DNA

Watson & Crick

James Watson & Francis Crick

Together they found the structure of DNA to be a Double Helix

Compiled data of several other scientists including Rosalind Franklin

Received a Nobel Prize for their work Significance of Photograph 51

1) was helical, 2) was likely a double helix with

antiparallel strands, 3) had the phosphate backbone on the

outside (thus the bases of DNA, which are the "code" for inheritance, were on the inside of the helix).

DNA (Deoxyribonucleic Acid)

DNA is located in the nucleus

Because it is large and double stranded, it cannot pass through the nuclear envelope

DNA is composed of 3 parts:

Deoxyribose: sugar Phosphate (phosphoric

acid) 4 Bases

Adenine (A) Guanine (G) Thymine (T) Cytosine (C)

A bonds with T A-T or T-A

C bonds with G C-G or G-C

Nucleotide

These 3 parts deoxyribose, phosphate 1 base

form a nucleotide

DNA Synthesis DNA must be replicated

before cell division in both mitosis and meiosis

DNA synthesis or replication occurs during the S (synthesis) phase of Interphase (before the start of mitosis or meiosis)

WHY?

*pg. 112 in your book

DNA Replication

Most of the time, DNA is coiled in the nucleus to save space.

In order to replicate, the DNA molecule must unwind and unzip.

An enzyme assists at each stage in this process.

Nucleotides (building blocks) are in the cell nucleus.

The DNA unwinds and unzips with the help of DNA polymerase

The complementary nucleotides combine with the exposed bases with the help of ligase

Watson and Crick also found that the bases Adenine and Thymine occur in the exact same amounts as do Cytosine and Guanine.

They can only bond with each other: Double H-bond for

Adenine:Thymine Triple H-bond for

Cytosine:Guanine

http://www.johnkyrk.com/DNAreplication.html

Two new DNA molecules form exactly like the original molecule.

The new DNA strands recoil and remain joined at the centromere until they move apart in anaphase.

*Centromere*

RNA is composed of 3 parts: Ribose: smaller sugar than

deoxyribose of DNA Phosphate 4 Bases

Adenine (A) Guanine (G) Uracil (U)* instead of T Cytosine (C)

RNA is single stranded and thus smaller & able to leave the nucleus of the cell

These 3 parts (ribose, phosphate and 1 base) still form a nucleotide when combined

RNA is used by DNA to carry the code and create proteins that control the functioning of the cell

There are two main types of RNA used: mRNA and tRNA.

Personal DNA