel color, and atavism in chickens.
• 🌿 Epistasis is divided into three types: dominant, recessive, and co-dominant, each producing different phenotypic ratios in F2 generation.
• 🐭 In mice, the color of fur can be determined by the interaction of multiple genes, demonstrating recessive epistasis.
• 🌸 The color of linaria maroccana flowers can appear purple due to the interaction of genes coding for pigment and plasma acidity.
• 🌾 Polygenic inheritance, like in wheat kernel color, involves the additive effect of multiple genes on a trait.
• 🌹 Complementary genes, such as in the case of Lady Rose flowers, require the presence of both genes to express a new phenotype.
• 🐔 Atavism is the re-emergence of a trait in offspring that was not present in the immediate parents but was in earlier generations.

Q & A

What is meant by 'pseudo-Mendelian inheritance'?

Pseudo-Mendelian inheritance refers to the deviations from Mendel's laws of inheritance where the phenotypic ratios in offspring do not match the expected ratios according to Mendel's laws.

What are the types of crosses that fall under pseudo-Mendelian inheritance?

The types of crosses that fall under pseudo-Mendelian inheritance include epistasis, hypostasis, cryptomerism, polygenic inheritance, complementary genes, and atavism.

How does epistasis differ from hypostasis?

Epistasis involves a gene or pair of genes that mask the expression of other non-allelic genes, while hypostasis is where a gene is overridden or masked by another gene during inheritance.

What is the phenotypic ratio for F2 generation in dominant epistasis?

In dominant epistasis, the F2 generation phenotypic ratio is 12:3:1.

Can you provide an example of a trait influenced by epistasis?

An example of a trait influenced by epistasis is the color of the onion's skin layer, where two types of dominant genes determine the color, and the presence of one dominant gene can mask the effect of the other.

What is meant by the term 'cryptomerism' in genetics?

Cryptomerism refers to the appearance of a certain trait only when specific dominant genes are combined, and the trait remains hidden if the genes are present alone.

How does polygenic inheritance differ from single-gene inheritance?

Polygenic inheritance involves the collective effect of multiple genes on a particular trait, whereas single-gene inheritance is determined by a single gene pair.

What is the role of complementary genes in inheritance?

Complementary genes are those that interact with each other to produce a new phenotype. If one of the genes is missing, the phenotype may not develop fully or may be altered.

What is atavism in the context of genetics?

Atavism is a genetic phenomenon where certain traits skipped a generation or more reappear in later generations.

Why do the F1 generation traits not always follow the parental traits in pseudo-Mendelian inheritance?

The F1 generation traits may not follow the parental traits due to the interaction of multiple genes, which can result in new or altered phenotypes that were not expressed in the parental generation.

How does the color of linaria maroccana flowers provide an example of cryptomerism?

The color of linaria maroccana flowers is determined by the interaction of two dominant genes. The purple color, which is unusual, appears only when these two genes are present together, illustrating cryptomerism.