Albert Ngwenya Biology

As long ungakaze upostwe ngumamazala ethi "Umuntu womntanami" uyazincengela nje dadewethu ayikho impilo lapho

Father God you taught us to pray ukuthi ungasingenisi ekulingweni manje izilingo sezingena kithi ngenkani. We pray again don't lead us into temptation and don't lead temptation into us. Amen

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Explain in detail control of gene expression in prokaryotes, the lac operon. (100 marks).



The Escherichia coli (E. coli) is a gut dwelling prokaryotic bacteria that can regulate the production of proteins that are not needed at a particular time so as to use resources efficiently through operon. E. coli uses glucose for its metabolic processes but when glucose is not available it can use lactose as a second option. Lac operon is an inducible operon that is usually off. A lactose inactivates the repressor and turns on transcription.
Gene expression is a process of converting genetic information that is stored in DNA into proteins. The lac operon is an inducible cluster of related genes responsible for lactose catabolism under control of a single regulatory region known as the promoter. An operon is the whole set of DNA including the operator, the promoter and all the genes they control.
The lac operon, as shown in figure 1, consists of two regions; control region and structural genes. The operon is controlled by a promoter (P) and an operator (O) region. The promoter region is the binding site for RNA polymerase to initiate transcription. The operator region is the binding site of the repressor protein. The structural genes; lacZ, lacY and lacA known as z, y and a encode for Beta-galactosidase, permease and transacetylase respectively. The repressor protein is encoded by lacI (i) which is located outside the operon and is encoded by its own promoter.

A promoter is a short sequence of DNA where RNA polymerase first attaches so as to begin transcription of the genes. A promoter signals where transcription is to begin. An operator is a short portion of DNA where a repressor binds. When a repressor binds to the operator, RNA polymerase cannot attach to the promoter, and transcription cannot occur. The operator controls transcription of structural genes in this way.

Today we think of those boys behaving like girls and Tomboys. What's your say as biologist?

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Coronaviruses are a family of viruses that can cause illnesses such as the common cold, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). In 2019, a new coronavirus was identified as the cause of a disease outbreak that originated in China.

The virus is now known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease it causes is called coronavirus disease 2019 (COVID-19). In March 2020, the World Health Organization (WHO) declared the COVID-19 outbreak a pandemic.

Public health groups, including the U.S. Centers for Disease Control and Prevention (CDC) and WHO, are monitoring the pandemic and posting updates on their websites. These groups have also issued recommendations for preventing and treating the illness.

Signs and symptoms of coronavirus disease 2019 (COVID-19) may appear two to 14 days after exposure. This time after exposure and before having symptoms is called the incubation period. Common signs and symptoms can include:

Fever
Cough
Tiredness
Early symptoms of COVID-19 may include a loss of taste or smell.

Other symptoms can include:

Shortness of breath or difficulty breathing
Muscle aches
Chills
Sore throat
Runny nose
Headache
Chest pain
Pink eye (conjunctivitis)
This list is not all inclusive. Other less common symptoms have been reported, such as rash, nausea, vomiting and diarrhea. Children have similar symptoms to adults and generally have mild illness.

The severity of COVID-19 symptoms can range from very mild to severe. Some people may have only a few symptoms, and some people may have no symptoms at all. Some people may experience worsened symptoms, such as worsened shortness of breath and pneumonia, about a week after symptoms start.

People who are older have a higher risk of serious illness from COVID-19, and the risk increases with age. People who have existing chronic medical conditions also may have a higher risk of serious illness. Serious medical conditions that increase the risk of serious illness from COVID-19 include:

Serious heart diseases, such as heart failure, coronary artery disease or cardiomyopathy
Cancer
Chronic obstructive pulmonary disease (COPD)
Type 2 diabetes
Severe obesity
Chronic kidney disease
Sickle cell disease
Weakened immune system from solid organ transplants
Other conditions may increase the risk of serious illness, such as:

Asthma
Liver disease
Chronic lung diseases such as cystic fibrosis
Brain and nervous system conditions
Weakened immune system from bone marrow transplant, HIV or some medications
Type 1 diabetes
High blood pressure
This list is not all inclusive. Other underlying medical conditions may increase your risk of serious illness from COVID-19.

Corona virus is real. Stay safe biologists

Bulk flow function in long-distance transport
This type of transport is usually along the vertical axis of the plant (up and down) from
the roots to the leaves and vice versa.
Vascular tissues are involved in this type of transport as diffusion would be too slow.
• Bulk flow (movement due to pressure differences) moves water and solutes
through xylem vessels and sieve tubes.
• Transpiration reduces pressure in the leaf xylem; this creates a tension which
pulls sap up through the xylem from the roots.
• Hydrostatic pressure develops at one end of the sieve tubes in the phloem; this
forces the sap to the other end of the tube.