On July 5, 1997, Ian Wilmut and a group of scientists announced that they had successfully cloned a sheep named Dolly. Dolly is a natural sheep and you would not notice any differences between the real sheep and Dolly. The only major distinguishing factor between the two is Dolly's conception because its embryo developed without the presence of sperm. Instead, Dolly began as a cell from another sheep that was fused via electricity with a donor egg. She is reproduced just by one sheep. Today, scientists have cloned many types of animals, such as mice, sheep, pigs, cows, and dogs. However human cloning has still been talked whether if they should do or not.
WHAT IS RNA SPLICING?
RNA splicing is a process that removes introns and joins exons in a primary transcript. An intron usually contains a clear signal for splicing. In some cases, a splicing signal may be marked by a regulatory protein, resulting in alternative splicing. In rare cases, a pre-mRNA may contain several ambiguous splicing signals, resulting in a few alternatively spliced mRNAs.
WHAT IS DNA A MICROARRAY?
A DNA microarray is a multiplex technology used in molecular biology. It consists of an arrayed series of thousands of microscopic spots of DNA oligonucleotides, called features, each containing picomoles of a specific DNA sequence. They can be a short section of a gene or other DNA element that are used to hybridize a cDNA or cRNA sample under high-stringency conditions.
Basically DNA microarray contains DNA sequences arranged on a grid and it is used for transcription.
-mRNA from a specific cell type is isolated.
-Fluorescent cDNA is produced from the mRNA
-cDNA is applied to the microarray
-Unbound cDNA is washed off
-Complementary cDNA is detected by fluorescence
SUMMARY:
Gene expression is the overall process of information flow from genes to proteins, mainly controlled at the level of transcription. Turned on gene is transcribed to produce mRNA that is translated to make its corresponding protein. Regulatory gene codes for a repressor protein. In the absence of lactose, the repressor binds to the operator and prevents RNA polymerase action. Lactose inactivates the repressor, so the operator is unblocked. There are some types of operon control: inducible operon, repressible operon for examples. For many operons, activators enhance RNA polymerase binding to the promoter. Differentiation is controlled by turning specific sets of genes on and off, which is only in eukaryotic cells. Eukaryotic chromosomes undergo multiple levels of folding and coiling, called DNA packing. DNA packing can prevent transcription.
X-chromosome inactivation is when one of the two X chromosomes is highly compacted and transcriptionally inactive. It occurs early in embryonic development and all cellular descendants have the same inactivated chromosome. Every eukaryotic gene has its own promoter and terminator/are usually switched off and require activators to be turned on/are controlled by interactions between numerous regulatory proteins and control sequences. During alternative RNA splicing, production of different mRNA from the same transcript, it results in production of more than one polypeptide from the same gene, and it can involve removal of an exon with the introns on either side. Control of gene expression also occurs with breakdown of mRNA/initiation of translation/protein activation/protein breakdown. There are many possible control points that exist. Such as chromosome changes, control of transcription, control of RNA processing, flow through nuclear envelope, breakdown of mRNA, control of translation, and control after translation. Role of gene expression in fruit fly developments are orientation from head to tail, segmentation of the body, and production of adult features.
Most differentiated cells retain a full set of genes, even though only a subset may be expressed. Nuclear transplantation can be used to clone animals. It is used by replacing the nucleus of an egg cell or zygote with a nucleus from an adult somatic cell. Cloned animals can show differences from their parent due to a variety of influences during development. Reproductive cloning is used to produce animals with desirable traits. Human reproductive cloning raises ethical concerns. Mutations in two types of genes can cause cancer, oncogenes, and tumor-suppressor genes. Usually, four or more somatic mutations are required to produce a cancer cell. One possible scenario for colorectal cancer includes, activation f an oncogene increases cell division, inactivation of tumor gene causes formation of a benign tumor, and additional mutations lead to a malignant tumor. Healthy lifestyle choices such as avoiding carcinogens, avoiding fat and including food with fiber and antioxidants, and regular medical checkups are very helpful for preventing cancer.
This is a diagram of operon turned on (lactose inactivates repressor.) RNA polymerase bound to promoter in DNA, and producing mRNA. This mRNA turns into protein. Then lactose comes in and attaches to the protein. The protein becomes inactive repressor. As RNA polymerase bound to promoter to make mRNA, enzymes for lactose utilization is produced as well.
This is a diagram of operon turned off (lactose absent.) On operon, protein is made by mRNA, which is made by DNA. This protein, called active repressor attaches to operator on operon. Sense active repressor is in the way, RNA polymerase cannot attach to promoter. So there is no lactose-utilization being produced.
KEY TERMS:
1) Operon: a group of genes under coordinated control in bacteria
2) Promoter: sequence where RNA polymerase binds
3) Differentiation: controlled by turning specific sets of genes on or off. It involves cell specialization. in both structure and function
4) Silencers: repressors hat inhibit transcription
5) DNA microarray: contains DNA sequences arranged on a grid, and used to test for transcription
6) Signal Transduction Pathway: a series of molecular changes that converts a signal at the cell's surface to a response within the cell
7) Carcinogens: cancer-causing agents that damage DNA and promote cell division
8) Nuclear Transplantation: replacing the nucleus of an egg cell or zygote with a nucleus from an adult somatic cell
9) Homeotic Genes: master control genes that determine the anatomy of the body, specifying structures that will develop in each segment
10) Alternative RNA splicing: production of different mRNA from the same transcript
5 FACTS:
1) Proteins interacting with DNA turn prokaryotic genes on/off in response to environmental changes.
2) DNA packing in eukaryotic chromosomes helps regulate gene expression.
3) Complex assemblies of protein control eukaryotic transcription.
4) Development of an animal is lead by cascades of gene expression.
5) Cancer results from mutations in genes that control cell division.
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