Cell membranehttp://www.youtube.com/watch?v=Qqsf_UJcfBc&feature=relatedhttp://www.youtube.com/watch?v=GW0lqf4Fqpg&feature=related

the cellhttp://www.youtube.com/watch?v=quOoax5RASk&feature=relatedhttp://www.youtube.com/watch?v=dCHre3-_KjA&feature=related

The tiny world of DNA

Chances are you've seen an illustration of DNA's double-helix structure and even pictures of the chromosomes that make up the human genome.But• where and how does the famous double helix fit into chromosomes, And• how do chromosomes relate to the human body?

Our body contains ~100 trillion cells, Excuding red blood cells, which contain no nucleus and no nuclear DNA, every one of these cells contains the human genome -- a string of three billion A's, C's, G's, and T's. And in every one of the 100 trillion cells, the sequence of these four letters, or bases, is nearly identical.

Although the DNA code from cell to cell is the same, there are many different types of cells within the body, each with a specific function. For example, the long, narrow muscle cell is designed to contract, and the squarish cell that lines the wall of the small intestine is designed to filter nutrients from food.

 These cells are exact copies of their parent cells. But sometimes cells need to become specialized. Within the first month of embryonic development, cells are changing into different forms, to form different tissues. This production of new types of cells is the result of DNA "turning on" and "turning off" different sections of the information it stores.

Within every cell (except red blood cells) is a nucleus; a sphere-like structure separated from the rest of the cell by a porous membrane. The nucleus acts as the cell's control center, regulating its growth, metabolism, and reproduction. At the heart of this control centre is the organism’s genome.

The human genome is comprised of two sets of 23 chromosomes -- 46 chromosomes in total. Each parent contributes a set. ~97 percent of the genome consists of sequences that don't code for proteins and have no known function. Within the rest of the genome are an estimated

70,000 genes.

The single chromosome displayed here and those on the previous screen are shown in their most compacted state -- they're about to divide, along with the cell, through the process of mitosis. When we see pictures of chromosomes, this is usually what we see. The reason is that chromosomes are most

visible during this time.

ΜΕΤΑΦΑΣΙΚΟ ΧΡΩΜΟΣΩΜΑ

CHO HELA HELA

85.000 βάσεις DNA ανά θηλιά

ΜΕΤΑΦΑΣΙΚΟ ΧΡΩΜΟΣΩΜΑ

When stained, chromosomes show bands of light and dark areas. The dark bands indicate areas where the structure of the chromosome is dense. Each of the 23 chromosome types has a unique banding pattern. (A chromosome pair has identical banding.) In fact, scientists can identify a chromosome based solely on its

banding pattern.

karyotype[1].swf

There's a lot of DNA within the nucleus. To fit such a long molecule within the tiny space of the nucleus, DNA bends and loops in several ways. The largest of these loops results from the helical coiling of chromatin (the thick line in this illustration). This coiling causes the chromosome to resemble a

spring.

Chromatin refers to proteins that help organize the long DNA molecule. The protein shown here supports and organizes

small loops of DNA.

Zooming to see portions of the DNA strand. The DNA is wrapped around histones -- protein structures that are sometimes depicted as discs. Histones carry a slight positive charge, and DNA carries a slight negative charge. Since opposite charges attract, the DNA is pulled in toward the histones. A nucleosome is a segment of the DNA wrapped around a

core of histones.

200 ζεύγη βάσεων ανά νουκλεόσωμα

ΝΟΥΚΛΕΟΣΩΜΑΤΑ

Histone Protein StructureHistones are the major structural proteins of chromosomes. The DNA molecule is wrapped twice around a Histone Octamer to make a Nucleosome.

ΔΟΜΗ &ΟΡΓΑΝΩΣΗ ΝΟΥΚΛΕΟΣΩΜΑΤΟΣ

Six Nucleosomes are assembled into a Solenoid in association with H1 histones. The solenoids are in turn coiled onto a Scaffold, which is futher coiled to make the chromosomal matrix.

DNAcompaction[1]toWMV.wmv

Genes determine whether you have brown eyes or blue, long toes or short, and much, much more.

Genes also control everything from how your

cells grow to how they interact with one another. A single gene can range in length from as few as

100 DNA bases to as many as several million.

Simplified view of the double helix -- the subject of Rosalind Franklin's Photo 51. Shown here is the structure of naked DNA -- DNA without all of the proteins that organize it into chromatin. Note how its structure resembles a twisted ladder. Note also that DNA with a "left-handed" twist, as this has, is a special kind of DNA known as Z-DNA.

The sides of the DNA ladder consist of a long string of sugar and phosphate molecules, to which the bases are attached. Each sugar-phosphate-base combination is called a

nucleotide.

The DNA molecule is made up of four basesadenine (A),cytosine (C), guanine (G), and thymine (T). Each rung of the DNA ladder consists of two bases.

In the DNA molecule, A always pairs up with T, and C always pairs up with

G.

A nucleotide is made up of ~30 atoms, Determining the sequence of bases in the human genome was such an accomplishment. And although the sequencing is over, understanding the sequence is far from it. Figuring out how these 3.000.000.000 bps code for a human being is

another story

ΔΙΠΛΗ ΕΛΙΚΑ DNA & ΑΖΩΤΟΥΧΕΣ ΒΑΣΕΙΣ

Watson was 23 at the time!!!

A Structure for DNA (typescript)

Watson & Crick [Nature 1953]

Rosalind Franklin took an exceptional X-ray photograph of a DNA molecule,

which provided Watson+Crick with the key to the double-helix puzzle.

Sodium deoxyribose nucleate from calf thymus, Structure B, Photo 51, (May 2, 1952)

taken by Rosalind E. Franklin and R.G. Gosling

nucDNA versus mtDNA

Alternative Vertebrate Genomes: nuclear & mitochondrial DNA

    The nucDNA genome in typical vertebrates consists of several billion base pairs of DNA, arranged on paired chromosomes, one inherited from each parent. The human genome shown here comprises 3 billion bp in 22 pairs of autosomal chromosomes and one pair of sex chromosomes, XY in this (male) individual.

    The mtDNA genome is a much smaller, circular molecule about 16 ~ 18,000 bp in circumferance in most vertebrate species. The genome comprises 13 protein-coding regions, two rRNA genes, a replication control region, and 22 tRNA genes. The order of these is broadly conserved across vertebrates. There are no introns: splicing out of tRNAs produces mRNA templates. The mtDNA genome is self-replicating with the aid of nucDNA-encoded polymerases. The genome is locted is the extranuclear mitochondria, the "powerhouses of the cell," where it contributes to cell respiratory systems in the Cytochrome Oxidase, ATP synthase, and NADH systems. The vertebrate mtDNA genetic code differs from the "Universal" code is several respects.

 Unlike the nucDNA genome, the mtDNA genome is inherited solely through the cytoplasm of the maternal egg, and does not undergo genetic recombination. It has therefore been widely used in evolutionary and population biology to trace maternal lineages within and between species.

The genome of the chloroplasts found in Marchantia polymorpha (a liverwort, one of the Bryophyta) contains 121,024 base pairs in a closed circle. These make up some 128 genes which include:                                                                      •duplicate genes encoding each of the four subunits (23S, 16S, 4.5S, and 5S) of the ribosomal RNA (rRNA) used by the chloroplast •37 genes encoding all the transfer RNA (tRNA) molecules used for translation within the chloroplast.• Some of these are represented in the figure by black bars (a few of which are labeled). •4 genes encoding some of the subunits of the RNA polymerase used for transcription within the chloroplast (3 of them shown in blue) •a gene encoding the large subunit of the enzyme RUBISCO (ribulose bisphosphate carboxylase oxygenase) •9 genes for components of photosystems I and II •6 genes encoding parts of the chloroplast ATP synthase •genes for 19 of the ~60 proteins used to construct the chloroplast ribosome All these gene products are used within the chloroplast, but all the chloroplast structures also depend on proteins •encoded by nuclear genes •translated in the cytosol, and •imported into the chloroplast. RUBISCO, for example, the enzyme that adds CO2 to ribulose bisphosphate to start the Calvin

cycle, consists of multiple copies of two subunits: •a large one encoded in the chloroplast genome and synthesized within the chloroplast, and •a small subunit encoded in the nuclear genome and synthesized by ribosomes in the cytosol. The small subunit must then be imported into the chloroplast.The arrangement of genes shown in the figure is found not only in the Bryophytes (mosses and liverworts) but also in the lycopsids (e.g., Lycopodium and Selaginella). In all other plants, however, the portion of DNA bracketed by the red arrows on the left is inverted. The same genes are present but in inverted order. The figure is based on the work of Ohyama, K., et al., Nature, 322:572, 7 Aug 1986; and Linda A. Raubeson and R. K. Jansen, Science, 255:1697, 27 March 1992. The evolution of eukaryotic chloroplasts by the endosymbiosis of cyanobacteria seems to have occurred on three different occasions producing as separate events: •the green algae and plants as described above •red algae •glaucophytes; a small group of unicellular algae

The Chloroplast Genome

ΟΡΓΑΝΩΣΗ ΓΟΝΙΔΙΟΥ

The largest known gene is associated with Duchenne muscular dystrophy (2.4 million bases in length)

ΑΡΙΘΜΟΣ ΒΑΣΕΩΝ ΣΤΟ ΓΟΝΙΔΙΩΜΑ ΟΡΓΑΝΙΣΜΩΝ

ΣΥΓΚΡΙΣΗ ΑΛΛΗΛΟΥΧΙΩΝ

Look for genesFunctionsGenetic variationEvolutionary relationships

BLAST (Basic Local Alignment Search Tool)

Sequence ID: A unique number used to identify the DNA sequence.Description: Describes the species from which the sequence comes and the gene it is associated with (if any).Query: Indicates how many bases are in the input (test) sequence.Match: The amount of shading on each graphic indicates how well the query sequence matches the hit (or subject) sequence. Note, the shading does not compare the similarities between the whole genomes.Expected (E) Value: Result of a mathematical calculation that describes the significance of a match. The lower the E value (closer to“0”), the better the match. An E value of less than 10-6 is a biologically significant match.

BLAST Search Terminology

CLUSTAL

For multiple alignments

Cystic fibrosis

bacterium E. coli (4.6 million)yeast S. cerevisiae (12 million)roundworm C. elegans (100 million)fruitfly D. melanogaster (180 million)mouse M. musculus (3 billion)

Map and sequence the genomes of model organisms

The approximate number of base pairs in each species’ genome is given in parentheses.

HUMAN GENOME PROJECT

• begun in 1990took 4 years to sequence 1 billion basestook 4 months to sequence the 2nd 1 billion basesIn January 2003, 1.5 billion bases were sequenced

In 1993: 10 dollars per baseIn April 2003: 10 cents per base

15 year project sequence 3.2 billion bases

1997: E. coli Genome Sequenced 1998: M. Tuberculosis Bacterium Sequenced 1998: Genome of Roundworm C. elegans Sequenced1999: Chromosome 222000: Free Access to Genomic Information 2000: Chromosome 21 2000: Drosophila and Arabidopsis genomes sequenced2001: First Draft of the Human Genome Sequence Released 2002: Mouse Genome Sequenced 2002: Rice Genome Sequenced2003: Human Genome Project Completed2003: ENCODE Program Begins2004: Rat and Chicken Genomes Sequenced2004: Refined Analysis of Complete Human Genome Sequence 2005: Chimpanzee Genomes Sequenced2005: Trypanosomatid Genomes Sequenced2005: Dog Genomes Sequenced2006: The Cancer Genome Atlas (TCGA) Project Started2006: Second Non-human Primate Genome is Sequenced2006: Initiatives to Establish the Genetic and Environmental Causes of Common Diseases Launched

THE FUTURE

Sequence data are piling upNeed better methods for analysisImproved software

AcquisitionStorageAnalysis

Collect and distribute data Distribute genomic information to the research community.Release all sequence data that spans more than 2000 base pairs within 24 hours.Create and run databases.Develop software for large-scale DNA analysis.Develop tools for comparing and interpreting genome information.Share information with the wider public.

Develop technologiesMake large-scale sequencing faster and cheaper.Develop technology for finding sequence variations.Develop ways to study functions of genes on a genomic scale.

Study the ethical, legal and social implications of genetic research

Transfer technology to the private sector

THE FUTURE

Chromosome structure.swf