PENYIMPANGAN SEMU HUKUM MENDEL : BIOLOGI KELAS 12 SMA

Summary

In this educational video, the host, Febri, explains the concept of Mendel's laws and their exceptions in biology, specifically focusing on 'pseudo Mendelian deviations.' The video covers five types of deviations: atavism, cryptomery, complementary genes, epistasis, and polygeny. Examples, including the inheritance of traits in chickens, flowers, and wheat, are used to illustrate these genetic interactions. The video aims to help viewers understand complex genetic concepts through practical examples and detailed genetic cross calculations, encouraging continued learning and engagement.

Takeaways

• 😀 Mendel's laws have exceptions called pseudo Mendelian deviations, which involve different inheritance patterns.
• 😀 Atavism refers to the reappearance of traits that have not appeared for a long time due to allele interactions, as seen in chicken comb types.
• 😀 In atavism, offspring may exhibit traits like walnut combs, despite the parents having different comb types.
• 😀 Cryptomeria describes hidden dominant traits that only appear when two dominant alleles interact, like in the Linaria maroccana flower color.
• 😀 The interaction between dominant genes in cryptomeria results in colors like purple when both bases are present, and white when neither is.
• 😀 Complementary genes must work together for a specific phenotype to emerge, such as in the case of deaf-mutism, where both dominant genes are necessary for a normal phenotype.
• 😀 The lathyrus odoratus flower exhibits complementary gene interaction for its purple color, where both pigment and enzyme genes must be present.
• 😀 Epistasis occurs when one dominant gene covers up the expression of another, as seen in the black wheat skin color, where the black allele hides the yellow allele.
• 😀 Epistasis and hypostasis describe how one gene can mask or suppress the effect of another gene, affecting phenotypic outcomes.
• 😀 Polygenic inheritance involves multiple gene pairs interacting to affect a trait, such as the red pigment in flowers, which is determined by more than one pair of alleles.

Q & A

What is the topic of the video discussed in the transcript?

The video discusses the topic of biological deviations from Mendel's laws, specifically focusing on five different types of deviations: Atavism, Cryptomery, Complementary Genes, Epistasis-Hypostasis, and Polymeric inheritance.

What does the term 'Atavism' refer to in the context of Mendel's laws?

Atavism refers to the reappearance of traits that have not appeared for a long time, or the emergence of a phenotype that is different from the parents due to genetic interaction between alleles.

Can you explain the concept of 'Cryptomery' in simple terms?

Cryptomery is when a dominant gene is hidden and does not express its phenotype on its own. It only shows when combined with another gene that activates its expression. For example, the flower color of Linaria maroccana depends on two genes, where one must be present for the color to appear.

What is the key difference between 'Complementary Genes' and 'Cryptomery'?

Complementary Genes involve two different genes that must both be present for a particular phenotype to be expressed, whereas Cryptomery involves a hidden dominant gene that only expresses when combined with a specific gene.

How does 'Epistasis' and 'Hypostasis' affect phenotype expression?

Epistasis occurs when one gene (dominant) masks or overrides the expression of another gene, while Hypostasis refers to a situation where a gene is masked by another dominant gene. Both interactions affect the resulting phenotype in different ways.

What is an example of an 'Epistasis' interaction provided in the transcript?

An example of Epistasis is found in the color of wheat seeds, where the black color (caused by the dominant gene H) masks the yellow color (caused by the gene K). If the wheat has the H gene, it will always be black regardless of the other gene.

What is the phenotypic ratio when two heterozygous individuals are crossed in the case of Atavism?

The phenotypic ratio in the case of Atavism when two heterozygous individuals are crossed is 9:3:3:1.

How does the concept of 'Polymery' work in genetics?

Polymery refers to the interaction between two or more gene pairs that influence a single trait, unlike typical single-gene inheritance. The presence of at least one dominant allele from each gene pair can result in a particular phenotype.

What is the inheritance pattern of flower color in Lathyrus odoratus according to Complementary Genes?

In Lathyrus odoratus, flower color is determined by two genes: one for pigment and one for the enzyme that activates it. If both dominant genes are present, the flower will be purple. If one is missing, the flower will be white or red, depending on other gene interactions.

What is the typical phenotypic ratio when using Polymeric inheritance for flower color?

The typical phenotypic ratio for flower color in Polymeric inheritance is 15:1, where 15 individuals will exhibit the red color and 1 will exhibit white, based on the presence of at least one dominant allele from each of the two gene pairs.