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Lecture 4

Lecture 4 Reading.docx

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University of Toronto St. George
James Thomson

Lecture 4 ReadingChapter 4 pp202 206 Eucaryotic DNA is Packaged into a set of chromosomes9 human genome 32X10 nucleotides is distributed into 24 different chromosomeseach chromosome consists of a single long linear DNA molecule associated with protein that folds itThe protein and the DNA collectively is called the chromatin Cells are homologous as they contain two copies of each chromosomenon homologs in sex cells strictly XX in females and XY in malesHuman karyotype is the 46 human chromosomes being displayed at mitosisBacteria carry genes on a single DNA molecule It is circular bacterial chromosome different in structure than that of the eukaryote chromosomesVery little is known on packaging as wellChromosomes contain long string of genes Genes on chromosomes make specific proteins and some genes make RNA as the final productThese RNA act as catalysts etc Complexity and number of genes is true However humans have less genes then some bacteria so it shows that having less DNA is no handicapjunk DNA in humansThe nucleotide sequence of the human genome shows how are genes are arranged human genome project showed that little of genome codes for proteinmost of DNA is made up of short pieces of DNA inserted over evolution transposable elementsaverage gene size is 27000 nucleotides THATS BIGOnly 13000 needed for the protein Rest noncodingcoding region called exons noncoding called intronsEach gene is also associated with regulatory DNA sequences ensuring that genes are turned on or off at the right time to the right extent and in the right cellspp 208218 Chromosomes exist in different states throughout the life of a cell Mitosis ensures that dna is portioned and sentinterphase is pre step to mitosis In interphase chromosomes are replicatedmitosis chromosomes become highly condensed and then are separated distributed to two daughter cells
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