<span>B is the correct answer. Multicellular organisms, as with almost all organisms, begin life as a single cell. The increase in the number of cells can be as a result of cell division or cells combining together. </span>
<span>In the six kingdom classification system bacteria are divided into two kingdoms which are known as Archaebacteria and Eubacteria. The archaebacteria are organisms that can dwell in hostile environments like deep sea vents, hot springs, and salt water; while Eubacteria include organisms that can be harmful to humans because they cause certain kinds of diseases like step-throat and botulism.</span>
Answer:
Explanation:Following are the techniques or methods or approaches we can say that were used by the scientists to determine the geologic age:
1. Relative age dating
2. Absolute age dating.
3. Radiation measurement.
4. Stratigraphic superposition.
5. The fossil record.
The scientists used the method of relative dating to divide Earth's past in different chunks of time when alike organisms were on Earth. After that, to discover the actual number of years ago that events occurred, the scientists used the method of absolute dating.
Answer:
c. YACs
Explanation:
YACs, the Yeast artificial chromosomes are the high capacity vectors designed to carry the eukaryotic genes and carry the insert of 200-2000 kb.
YACs carry origin of replication from yeast, selectable markers and sequences derived from telomeres and centromere to maintain the stability of the insert during cell division.
The insert size for plasmids, bacteriophage, PACs, and cosmids is about 0.1-10 kb, 5-25 kb, 100-300 kb, 35-45 kb respectively.
Answer:
Prophase 1
Explanation:
Prophase I :It can be divided into five stages:
1)Leplotene: In this stage, chromosome becomes visible and shorten as a single structure.
2)Zygotene: Homologous / sister chromosome pair up. This process is known as synapse. Synapse is the process of attachment of homologous /sister chromosome. One pair comes from the male parent while the other comes from the female parent.
3)Pachytene: Bivalents shorten.
4)Diplotene:Point of attachment of non-sister chromatids. The two chromosomes are seen to be joined at several points along their length. These points are known as Chiasmata.(Chiasmata, a cross). The paternal gene A, B, C may swap for the maternal gene a, b, c for instance, leading to a new gene combination in the resulting chromatids. This is referred to as *CROSSING OVER*.
5)Diakenesis: Homologous centromere move apart.
So, crossing over occurs in *Prophase 1.
