1 Genetics The Study of Biological Information

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

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

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

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

6 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 The entire collection of chromosomes in each cell of an organism is called a genome Human cells have 24 distinct kinds of chromosomes Human cells have 24 distinct kinds of chromosomes The human genome has about 3 x 10 9 base pairs and 20,000 – 30,000 genes The human genome has about 3 x 10 9 base pairs and 20,000 – 30,000 genes Fig. 1.4

7 Biological function emerges primarily from proteins. Figure 1.5a Alanine has a relatively simple CH side chain Tyrosine has a more complex aromatic side chain Amino acids have a basic amino group (-NH) and an acidic carboxyl group (-COOH)

8 A comparison of equivalent chains of two digestive proteins Figure 1.5b

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

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

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

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

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

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

15 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 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. Some model organisms include bacteria, yeast, roundworms, fruit flies, and mice. Model organisms may have simpler biological networks and can be manipulated experimentally. Model organisms may have simpler biological networks and can be manipulated experimentally.

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

17 The process of duplication and divergence Fig. 1.10

18 Duplication and divergence has made rapid evolution possible.

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

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

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

22 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 Fig. 1.13c

23 Focus on human genetic Genetics is a field of science that will have an enormous impact on society 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 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 Recent technological advances have shifted the focus of genetics from analysis of single genes and proteins to entire networks – the Systems Approach

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

25 Social issues and genetics Should an individual’s genetic profiles be freely available to insurance companies, employers, government? 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? 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? Is it okay to permanently alter genes in humans for medical or social reasons?