Correct answer:
"<span>B- homologous chromosomes join together to form tetrads during prophase I"
</span>It is during prophase I that homologous chromosomes join together (<span>synapsis)</span> and form tetrads - four chromatids are together in the new structure of two chromosomes - and this is the reason why crossing-over occurs in this phase. It is in this tetrad that both arms of both chromosomes may crossover and matching regions exchange places. This process results in homologous chromosomes recombination leading to genetic variability.
Answer:
Lack of oxygen
Explanation:
There are two mechanisms for energy production (glucose breakdown), aerobic and anaerobic. When adequate amounts of oxygen are present, aerobic mechanism is used. However, when there is insufficient oxygen, such as during exercise, the anaerobic mechanism is used.
