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BIOL 4410 (1)
Lecture

Advanced Drosophila Genetics

4 Pages
67 Views

Department
Biology
Course Code
BIOL 4410
Professor
Arthur Hilliker

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ADVANCED DROSOPHILA GENETICS SEPTEMBER 16 y Morgan realized that Mendelian Genetics was right y Morgan also established the chromosome theory ofheredity meaning that genes are present on chromosomes y He also showed crossing over which is the basis of chromosome mapping y In drosophila there is mitotic somatic pairing y In the chromosome picture of the drosophila metaphase we see that the Y chromosome is very darkly stained meaning that it is very dense Y chromosome is completely made ofheterochromatin y There is two types of chromatin 1Heterochromatin which is very dense2Euchromatin which is less stained y The heterochromatin in Drosophila is o Dark staining during Intrphase o Located near centromere all centromeres are heterochromatin in Drosophila o Has high amount of repeated sequence of DNA AATAT31 of genome or AAGAG56 of genome y Most of the genes are located in the euchromatiny In the interphase nuclei there are also some dense chromosome regions heterochromatin that are referred to as chromocenters y Another term for centromere is kinetochore or primary constriction y The kineticore is the engine of mitosis because the spindle fiber attaches to it and pulls it to the pole y There is also secondary constriction which is divided into two parts NC y The N is nucleolus organizer rRNA is synthesized at this site o The nucleolus is visible in an interphase nucleusy rRNA genes are unusual comparing to other genes because o they arent translated into protein o there is multiple copies of them for higher expression o they have their own distinct RNAPOL y C encodes the histoneso Histone genes like those of the rRNA are present in multiple genes y In drosophila Y chromosome there is sister chromatid apposition meaning that bthe chromatids dont separate it looks like that there is only one chromatid but in fact there is two y Each chromosome has two arms o X and Y chromosome are acrocentric one long arm and one short arm XX LS YY LSo Second and third chromosomes are metacentricboth arms are the same size and the centromere is right between them has 2R and 2L or 3R and 3Ltho The 4 chromosome is also acrocentric 4L and 4R y The Y chromosome is completely made of heterochromatin and X chromosome is 50 thand major autosomes 23 are 25 and the 4 chromosome is about 50
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