molecular genetics

Question 1

DNA (6)

Answer 1

• anti-parallel strands
• genetic material in living org
• store genetic info control characteristics
• inherited from parents
• double helix structure, found in nucleus of cell
• transmitted to nxt gen

Question 2

What is genetic engineering?

Answer 2

technique used to transfer genes from one org to another. indiv genes may b cut off from the cells of one organism & inserted into the cells of another org of the same or diff species. transferred gene can express itself in the recipient organism.

Question 3

what is required for gene transfer?

Answer 3

a vector(usually a plasmid)

Question 4

what is a vector

Answer 4

• another DNA molecule
• a bacterium
• virus
  used to carry the genes of one organism into another. small circular DNA called plasmid, obtained from bacterium can b used to transfer genes

Question 5

what is a transgenic organism?

Answer 5

one that has acquired a foreign gene(not found in the organism)

Question 6

step 1 of production of insulin by bacteria using genetic engineering(hint: cutcut cucumber, and what does it produce?)

Answer 6

Isolation of insulin gene:
- use restriction enzyme(like scissors) to ‘cut’ the insulin gene from the human DNA by breaking the bonds between the bases
- produces a DNA fragment containing the insulin gene w sticky ends on both sides->(means thy can join to another single-stranded gene later)
- each sticky end is a single strand of DNA bases -> can pair w complementary bases to form a double strand
(the 2 sticky ends r gna b complementary bcos the enzyme only cuts a specific base pattern)

Question 7

step 2 of production of insulin by bacteria using genetic engineering(hint: keep cutting don’t stop cutting, specify cut with what?)

Answer 7

Isolation of plasmid DNA frm bascterial cell:

• plasmid DNA is isolated from the bacterial cell
• using the same restriction enzyme, the plasmid DNA is cut to produce a linear strand of plasmid DNA w complementary sticky ends(bcos u use same restriction enzyme)

Question 8

step 3 of production of insulin by bacteria using genetic engineering(hint: ur making a salad, aft cutting all the vegas, u put them in a bowl and ?)

Answer 8

Insertion of insulin gene into the plasmid DNA:

• the DNA fragment w the insulin gene is MIXED w the cut plasmid DNA
• enzyme DNA ligase is used to seal/join the insulin gene to the plasmid by catalysing the formation of bonds btwn the complimentary bases

Question 9

step 4 of production of insulin by bacteria using genetic engineering(hint: what is a way to give death sentence/ torture method)

Answer 9

Introduce the (recombinant) plasmid carrying the insulin gene into the bacterial cell:

• mix the recombinant plasmid w the bacteria(E.Coli)
• apply temporary heat or electric shock to open up the pores on the cell membrane of the bacteria for plasmid to enter
• thus plasmid acts as a vector(carrier/vehicle) to carry the insulin gene into the bacterium
• once this is successful, the bacterium will multiply and all the bacteria produced will hv the human insulin gene in them
• each bacterial cell will start to make insulin molecule

Question 10

how to extract the insulin frm the bacteria?

Answer 10

kill the bacteria and burst it so tht all of the insulin will cm out which has to b purified b4 it can b used

Question 11

concerns of the previous way of obtaining insulin?(5)

Answer 11

• disease(MERs, SARs. Covid-19) that may not be fatal to animals but could be to use due to cross-breeding
• very inefficient
  -development of allergies against it aft a prolonged use
• many diabetics develop antibodies against animal insulin aft prolonged treatment: hv to take immuno-suppressive drugs to suppress the immune system so thyll b more vulnerable to diseases–>
  become more susceptible to diseases

Question 12

advanatages of insulin produced by genetic engineering(5)

Answer 12

exactly same as ordinary human insulin, so:

• does not induce allergic response in the patients as the insulin produced is identical to human inculin
• easier and cheaper to produce insulin(since it is produced in a short time n in large quantities compared to when extracted from animals)
• less risk of contamination by disease-causing microorganisms like bacteria as compared to insulin obtained from the increases of animals
• body will not develop antibodies against it–> patients does not need to use immuno-suppresive drugs to suppress immune system
• ethical concerns of vegetarians or religious grps can b overcomes since vegetarians may object to the use of insulin obtained from slaughtered animals

Question 13

DNA winds around…

Answer 13

proteins to form chromatin

Question 14

chromatin winds around…

Answer 14

itself during cell division to form chromosome (in nucleus of every cell)

Question 15

each DNA strand has

Answer 15

• 2 parallel poly nucleotide chains that run in opp direction (anti parallel) twisted to form the double helix
• sugar phosphate backbone
• sides made up of sugar and phosphate molecules
• rungs made up of base pairs (ATCG)

Question 16

complementary base pairing

Answer 16

• Adenine pair with Thyamine/Uracil

- Cytosine pair with Guanine

Question 17

gene (4)

Answer 17

• basic unit of inheritance
• sequence of nucleotide that determines formation of a single polypeptide (simpler ver of protein) which is used to make protein, codes for polypeptide when expressed
• 2 polynucleotide chain but only one determines type of protein made ( junk gene)
• stores info for a specific type of protein

Question 18

type of protein produced controls…

Answer 18

… characteristic and behaviour of cell
- determines traits/ observable features
protein –> ribosome –> outside nucleus –> modified in golgi apparatus

Question 19

protein synthesis methods

Answer 19

transcription and translation

Question 20

transcription (whr, what, how)

Answer 20

• nucleus
• process whr DNA template is copied into single stranded messenger RNA

only 1 side has genetic codes, other side is junk so…

• DNA unwinds and unzips
• mRNA molecule copies genetic code in DNA template
• following the rule of complementary base pairing but A pairs with U instead

Question 21

translation (whr, what, how)

Answer 21

• in cytoplasm
• whr sequence of mRNA codons is used to make polypeptides
• every 3 nucleotide = 1 amino acid
• AUG –> start codon
• UAG, UAA, UGA –> stop codon
• mRNA attaches to a ribosome that moves along mRNA and translated the msg into a sequence of aa joined 2gt forming polypep
• tRNA brings aa to ribosome (transfer RNA)
• as ribo moves along, polypep gets longer
• at end of mRNA strand, ribo detaches, polypep released

Question 22

how is insulin commerically produced?

Answer 22

the recombinat bacterium can b isolated & cultured in large sterile containers called fermentors to produce human insulin on large scale, under optimum conditions(o2 conc, pH, temp&; conc of nutrients–> carefully monitored by a computer), when a large population of bacteria is produced–> removed from the fermenter and insulin is extracted from them–> it is then purified, tested and packaged and sold

Question 23

benefits of GE (4) - plants + meds + rice

Answer 23

• prod crops that can grow under extreme conditions(eg, droght-resistant crops, salt-tolerant crops, crops that make more efficient use of nutrients)–> allows farmers to grow crops even when the envo conditions is not suitable 4 cultivation most crops
• development of pesticide resistant crops + crops that produce toxins that kill insects: the use of costly pesticides that may damage the envo is reduced
• low cost prod of medicine–> ge of impt drugs such as human insulin has drastically reduced the cost of these medicines, w these drugs becoming more affordable, more patients can get access to them and be treated
• improved nutritional quality–> golden rice–> high vitaminA content

Question 24

risks of GE (3)

Answer 24

• ppl allergic to transgenic food (lectin that deters aphids from feeding may be transferred to the potato plant)
• genes coding fot antibiotic resistance may accidentally be incorporated into bacteria –> diseases in humans
• deliberate abuse bio warfare, designer babies :((

Question 25

social and ethical implications (6)

Answer 25

1)designer babies
gene selection & transformation, if applied on humans, lead to attempts to make superheros/ gud looking ppl –> unfair advantage (esp on poor)

2)Eugenics
improve genetic quality of human repro, promo high repro of ppl w desired traits, reduced repro of ppl w undesired traits

1&2 unethical bc abnormal/ deformed kids have to bear the consequences of mistakes/ errors

3) embryo selection (can be useful)
save kids from horrible death, DNA tested for genetic diseases causing suffering anf mortality (tay sachs disease –> child lose nervous function)

4) objection to consume animal genes in plants (vice versa) by vegetarians
5) ppl feel its moraly wrong to exploit animals for medical research –> designed to suffer
6) genetic engineering may lead to class distinctions, only indivs w sufficient financial means can afford certain gene technologies

Question 26

transgenic plant(4)

Answer 26

a foreign gene may b inserted into a crop plant to make it

• frost resistant
• herbicide resistant(kill weeds)
• to hv built-in insecticide
• pest resistant

Question 27

transferring of a pest-resistant gene from a bacterium to a crop plant:

Answer 27

a gene may also b inserted into a crop plant to enable the production of a chemical that kills insect pests. the vector is another bacterium that can infect plant cells but does not cause disease in the plant

Question 28

step 1 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: cut-cut ladysfinger)

Answer 28

use restriction enzyme to cut out the gene from the bacterial DNA to produce sticky ends

Question 29

step 2 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: keep cutting but speciy with what & to produce what!)

Answer 29

use the same restricition enzyme to cut the plasmid to produce complementary sticky ends

Question 30

step 3 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: ur making a salad, aft cutting all the veges, u put them in a bowl and ? + glue)

Answer 30

• mix the plasmid w the DNA fragment containing the pest-resistant gene.
• the pest-resistant gene will bind to the plasmid by complementary base pairing btwn their ‘sticky ends’
• add the enzyme DNA ligase to seal the pest-resistant gene to the plasmid and this plasmd containing DNA from 2 diff organisms is called recombinant plasmid

Question 31

step 4 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: torture method hehe)

Answer 31

use heat/electric shock to insert plasmid into bacterium by opening up pores in the cell surface membrane of the bacterium for the plasmid to enter

Question 32

step 5 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: division & ? )

Answer 32

bacterium will multiply in growth medium

Question 33

step 6 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: subtraction & ?)

Answer 33

add pieces of leaf

Question 34

step 7 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: aft a breakup its time to?)

Answer 34

move leaf to growth medium

Question 35

step 8 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: the leafs r gna write an exam now)

Answer 35

spray herbicide, only those who took up the vector will survive

Question 36

step 9 of transferring of a pest-resistant gene from a bacterium to a crop plant (hint: time to pack up)

Answer 36

transfer to the growth chamber

Question 37

advantages of transgenic plants (3)

Answer 37

• more food prod
• farmer can grow larger crop as its easier to fight pest
• less envi pollution as lesser pesticide used

Question 38

disadvantages of transgenic plants (6)

Answer 38

• insect pests may develop resistance to poison prod by plants
• pest resistance may spread to weeds (cross polli)
• useful insects will be killed
• lead to more effective killing of weeds –> kill insects –> break links in food web + upset the ecological balance
• GM food may prove to b toxic or cancer-causing to ppl that consume them bcos modifying a single gene in plants cld result in the alteration of sm metabolic processes within the plant–> result in production of toxins not usually found within these plants–> consume these plants can pose serious health problems
• sm biotech companies hv engineered crop plants such that these plants produce seeds that cannot germinate–> means that farmers hv to buy special seeds from these companies every yr–> poses a serious prblm to poorer society whr farmers r struggling to make a living

Question 39

how is a transgenic plant formed?

Answer 39

allow the bacteria to infect plant cells, once inside plant cells, the foreign gene will b inserted into the plant chromosome, induce the plant cells to produce recombinant plants

Question 40

differences btwn selective breeding and genetic engineering(4)

Answer 40

1. in sb organisms used must b closely related or belong to the same species, however in ge organisms can b inserted w a foreign gene from any other organism(non-related species or diff species)
2. in sb, healthy and defective genes may b transmitted tgthr to the offspring however in ge specific genes r carefully selected b4 thy r transferred into an org–> reduces the risk of genetic defects being passed on to offsprings
3. sb, a slow process which involves breeding over several generations, req large amts of land however in ge, indiv cells used in ecpt which reproduce rapidly in the lab in a small container ( save space + resources)
4. sb is less efficient as org grow slower and may req more fd while ge is more efficient bvos for eg, transgenic salmon grow faster and req less fd than ordinary salmon (save time)