Human Bio Ch 8

Question 1

What is recombinant DNA technology?

Answer 1

Synthetic DNA made by inserting genes from one source into a DNA molecule from a different source.

Recombinant DNA technology or genetic engineering, involves artificially changing DNA and produces a genetically modified organism. If this organism has DNA from another species it is called a transgenic organism.

Question 2

What is artificial selection?

Answer 2

Artificial selection - an ancient form of genetic engineering where humans select desired traits and choose parents based on these traits.

Question 3

What are restriction enzymes?

Answer 3

An enzyme that cuts strands of DNA at a specific sequences of nucleotides.
The cut sute of the restriction enzyme is known as the recognition site.
It is called a restriction enzyme as is restricts the duplication of the bacteriophages.
Each restriction enzyme will:
- recognise a certain base sequence
- cut at a certain point

Examples
- BamHI
- EcoRI
- HindIII
- TaqI
- PvuII

Question 4

What are the different types of cuts?

Answer 4

Straight cut - a cut produces when a restriction enzyme make a clean break across the 2 strands of DNA so that the ends terminate in a base pair, called blunt ends

Staggered cut - a cut produced by when a restriction enzyme creates fragments of DNA with unpaired nucleotides that overhang at the break in the strands, called sticky ends.

Question 5

What does it mean by a recognition site being palindromic?

Answer 5

Recognition sites are 4 to 8 base pairs in length and have the same sequence when read both forward and backwards. - Palindromic

Question 6

What is DNA ligase and what is the process of ligation?

Answer 6

DNA ligase is an enzyme capable of combining 2 small components of single-strand DNA into 1 single structure. Works by joining the phosphate group at the end of one strand to the sugar molecule at the end of another strand.
- Escherichia (E.coli)

The process of ligation is the joining of short strands of DNA during replication.

Question 7

What is a vector and how is it used in recombinant DNA?

Answer 7

A vector is a DNA molecule that is used to carry DNA into a cell. This help in recombinant DNA by:
1. identify the desired gene
2. using a restriction enzyme cut the DNA on either side of the gene
3. using the same restriction enzyme to cut the DNA vector
4. adding the desired gene to the vector
5. use the DNA ligase to join the 2 sections of DNA

Question 8

What is a plasmid?
plasmid is an example of a vector**

Answer 8

A plasmid is in a bacterial cell and is small circular strands of DNA distinct from the main bacterial genome, composed of only a few genes and able to replicate independently within cells. The gene of interest is integrated into the plasmid and is now referred to as recombinant DNA.
PLASMID IS A VECTOR

Question 9

What is the process of making a hormone using recombinant DNA technology?

Answer 9

1. Isolate the gene of interest and cut it out with a restriction enzyme at the recognition site. DNA fragment is left with sticky ends.
2. Isolate a plasmid (vector) from a bacterial cell and cut it using the same type of restriction enzyme in step 1.
3. Splice (glue together) the human DNA into the plasmid using DNA ligase enzymes to join the sticky ends.
4. Treat the bacterium to that is takes up the recombinant DNA plasmid. Once this is successful, the bacterium will multiply so that either the human gene or the product of the gen can be used.

Question 10

How can recombinant DNA be used to make a recombinant vaccine for Hep B?

Answer 10

1. Cut the Hep B viral DNA with a restriction enzyme that will leave sticky ends
2. Isolate a plasmid from a bacteria using the same restriction enzyme
3. Splice the Hep B DNA and the plasmid using DNA ligase which creates recombinant DNA
4. Introduce the recombinant DNA into a yeast cell
5. Put this recombinant yeast cell into a fermentation tank which increases in temperature and moisture
6. Recombinant yeast cell multiplies and produces the Hep B antigen in the fermentation tank
7. Extract and purify the Hep B antigen from the cell so that it can now be put into a vaccine.

Question 11

What is the need for synthetic hormones?

Answer 11

Synthetic hormones are used for people who cannot create the desired hormone themselves and need it to maintain homeostasis. The diseases that may need synthetic hormones include, Type 1 diabetes, hypothyroidism, hyperthyroidism.

Question 12

What is Diabetes Mellitus and what are the 2 types?

Answer 12

A group of diseases, all of which result in an abnormally high level of glucose in the blood and excretion of glucose in the urine. Two types are:
- Type 1
- Type 2

Question 13

What is Type 1 diabetes?

Answer 13

Sometimes called insulin-dependent diabetes, is a form of diabetes that develops rapidly usually before the age of 20. Caused by a decline in insulin producing cells of the pancreas (Beta cells), treated by injections of insulin at regular intervals.

Insulin cannot be taken in tablet form as it is digested in the alimentary canal, hence the only treatment is regular injections or a pump.

The patient must have insulin to survive, but even with injections the long term effects include, kidney failure, heart attack, stroke, amputations, blindness and nerve damage.

Question 14

What is Type 2 diabetes?

Answer 14

Also known as adult-onset diabetes, is a common form of diabetes that usually occurs in people over the age of 45 who are overweight, it can usually be controlled by diet.
Lifestyle factors that increase the risk are:
- lack of physical activity
- being overweight
- a diet that is regularly high in fat and sugar
- high blood pressure
- high blood cholesterol
- smoking

There is no cure for Type 2 diabetes, but the earlier the diagnosis the better the chances of successful management. This include:
- a careful diet
- regular physical activity
- maintaining a healthy weight
- monitoring blood glucose
- sometimes medication

Type 2 diabetes is preventable with a healthy lifestyle.

Question 15

How can recombinant DNA be used to produce insulin?

Answer 15

Insulin injections treat people with type 1 diabetes and sometimes type 2. Insulin used to be obtained from the pancreas of cows and pigs making it very expensive and limited. Now we use recombinant DNA in the following way:
1. extract the insulin gene from the human cell using a restriction enzyme
2. extract the plasmid from a bacteria cell using the same restriction enzyme
3. splice the plasmid and DNA together to produce a recombinant DNA
4. insert the recombinant DNA into a bacteria cell
5. let the bacteria grow in culture
6. extract the insulin

Question 16

What is Hyperthyroidism?

Answer 16

Is the overactivity of the thyroid gland resulting in abnormally high levels of thyroid hormones in the blood.

They most common type of hyperthyroidism is graves disease which is the excessive secretion of thyroid hormones, which causes protruding eyeballs.

Because the cells are over stimulates and the metabolic rate increases, the symptoms include:
- rapid heart rate
- weight loss
- increased appetite
- in cases of graves disease, protruding eyeballs (exophthalmia)

During the production of thyroxine iodine is absorbed from the bloodstream, concentrated in the cells of the thyroid and then incorporated in the cells that produce the hormones. Hyperthyroidism can be treated with drugs that block the thyroid glands use of iodine. Another method is by giving the patient a drink that contains radioactive iodine which will be absorbed the cells and then destroy them. Another method is to have surgery to remove part of the thyroid.

Question 17

What is Hypothyroidism?

Answer 17

Underactivity of the thyroid gland resulting in low levels of thyroid hormones in the blood. Much more common than hyperthyroidism.

Symptoms arise from a decrease in metabolism and include:
- slow heart rate
- unexplained weight gain
- fatigue or lack of energy
- intolerance to cold
- swelling of the face
- goitre (enlargement of the thyroid)

If there is a lack of iodine in the diet it can prevent the thyroid gland from making enough hormones. To help with this common iodine deficiency the federal government made it compulsory for iodine to be included in bread apart from organic and bread mixes.

Although iodine deficiency is a big factor to hypothyroidism the main one is an attack on the thyroid by the immune system, known as Hashimoto’s disease. Can also happen when a part of the thyroid is removed for cancer treatment.

Treatment includes extra iodine in the diet, tablets containing thyroid hormones that the person will have to take for life monitoring the levels (Levothyroxine - manufactured form of thyroxine).

Question 18

What is gene therapy?

Answer 18

Is the treatment of a disease by replacing, manipulating or supplementing non functioning genes in cells and tissues.
Some areas of possibility include:
- replacing a mutated gene with a healthy copy
- fixing or inactivating a mutated gene
- inserting a new gene that will fight the disease
- making the immune system recognise diseased cells

Question 19

What are the steps included in gene therapy?

Answer 19

1. Place the new and healthy gene into a virus vector
2. The vector binds to the cell
3. The vector is packages into a vesicle on the cell membrane
4. Vesicle moves through the cytoplasm and breaks down and is released
5. The new gene is injected into the nucleus

Used for:
- Type 1 diabetes (introducing a healthy gene for insulin into the alpha cells so that they can produce the hormone)
- Huntington’s
- Cystic Fibrosis

Question 20

What is Cystic Fibrosis and how can is be treated by gene therapy?

Answer 20

A single gene disorder controlled by the recessive allele carried on an autosome that is incurable but can be detected during foetal development. Mucus-secreting glands, particularly in the lungs and pancreas, become fibrous and produce abnormally thick mucus, resulting in among other things, chest infections.

In the lungs the mucous traps the air passages and trap bacteria making the patient susceptible to infection.
The pancreas is also affected as it blocks the secretion of enzymes required for digestion.

In 1991 scientists successfully corrected fault CTFR (cystic fibrosis transmembrane regulator - gene) genes in cultured cells by adding normal copies of the gene to the culture, this was the first step towards gene therapy for CF. Safety is a huge concern so trials are continuing.

Question 21

What is Huntington’s disease and how can is be treated with gene therapy?

Answer 21

An inherited disease that causes the death of brain cells and results in a change in mood, a lack of coordination and unsteady gait, flailing movements of the limbs and progressive dementia (loss of ability to be able to think clearly)

Caused by a mutation of a single gene on chromosome 4 called IT15. Symptoms usually begin before the age of 40.

Research on mice has shown that gene therapy could be effective for huntington’s disease in humans. Further research has used a modified virus to deliver a corrective gene into brain cells that boosts a natural shield against the effects of the huntington’s protein.

Question 22

What is cell replacement therapy?

Answer 22

The replacement of damaged cells with new ones.

Cell replacement therapy for the NS has generated the most interest due to debilitating nature and widespread occurrence of disorders such as Parkinson’s and Alzheimer’s.

In Parkinson’s cell replacement therapy would replace dying neurons will healthy neuronal tissues. This was found successful as they not only grew but established connections with other neurons. However the use of human embryonic stem cells is controversial and raises many ethical concerns.

Question 23

What is tissue emgineering?

Answer 23

The rebuilding of damaged tissue by the use of biology, medicine and engineering.

Primary objective is to restore healthy tissues or organs and eliminate the need for tissue or organ transplants.