Chapter 2 single gene inheritance

Chapter 2 single gene inheritance - Chapter 2 Single Gene...

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Unformatted text preview: Chapter 2 Single Gene Inheritance Suggested Problems: #5,6,8,9,11,13,16,20,21,25,26,29,30, 32,34,35,36,38,39,50,52,62,63,64 Gene discovery: • choose a particular trait to study • find individuals (“mutants”) who vary in that trait (either naturally occurring or by inducing variants with mutagens) • test how the mutant trait is inherited • single gene inheritance was first described by Mendel discontinuous variation versus continuous variation { { { traits chromosomes DNA Three different levels to study genetic inheritance Chromosomes Chromosomes of Indian Muntjac • members of a species have a characteristic chromosome number • diploid organisms (most plants and animals) have two of each chromosome • diploid number (2n) = total chromosomes • haploid number (n) = number of different chromosomes (ie, the basic genomic set) • chromosome pairs are called homologous chromosomes Chromosome Number: complexity of an organism is not predicted by chromosome number *some ferns have hundreds of chromosomes Haploid Organisms (fungi, algae) most of life cycle takes place with one chromosome set (n) more later on this…. Chromosomes Terms: centromere telomere nucleolar organizer nucleolus chromatin heterochromatin euchromatin How is DNA packed into the nucleus? approximately 2 meters of DNA per cell needs organization! Level 1: nucleosomes • in certain experimental conditions, DNA will open up to look like beads on a string • the “beads” are aprox. 10-11 nm wide • the “beads” are nucleosomes, made up of histone proteins • one nucleosome consists of 2 molecules each of H2A, H2B, H3, and H4 • 146 base pairs of DNA wrap twice around a nucleosome Level 2: solenoid • 6 coiled nucleosomes • solenoid is stabilized by another histone protein, H1 • approx. 30 nm diameter How is DNA packed into the nucleus? How is DNA packed into the nucleus? Level 3: scaffold • solenoid DNA loops attach to a scaffold • scaffold is made up of the protein topoisomerase II • scaffold is 300 nm wide • DNA has certain sequence that binds to topoisomerase II, called scaffold attachment regions (SARs) Level 4: supercoiled scaffold ~700 nm wide, the approx. size of metaphase chromosomes { { { traits chromosomes DNA Three different levels to study genetic inheritance …we finally get to Mendel, the father of genetics Gregor Mendel 1822-1884, the founder of genetics 1865 published a paper on his experiments with garden peas his work “languished in obscurity”, until rediscovery in the early 1900s Terminology phenotype: the form taken by a particular character/trait true-breeding (pure) line : for the phenotype being examined, all offspring were always the same Cross-pollination and selfing are two types of crosses (parental) (first filial) F...
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This note was uploaded on 05/28/2011 for the course BIO 220 taught by Professor Dr.leatherman during the Spring '10 term at N. Colorado.

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Chapter 2 single gene inheritance - Chapter 2 Single Gene...

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