Ch.2Objectives

Ch.2Objectives - Embryology Chapter 2 Learning Objectives...

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Unformatted text preview: Embryology Chapter 2 Learning Objectives Genomic Equivalence-The theory that every cell of an organism has the same genome as every other cell Differential Gene Expression Three Postulates: 1. Every cell nucleus contains the entire genome established in the fertilized egg. 2. The unused genes in the differentiated cell are neither destroyed nor mutated, but retain the potential for being expressed. 3. Only a small percentage of the genome is expressed in each cell and only a portion of the RNA synthesized is specific for that cell type. Gene expression can be regulated at several levels such that different cell types synthesize different sets of proteins:-Differential Cell Transcription Regulates which nuclear genes are transcribed into nuclear RNA-Selective Nuclear RNA processing Regulates which transcribed RNAs enter into cytoplasm and become messenger RNAs.-Selective Messenger RNA Translation Regulates which mRNAs in cytoplasm are translated to proteins.-Differential Protein Modification Regulates which proteins remain and function in the cell. Describe the basic design of the nuclear transplantation experiments and conclusions drawn from this (cloning in mammals).-Scient ists took cells from mammary gland of pregnant ewe (sheep) and put them into culture.-The culture medium was formulated to keep the nuclei in these cells at the intact diploid stage (G1) of the cycle. (The G1 cell cycle stage was crit ical)-Researchers then obtained oocytes from a different strain of sheep and removed their nuclei.-Oocytes had to be in 2 nd meiotic metaphase (stage usually fertilized).-Fusion of the donor cell and the enucleated oocyte was accomplished by bringing to two cells together and sending electric impulses through them destabilizing cell membranes, allowing cells to fuse.-The same electric impulses that fused the cells activated the egg to begin development.-Resulting embryos were eventually transferred into the uteri of pregnant sheep. Out of 434 sheep oocytes, 1 survived: Dolly There is problems with health in cloned animals o Immunity o Genetic information is not in the same state in all cells Describe the structure of chromatin and explain the differences between active and repressed chromatin.- Eukaryotic genes are contained within a complex of DNA and protein Chromatin o Protein component constitutes half the weight of chromatin o Nucleosome the basic unit of chromatin structure Nucleosome is composed of an octamer of histone proteins (2 molecules each of histones) wrapped with 2 loops containing about 140 base pairs of DNA Histone H1 bound to linker DNA between the nucleosome 14 points of contact between the DNA and histones o Active Chromatin accessible, available for transcription o Inactive (repressed) Chromatin- condensed, unavailable for transcription- Described genes as strings on the beadsbeads are nucleosomes- Most of the time, nucleosomes are wound into tight solenoids,...
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This note was uploaded on 11/10/2010 for the course BIOS 7676 taught by Professor Sanders during the Spring '10 term at LA Tech.

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Ch.2Objectives - Embryology Chapter 2 Learning Objectives...

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