Persilangan monohibrid, Latihan Soal

Summary

This video explains the concept of monohybrid crosses, which involve crossing two individuals of the same species differing in a single trait. It relates to Mendel's first law and introduces important terms like parental, dominant, recessive, and intermediate traits. Using the example of red and white roses, the video demonstrates how the dominant trait (red) overpowers the recessive trait (white). The offspring from the first generation (F1) are red, and when these F1 individuals are crossed, the second generation (F2) produces a 3:1 ratio of red to white flowers. The video concludes by encouraging viewers to revisit the material for better understanding.

Takeaways

• 😀 A monohybrid cross is the mating of two individuals from the same species that differ in a single trait.
• 😀 The concept of Mendel's first law is essential to understanding monohybrid crosses.
• 😀 The main terms related to monohybrid crosses include parental, filial, dominant, recessive, and intermediate traits.
• 😀 In a monohybrid dominant cross, the dominant trait will mask the recessive trait.
• 😀 An example of a monohybrid cross is crossing red roses (dominant) with white roses (recessive).
• 😀 The genotypes for red roses (M) and white roses (m) are represented as M (dominant) and m (recessive).
• 😀 The first filial generation (F1) from the red and white rose cross will have the genotype Mm and will appear red because the dominant allele masks the recessive one.
• 😀 When F1 roses are crossed with each other, the resulting second filial generation (F2) will have various combinations of alleles: MM, Mm, and mm.
• 😀 The genotype ratio for the second filial generation is 1 MM : 2 Mm : 1 mm.
• 😀 The phenotype ratio for the second filial generation is 3 red : 1 white because red is dominant over white.
• 😀 This process demonstrates the principles of genetic inheritance, specifically Mendel’s law of segregation, where alleles separate during gamete formation.

Q & A

What is a monohybrid cross?

A monohybrid cross is a genetic cross between two individuals that differ in only one trait, typically involving dominant and recessive alleles for that trait.

How is a monohybrid cross related to Mendel's First Law?

A monohybrid cross is directly related to Mendel's First Law, the Law of Segregation, which states that alleles for a given trait segregate, or separate, during gamete formation, and each gamete carries only one allele for each gene.

What is the role of the 'parental' generation in a monohybrid cross?

The 'parental' generation (P generation) refers to the two original organisms involved in the cross. They carry different versions of the gene for a specific trait, which are passed on to their offspring.

What does 'filial generation' mean?

The 'filial generation' refers to the offspring produced from a genetic cross. The first filial generation is labeled F1, while the second filial generation is labeled F2.

What is the difference between dominant and recessive alleles?

Dominant alleles are those that express their traits even when only one copy is present in an organism (represented by a capital letter, e.g., M). Recessive alleles only express their traits when both copies are present (represented by a lowercase letter, e.g., m).

How does the example with red and white roses illustrate the concept of a monohybrid cross?

In the red and white rose example, red color (M) is dominant and white (m) is recessive. When a red rose (MM) is crossed with a white rose (mm), all F1 offspring are heterozygous (Mm) and display the red color because the dominant red allele masks the recessive white allele.

What is the genotypic ratio in the F2 generation from the cross Mm x Mm?

The genotypic ratio in the F2 generation would be 1 MM (homozygous dominant): 2 Mm (heterozygous): 1 mm (homozygous recessive).

What is the phenotypic ratio in the F2 generation from the cross Mm x Mm?

The phenotypic ratio in the F2 generation would be 3 red: 1 white, since both MM and Mm individuals display the red phenotype, while only mm individuals display the white phenotype.

Why does the F1 generation all have the same phenotype, even though they are heterozygous?

The F1 generation all have the red phenotype because the dominant allele (M) masks the recessive allele (m), so even though the individuals are heterozygous (Mm), the dominant trait is expressed.

Can a monohybrid cross include intermediate traits?

While this example does not show intermediate traits, it is possible for a monohybrid cross to involve intermediate inheritance. This occurs when neither allele is completely dominant, leading to a blending of traits, but this concept was not emphasized in the provided script.