Answer:
a) Mitotic metaphase
8 picograms
b) a primary oocyte (metaphase)
8 pecograms
c) a secondary oocyte (metaphae)
4 pecograms
d) a first polar body (metaphase)
4 pecograms
Explanation:
a) In mitotic phase the chromosome numbers remains same as 8 because in this phase duplicated chromosomes align in center and separate to other poles. Therefore the amount of DNA will be 8 pecograms.
b) after the mitotic meta phase the cells divide into daughter cell with equal proportion of DNA which means each cell have 8 chromosomes. therefore they both contain 8 pecograms of DNA. The new daughter cells called as primary oocytes.
c) These primary oocytes (8 chromosomes) divides into two secondary oocyte each contain 4 chromosomes which means each cell have 4 pecograms of DNA.
d) Duplication of chromosomes occur in secondary oocyte and cell divides into polar body (4 chromosomes) and ovum (4 chromosomes). Therefore first polar body have 4 pecograms of DNA in it.
See the attachment for clarification.
Answer:
The semilunar valves prevent backflow of blood into the ventricles.
Explanation:
The semilunar valves are valves found at the junction between the left ventricle and the aorta and also between the right ventricle and the pulmonary artery. They are cup-like in shape and prevent blood from flowing back into the ventricles which are the pumping chambers.
There are two types of semilunar valves. The aortic semilunar valves and the pulmonary semilunar valves. They are made up of the endocardial and connective tissue.
The closure of the semilunar valves causes the second heart sound detected on the stethoscope.
Diseases that arise from the semilunar valves are caused by its stenosis which is the narrowing of the valves and regurgitation where the heart valves can no longer hold firm enough to prevent the backflow of blood.
Answer:
The smallest particle is the electron (option D).
Explanation:
The electron is a subatomic particle, which is part of an atom and has a negative electrical charge.
Electron is a small particle, if compared to protons -electrically positive particles- whose size is about 1800 times bigger. In fact, the electron is the smallest particle inside the atom.
<em> According to this, the other options, </em><u><em>atom</em></u><em>, </em><u><em>nucleus</em></u><em> and </em><u><em>proton</em></u><em> are structures larger than an electron.</em>