The countercurrent heat exchanger that prevents arterial blood from overheating the testes is the pampiniform plexus of veins. The pampiniform plexus helps to regulate testicular temperature, allowing sperm maturation. It surrounds the testicular arteries and works as a countercurrent heat-exchanger system to cool the arterial blood before entering the testes. This is because the sperms can not develop if the testis is at body temperature.
Answer: Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).
By the end of meiosis, the resulting reproductive cells, or gametes, each have 23 genetically unique chromosomes. The overall process of meiosis produces four daughter cells from one single parent cell.
Explanation:
During meiosis, homologous chromosomes (1 from each parent) pair along their lengths. The chromosomes cross over at points called chiasma. At each chiasma, the chromosomes break and rejoin, trading some of their genes. This recombination results in genetic variation.
Answer:
The correct answer is A.) during transcription
Explanation:
The pairing during DNA replication and transcription is a little bit different. During replication, A pairs with T, T with A, C with G, and G with C. In transcription T is replaced by U so when there is nucleotide adenine is present in the DNA sequence than uracil will be added against it as complementary nucleotide in mRNA during transcription.
So here 5'-GAT-3' nucleotide sequence is present in DNA and after transcription the nucleotide sequence will be 5'-CUA-5' because U is added against A during transcription. Therefore the correct answer is A.
Answer:
<em>Liver is the </em><em>l</em><em>argest gland in human body</em><em>.</em>
