What is the significance of DNA replication?

Question

can someone help me answer that what i got is to vague i think...



... this is what i have so far...
In sexual reproduction half the genetic information from each parent cell is passed to the offspring.
All information for the structure and chemistry of an organism is contained within this sequence of genes.


and thts supposed to get me two marks :S :( help me please :)

Answer 1

In sexual reproduction half the genetic information from each parent cell is passed to the offspring. = through a chromosome set: “Human cells have 23 pairs of large linear nuclear chromosomes, giving a total of 46 per cell which composes the human genome.”

All information for the structure and chemistry of an organism is contained within this sequence of genes. = A genome is the collection of possible chromosome matches. The chromosomes are formed out of DNA and the units of DNA are called genes. So when various chromosomes match up the DNA strands combine and the genes form new pairs and new sequences. Each sequence is a subroutine in the instruction code to create the organism. For example one gene sequence determines how the liver is formed, but only one gene itself holds the instructions for the color of your eyes. The more complex the more genes needed, or so you would think. We share over 90% of the same genes as that of the great apes. What makes us different is the little details on how those genes combine. For example the great apes have more hair than humans do and modern humans have less hair than Stone Age humans did. A subtle change in the formation of the hand gives us opposable thumbs and other subtle changes have us walking upright and growing bigger brains. As a species we are getting taller as we eat a better diet, this means that the potential was always locked in our genes it just took a better diet to bring it out.

DNA is the key to sexual reproduction and it does so by forming itself as paired chemical bonds and then splitting in half (almost like a zipper unzipping) to create two identical strands; do this enough times and you have the instructions to form a whole lot of cells.

When a sperm hits and egg they are two cells that become one. The chromosomes from each one combine inside the nucleus of the egg cell and form a complete copy of the directions on how to create that life form. Now the egg cell can divide, and it keeps dividing and forming new copies of itself until the instructions encoded in the DNA tell them to change and to do other things; like form a brain or a face, and to stop at a specific point. The DNA pattern holds the instructions to create a cell just like computer code holds the instructions to create and run a computer program.

Without DNA sexual reproduction won’t work. Asexual reproduction creates a clone of the original; only sexual reproduction combines the two sets of chromosomes to form a NEW but SIMILAR creature. This is why you are not a carbon copy of your parents, but you have some of their traits. Not only that but DNA is much more complicated since it has recessive genes. The most famous of these are the genes that cause Hemophilia; an inability for the blood to clot. The royal families of Europe had this gene and by continued inbreeding the trait kept reappearing. As a descendent of that royal line Prince Charles may have that recessive gene. By marrying a commoner; Princess Diana he insured that the gene would remain recessive and not both his sons. The gene is only expressed; used to create the organism, with both sets of chromosomes have the same recessive gene. The taboo against marrying any closer than a second cousin is based on this idea, continued breeding like this only magnifies the faults in a blood line.

Evolution is dependant on sexual reproduction because there is much more possibility for variance in the organism. Asexual reproduction only has a change introduced when an error is made in copying a cell; usually this is harmful like cancer. Sexual reproduction allows a shuffling of the genes to try and produce a variation that might succeed better in life; this is the heart of evolution.

According to Wikipedia: http://en.wikipedia.org/wiki/Chromosomes
“Chromosomes are the organized form of DNA found in cells. Chromosomes contain a single continuous piece of DNA, which contains many genes, regulatory elements and other intervening nucleotide sequences. A broader definition of "chromosome" also includes the DNA-bound proteins which serve to package and manage the DNA…

The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes; the region of the chromosome at which a particular gene is located is called its locus. A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded.”

According to Wikipedia: http://en.wikipedia.org/wiki/DNA
“Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.”

According to Wikipedia: http://en.wikipedia.org/wiki/Genes
“A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions. The physical development and phenotype of organisms can be thought of as a product of genes interacting with each other and with the environment. A concise definition of gene taking into account complex patterns of regulation and transcription, genic conservation and non-coding RNA genes, has been proposed by Gerstein et al. "A gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products".”

Answer 2

Mitosis? here are the processes of chromosome division. which is dna Prophase- spindle fibers are visible, and chromosomes too. nuclear envelope starts to disappear. Metaphase-Chromosome line up in the middle spindle fiber attact and the break apart and go towards the "poles" of the cell. Anapahse- chromo. go to both sides and the the nuclear envelope starts to re-appear. Telophase- you can see nuclear envelope and it seperates into 2 daughter cells Cytokinsis(sp?)- when the 2 daughter cells fully seperate into 2 seperate cells