CH 8 TECHNOLOGY

Question 1

what do you know about DNA? (recap)

Answer 1

each nucleotide made of;

• deoxyribose sugar molecule
• phosphate group
• nitrogenous base (thymine, cytosine, adenine, guanine)

bases of strands attracted to each other by hydrogen bonds

Question 2

what is artificial selection / selective breeding

Answer 2

• modification of organisms for desirable traits
• selecting which male and female organisms are crossed to produce offspring to increase/decrease the chances of certain traits showing up in future generations
• slow, inefficient process, genes are passed by chance, must wait for offspring to mature before knowing the outcome

Question 3

what is genetic engineering / recombinant DNA technology

Answer 3

• DNA is either added or removed from a cell

- DNA produced is called recombinant DNA and the organism is called a genetically modified organism (GMO)

Question 4

what is a transgenic organism?

Answer 4

• organism produced when DNA from one species is introduced to another species
• the aim of such an organism is to introduce a trait that is not normally present

Question 5

who first created recombinant DNA and what was their technique?

Answer 5

• Stanley Norman Cohen and Herbert Boyer (1973)
• their technique: isolate and amplify genes or DNA segments and insert them into a bacterial cell, creating a transgenic bacterium

Question 6

what are restriction enzymes?

Answer 6

• certain enzymes in bacteria that are able to restrict the duplication of bacteriophages by cutting up the viral DNA
• scientists found that these enzymes always cut the DNA at a point where there is a certain sequence of bases [sequence known as recognition sequence]

Question 7

what is an endonuclease?

give an example of one

Answer 7

enzymes that cut within a DNA molecule by separating two nucleotides
e.g. restriction enzyme

Question 8

differentiate between a straight cut and a staggered cut

Answer 8

straight cut: restriction enzyme makes a clean break across the two strands of DNA to produce a blunt end (blunt end; where both ends terminate in a base pair)
staggered cut: results in fragments with sticky ends (sticky end; a stretch of unpaired nucleotides in the DNA molecule that overhang in the break in the strands)

Question 9

what are some characteristics of recognition sites?

Answer 9

• 4-8 base pairs in length
• palindromic
• same sequence occurs on both strands within the site due to the complementary nature of the bases

Question 10

what will each restriction enzyme do when cutting DNA strands?

Answer 10

• recognise a certain base sequence
• cut at a certain point

both these factors contribute to the type of cut

Question 11

why can sticky ends be useful?

Answer 11

• they possess the ability to combine with sections of DNA that have a complementary ending
• this allows a single-stranded overhang from one DNA fragment to be paired with any other piece of DNA that has the corresponding sequence
• this DNA could be from the same or different organism

Question 12

how does the name of each enzyme reflect its origin?

Answer 12

• 1st letter: genus of the bacterium from which it is isolated
• 2nd two letters: species
• next letter: strain of the bacterium
• the roman numerals represent when the enzyme was isolated; I is the first enzyme isolated, II is the second enzyme isolated etc…

e.g. EcoRI is the first restriction enzyme isolated from the RY13 strain of the bacterium Escherichia coli

Question 13

what is DNA ligase?

Answer 13

• DNA-joining enzyme that allows the modification of genes through the ability to join, recombine or separate pieces of DNA
• found in Escherichia coli
• some version is used by every living cell to ‘glue’ together short strands of DNA during replication (a process called ligation)

Question 14

how does DNA ligase work?

Answer 14

• works by joining the phosphate group at the end of one strand to the sugar molecule at the end of another strand
• for this to be possible, the complementary bases must first from hydrogen bonds, then the DNA ligase can join the backbone of each strand

Question 15

when producing an organism with recombinant DNA, the gene of interest is isolated, inserted into a vector and then cloned. how is this achieved?

Answer 15

1. identifying the desired gene
2. using a restricted enzyme to cut the DNA on either side of the gene
3. using the same restriction enzyme to cut the DNA of the vector
4. adding the desired gene to the vector
5. using DNA ligase to join the two sections of DNA

Question 16

what are plasmids?

Answer 16

• usually circular, double-stranded units of cytoplasmic DNA

- capable of replicating within a cell independently of the chromosomal DNA

Question 17

what happens after the gene of interest is integrated into the plasmid or phage?

Answer 17

• the gene is now called recombinant DNA
• cloning of the vector then occurs so that numerous copies of the DNA are available to insert into the host cells
• once large quantities of the vector have been produced, they can be introduced into the selected host cell such as special bacterial, yeast or mammalian cells
• these cells can then produce the foreign protein using the instructions in the gene in the recombinant DNA

Question 18

how might recombinant DNA be used?

Answer 18

• diagnosis and treatment of diseases and genetic disorders
• enable the manufacture of large quantities of pure protein for many medical products (e.g. insulin, growth hormone, FSH)

Question 19

what is a recombinant vaccine?

Answer 19

• vaccines produced using recombinant DNA
  e. g.
• using recombinant bacterium E. coli or cells from mammals, insects or yeast to produce antigens
• these can be introduced to the body, where they will elicit an immune response

Question 20

what was the first recombinant vaccine?

Answer 20

• hepatitis B
• 1986
• produced by inserting a gene from the hepatitis B virus into the cowpox virus

Question 21

how is the vaccine for hepatitis B produced?

Answer 21

• the gene for a surface antigen on the virus is isolated and added to a plasmid
• the plasmid is introduced into a yeast cell. when the yeast cell divides, the new cells also contain the plasmid with the gene for the antigen
• this gene allows the yeast cells to produce the antigen protein, which can be collected and purified

Question 22

how do DNA vaccines work?

Answer 22

• similar to recombinant vaccines but;
• the DNA for the antigen is produced in the vaccine instead of the antigen itself
• the DNA is incorporated into the host’s cells, which will produce the antigen
• the antigen will then be expressed by host cells, in a similar way to what happens during viral infection

Question 23

are there any disadvantages to recombinant DNA vaccines?

Answer 23

• expensive - antigens need to be located, cloned and expressed efficiently in a new vector
• those involved in vaccine research must be conservative

Question 24

what is diabetes mellitus?

Answer 24

• hormonal problem that disrupts homeostasis
• includes hyperglycaemia (increased BGL)
• high BGL leads to increased glucose excretion in urine

Question 25

what is type 1 diabetes?

Answer 25

• insulin-dependent diabetes usually begins in childhood
• fault in immune system causes the destruction in beta cells –> no insulin production
• in most cases, disease can be handled by giving the person insulin either by injection or by pump under skin
  (cannot be taken by pill as it is digested in the alimentary canal)
• long-term effects can include kidney failure, heart attack, stroke, amputations, blindness or nerve damage

Question 26

what is type 2 diabetes?

Answer 26

• adult-onset-diabetes usually develops in people over the age of 45 years
• able to produce insulin, but cells respond to it
• risk factors include; overweight/obese, lack of physical activity, high BP, high cholesterol, smoking, diet high in fat, sugar, salt and low in fibre
• little to no symptoms
• no cure
• early diagnosis helps prevent risk of heart disease, stroke, kidney disease, eye problems, nerve damage, skin and foot problems
• can be managed by careful diet, regular physical activity, maintaining healthy weight, monitoring blood glucose, and sometimes by medication
• IS PREVENTABLE

Question 27

talk about the treatment of diabetes via injection

Answer 27

• type 1, sometimes type 2
• used to be obtained from pancreases of pigs and cows - had to be purified, some people allergic
• 1980s - genetically engineered human insulin produced.
• • insulin inserted into DNA of bacterium Escherichia coli. The bacteria were cultures, and the transgene allowed bacterial cells to produce the protein of human insulin. this was then extracted and used to treat people
• yeast now used to make insulin

Question 28

what is the role of thyroxine?

Answer 28

• affects nearly every tissue in the body by stimulating carbohydrate, protein and fat metabolism
• secretion regulates metabolic rate
• some energy released from chemical reactions stimulated by T4 is in heat form
• therefore thyroid hormones important in long-term homeostasis of body temp
• excess/deficiency can cause disorders, due to thyroid problem or imbalance in TSH

Question 29

what is hyperthyroidism?

Answer 29

• too much thyroxine produced by thyroid gland
• most common type = grave’s disease
• • enlargement of the thyroid gland caused by immune system reaction
• not inherited
• cells are overstimulated, metabolic rate is increased
• symptoms: rapid heartbeat, weight loss, increased appetite, fatigue, sweating, anxiety, and (in grave’s disease) protruding eyeballs

Question 30

how are T3 and T4 produced?

Answer 30

iodine is absorbed from the bloodstream, concentrated in cells and in the thyroid and then incorporated into the molecules to make hormones

Question 31

how can hyperthyroidism be treated?

Answer 31

• drugs that block the thyroid gland’s use of iodine
• drink containing radioactive iodine which will kill thyroid cells after being taken up by them (due to radioactive activity) — cells elsewhere in body do not take up iodine and are unaffected. radioactive iodine excreted in urine
• surgery for removal of some or all of gland - less hormone produced
• when cells in thyroid destroyed, risk of developing hypothyroidism

Question 32

what is hypothyroidism?

Answer 32

• too little thyroxine produced
• more common than hyper
• problems with thyroid, pituitary or hypothalamus
• symptoms due to decrease in metabolism and may include slow heart rate, unexplained weight gain, fatigue, lack of energy feeling, intolerance to cold, swelling of face, goitre
• may be due to deficiency of iodine in diet - lack of production of T3 and T4
• gland may become enlarged in an effort to increase hormone production

OTHER CAUSES

• Hashimoto’s disease - an attack on the thyroid gland by the immune system
• surgery for removal of all or part of gland due to cancer

Question 33

how is hypothyroidism treated?

Answer 33

for lack of iodine:
- inclusion of extra iodine in diet

for other causes:

• tablets containing thyroid hormone taken for rest of life
• must take correct amount (too much=hyper, too little=hypo)
• pills were from pigs, now by synthetically made pills in chemical process

Question 34

what is gene therapy?

Answer 34

• the treatment of disease by replacing, manipulating or supplementing non-functional genes in cells and tissues
• aims to treat or cure genetic abnormalities by identifying faulty genes and inserting healthy ones