the structure and function of...

© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko

PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and

Campbell Essential Biology with Physiology,

Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece

Chapter 10Chapter 10The Structure and Function of DNA

1 DNA: STRUCTURE AND REPLICATION

• DNA

– was known to be a chemical in cells by the end of the nineteenth century,

– has the capacity to store genetic information, and

– can be copied and passed from generation to generation.

• The discovery of DNA as the hereditary material

ushered in the new field of molecular biology, the

study of heredity at the molecular level.

© 2013 Pearson Education, Inc.

4

Watson and Crick’s Discovery of the Double Helix

• James Watson and Francis Crick determined that

DNA is a double helix.

• Watson and Crick used X-ray crystallography data

to reveal the basic shape of DNA.

• Rosalind Franklin produced the X-ray image of

DNA.


5 Figure 10.3a

James Watson (left) and Francis Crick

6

Figure 10.3b

X-ray images of DNARosalind Franklin

7

• The model of DNA is like a rope ladder twisted into

a spiral.

– The ropes at the sides represent the sugar-phosphate backbones.

– Each wooden rung represents a pair of bases connected by hydrogen bonds.



8

Figure 10.4

Twist

9

• DNA bases pair in a complementary fashion:

– adenine (A) pairs with thymine (T) and

– cytosine (C) pairs with guanine (G).



10

Figure 10.5

(c) Computer model(b) Atomic model(a) Ribbon model

Hydrogen bond

11 The Central Dogma of Molecular Biology

• Central dogma of molecular biology

– Formulated by Francis Crick

– Genetic information is transferred within biological system in 3 distinct processes

– Replication

– Transcription

– Translation


12

The Central Dogma of Molecular Biology

• Replication

– creating an exact copy. Using nucleotide sequence in DNA to produce another double stranded DNA molecule with the exact same sequences

• Transcription

– Same language and essentially the same words but in a slightly different format. Uses nucleotide sequence in DNA to produce an equivalent nucleotide sequence in an RNA molecule

• Translation

– Converting words from one language into different words in a different

language. Using nucleotide sequence in RNA to produce a sequence of

amino acids in a polypeptide according to specific translation rules. In

essence going from the language of nucleotides to the language of amino

acids.


13

Replication Transcription Translation

Template DNA DNA RNA

Polymer synthesized

DNA RNA Polypeptide

Monomernucleotide (deoxyribose)

nucleotide (ribose)

Amino acid

Polymerizing enzyme

DNA polymerase RNA polymerase ribosome

initiation site origin of replication promoterstart site (start codon)

termination site none terminator1 of 3 stop codons

14

DNA and RNA Structure

• DNA and RNA are nucleic acids.

– They consist of chemical units called nucleotides.

– A nucleotide polymer is a polynucleotide.

– Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.


15


Animation: DNA and RNA Structure

Right click slide / select “Play”

16

Figure 10.1

Sugar-phosphatebackbone

Phosphate

group Nitrogenous base

DNA nucleotide

DNAnucleotide Thymine (T)

Sugar

Polynucleotide

DNAdoublehelix

Sugar

(deoxyribose)

Phosphategroup

Nitrogenous base(can be A, G, C, or T)

17

• The sugar in DNA is deoxyribose. Thus, the full

name for DNA is deoxyribonucleic acid.



18

• The four nucleotides found in DNA differ in their

nitrogenous bases. These bases are

– thymine (T),

– cytosine (C),

– adenine (A), and

– guanine (G).

• RNA has uracil (U) in place of thymine.



19 Figure 10.2

Sugar(ribose)

Phosphate

Adenine

Uracil

Guanine

Cytosine

20

DNA Replication

• When a cell reproduces, a complete copy of the

DNA must pass from one generation to the next.

• Watson and Crick’s model for DNA suggested that

DNA replicates by a template mechanism.


21


Bioflix Animation: DNA Replication

22

Figure 10.6

Parental (old)DNA molecule

Daughter (new) strand

Daughter DNA molecules (double helices)

Parental (old) strand

23

• DNA can be damaged by X-rays and ultraviolet

light.

• DNA polymerases

– are enzymes,

– make the covalent bonds between the nucleotides of a new DNA strand, and

– are involved in repairing damaged DNA.

DNA Replication


24

• DNA replication ensures that all the body cells in

multicellular organisms carry the same genetic

information.

DNA Replication


25

• DNA replication in eukaryotes

– begins at specific sites on a double helix (called origins of replication) and

– proceeds in both directions.

DNA Replication


26

Figure 10.7

Origin ofreplication



Parental strands

Parental strand

Daughter strand

Two daughter DNA molecules

Bubble

27 THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN

• DNA provides instructions to

– a cell and

– an organism as a whole.


28

How an Organism’s Genotype Determines Its Phenotype

• An organism’s genotype is its genetic makeup, the

sequence of nucleotide bases in DNA.

• The phenotype is the organism’s physical traits,

which arise from the actions of a wide variety of

proteins.


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