Transcript Chromosomes
http://www.alumni.ca/~laue d3e/chromosome.jpg Chromosomes and Cell Division New Cells Are Formed by Cell Division • About 2 trillion cells are produced by an adult human body every day. • This is about 25 million new cells per second. • Why would cells divide or reproduce? Different Types of Cell Division • 1. Bacteria reproduce by binary fission. – Binary Fission= a form of asexual reproduction that produces identical offspring – If the offspring are identical, what is true about the DNA? • 2. Eukaryotic organisms undergoing growth, development, repair or asexual reproduction • 3. The formation of gametes or sex cells Rod-shaped Bacteria Dividing by Binary Fission http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookmito.html Binary Fission Video Clips • http://www.youtube.com/watch?v=gEwzDy dciWc&feature=related • http://www.youtube.com/watch?v=3cD3U2 pgb5w&playnext_from=PL&feature=PlayLi st&p=91845E3E72841AFE&playnext=1&in dex=7 • http://www.youtube.com/watch?v=K0ZP8V txUZ0&playnext_from=PL&feature=PlayLi st&p=91845E3E72841AFE&index=8 Eukaryotic cells form chromosomes before cell division • gene = a segment of DNA that codes for a protein or RNA molecule • As a eukaryotic cell prepares to divide the DNA and proteins associated with the DNA coil into a structure called a chromosome. • Before DNA coils, the DNA is copied. • The two exact copies of DNA that make up the chromosome are called chromatids. • Genes are found on chromosomes • They are sections of DNA • Here is the gene for Parkinson’s Disease. • The chromatids attach at a point called the centromere. http://www.ams.org/ new-inmath/cover/images/ chromosome.gif • Homologous Chromosomes = chromosomes that are similar in size, shape, and genetic content • Each homologue in a pair of homologous chromosomes comes from one of the two parents. • There are 46 chromosomes in human somatic or body cells or 2 sets of 23 chromosomes. • Diploid= two sets of chromosomes • Haploid= one set of chromosomes • Zygote= a fertilized egg cell, the fusion of two haploid gametes • autosomes= chromosomes that are not directly involved in determining sex – 22 pairs • Sex chromosomes= determine sex – XX=female XY=male chromatids http://www.genomesize.com/rgreg ory/Chromosome.JPG • Karyotype = a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size. Is this a karyotype of a male or female? Do you notice anything about this karyotype? • Down’s syndrome http://www.ucl.ac.uk/~ucbhjow/bmsi/lec7_images/47_xx_21.gif What do you notice about this karyotype? • Turner Syndrome http://www.antenataltesting.info/images/karyotypeTurners.jpg • 1. Why is cell division important? • 2. What are chromosomes made up of? • 3. Where are genes found? Homework Directed Reading 6-1