Biotechnology - Chapter 10

Question 1

Polymerase chain reaction

Answer 1

a technique used in molecular biology for producing multiple copies of DNA from a sample; used in DNA fingerprinting and identifying disease.

Question 2

3 Steps to PCR testing

Answer 2

1. denaturing
2. annealing
3. extension

Question 3

Denaturing

Answer 3

• heat is used to seperate two strands of DNA
• temperatures of 94-96ºC are used to break hydrogen bonds holding the two strands together

Question 4

Annealing

Answer 4

• during this process, temperatures decrease to 50-60ºC
• this allows short strands of DNA (primers) tp bind to the single DNA strands

Question 5

Extension

Answer 5

• also known as elongation mimics DNA replication
• this process is carried out at 68-72ºC
• DNA polymerase is used to join new, complimentary nucleotides to sections originating with primers
• the nucleotide chain extends and creates a new strand of DNA
• this new strand is not as long as the original strand as it starts at a primer
• DNA polymerase attaches to the double stranded DNA
• Primers initiate DNA replication

Question 6

Taq Polymerase

Answer 6

heat sustainable DNA polymerase
- does not denature when heated
- optimal temp 68-72ºC

Question 7

Gel electrophoresis

Answer 7

a process used to seperate charged molecules based on their size by pushing them through gel.

Question 8

Steps to gel electrophoresis

Answer 8

1. DNA pieces placed in wells in semi-solid gel that is immersed in a solution of electrolyte
2. (electrodes at either end of gel) negative electrode is closest to the DNA and positive is on the opposite side
3. when electric current is passed through the gel, negatively charged DNA moves towards the positive electrode. when current is stopped, smaller DNA is further from negative electrode as they move faster.
4. results in a pattern of bands, which is a persons DNA profile/DNA fingerprint

Question 9

Micropipette

Answer 9

a fine pipette used to measure and transfer very small volumes of liquid.

• has disposable tips that can be put on and off the end of the pipette without contact, reducing any chance of cross-contamination.

Question 10

DNA ladders

Answer 10

• run at the same time as samples and has known lengths
• used to compare lengths of DNA samples

Question 11

Visualising DNA

Answer 11

ethidium bromide, methylene blue, DNA probes

Question 12

Ethidium bromide

Answer 12

can be added to agar. as DNA moves through, it picks up some of the chemical. special ultraviolate light is shown over the gel and DNA fluoresce

Question 13

Methylene blue

Answer 13

a dye that binds to DNA. when gel is soaked in dye, DNA stains a deeper blue - visible to the naked eye.

Question 14

DNA probes

Answer 14

are short sections of a single strand of DNA with a radioactive fluorescent molecule that binds to DNA.

Question 15

DNA sequencing

Answer 15

the determination of the precise order of nucleotides in a sample of DNA.

Question 16

Dideoxyribonucleotide

Answer 16

a modified deoxyribonucleotide that lacks a hydroxyl group of the sugar component.

Question 17

Sangers method

Answer 17

• adds dideoxyribonucleotide to the growing strand
• this synthetic nucleotide stops the elongation as there is no OH group for the next nucleotide to attach to
• this happens to each nucleotide, creating different lengths of DNA
• can be separated using gel electrophoresis - knowing which base was added to create each length allows determination of order of nucleotides

Question 18

Uses of DNA sequencing

Answer 18

• identifying mutations
• identifying sickle-cell anaemia, cystic fibrosis and other forms of cancer
• for maternity and paternity tests
• to compare species

Question 19

Ethical considerations with genetic info

Answer 19

autonomy - the right to be self determining and choose whether or not to be testes on

confidentiality - the use of genetic info is treated sensitively, and is accessed only by those who are authorised to access it.

equity - right to fair and equal treatment, regardless of genetic info

privacy - right to be left alone and make decisions independent of others.

Question 20

Genome

Answer 20

a complete set of genetic material in a cell; an organisms complete set of DNA

Question 21

Comparative genomics

Answer 21

the comparison of genome sequences of different species.

• allows researchers to find areas of similarity and differences
• provides effective means of studying evolutionary changes
• humans share 98% of DNA with chimpanzees

Question 22

Junk DNA

Answer 22

non-coding sequences that have no apparent function and appear to serve no purpose.
- more closely related species have more junk sequences in common.

Question 23

Endogenous retrovirus

Answer 23

non-functional DNA (viral sequence). they store their genetic information as RNA.

Question 24

Reverse transcription

Answer 24

upon entering a cell, a retrovirus copies its RNA genome into DNA in a process known as reverse transcription. the DNA then becomes inserted into one of the host cells chromosomes.

Question 25

When is a retrovirus endogenous?

Answer 25

only becomes endogenous if it is inserted into a cell who’s chromosome will be inherited by the next generation - an ovum or sperm cell.

• offspring of the individual will then have a copy of the ERV in the same place, in the same chromosome, in every single one of their cells.

Question 26

Mitochondrial DNA

Answer 26

DNA found in the mitochondria of the cells, rather than the nucleus.
- in the form of small circular molecules
- 5-10 of these molecules in each mitochondrion
- has 37 genes

Question 27

37 Genes of the mitochondria

Answer 27

24 code for making transfer RNA molecules, which are involved in protein synthesis.

13 have instructions for making some of the enzymes necessary for the reactions of cellular respiration.

Question 28

Inheritance of mtDNA