Chapter 10 - Biotechnology provides evidence of evolution

Question 1

What is PCR

Answer 1

Polymerase chain reaction. A technique used to produce multiple copies of DNA from a sample. Used in fingerprinting and in identifying diseases

Question 2

what are the three steps of PCR

Answer 2

Denaturing, Annealing and extension

Question 3

Thermocycling

Answer 3

processes used in PCR of repeated heating and cooling. Takes two to three hours to produced a billion copies of DNA

Question 4

Explain denaturation in PCR

Answer 4

Using heat to seperate the two strands of DNA. Temps of 94-96ºC are used to break the hydrogen bonds holding the strands together, separating the strands without disrupting each individual strand

Question 5

explain annealing in PCR

Answer 5

Temperature decreased to 50-60ºC, allowing primers to bind to the single DNA strands. Primers are complementary to either end of the section of DNA to be copied

Question 6

explain extension in PCR

Answer 6

also known as elongation, the enzyme DNA polymerase is used to join new, complementary nucleotides to the sections originating with the primers. This extends, or elongates, the nucleotide chain and creates a new strand of DNA

Question 7

Primers

Answer 7

a strand of DNA or RNA that serves as a starting point for DNA replication

Question 8

what is taq polymerase

Answer 8

A heat stable DNA polymerase that does not denature when heated and has allowed the procedure to be simplified and automated, permitting the pCR sample to be alternately heated and cooled. taq polymerase’s optimal temperature is 68-72ºC, therefore the extension phase is carried out at this temperature

Question 9

restriction enzymes

Answer 9

An enzyme that cuts strands of DNA at a specific sequence of nucleotides. When added to DNA it cuts the strands into different lengths depending on the base sequence of the specific DNA sample

Question 10

gel electrophoresis

Answer 10

a technique that is able to seperate DNA strands based on their lengths. The negative electrode is closest to the DNA and the positive electrode is at the opposite side. When an electric current is passed through the gel, the negatively charged DNA moves towards the positive electrode. The smaller DNA pieces move faster than the larger ones and so are located further away from the negative electrode when the current is stopped. results in an individuals DNA profile

Question 11

DNA profile/fingerprint

Answer 11

A technique that uses the banding patterns of DNA fragments as a means of identification. A DNA fingerprint is unique to a particular individual

Question 12

DNA ladders

Answer 12

Contain segments of DNA with known lengths. The results from the unknown sample are compared to the ladder to determine the length of the DNA strands in the sample

Question 13

what are the different methods used to visualise DNA after they have been separated

Answer 13

• Ethidium bromide: added to gel, as DNA moves through picks up some of the chemical which is visible under UV light.
• Methylene blue: dye that binds to DNA, when gel is soaked in dye the areas containing DNA stain a deeper blue and are visible to naked eye
• DNA probes: short sections of single stranded DNA with a fluorescent molecule that binds to the DNA being tested

Question 14

DNA sequencing

Answer 14

the determination of the precise order of nucleotides in a sample of DNA. Most frequently used method is the sanger method.

Question 15

what is the more correct name for nucleotides

Answer 15

Deoxynucleotide triphosphate as they consist of three phosphate groups joined to the sugar deoxyribose with its base

Question 16

what happens when DNA forms

Answer 16

• Each nucleotide loses two phosphate groups
• The sugar molecule loses a hydrogen atom from the hydroxy group (OH) when it bonds to the phosphate group of an adjacent nucleotide

Question 17

what are dideoxyribonucleotides (ddNTPs)

Answer 17

a modified deoxyribonucleotide that lacks a hydoxyl group of the sugar component, stopping the elongation of the sequence because there is no OH group for the next nucleotide to attach to.

Question 18

how are ddNTPS used

Answer 18

Added to the growing strand, stopping the elongation of the sequence as there is no OH group for the next nucleotide to attach to. This happens at each of the nucleotides in the DNA sample, creating different lengths of DNA. These can then be separated using gel electrophoresis.

Question 19

uses for DNA sequencing

Answer 19

• Identify mutations
• Compare DNA from different organisms
• identify inherited disorders such as sickle cell anaemia, CF, some forms of cancer
• Maternity and paternity test
• Compare species to track evolutionary change

Question 20

ethical considerations with genetic information

Answer 20

• Autonomy: respect for the right to be self determining and to choose whether or not to be tested and if tested to know and share the information. Includes the right of an individual to decide their own future
• Confidentiality: the use of genetic information is treated sensitively, and accessed only by those who are authorised
• Equity: The right to fair and equal treatment regardless of genetic information
• Privacy: the right to be ‘left alone’ and to make decisions regarding genetic testing and the resulting information, independent of others

Question 21

Genome

Answer 21

The complete set of genetic material in a cell. An organisms complete set of DNA

Question 22

Comparative genomics

Answer 22

The comparison of genome sequences of different species, allowing researchers to identify regions of similarity and difference. This provides an effective means of studying evolutionary changes among organisms, helping to identify genes that are preserved among species, as well as genes that give each organism its unique characteristics

Question 23

what are Endogenous retroviruses (ERVs)

Answer 23

A viral sequence that has become part of an organism’s genome. Retroviruses store their genetic information as RNA, not DNA. Upon entering a cell, a retrovirus copies its RNA genome into DNA through reverse transcription. The DNA the becomes inserted into one of the host cell’s chromosomes. A retrovirus only becomes endogenous if it inserts into a cell whose chromosomes will be inherited by the next generation (Ovum or sperm)

Question 24

example of the use of ERVs

Answer 24

When comparing the chromosomes of humans and chimpanzees, it has been discovered that the same ERVs are located in the same part of the chromosome in both species. Evidence that humans and chimpanzees share a common ancestor

Question 25

Reverse transcription

Answer 25

A process where the base sequence in RNA is copied during the synthesis of DNA

Question 26

Mitochondria

Answer 26

structure in the cytoplasm of a cell in which the aerobic stage of respiration occurs. Contains a small amount of DNA

Question 27

Mitochondrial DNA (mtDNA)

Answer 27

DNA found in the mitochondria of a cell, rather than the nucleus. In the form of small circular molecules

Question 28

Inheritance of mitochondrial DNA

Answer 28

We inherit nuclear DNA from both parents, but we inherit mitochondrial DNA only from our mothers as when the sperm penetrates the egg, its mitochondria are rapidly destroyed

Question 29

Evidence from mitochondrial DNA

Answer 29

DNA found in the mitochondria has a higher rate of mutation than nuclear DNA. Because of these mutations, human mtDNA has been slowly diverging from the mtDNA of our original female ancestor, and the amount of mutation is roughly proportional to the amount of time that has passed. Scientists are able to use the similarity between the mtDNA of any two individuals to provide an estimate of the closeness of their relationship through their maternal ancestors. If their mtDNA is identical they will be closely related. On the other hand, if the mtDNA is very different their last common maternal ancestor lived long ago.

Question 30

Use of mtDNA analysis

Answer 30

Comparing individuals within a species and for species that are closely related. Allowing scientists to track the ancestry of many species back hundreds of generations. Eg, tracing migration routes of ancient peoples.

Question 31

still n eed to do

Answer 31

protein sequences, bio informatics. 10.3