<u>Answer:</u>
During Meiosis I the cell transform from diploid cell to haploid and ends after Telephase I.
<u>Explanation:</u>
The one and only purpose of Meiosis is to produce gametes-sex cells or sperm and eggs in the human body. The objective is to make daughter cells with precisely half the same number of chromosomes as the starting cell. In humans, meiosis is a cycle of division that .allows cell transformation from a diploid cell (one with two sets of chromosomes) to haploid cells (one with one set of chromosomes).
Their is a two-step division cycle in meiosis. During the first round of cell division, homologue pairs divide, called meiosis I. During a second round, sister chromatids split, called meiosis II. As the cell division during meiosis occurs twice, one starting cell can produce four gametes (eggs or sperm). Cells pass through 4 stages in each round of division like prophase, metaphase, anaphase, and telophase. The cycle can be understood as follows:
<u>Meiosis I: </u> Before entering meiosis I, a cell must under go an interphase. The meiosis-I involve prophase-I , metaphase-I , anaphase-I and telophase-I. The starting cell is diploid (2n=4)
- during prophase-I homologous chromosomes pair-up and exchange fragments called as "crossing over".
- during metaphase-I homologue pairs line up at the metaphase plate.
- during anaphase-I homologues separate to opposite ends of the cells and then sister chromatids stay together.
- during telophase-I the chromosomes reach at opposite poles of the cell and result each chromosome has two sister chromatides, non identical in nature.
- Finally the newly forming cells are "haploid" i.e n=2.
the complement system is a group of proteins in the blood that attack pathogens that enter the body and kill them.
1590: Jansen was a Dutch spectacle-maker. He continued to the cell theory because he made the microscope that all future scientists used to see cells. Also, he was the first creator of a compound microscope, the accomplishment is dated around 1590. When he invented the microscope it eventually lead to making other inventions used today
1660: Robert Hooke discovered the cell. When Hooke first saw it he called them cells and the name still stuck. He didn't know the real structure or function of the cell when he first discovered it. This helped scientist bc he discovered the basic unit all the other scientist have to just go deeper into his study
1674: He was a Dutch tradesman and scientist, best known for his work on the development and improvement of the microscope. Anton van Leeuwenhoek is another scientist who saw these cells soon after Hooke did. He made use of a microscope improving lenses that could magnify objects even more.
1838: He proved that all living things are composed of cells and cell products. With the help of schleiden they both concluded that plants are made up of cells. This showed that everything was made up up cells which helped prove what the other scientist had to say
1839: Schleiden found that all plants are composed of cells. He also stated that the different parts of the plant organism are composed of cells.This help scientist know that there are more than one type of cells so they will keep trying to find other cells leading them to more information
1855: He stated that not all plants are made up of cells ,which eventually leads to the creation of the cell theory. This lead to many scientist trying to prove which is right and wrong, leading to many more discoveries to come.
Answer:
Patent ductus arteriosus (PDA) is an extra blood vessel found in babies before birth and just after birth.
Explanation:
The ductus arteriosus is a normal blood vessel that connects two major arteries — the aorta and the pulmonary artery — that carry blood away from the heart.
The lungs are not used while a fetus is in the womb because the baby gets oxygen directly from the mother's placenta. The ductus arteriosus carries blood away from the lungs and sends it directly to the body. When a newborn breathes and begins to use the lungs, the ductus is no longer needed and usually closes by itself during the first 2 days after birth.
If the ductus doesn't close, the result is a patent (meaning "open") ductus arteriosus. The PDA lets oxygen-rich blood (blood high in oxygen) from the aorta mix with oxygen-poor blood (blood low in oxygen) in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.
