Question

Что такое кроссинговер? Какой опыт дал возможность его определить?​

Answer 1

Объяснение:

процесс обмена участками гомологичных хромосом во время конъюгации в профазе первого деления мейоза, которое происходит, например, при образовании гамет или спор. Помимо мейотического, описан также митотический

Частота кроссинговера определяется на основе результатов анализирующего скрещивания. Процент кроссинговера рассчитывается как отношение числа кроссоверных особей Fа (т. е. особей с новыми сочетаниями родительских признаков) к общему количеству особей этого потомства (в %).

Answer 2

What is a crossing over?

Crossing over is a genetic process that occurs during meiosis, the cell division process that produces gametes (sperm and egg cells). During crossing over, homologous chromosomes exchange genetic material, resulting in the recombination of genes. This process contributes to genetic diversity by creating new combinations of alleles on chromosomes.

How does crossing over occur?

Crossing over occurs during the prophase I stage of meiosis. During this stage, homologous chromosomes pair up and form structures called bivalents or tetrads. Within the bivalents, the chromatids of the homologous chromosomes align closely and undergo physical exchange of genetic material. This exchange is facilitated by the formation of chiasmata, which are points of contact and crossover between non-sister chromatids of homologous chromosomes.

The exchange of genetic material between non-sister chromatids results in the swapping of genetic information. This process leads to the creation of new combinations of alleles on the chromosomes, contributing to genetic variation.

What is the significance of crossing over?

Crossing over is a crucial process in meiosis because it promotes genetic diversity. By shuffling genetic material between homologous chromosomes, crossing over creates new combinations of alleles. This genetic variation is important for the survival and adaptation of species.

The significance of crossing over can be observed in several ways:

1. Increased genetic diversity: Crossing over generates new combinations of alleles, increasing the genetic diversity within a population. This diversity provides a wider range of genetic traits that can be selected for in changing environments.

2. Recombination of linked genes: Crossing over allows for the recombination of genes that are located close to each other on the same chromosome. This breaks up the linkage between genes and can lead to the production of new combinations of traits.

3. Evolutionary advantage: The genetic variation created by crossing over provides the raw material for natural selection to act upon. It allows for the adaptation of populations to changing environmental conditions and the evolution of new species.

How was crossing over discovered?

The discovery of crossing over can be attributed to the work of several scientists, including Thomas Hunt Morgan and Alfred Sturtevant. In the early 20th century, Morgan and his colleagues conducted experiments using fruit flies (Drosophila melanogaster) to study the inheritance of traits.

Through their experiments, Morgan and Sturtevant observed that certain traits that were thought to be inherited together actually showed independent assortment. This led them to propose the concept of crossing over as a mechanism for the recombination of genes during meiosis.

The experimental evidence for crossing over came from the observation of recombinant phenotypes in offspring. Recombinant phenotypes are traits that differ from those of the parental generation due to the exchange of genetic material between homologous chromosomes.

Overall, the discovery of crossing over provided a better understanding of the mechanisms of inheritance and genetic variation, contributing to the field of genetics as a whole.