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Unformatted text preview: Handout for CHAPTER 9 - Cellular Reproduction Quick reminder of what we know so far (where we stand) DNA replication makes 2 copies of al dna ch 11 The link between genes, DNA and Chromosomes What is the link between these 3? Genes- small sections of DNA with discrete instructions Locus-physical location of a gene on a strand of DNA (its address) DNA- very long (millions of base pairs) double strand of nucleotides Details about chromosomes Chromosome=combo. Of one strand of DNA and many support proteins. So, genes are found on DNA which is found in chromosomes. Chromosomes in humans Contains 2 additional structures 2 telemeres (one on each end)-prevent fraying and linking of chrom. Ex. Telemere is like lighting the end of thread DNA to keep it from unraveling 1 centromere middle body- Connection point for the two copies of a chrom. Following DNA replication. Each copy= sister chromatid There are 23 different chrom.-22 autosomes. 1 sex chromosomes 1 Autosomes are numbers 1-22 (largest to smallest)- (biggest) contains 3000 genes- 22 (smallest) 600 genes- The 23 rd corm. Are called X and Y (not 23)- Karyotpe- photos of the chrom. Cells that have 2 copies of each chromosome- All cells (except gametes) have 2 copies of each of the 23 chrom. One cope ( set of 23) from mom (egg), one cope set of 23 from dad (sperm)- Diploid (2n) so 46 chrom. In human cells Cells that have 1 copy of each chromosome Gametes (egg/sperm) have 1 copy of each of the 23 chrom.-haploid (1n or n) During fertilizations, egg and sperm chrom. Combine to make a diploid cell (n+ n =2n) -fertilized egg Examples of chromosome counts in other organisms Organism n (haploid number) 2n (diploid number) Humans 23 46 Gorillas 24 48 Dogs 39 78 Shrimp 127 254 Sweet potatoes 45 90 # of chrom. In other organisms note doesnt relate to # genes or complexity of the organism!...
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