Nilai Pindah Silang Genetika dan Peta Kromosom I BAB POLA HEREDITAS

Summary

This video tutorial explains the process of crossing over in biology, where chromatids from homologous chromosomes exchange genetic material. It covers the concept of recombinant chromosomes, which result from this genetic exchange, and provides examples such as corn crosses with smooth yellow and wrinkled white traits. The video also demonstrates how to calculate recombination frequencies using real data, explaining the formulas for determining recombination percentages and parental versus recombinant combinations. Finally, the tutorial introduces chromosome mapping, showing how gene distances are calculated using centimorgans and recombination frequencies, ultimately enhancing understanding of genetic variation.

Takeaways

• 😀 Crossing over refers to the exchange of chromatids between homologous chromosomes during meiosis.
• 😀 Homologous chromosomes have the same structure, size, and genetic content, including genes such as Gene A and Gene C.
• 😀 A chromosome consists of two chromatids, and crossing over involves swapping sections of these chromatids.
• 😀 Crossing over results in recombinant chromosomes, which are combinations of genes from both parents.
• 😀 The formula to calculate the crossing over percentage (Recombinant Percentage) is: (Number of recombinant offspring / Total offspring) * 100%.
• 😀 In a genetic experiment with corn, the recombinant phenotypes (smooth yellow and wrinkled white) total 450, while the parental phenotypes total 6070.
• 😀 Recombinant offspring percentages are calculated as 6.9%, while the parental phenotype percentage is 93.1%.
• 😀 The concept of a chromosome map is introduced, which measures the distance between loci on a chromosome in centimorgans (cM).
• 😀 One centimorgan (cM) corresponds to a 1% recombinant frequency (RF), and the distance between genes can be calculated based on this.
• 😀 In a scenario with genes A and B, the distance between them is 2 cM, which corresponds to a recombinant frequency of 2%.
• 😀 The formula for calculating the chromosome map distance is: (100% * Recombinant frequency) = Parental Percentage, leading to a result of 98% parental phenotype in the example given.

Q & A

What is the main concept discussed in the video?

The video discusses the concept of 'pindah silang' or crossing over, which involves the exchange of genetic material between homologous chromosomes during meiosis, contributing to genetic variation.

What are homologous chromosomes?

Homologous chromosomes are chromosome pairs that have the same structure, size, and genetic content. They carry genes for the same traits but may have different alleles.

What is the difference between chromosomes and chromatids?

A chromosome consists of two chromatids joined at the centromere, while a chromatid is one half of a chromosome, which becomes visible during cell division.

How does crossing over contribute to genetic variation?

Crossing over results in recombinant chromosomes, where segments of chromatids from homologous chromosomes are exchanged, leading to new combinations of genes and increasing genetic diversity.

What are recombinant chromosomes?

Recombinant chromosomes are chromosomes that have undergone crossing over and contain a mix of genetic material from both parent chromosomes.

What is the formula for calculating recombinant percentage?

The formula for calculating recombinant percentage is: (Number of Recombinant Offspring / Total Number of Offspring) × 100.

In the corn example, which phenotypes are considered recombinant?

In the corn example, the recombinant phenotypes are smooth white and wrinkled yellow, as they differ from the parent phenotypes.

What is the meaning of the term 'centimorgan' in chromosome mapping?

A centimorgan (cM) is a unit of measurement used in chromosome mapping. It represents the distance between genes where there is a 1% probability of recombination occurring.

How is the distance between genes measured in chromosome mapping?

The distance between genes in chromosome mapping is measured in centimorgans, based on the frequency of recombination between them.

How do you calculate the parental combination percentage (KP) in chromosome mapping?

The parental combination percentage (KP) is calculated as: 100% - Recombinant Percentage (RK). For example, if RK is 2%, KP would be 98%.