Answer: Crossing-over allows the genes that come from each parent to recombine before they are passed on to future generations because chromatids of homologous chromosomes mate and exchange sections of their DNA.
Explanation:
Chromosome crossing-over is the process by which chromatids of homologous chromosomes mate and exchange sections of their DNA during prophase I of meiosis, when pairs of homologous chromosomes, or of the same type, are aligned. The chromatids of the homologous chromosomes break off in the chiasmas and rejoin to allow recombination of the linked genes. So it occurs when regions at chromosome breaks mate and then reconnect to the other chromosome. <u>The result of this process is an exchange of genes, called genetic recombination</u>.
This allows the genes that come from each parent to recombine before they are passed on to future generations. Then, <u>it is an important source of genetic variability</u>, since it involves an exchange of segments between homologous chromosomes during the development of gametes. <u>This process allows that the descendants of an individual are genetically very different</u>, since it is very unlikely that an individual produces two equal gametes, because all of them have different segments of the homologous chromosomes.
Answer:
The light from Alpha Centauri system takes 4.37 light-years and Sirius star system takes 8.6 light-years to reach the Earth.
Explanation:
Light from millions of stars in more distant galaxies takes a long time to reach the Earth. Light travels at a speed of 300,000 kilometers per second. The time taken for light from these stars to reach the Earth is the distance to the star divided by the speed of the light. The distance traveled by light in one year is known as a light year and the distance to the stars that are farther away is expressed in light years.
The Sun is the closest star to the Earth and the sunlight takes about 8.3 minutes to reach on Earth. Apart from the Sun, the other stars closest to Sun include Alpha Centauri system and the Sirius star systems.
The Alpha Centauri system includes the stars Alpha Centauri A, Alpha Centauri B and Proxima Centauri. This system is 4.37 light-years away from the Earth. The third star, Proxima Centauri is 4.24 light-years away from the Earth i.e., the light from it takes 4.24 years to reach the Earth.
The Sirius star systems include Sirius A (Dog Star) and Sirius B. It is about 8.6 light years from Earth and so the light about 8.6 years to reach the Earth.
d) recessive, alleles, dominant, homologous.
Homologous is when organisms have the similar structures.
Dominant that means the child inherited the dominant gene.
