Watson and Crick create the DNA model
Watson And Crick with their double helix model.
In the 1950s, James Watson and Francis Crick started to be convinced that DNA was a helix. They began to make models of DNA out of scrap metal and wire. This model was correct and the double helix model is still used today. The Structure of the double helix is made from two phosphate-sugar chains going in opposite directions and paired bases inside.
In 1950, Erwin Chargaff realized two very important things about DNA. He made two rules for DNA from this discovery. Chargaff's First Rule is that the number of thymine and adenine as well as the amount of cytosine and guanine are the same in DNA. Chargaff's Second Rule is that based on the species, the proportion of adenine and guanine are different.
How do base pairs bind?
The base pairs in DNA bond using hydrogen bonds. The base of each nucleotide within a strand bonds with a suitable partner on the other strand.A to T and G to C are the only bonding pairs on all types of DNA.
What is a chromosome?
A chromosome is a structure that holds DNA and its assorted proteins. This carries part or all of the genetic information for the cell. Chromosomes have such an effect on the cell that normally there are 23 chromosomes in the nucleus. Some people develop a second copy of the 21st Chromosome, and thus suffer from down-syndrome as an effect. A histone is related to the Chromosome because it is a protein that organizes eukaryotic chromosomes. A nucleosome is a length of DNA wound twice around the histone proteins. When cells divide, a chromosome duplicates. Each species has a characteristic for the number of chromosomes they should have. As stated before, going higher or lower can effect the development of the species.
What is a karyotype?
A karyotype is an image of a certain indviidual's diploid set of chromosomes. For Humans, this would be an image of both of their sets of 23 chromosomes.