Chaptepr 8 Vincent afrrunti

James Watson and Francis Crick

James Watson and Francis Crick

James Watson and Francis Crick are the first two scientists that put together the model of DNA (deoxyribonucleic acid). The structure that they put together and discovered is known as a double helix. These men, Watson and Crick, were assisted by Rosalind Franklin. Although, sadly, she died of cancer before Watson and Crick were credited with this discovery, so some do not consider her to be part of the discovery.

Erwin Chargaff

Ghargaff Rule

The chargaff rule has two critical parts. The first, "the amounts of thymine and adenine are identical, as are the amounts of cytosine and guanine (A = T and G = C)." The second, "DNA of different species differs in its proportions of adenine and guanine." This means that the different molecules should have a 1:1 ratio, and the only accepting to that is the amount of adenine and thymine are equal. This is found is both DNA strands

How the bases of helix's bond

How do the base pairs bind?

The base pairs bond with hydrogenation bonds, which aren't exactly bonds, but more like attractions, keep them close but not too tight. These hydrogen bonds or attractions are internally positioned. The other way they bond is with support to Chargaff's first rule (A to T and G to C)


What is a chromosome?

A structure that consists of DNA and associated proteins. These carry parts or all of the cells genetic information. They are organized by histones and nucleosomes. Each chromosome consists of exactly one DNA molecule. When a cell prepares to divide, it also divides te chromosome into two parts by DNA replication. After the duplication, each DNA now consists of two DNA molecules.


What is a karyotype?

A karyotype is "an image of an individual’s diploid set of chromosomes." This means that these a their number will determine the physical appearance of a thing.

DNA replication

How does DNA replicate?

First, this process is when a chromosome duplicates its chromosome before division is called DNA replication. Enzymes break the hydrogen bonds that hold the bases of the double helixs and begin to unwind the DNA. While it is unwinding, it separates. Another enzyme constructs primers which are short single strands of nucleotides. Primers serve as the points at which polymerase go, which is the enzymes the assembled new strands of DNA. The establishment of base-pairing between two strands of DNA is called nucleic acid hybridization. After this, they attach and begin DNA synthesis. Each attacked strand provides its own energy for this. After they are formed, they grow and this process repeats to create more.


What damages DNA?

What damages DNA is a mess up during the DNA replication. For example, the wrong base can be added to the wrong strand of DNA during mutation, or, a nucleotide can get lost or slip in. Most of these occur because polymers work very fast, but they go over their work before they proceed, and, thankfully, most of the time the mistake is caught and the process of the replication or DNA synthase is reversed and corrected. But, the most harmful damage comes from the following: Ionizing radiation from x-rays, most UV light, and gamma rays may cause DNA damage: It breaks DNA, causes covalent bonds to form between bases on opposite strands, fatally alters nucleotide bases, and even causes adjacent nucleotide dimers to form

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