Monohibrid (Hukum Mendel 1)

Summary

In this educational video, the host explains Mendel's laws of inheritance with a focus on monohybrid crosses. Using the example of flower color in pea plants, the video demonstrates how dominant and recessive traits are inherited through generations. The host covers key concepts such as genotype, phenotype, and the resulting ratios of traits in offspring. Practical examples, including human hair texture and pea plant flower color, illustrate the process of predicting genetic outcomes. The video concludes with a brief introduction to more complex inheritance patterns like intermediate inheritance and codominance.

Takeaways

• 😀 Monohybrid cross involves the breeding of organisms with a single trait difference.
• 😀 In a monohybrid cross, 'dominant' traits are represented by uppercase letters, and 'recessive' traits by lowercase letters.
• 😀 The F1 generation resulting from a cross between two pure-bred plants (e.g., purple and white flowers) will show the dominant trait, with all offspring being heterozygous.
• 😀 In the second cross (P2), the F1 generation individuals are crossed with each other to produce four possible genotypes and two phenotypes.
• 😀 The phenotypic ratio of the second cross in a monohybrid cross is 3:1 (dominant trait to recessive trait).
• 😀 The genotypic ratio of the second cross is 1:2:1 (homozygous dominant: heterozygous: homozygous recessive).
• 😀 The probabilities of obtaining different phenotypes in a monohybrid cross can be calculated, with 75% expressing the dominant phenotype and 25% the recessive phenotype.
• 😀 A real-life example of monohybrid inheritance is the inheritance of curly vs. straight hair in humans, where curly hair is dominant.
• 😀 A cross between two individuals with curly hair, where both are heterozygous, can result in offspring with either curly or straight hair.
• 😀 A different example from plants shows that purple flower color in peas is dominant over white, and the F2 generation can be used to calculate the resulting phenotypic and genotypic ratios.

Q & A

What is a monohybrid cross?

A monohybrid cross is a genetic cross between two individuals that differ in only one trait, such as flower color or hair texture.

What does the term 'dominant' mean in Mendelian inheritance?

Dominant traits are those that are expressed in the organism even if only one allele is present. They are denoted by uppercase letters (e.g., 'U' for purple flowers).

What is a recessive trait?

A recessive trait is one that is only expressed if both alleles for that trait are recessive. These traits are denoted by lowercase letters (e.g., 'u' for white flowers).

What is the phenotypic ratio of a monohybrid cross between two heterozygous individuals?

The phenotypic ratio of a monohybrid cross between two heterozygous individuals (e.g., Uu x Uu) is typically 3:1, where 3 offspring show the dominant phenotype and 1 shows the recessive phenotype.

What is the genotype of F1 offspring in a cross between a purebred purple flower (UU) and a purebred white flower (uu)?

The genotype of F1 offspring from a cross between a purple flower (UU) and a white flower (uu) will be Uu, as the dominant purple allele (U) will be inherited from the purple parent.

What is the expected genotypic ratio in the F2 generation of a cross between two F1 individuals (Uu x Uu)?

The genotypic ratio in the F2 generation of a Uu x Uu cross is 1 UU, 2 Uu, and 1 uu, where UU and Uu represent the dominant purple phenotype and uu represents the recessive white phenotype.

How does Mendelian inheritance apply to human traits like hair texture?

Mendelian inheritance applies to human traits such as hair texture, where curly hair (C) is dominant over straight hair (c). A cross between two heterozygous curly-haired individuals (Cc) can produce both curly and straight-haired offspring.

What is the phenotypic ratio of offspring from a cross between two heterozygous individuals for curly hair?

The phenotypic ratio of offspring from a cross between two heterozygous curly-haired individuals (Cc x Cc) is 3 curly-haired to 1 straight-haired.

What happens when a purple flower (UU) is crossed with a white flower (uu)?

When a purple flower (UU) is crossed with a white flower (uu), all the F1 offspring will be purple (Uu) because the purple allele is dominant over the white allele.

How does a Punnett square help in understanding inheritance?

A Punnett square is a tool that helps predict the possible genetic outcomes (genotypes) of offspring from a cross, showing the probability of different traits being inherited.