7: DNA
- Page ID
- 16134
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)DNA: the stuff of life. Well, not really, despite the hype. DNA does contain the instructions to make a lot of the stuff of life (proteins), although again, not all the stuff of life. At least not directly. Deoxyribonucleic acid (and its very close cousin ribonucleic acid, or RNA) is a very long chain polymer. You may recall that a polymer is just a really big molecule made by connecting many small similar molecules together). In this polymer, the small (monomer) molecules are known as nucleotides, and are composed of a pentose (5-carbon sugar either deoxyribose or ribose), a nitrogenous base, and a phosphate group.
- 7.1: DNA Structure
- This page covers the structures of DNA and RNA, focusing on nucleotides, sugar-phosphate backbones, and base-pairing stability in double-stranded DNA. It details variations of DNA and their cellular implications, as well as how eukaryotic DNA is packaged with histones into nucleosomes, forming a 30-nm fiber structure.
- 7.2: Semi-Conservative DNA Replication
- This page explains DNA replication, highlighting that it involves a polymerase enzyme synthesizing new strands while reading a template. The process is semi-conservative, producing double helices with one original and one new strand.
- 7.3: Prokaryotic Replication
- This page details the process of DNA replication in prokaryotes, particularly E. coli, focusing on initiation at oriC and the roles of various proteins. DnaA proteins create a loop for unwinding, with helicase DnaB and other enzymes supporting strand separation and synthesis. The leading strand forms continuously, while the lagging strand consists of Okazaki fragments.
- 7.4: Eukaryotic Replication
- This page discusses eukaryotic DNA replication, highlighting its similarities and differences from prokaryotic replication. It emphasizes the presence of multiple origins of replication in eukaryotes, requiring a licensing mechanism to ensure proper activation. The establishment of the pre-replicative complex (pre-RC) at these origins involves the origin recognition complex and essential proteins.
- 7.5: DNA Lesions
- This page covers the fragility of DNA, detailing its various damage types such as depurination and deamination, and the role of environmental agents like carcinogens. It emphasizes the importance of thymine in DNA stability and discusses specific damaging compounds, including cisplatin and aflatoxin B1, and associated regulatory measures.
- 7.6: DNA Repair
- This page provides an overview of DNA repair mechanisms, including basic processes like dealkylation and light-dependent repair by DNA photolyases. It explains more complex systems such as base excision repair (BER) and nucleotide excision repair (NER), as well as mismatch repair (MMR) and the SOS response. Additionally, it details double-strand break repair, emphasizing the Ku protein's role in recognizing DNA ends and the potential consequences of inaccurate repairs leading to mutations.
- 7.7: Telomeres
- This page discusses the end-replication problem in linear eukaryotic chromosomes, where DNA replication leads to the loss of essential genetic information at the 5' ends. It highlights the role of telomerase in adding non-coding telomere sequences to protect functional genes, noting its high activity during embryonic development and limited presence in adults.
Thumbnail: DNA double helix. (public domain; NIH - Genome Research Institute).