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Learn about the methods cells use to control gene expression, such as transcriptional regulation and the lac operon. Explore how mutations and adaptations, like lactose tolerance and malaria resistance, can impact gene expression.
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Control of Gene Expression Cells have developed methods by which they can control the ________________________of genes - called _____________ Genes that are _______________(always being ____________) are known as ____________________________ Other genes can be turned on and off by _________________ turn genes on when required. Regulation occur at ________________:
The lacOperon ______________use ____________ to control gene expression. An ____________ is composed of a cluster of __________ ________, a ____________, and, between these two regions, a short sequence of bases known as an _________. The lacoperon uses _________________to control the ___________________________of the ________________gene, the enzyme used to break down lactose
1. Made of three genes, ______________________. 2. The ____________is a ______________that blocks the transcription of the ____________________ gene by binding to the ___________________, which covers part of the promoter and therefore gets in the way of the ___________ ________________________________
3. Lactose acts as an ___________ (controls specific _______________). If lactose ______________, it binds to the _____________ changing its shape. (Signal molecule _____________) 4. RNA ______________can now transcribe the ____ ________________ http://www.biocourse.com/ui/swf/iLabs/lac_operon.swf
The trpoperon In contrast to the lacoperon, the trpoperon is ___________________ ________________________________________________ The _______________ is the _______________________.
3. When the level of this _____ _____________________, the _________________protein ___________________(lack of the corepressor). 4. The trprepressor ________ ________________________. 5. The ________________is free to _______________ (increasing in tryptophan production) 1. When tryptophan levels ___________, the amino acid binds to the ____________________, altering its shape. 2. The trprepressor–_____________complex can now bind to the _____ ___________. Tryptophan is called a ________________.
Mutations Mutationsare _______________________________ Mutations may cause _________________________ _____________________________for an organism. Hemophilia can be caused by a mutation that changes the ___________________________!
Lactose Tolerance The domestication of plants and animals roughly 10,000 years ago profoundly changed human diets, and it gave those individuals who could best digest the new foods a selective advantage. The best understood of these adaptations is lactose tolerance (Sabeti et al., 2006; Bersaglieri et al., 2004). The ability to digest lactose, a sugar found in milk, usually disappears before adulthood in mammals, and the same is true in most human populations. However, for some people, including a large fraction of individuals of European descent, the ability to break down lactose persists because of a mutation in the lactase gene (LCT). This suggests that the allele became common in Europe because of increased nutrition from cow's milk, which became available after the domestication of cattle. This hypothesis was eventually confirmed by Todd Bersaglieri and his colleagues, who demonstrated that the lactase persistence allele is common in Europeans (nearly 80% of people of European descent carry this allele). Indeed, lactose tolerance is one of the strongest signals of selection seen anywhere in the genome. Sarah Tishkoff and colleagues subsequently found a distinct LCT mutation also conferring lactose tolerance, in this case in African pastoralist populations, suggesting the action of convergent evolution (Tishkoff et al., 2007).
Malaria Resistance The development of agriculture also changed the selective pressures on humans in another way: Increased population density made the transmission of infectious diseases easier. That role is reflected in the traces left by selection in human genetic diversity; multiple loci associated with disease resistance. In most cases, the resistance is to the same disease— malaria (Kwiatkowski, 2005). Malaria's power to drive selection is not surprising, as it is one of the human population's oldest diseases and remains one of the greatest causes of morbidity and mortality in the world today, infecting hundreds of millions of people and killing 1 to 2 million children in Africa each year. In fact, malaria was responsible for the first case of positive selection demonstrated genetically in humans. In the 1940s and 1950s, J. B. S. Haldane and A. C. Allison demonstrated that the geographical distribution of the sickle-cell mutation (Glu6Val) in the beta hemoglobin gene (HBB) was limited to Africa and correlated with malaria endemicity, and that individuals who carry the sickle-cell trait are resistant to malaria (Allison, 1954). Since then, many more alleles for malaria resistance have shown evidence of selection, including more mutations in HBB, as well as mutations causing other red blood cell disorders (e.g., a- thalassemia, G6PD deficiency, and ovalocytosis) (Kwiatkowski, 2005). Malaria also drove one of the most striking genetic differences between populations. This difference involves the Duffy antigen gene (FY), which encodes a membrane protein used by the Plasmodium vivax malaria parasite to enter red blood cells, a critical first step in its life cycle. A mutation in FY that disrupts the protein, thus conferring protection against P. vivax malaria, is at a frequency of 100% throughout most of sub-Saharan Africa and virtually absent elsewhere; such an extreme difference in allele frequency is very rare for humans.
Diploid organisms have _____________________; hence, if an error is made ___________________ ________________________________________. Each of us may have ______________________ _____________________________________. Types of Mutations _________________have ____________on the operation of the cell. - occur in the ________________________________________ - can also change a ___________. Both ____________________ ________________________ (mistake effect of the mutation will go unnoticed (silent). ________________________arises when a change in the base sequence of DNA _______________________________________ ______________________________________________________ ex. cystic fibrosis
1000 different mutations that have been found in patients with cystic fibrosis. Each of these mutations occurs in a huge gene that encodes a protein (of 1480 amino acids) called the cystic fibrosis transmembrane conductance regulator (CFTR). The protein is responsible for transporting chloride ions through the plasma membrane. The gene encompasses over 6000 nucleotides spread over 27 exons on chromosome 7. The numbers in the mutation column represent the number of the nucleotides affected. Defects in the protein cause the various symptoms of the disease. Unlike sickle-cell disease, no single mutation is responsible for all cases of cystic fibrosis. People with cystic fibrosis inherit two mutant genes, but the mutations need not be the same.
_________________________- occurs when a change in the DNA sequence causes ________________________________ __________________________________________________ ___________________________________________________
____________________________________is caused by a nonsense mutation within the protein dystrophin. _______________________________is a lethal condition for boys that causes a devastating muscle-wasting condition which leads to difficulty walking, breathing. By their late teens the condition is so serious, it leads to an early death. _________________________________________arise from the _______________________________________
Some mutations cause a _________________, where one or more nucleotides are _____________________ Ex. if the ________________________from: AUG GGA UUC AAC GGA AUA, the codon sequence becomes: . This results in a ______________________ This type of ____________________________can also be caused by the ____________________________________. An insertion or deletion of 2 bases would also be negative but an event involving 3 may not be as detrimental. Why?
All of the previous mutations belong to a category known _________________________________________________________ Mutations involving large segments of DNA are known as __________________________.They involve the ______________ _____________________________________________
2 fragments on 2 different chromosomes (nonhomologous) _________________, sometimes disrupting the normal structure of genes. Can result in a _____________. Some types of ____________ are associated with translocations.
Some fragments of DNA are consistently on the move. These _______________________________________________or “_________________" are pieces of DNA that continually ______________________________________ in the genome.
Another type of mutation is when an ___________________. This happens when a chromosomal __________________ ____________________________________________
Causes of Genetic Mutations _________________________of cells are known as ______________________________________. Other mutations are caused by exposure ____________ _______________________________________________
Cancer is considered a _____________________because it is always a result of ____________________________________________. Mutations result in _________________________, which are mutant versions of genes that ________________________________________. You read section 5.7 and make note of the: " Key Differences Between Eukaryotes and Prokaryotes"
Biotechnology Biotechnology involves the use of living organisms or parts of living organisms to provide new methods of production and the making of new products including: New vaccines to prevent disease; Genetically modified plants with resistance to pests; Repair of damaged organs and tissues and improved detection of diseases; Treatments for human infertility; Bacteria capable of cleaning up oil spills; and Environmentally friendly biofuels. Biotechnology is also referred to as genetic modification, genetic engineering or genomics.
Many biotech processes involve cutting, joining, and replicating DNA. This makes it possible to move DNA from one DNA molecule to another, forming what is called RECOMBINANT DNA.
A number of the tools are used to manipulate DNA and most are biological molecules. An example of a biotech tool are restriction enzymes or restriction endonucleases. Bacteria use these enzymes as a defense mechanism to cut up viral DNA to make it non-functional. They do this by recognizing specific sequences of DNA called recognition sites.
Most recognition sites are 4-8 base pairs long Most are a complementary palindromic sequence Ex. EcoRI 5'-GAATTC-3' 3'-CTTAAG-5'. EcoRI scans DNA for its recognition site. Once bound, it disrupts a phosphodiester bond between the guanine and adenine breaking the DNA strand into 2.
Different restriction enzymes recognizes different sequences.
Molecular biologists can use these enzymes to cut DNA in a precise manner. If two fragments of DNA have been cut using the same restriction enzyme, they will naturally be attracted to each other if "sticky ends" are present. To reform the phosphodiester linkage between the backbones of the double strands DNA ligase is used.
