Environment guide

There are four phases in cell division, or mitosis (normal cell division, meiosis forms sex cells).

Prophase: Pairing of chromosomes occurs and following replication, the parent cell has two complete sets. Two poles are formed as the nucleus disappears.

Metaphase: Alignment of the chromosomes is at the equator between the two poles.

Anaphase: The chromosomes split up towards each pole. Cell membrane division begins.

Telophase: Appearance of nuclei is at each pole and membrane divides. Two cells possess identical chromosomes.

DNA Replication

The DNA composition where two separate strands store all genetic information, replicate easily. A DNA molecule has a polymer opposite of the other, like a photonegative. One side enables the other to be recreated. This duality simplifies copying a DNA molecule remarkably.

Replication causes synthesization of DNA molecules. First a helicase enzyme unwinds the double helix, at any point on the strand, progressing to two replication forks by enzymes extending the helix release in both directions. With unwinding and straightening out of the DNA, DNA polymerase, another enzyme functions. It matches the exposed nitrogenous bases with new nucleotides from the surrounding nuclear fluid. The nucleotides and separated polymers fuse as per the regular Watson-Crick pairing rules. The completion of the separation and re-matching of the DNA molecule makes two perfect copies.

DNA replication remains partially unknown. Signals that start the process, the reason some cells don’t replicate and the cause of uncontrollable replication of cancerous cells remain unexplained.

Replication in Prokaryotes

Prokaryotes or bacteria store almost the entire genetic information of an organism in a single large circular DNA ring and not in multiple chromosomes of DNA strings with unconnected ends. This replication is almost identical to eukaryotic DNA except in the use of only two replication forks. Eukaryotes and prokaryotes differ, with multiple replication sites active simultaneously in the former and the speed of the latter requiring only two, one for each direction The rate of replicating bacterial DNA is almost one million base pairs per minute whereas the average is 500 to 5000 pairs for other organisms.

DNA Replication is Semi-Conservative

On completion of the replication process, two DNA molecules result, which are identical both to each other as well as to the original. There is not the slightest alteration in each strand of the original molecule due to its role as the template for the synthesis of a complementary strand. This replication method has been termed semi-conservative; as one half of each new DNA molecule is old while the other half is new.

Finally…

The need for DNA replication or cell genome duplication is created by each cell division. As with all cellular activities, specialized proteins are needed for the purpose of replication. DNA replication is surprising as a process in all organisms except in the case of humans where comprehension can prove very complex.

Learn more about

Cell Biology and DNA replecation , visit http://www.biology-online.org]]>

In a natural scenario, the conception of a baby occurs when the ovum, travels from the ovaries, through the fallopian tube to be fertilized by the sperm of the father during sexual intercourse. From this point on, the fertilized egg will travel down towards the uterus and during the process division of cells will occur until it reaches its final destination at the wall of the uterus. However, in the cases of block fallopian tubes, the eggs are unable to travel from the ovaries to the uterus and conception cannot happen.

Developed in the United Kingdom by Dr. Patrick Steptoe and Dr. Robert Edwards, the process of in-vitro fertilization involves removing eggs from the ovaries of the mother and combining them with the sperm of the father in a lab environment. The fertilized egg is then placed back into the uterus of the mother after 3 to 5 days and will remain there to grow till birth. Because of the low success pregnancy rate of this procedure, a few eggs are placed in the uterus to increase the odds of success. With this process, statistics have shown that the rates of multiple births have increased where 24 percent of the in-vitro fertilization births have produced twins.

The first test-tube baby, Louise Brown, who was born on the 25th July 1978, marked hope for other infertile couples to have a baby through this procedure. However, many others were concerned about the ethical issues surround this. One major area of concern was the fact that as the egg is located outside the womb for a few days while the cells multiplied before being put back inside the uterus, the health issues affecting this baby is unknown. Indeed, research has been shown that test-tube babies have a higher chance of birth defects and low birth weight, and researchers still have not been able to determine the reason for this.

Other issue of concern is that through this procedure, some of the eggs fertilized in the lab are later discarded. Does this procedure mean that the researchers are actually killing potential people? How is the line drawn in this case?

Then there is also the issue of commercial opportunities for eggs and sperms to be bought and surrogate wombs to be rented with the purpose of creating babies. This process of embryo transfer to another mother, not necessarily the same woman who had provided the eggs, is known as placing the embryo in a gestational carrier. This procedure has been becoming increasingly common through technological advancement, which has made couples including women with uterus problems, have a chance in having their baby.

Test-tube babies have really brought changes to the way in which babies are conceived and have given much hope to many who have had problems having babies through the process of . However, the downside of this are the ethical issues behind the procedure, with which still poses a big question mark and with which is still opposed by many factions.For more details on cell,

molecular and human biology

please visit http://www.biology-online.org/tutorials/1_cell_biology.htm]]>

What is elearning? Elearning refers to any education that you receive electronically whether it is through the Internet or from a software program. Elearning is sweeping the nation because it has become affordable and is easy to access from the comfort of your own home. Plus, you can work on your own schedule. You don’t have to worry about hiring a babysitter while you head off to class. The class comes to you through your computer when you have an hour or even minutes to spare during your hectic day.

Elearning began through various software programs available for your computer. You just popped in a disk or CD-rom into your computer and you were set to go. You could practice your typing skills at home and your children could practice their math skills through computer drills and games. This type of learning provided extra practice for your child. The software programs increased in number, but you were still limited to interacting only with the disk or CD-rom. You didn’t have access to the software program’s creator or additional resources to peruse through at your leisure.

Internet based elearning programs stepped in to fill these needs. Elearning on the Internet allowed users to break the confines of their personal computer and interact with the global community. The options to connect with the course creator/teacher, fellow students, and have live class discussions were now available. Additional resources for exploration and study are endless with the use of the Internet as an educational tool. Therefore, the growth rate of elearning has skyrocketed since the Internet has become a daily resource for many users.

Elearning contains so many different levels of interest. More in depth courses are provided at a cost, while free courses are also available. Users should take advantage of the elearning opportunities available on the Internet. You can start by typing your topic of interest in an Internet search engine. You will most likely find a course that suits your needs.]]>