1.What is gene expression?
It is the overall process by which genetic information flow from genes to proteins-that is, from genotype to phenotype.
2.What are the histones used for?
Histones are small proteins that help DNA packing by supporting the shape of the DNA.
3.Do small RNAs have a role in gene expression?
Yes, they do. The micro RNAs can bind to complementary sequences on mRNA molecules. They can degrade mRNA or block its translation.
Five main factors from the reading:
1.Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes.
2.DNA packing in eukaryotic chromosomes helps regulate gene expression.
3.In female mammals, one X chromosome is inactive in each somatic cell.
4.Cascades of gene expression direct the development of an animal.
5.DNA micro-arrays test for the transcription of many genes at once.
Diagram:
Link: http://www.accessexcellence.org/RC/VL/GG/induction.php
Summary:
The introduction of the chapter was talking cloning. A clone is an individual created by asexual reproduction and thus genetically identical to a single parent. After this we learned that proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes. Gene regulation - the turning on and off of genes - can help organisms respond to environmental changes. The overall process by which genetic information flows from genes to proteins-that is, from genotype to phenotype-is called gene expression. The control of gene expression makes it possible for cells to produce specific kinds of proteins when and where they are needed. The turning on and off of transcription is the main way that gene expression is regulated in all organisms.The chapter talked about the lac operon and the trp operon. Adjacent to the group of lactose enzyme genes are two control sequences, short sections of DNA that help control the enzyme genes. One stretch of nucleotides is a promoter, as site where the transcription enzyme, RNA polymerase, attached and initiates transcription. Between the promoter and the enzyme genes, a DNA segment called an operator acts as a switch. The operator determines whether RNA polymerase can attach to the promoter and start transcribing the genes. Such a cluster of genes with related functions, along with a promoter and an operator, is called an operon. A gene called a regulatory gene, located outside the operon, codes for the repressor. Another type of operon control involves activators, proteins that turn operons on by binding to DNA. Differentiation is the process by which cells become specialized in structure and function. Differentiation results from the expression of different combinations of genes. DNA packing in eukaryotic chromosomes helps regulate gene expression. A crucial aspect of DNA packing is the association of the DNA with small proteins called histones. In fact, histone proteins account for about half the mass of eukaryotic chromosomes. In female mammals, one X chromosome is inactive in each somatic cell. Female mammals, including humans, inherit two X chromosomes. So why don;t females make twice as much of the proteins encoded by genes on the X chromosome compared to the amount in males? it turns out that in female mammals, one X chromosome in each somatic cell exists in a highly compacted and almost entirely inactive form. This X chromosome inactivation is initiated early in embryonic development, when one of the two X chromosomes in each cell is inactivated at random. The inactive X in each cell of a female condenses into a compact, called a Barr body. Complex assemblies of proteins control eukaryotic transcription. In order to function, eukaryotic RNA polymerase requires the assistance of proteins called transcription factors. Eukaryotic RNA may be spliced in more than one way. With an alternative RNA splicing, an organism can get more than one type of polypeptide from a single gene. Small RNAs play multiple roles in controlling gene expression. Translation and later stages of gene expression are also subject to regulation. After a eukaryotic mRNA is fully processed and transported to the cytoplasm, there are additional opportunities for regulation. These include mRNA breakdown, initiation of translation, protein activation, and protein breakdown. Cascades of gene expression direct the development of an animal. A homeotic gene is a master control gene that regulates batteries of other genes that actually determine the anatomy of parts of the body. DNA microarrays test for the transcription of many genes at once. A DNA microarray is a glass slide with thousands of different kinds of single-stranded DNA fragments fixed to it in a tightly spaced array, or grid. Signal transduction pathways convert messages received at the cell surface to responses within the cell. Cell-to-cell signaling, with proteins or other kinds of molecules carrying messages from signaling cells to receiving cells is a key mechanism in the coordination of cellular activities. In most cases, a signal molecule acts by binding to a receptor proteins in the plasma membrane of the target cell and initiating a signal transduction pathway in the cell. Cell-signaling systems appeared early in the evolution life. Plant cloning shows that differentiated cells may retain all of their genetic potential. Nuclear transplantation can be used to close animals. Reproductive cloning has valuable applications, but human reproductive cloning raises ethical issues. Therapeutic cloning can produce stem cells with great medical potential. Cancer results from mutations in genes that control cell division. Multiple genetic changes underlie the development of cancer. Faulty proteins can interfere with normal signal transduction pathways. Lifestyle choices can reduce the risk of cancer.
Key Terms:
1.Clone - an individual created by asexual reproduction.
2.Operon - a cluster of genes with related functions, along with a promoter and an operator.
3.Differentiation - an individual's cells become specialized in structure and function.
4.Homeotic gene - a master control gene that regulates batteries of other genes that actually determine the anatomy of parts of the body.
5.DNA microarray - a glass slide with thousands of different kinds of single-stranded DNA fragments fixed to it in a tightly spaced array, or a grid.
6.Nuclear transplantation - the technique used to achieve animal cloning.
7.Reproductive cloning - a type of cloning, which results in birth of a new individual.
8.Therapeutic cloning - when the major aim is to produce embryonic stem cells for therapeutic treatments.
9.Adult stem cells - cells that are able to give rise to many but not all cell types in the organism.
10.Oncogene - a gene, which can cause cancer when present in a single copy in the cell.
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