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Lecture 5


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Biology 1001A
Beth Mac Dougall- Shackleton

Biology Lecture 5 - Genomic Variation Independent Study Outcomes 1. The meaning of C-Value. - refers to the amount of DNAcontained within a haploid nucleus (a gamete for ex) - OR one half the amount in a diploid somatic cell of a eukaryotic organism - expressed in picograms - the terms C-value and genome size are sometimes used interchangeably (in some cases) - in polyploids (cells and organisms that contain more than two paired, homolo- gous, sets of chromosomes) the C-value may represent two or more genomes contained within the same nucleus - polyploidy is most common in plants 2. The “paradox” or “enigma” associated with C values. - complex puzzle surrounding the extensive variation in nuclear (the evolution of the) genome size among eukaryotic species - at center of enigma is the observation that genome size does not correlate with organismal com- plexity 3. The meaning of haploid (n) and diploid (2n). - gametes are haploid - 23 chromosomes - somatic cells are diploid - 46 chromosomes 4. The relationship between C and n as measures of genome size. - C = n 5. The proportion of the human genome that codes for protein. - 8.3a - Chromosomes are the Genetic Units Divided by Mitosis - most eukaryotes have two copies of each type of chromosome in their nuclei - chromosome is said to be diploid (2n) - humans have 23 different pairs of chromosomes ~> diploid # of 46 chromosomes (2n=46) - other eukaryotes only have one copy of each type of chromosome in their nucleus, haploid (n) - 2n=32 and n=16 - some plants species have 3, four, or even complete sets of chromosomes in each cell - number of chromosome sets is called ploidy - equal distribution of daughter chromosomes is called chromosome segregation - since sister chromatids remain attached to each other at their centromeres following DNA synthesis, the pair of them is still referred to as just one chro- mosome - two daughter cells can each receive eight chromosomes even though there were only eight chromosomes in the original cell 15.3b - Genome Sequence Determination and Annotation Involves Obtaining and Analyzing the Sequence of Complete Genomes Biology Lecture 5 - Genomic Variation - Genome Shotgun Sequencing 1. isolate genomic DNAand break it into random overlapping fragments 2. clone each DNAfragment (ex - plasmid cloning vector) 3. sequence the genomic DNAfragment in each clone 4. Enter DNAsequences into computer and use computer to assemble overlapping se- quences into the continuous sequence of each chromosome of the organism. - after genome has been sequenced the next step is annotation - the identification of genes and other sequences of importance - Bioinformatics - fuses biology with mathematics and computer science and is used to pre- dict the structure and function of gene products and to postulate evolutionary relationships of se- quences. - eukaryotic genomes contain large numbers of noncoding sequences, most of them in the form of repeated sequences of nucleotides of various lengths and numbers - all the protein coding sequences occupy less than 2% of the human genome - introns occupy 24% - 50% of the total genome consists of repeated sequences that have no known function Lecture Outcomes 1. The non-nuclear genomes in typical plant and animal cells. - plants have three different genomes, a nuclear one, a mitochondria one, and a chloroplast one - animals have ove
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