This document provides an overview of cell biology and cell organelles. It discusses the nucleus and DNA structure, including Watson and Crick's discovery of the DNA double helix. It explains DNA replication, where the parent DNA molecule unwinds and two new daughter strands are built based on base pairing rules. The document also briefly mentions the endoplasmic reticulum, Golgi complex, lysosomes, and mitochondria as important cell organelles, and includes various figures to illustrate structures and processes.
5. Watson and Crick deduced that DNA was a
double helix
Through observations of the X-ray
crystallographic images of DNA
G C
A T
T A
1 nm
C
G
3.4 nm
C G
A T
C G
T A
T A
A T
T
A
G C
0.34 nm
A T
Figure 16.7a, c (a) Key features of DNA structure (c) Space-filling model
6. In DNA replication
The parent molecule unwinds, and two new daughter
strands are built based on base-pairing rules
T
T
A T T A
A T T
A A A
G C G
C G G C
G G
C C C
A
T A A T A
A A
T T T
T
T T
A T T A
A A T A T
A
G C C C G C
C C
G G G
G
(a) The parent molecule has two (c) Each parental strand now (d) The nucleotides are connected
(b) The first step in replication is
complementary strands of DNA. serves as a template that to form the sugar-phosphate
separation of the two DNA
Each base is paired by hydrogen determines the order of backbones of the new strands.
strands.
bonding with its specific partner, nucleotides along a new, Each daughter DNA
A with T and G with C. complementary strand. molecule consists of one parental
strand and one new strand.
Figure 16.9 ad