The Study of Biological Information Genetics The Study of Biological Information

Chapter Outline DNA molecules encode the biological information fundamental to all life forms Proteins are the primary unit of biological function Regulatory networks specify the behavior of genes All living forms are closely related Genomes are modular, allowing rapid evolution Genetic techniques permit dissection of biological complexity Focus of this course is on human genetics

Information in DNA generates diversity Four bases – G (guanine), A (adenine), T (thymine), and C (cytosine) are the nucleotide building block of DNA DNA is a double stranded helix composed of A-T and G-C complementary bases Order of nucleotide sequences determine which proteins are synthesized, as well as when and where they the synthesis occurs. Figure 1.1a Fig. 1.1a

Genetic Information is Digital The sequence of bases in DNA can be read by DNA sequencers, stored in computers, and synthesized by DNA synthesizers Figure 1.3 Fig. 1.3

Genes are sequences of DNA that encode proteins Figure 1.2 Fig. 1.2

DNA resides in within cells packaged as units called chromosomes The entire collection of chromosomes in each cell of an organism is called a genome Humans have 24 chromosomes The human genome has about 3.2 x 109 base pairs and 30,000 – 35,000 genes Figure 1.4 Fig. 1.4

Biological function emerges primarily from proteins Figure 1.5a Figure 1.5a

Proteins are polymers of amino acids Proteins have three dimensional structures Information in DNA dictates the sequence of its amino acids There are 20 different amino acids The order of amino acids determines the type of protein and its structure

The diversity of protein structure generates extraordinary diversity Figure 1.5b Fig. 1.5b

Proteins interact with DNA and other proteins Biological systems function as complex interactive networks of proteins and DNA that interact with one another Figure 1.6 Fig. 1.6

All living things are closely related RNA was probably the first information-processing molecule RNA is composed of four bases: guanine (g), adenine (a), thymine (t), and uracil (u) Figure 1.7a Fig. 1.7a

All living organisms use the same arbitrary codes for RNA, DNA, and protein Figure 1.7b Fig. 1.7b

Many genes have similar functions in very different organisms Figure 1.8 Fig. 1.8

Relatedness among organisms is important for the study of human genes Studies of genetics in model organisms help us understand how genes work in humans Some model organisms include bacteria, yeast, roundworms, fruit flies, and mice. Model organisms may have simpler biological networks and can be manipulated experimentally.

Modular construction of genomes has allowed rapid evolution of complexity Gene families arise from primordial genes through duplication and rearrangements Duplication and divergence of new genes can generate genes with new functions

The process of duplication and divergence Figure 1.10 Fig. 1.10

Duplication and divergence has made rapid evolution possible

Rapid change in regulatory networks specify how genes behave Figure 1.9 Fig. 1.9

Genetic techniques permit the dissection of complexity Genes can be identified and inactivated one at a time using genetic techniques Dissection of genomes gene-by-gene unravels the complexity of biological systems The challenge for modern biology lies in understanding how the multitude of networks of genes and higher level systems interact to produce complex systems.

Genome sequencing projects are a step in understanding the complexity of genomes Figure 1.12 Fig.1.12

New technological tools facilitate the dissection of genomes and integration of information DNA chips detect the expression of thousands of genes in response to environmental changes Figure 1.13c Fig. 1.13c

Focus on human genetic Genetics is a field of science that will have an enormous impact on society Our understanding of biological complexity using genetic approaches is proceeding at a very rapid pace Recent technological advances have shifted the focus of genetics from analysis of single genes and proteins to entire networks – the Systems Approach

Genetics Predictive and Preventative Medicine Discovery of genes with variations that cause or predispose one to disease will continue at a rapid pace. Gene therapy Diagnostics Therapeutic drugs to block or reverse effects of mutant genes Detection of disease and treatment before onset may increase life span significantly

Social issues and genetics Should an individual’s genetic profiles be freely available to insurance companies, employers, government? Should our government regulate the use of genetic and genomic information to reflect societies social values? Is it okay to permanently alter genes in humans for medical or social reasons?