exam questions

Question 1

describe how an isolated human insulin gene is inserted into a bacteria plasmid (4)

Answer 1

• restriction endonucleases cut open DNA at recognition site
• forming sticky ends
• same enzymes cuts open plasmid
• forms complementary sticky ends which bind to DNA
• DNA ligase joins gaps

Question 2

suggest two ways that bacteria which take up modified plasmids can be identified (2)

Answer 2

• fluorescent dye: glowing bacteria have plasmid
• antibiotic resistant genes: survivors have plasmid

Question 3

suggest why it is preferable to use genetically engineered sources of human insulin rather than insulin obtained from pigs (2)

Answer 3

• no religious objections
• cheaper
• more efficient

Question 4

suggest one ethical objection to the use of stem cells from human embryos (1)

Answer 4

• form of abortion
• kills a potential human

Question 5

explain what is meant by a restriction enzyme (3)

Answer 5

• enzyme which cuts through DNA
• at a specific site called a recognition site
• forming sticky ends

Question 6

outline the formation of recombinant DNA (4)

Answer 6

• restriction endonucleases cut through DNA and forms sticky ends
• same enzyme cuts plasmid to form complementary sticky ends
• bind with hydrogen bonding
• ligase joins gaps in backbone

Question 7

explain what is meant by recombinant DNA (1)

Answer 7

2 sources of DNA joined together

Question 8

describe how genetic engineering has been used to produce human insulin (3)

Answer 8

• DNA is isolated using restriction enzymes
• plasmid bacteria is cut open using same enzymes
• forms complementary sticky ends
• gene is inserted into plasmid - forms H bonds
• ligase joins gaps in backbone

Question 9

what are the advantages of using genetic engineering to produce human insulin (3)

Answer 9

• rapid process
• body won’t reject
• reliable supply

Question 10

describe the role of restriction enzymes in genetic engineering (3)

Answer 10

• cut DNA at recognition sites
• cut plasmid
• form complementary sticky ends

Question 11

describe the role of ligase in genetic engineering (2)

Answer 11

• joins sticky ends of DNA and plasmid
• seals DNA backbone

Question 12

describe the role of DNA polymerase in genetic engineering (1)

Answer 12

forms double strand, used in PCR

Question 13

explain the role of a promoter in genetic engineering (2)

Answer 13

turns on transcription & binds RNA polymerase

Question 14

discuss benefits and problems with using gene therapy in treatment of diabetes rather than taking insulin (4)

Answer 14

benefits
- avoids injections
- less restriction on lifestyle

problems
- takes a long time to have effects
- rejection

Question 15

suggest why humans have more DNA than bacteria (2)

Answer 15

• humans are eukaryotes
• so have larger proteins
• bacteria are much smaller

Question 16

which enzyme removes the gene from the genome? (1)

Answer 16

restriction endonuclease

Question 17

which enzyme inserts the gene into the new DNA? (1)

Answer 17

ligase

Question 18

discuss the advantages and disadvantages of genetic screening (6)

Answer 18

advantages
- early intervention of treatment
- removes uncertainty
- can increase life expectancy

disadvantages
- false result
- presence may not result in condition
- distressing

Question 19

how is the knowledge of genomes used in medicine? (4)

Answer 19

• screen for heritable disease
• early diagnosis
• target drug treatment
• develop more efficient drugs

Question 20

explain the arguments against genetic screening (4)

Answer 20

• expensive
• moral issues
• false results
• there are many diseases we can test but have no treatment for

Question 21

suggest how bioinformatic may be useful in determining whether a newly sequenced allele causes disease (2)

Answer 21

• base sequence of normal allele and alternatives are held in a database
• computational analysis allows comparisons to be made

Question 22

explain why only selected sections of non-coding DNA are used when profiling a human (3)

Answer 22

• in most people, genes are same
• coding sequences would not provide unique profiles
• non coding DNA contains variables of repeating sequences

Question 23

why are protease enzymes used before PCR? (1)

Answer 23

digest proteins associated with DNA to purify

Question 24

why do proteins need to bind to substance in the agar gel in electrophoresis? (2)

Answer 24

• different proteins have different overall charges
• binding makes them all negatively charged
• so proteins will move in the same direction

Question 25

what needs to be done with mRNA in order for rest of genetic modification to occur? (2)

Answer 25

• make single stranded DNA (cDNA)
• using reverse transcriptase

Question 26

suggest one concern that people have about the genetic modification of bacteria (1)

Answer 26

resistance (antibiotic)

Question 27

state 3 differences between somatic & germ line cell gene therapy (3)

Answer 27

• somatic cannot be passed to offspring
• somatic introduced to body cell, germ line introduced to gamete
• somatic is short term