BIOC15 Lecture 1

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Biological Sciences
Clare Hasenkampf

BIOC15 Genetics Professor Hasenkampf -office hour: 4-6 pm in SW242 -not available on June 19 -e-mail: [email protected] Announcement -lab starts this week! -partner with group members for the fruit fly assignment Midterm -1 exam: June 5, 2012 in class (Attend class!! just in case you do not go to lecture) -2 exam: July 10, 2012 in class -if sick for the 1 exam, no make-up exam, mark is counted toward 2 exam nd Inheritance -how is genetic material passed from one to the next generation -around 1950s, the genetic material is known to be DNA Characteristics of genetic material (DNA) 1) Stable 2) Replicate-able & transmittable -can be passed from one to the next generation 3) Informational -capable of directing cellular activity 4) Mutate-able -capable of variation Structure of DNA -polymer of nucleotides -composes of 3 parts 1) Deoxyribose 5 carbon sugar rd th -3 & 5 carbons give polarity 2) Nitrogenous base -A, T, C, G 3) Phosphate group -nitrogenous base is linked to carbon 1 of sugar through glycosidic linkage -phosphate group is attached to carbon 5 -phosphodiester linkage is between carbon 3 of one sugar with the phosphate and a carbon 5 of another sugar attached to the phosphate group -double stranded, 2 polymers -hydrogen bonds hold the strands together -hydrogen bond is a weak bond -but, many hydrogen bonds make DNA stable -chromosome carries hereditary materials from the clue that chromosome divides in mitosis -chromosome contains protein & DNA -debate over whether protein or DNA is the genetic material -back in the day, most people voted for protein -because thousands of proteins are responsible for biochemical activity, seem more important -DNA only has 4 nitrogenous bases, not much difference/ diversity between them to be important enough than protein -concentration of guanine equals that of cytosine, concentration of adenine equal that of thymine -Franklin: used X-ray crystallography to find the structure of DNA died of cancer, could not receive Nobel Prize -DNA has repeating structure, helical molecule (spiral staircase) -adenine & guanine: both double ring -cytosine & thymine: similar in shape Complimentary Base Pairing -A pairs with T (2 hydrogen bonds) -C pairs with G (3 hydrogen bonds) Watson & Crick -how DNA is replicable is due to its double stranded structure -semi-conservative replication -DNA is never naked, always associated with proteins -positively charged histone binds to negatively charged DNA, leading to a neutral compound Prokaryote -has nucleic region, no nucleus Eukaryote -genetic material is kept in the nucleus -DNA never leaves nucleus RNA -found in both nucleus & cytoplasm -DNA makes RNA, RNA makes protein, known as central dogma of molecular biology -protein directs cellular activities -RNA is an intermediate for information of DNA to be transmitted despite it never leaves the nucleus -ribose: OH group in both carbon 2 & 3 -deoxyribose: OH group in only carbon 2 -RNA is less stable than DNA -OH group in carbon 2 is more susceptible to reactivity & mutation -uracil is more mutate-able than thymine -instable is an advantage, easy to get rid, most proteins are needed temporarily Why RNA is not double stranded? -only one DNA strand is serv
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