William S. Klug Michael R. Cummings Charlotte A. Spencer Concepts of Genetics Eighth Edition Chapter 1 Introduction to Genetics Copyright © 2006 Pearson Prentice Hall, Inc.

Why do we have to learn genetics? 生命的傳承 生物醫學上的應用 生物多樣性上的應用

Chapter 1 Introduction to Genetics 1.1 From Mendel to DNA in Less Than a Century 1.2 Discovery of the Double Helix Launched the Recombinant DNA Era 1.3 Genomics ( 基因體學 ) Grew Out of Recombinant DNA Technology (DNA 重組技術 ) 1.4 The Impact of Biotechnology Is Growing 1.5 Model Organisms ( 模型生物, 動物模型 ) Play Important Roles in Genetics and Biology 1.6 We Live in the "Age of Genetics"

1.1From Mendel to DNA in Less Than a Century In eukaryotes, DNA resides in the nucleus and organelles reside in the cytoplasm (Figure 2 ‑ 1).

Genetics Mendel (1866) Rediscovery (1900) Carl Correns de Vries von Tschermak Watson and Crick (1953)

Genes and chromosomes are the fundamental units of genetics What does “ genetics ” mean? Heredity 承傳 / 遺傳 ; variation 變異 Inherited variation and the underlying molecular basis

What is the center of heredity in a cell? What is a gene? What is a chromosome? When and how can chromosomes be visualized?

According to the chromosome theory of inheritance, inherited traits are controlled by genes residing on chromosomes. The genes are faithfully transmitted through gametes, maintaining genetic continuity from generation to generation.

How many chromosomes can an organism have? diploid (2n) 雙倍體 homologous chromosomes 同源染色體 Centromeres 著絲點 Locus/Loci 基因座 Haploid Polyploid

1.1From Mendel to DNA in Less Than a Century 1.1.1Mendel’s Work on Transmission of Traits 1.1.2The Chromosome Theory of Inheritance: Uniting Mendel and Meiosis 1.1.3Genetic Variation

Figure 1-2 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-3 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-5 Copyright © 2006 Pearson Prentice Hall, Inc.

What is accomplished during the process of mitosis and meiosis? In mitosis, chromosomes are copied and distributed so that the two resulting daughter cells each receive a diploid set. In meiosis, the gametes produced are haploid. What are the sources of genetic variation? Recombination during meiosis Chromosomal mutations (aberrations): duplication 複製, deletion 缺失, rearrangement 重組 Gene mutations: smaller changes in DNA

Variation Alleles 等位基因 Mutations produce alleles of a gene and are the source of genetic variation. Genotypes 基因型 vs. phenotype 表現型

Figure 1-6 Copyright © 2006 Pearson Prentice Hall, Inc.

1.1From Mendel to DNA in Less Than a Century 1.1.4The Search for the Chemical Nature of Genes: DNA or Protein?

DNA, not protein, is the carrier of genetic information.

Figure 1-7 Copyright © 2006 Pearson Prentice Hall, Inc.

1.2Discovery of the Double Helix Launched the Recombinant DNA Era 1.2.1The Structure of DNA and RNA

DNA is an antiparallel, double-stranded helix made up of the nucleotides A, C, G, and T. The sugar in its nucleotides is deoxyribose. These nucleotides form A – T and G – C base pairs across the helix (Figure 1 ‑ 8).

Figure 1-8 Copyright © 2006 Pearson Prentice Hall, Inc.

RNA is similar to DNA except that it is usually single-stranded and has U in place of T. In addition, the sugar in its nucleotides is ribose instead of deoxyribose. DNA is transcribed to RNA, which is translated into protein (Figure 1 ‑ 9). This is known as the central dogma of genetics.

Figure 1-9 Copyright © 2006 Pearson Prentice Hall, Inc.

The genetic code and RNA triplets 三聯體 AUGMet UUUPhe UUC The genetic code consists of triplet nucleotides present in mRNA. Each triplet encodes for insertion of a specific amino acid into a growing protein chain.

1.2.2Gene Expression 基因表達 : From DNA to Phenotype Once a protein is made, its action or location in a cell plays a role in producing a phenotype.

1.2.3Proteins and Biological Function Enormous structural diversity primary structure secondary structure tertiary structure quaternary structure

Figure 1-10 Copyright © 2006 Pearson Prentice Hall, Inc.

1.2.4Linking Genotype to Phenotype: Sickle-Cell Anemia

Figure 1-11 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-12 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-13 Copyright © 2006 Pearson Prentice Hall, Inc.

1.3Genomics Grew Out of Recombinant DNA Technology 1.3.1Making Recombinant DNA Molecules and Cloning DNA Restriction enzymes ( 限制酶 ) have allowed the advent of recombinant DNA and cloning ( 複製, 克隆 ) (Figure 1 ‑ 14).

Figure 1-14 Copyright © 2006 Pearson Prentice Hall, Inc.

1.3Genomics Grew Out of Recombinant DNA Technology 1.3.2Sequencing Genomes: The Human Genome Project

Genomics analyzes genome sequences to study the structure, function, and evolution of genes and genomes.

1.4The Impact of Biotechnology Is Growing 1.4.1Plants, Animals, and the Food Supply Biotechnology has been used for the genetic modification of crop plants for increased herbicide, insect, and viral resistance, as well as for nutritional enhancement. Some genetically altered traits in crop plants are shown in Table 1 ‑ 1.

Table 1-1 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-16 Copyright © 2006 Pearson Prentice Hall, Inc.

1.4The Impact of Biotechnology Is Growing 1.4.2Who Owns Transgenic Organisms?

Figure 1-17 Copyright © 2006 Pearson Prentice Hall, Inc.

1.4The Impact of Biotechnology Is Growing 1.4.3Biotechnology in Genetics and Medicine

The molecular basis for hundreds of genetic disorders is known (Figure 1 ‑ 18). Gene therapy and genetic testing are important parts of medicine.

Figure 1-18 Copyright © 2006 Pearson Prentice Hall, Inc.

Figure 1-19 Copyright © 2006 Pearson Prentice Hall, Inc.

1.5Genetic Studies Rely On the Use of Model Organisms Model Organisms Play Important Roles in Genetics and Biology

1.5Genetic Studies Rely On the Use of Model Organisms 1.5.1The Modern Set of Genetic Model Organisms Model organisms for genetic study are easy to grow, have a short life cycle, and produce many offspring.

1.5Genetic Studies Rely On the Use of Model Organisms 1.5.2Model Organisms and Human Diseases

All life has a common origin, and genes with similar functions in different organisms are similar in structure and DNA sequence.

Recombinant DNA technology and the ability to transfer genes across species has made it possible to develop models of human diseases (Table 1.2).

Table 1-2 Copyright © 2006 Pearson Prentice Hall, Inc.

1.6 We Live in the "Age of Genetics" Genetics is the core of biology and the method of choice for understanding the functions and malfunctions of a biological system.