DNA Function and History Chapter 8

Watson & Crick:

Watson and Crick were two scientists that discorvered the double helix formation of DNA in the 1950s. James and Francis's discory help give rise to modern molecular biology.

James Watson on the Left, Francis Crick on the right

Chargaff Rule:

Erwin Chargaff created two rules about the bases adnbase pairings of DNA. He stated that species vary in DNA composition, based on the amounts of A,C,T,G. Also, A's paired with T's, so there is an equal number of them. The same thing with C's and G's, there will be a 1:1 ratio between them.

_______Amount of A = Amount of T; Amount of C = Amount of G;_______ Therefore, A + C = T + G

How do the base pairs bind?

The two types of base pairs, A & T and C & G, bind differently but they are both complementary to their partner. A & T bind with the help of two hydrogen bond formed between them. C & G bind when three hydrogen bind are formed.

The two dotted lines between A & T represent the two hydrogen bonds that binds them. The three dotted lines between C & G are their hydrogen bonds.

What is a chromosome?

A chromosome is an organized structure that contians DNA and some protein. This thread like structure caries the genetic materials of the cell. The chromosome inside cells vary in number from species to species.

Diagram of a chromosome

What is a karyotype?

A karyotype is a profile, or visual representation, of someone's chromosomes in his or her cell. Two chromosomes are arranged XX, for females, or XY, for males, and the other chromosomes, autosomes, are arranged in pairs.

These are Chromosomes from ones cell. They are arranged, 1-22 , in size order and the last two are the X and Y chromosomes or X and X.

How does DNA replicate? (This should be in depth)

The process of DNA replication begins when an enzyme that breaks the hydrogen binds between the base pairs in the double helix of DNA. The two single strands of DNA now are arranged with primer, a strand of nuceotide. The primer helps the enzyme Polymerase attach to the DNA single strand and it begins synthesizing new DNA. The nucleotide will break off two phosphate groups to provide energy so it can attach to the DNA strand. Lastly, DNA Ligase, another important enzyme, will seal any gaps to complete the DNA double helix.

DNA Replication, also called Semiconservative Replication

What damages DNA?

DNA can be damaged by the ionizing radiation of gamma rays and X-rays, and UV rays. Also, many chemical found in the environment can damage DNA.

This picture shows the various things that can damage DNA and what will happen to the DNA as a result.
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Christopher Callan

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