Answer:
Microfilaments, Intermediate filaments and microtubules
Explanation:
Three distinct elements make up the cytoskeleton in eukaryotic cells are:
1. Microfilaments or actin filaments which are composed of actin proteins. The functions of those filaments are: muscle contraction (myosin heads move “walk” on actin filaments), the movement of the cell, intracellular transport, maintaince of the cell shape..
2. Intermediate filaments which can be made of vimentins, keratin, lamin, desmin… Their functions are: the maintenance of cell shape, anchoring organelles, structural components of the nuclear lamina, cell-cell and cell-matrix junctions…
3. Microtubules are filaments polymers of alpha and beta tubulin. Their roles are in intracellular transport (associated with motor protein dyneins and kinesins), formation of the axoneme of cilia and flagella, formation of the mitotic spindle.
Answer:
B
Explanation:
DNA replication is semiconservative- meaning the old template strand will form a double helix with the newly synthesized strand. The DNA polymerase can only replicate DNA in the 5’ -> 3’ direction on a DNA strand. However, because the two strands of a DNA double helix run antiparallel (and they are replicated together), then during replication, one strand will be oriented in the opposite direction (i.e 3’ -> 5’ direction).
Because DNA polymerase requires a primer to begin replication, the leading strand will require one primer, because replication on this strand occurs continuously. On the lagging strand, many primers are required because replication is done piecemeal forming fragments called Okazaki fragments. The fragments are later joined by DNA ligases.
Answer:
The stem cells was discovered by Ernest McCulloch and James Till in 1981. Studies conducted for stem cells can be used for bone marrow transplantation and to treat various diseases.
Explanation:
Stem cell are the cells that has the ability to differentiate into different cells of the body. In 1978 human cord blood discovered as stem cell. The stem cell research come to known in 1981.
Ernest McCulloch and James Till discovered the stem cell research while working on the mice bone marrow. He found that the different blood cells were formed by the single class of cells.
Experiments on mice and other animals have been conducted to study the stem cells so far. The study of stem cell is useful to cure the genetic defects, Cancer and other harmful diseases.
