4 - DNA and Chromosomes – Chapter 5 • Historical...

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Unformatted text preview: DNA and Chromosomes – Chapter 5 • Historical Perspective – Life depends on genetic instructions from a mother cell to daughter cell to be stable, retrievable and useful. – Beginning of 20 th Century, Genetics emerged as a field of study and began to address specific questions about the genetic instructions. • In the 1940’s the genetic information was found to contain the instructions for making proteins. • And in the 1940’s DNA was recognized as the carrier of this genetic information. • Finally in 1953, the structure of DNA was elucidated. • In this chapter we will learn how to interpret and describe the structure of DNA in biological terms. And we will explore how the structural and chemical properties of DNA make it an ideal raw material for genes. Key Concepts • Life depends on stable and compact storage of DNA • Genetic material is carried on DNA and is encoded in linear sequence of nucleotides (A, T, G and C) • DNA is a double helix composed of a pair of complementary strands. • Each strand has a polarity due to alternating sugar-phosphate backbone. The two strands run antiparallel. • Genetic material contained in chromosomes. • DNA in eukaryotic chromosomes contains, in addition to genes, many replication origins, one centromere and two telomeres. • Chromosomes consist of DNA tightly bound to specialized proteins. These proteins make the DNA compact enough to fit into nucleus. • Histones pack DNA into DNA-Protein particles called nucleosomes. And nucleosomes pack together to produce compact chromatin structures. • Chromatin structures are dynamic allowing the cell to be involved in gene expression, replication, repair. Early in the 19 th century, Biologists knew that genes were carried on chromosomes – threadlike structures in the nucleus. Biochemical analyses indicated that the chromosomes contained both DNA and protein. Initially scientists did not know which was the genetic information....
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This note was uploaded on 04/13/2008 for the course BIOL 308 taught by Professor Ragsdale during the Fall '07 term at Winona.

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4 - DNA and Chromosomes – Chapter 5 • Historical...

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