Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
The answer is a beaker.
~ThePirc
Answer: Option B.
Neural crest and peripheral nervous system.
Explanation:
Neural crest are bilateral paired cells of the neural tube that arise from the ectoderm layer of the embryo. Thesescells move to different part of the body and differentiate into various cell types like melanocytes,cartilage and bone, smooth muscle, craniofacial, neurons, gangalia e.t.c. The neural crest running through neural tube develop into peripheral nervous system after birth. Peripheral nervous system consist of neurons and gangalia outside the nervous system The peripheral nervous system connect the central nervous system to organs, skin and limbs.
1) RNA polymerase finds the promoter sequence on DNA.
2)RNA polymerase reads the DNA and builds complementary sequence.
3) Intron séquences are spliced out and exons are joined together.
4) The ends of the mature transcript are protected before it leaves the nucleus.
5) The mRNA attachés to the ribosome.
6) transfer RNA arrives at the ribosome and the anticodon complements to the mRNA codon.
7)amino acids form peptide bonds as tRNA molecules match the mRNA.
Planting the same crop in the same place each year zaps nutrients from the earth and leaves soil weak and unable to support healthy plant growth. Because soil structure and quality is so poor, farmers are forced to use chemical fertilizers to encourage plant growth and fruit production.
