chapter 10

Question 1

What does ‘PCR’ stand for?

Answer 1

Answer: Polymerase chain reaction

Question 2

List the three steps in PCR

Answer 2

• Denature
• Anneal
• Extend

Question 3

3 Explain the role of a primer in PCR.

Answer 3

The primers are complimentary to either rend of the section of DNA to be copied. They act as the starting point for elongation of the DNA strands.

Question 4

What is the advantage of using Taq polymerase over other DNA polymerases?

Answer 4

Taq polymerase is a heat tolerant polymerase, its optimum temperature is 72oC, and will not denature at 96oC when the DNA is melted.

Question 5

Explain the role of restriction enzymes in DNA profiling.

Answer 5

Answer: When restriction enzymes are added to DNA, it cuts the strand into different lengths depending on the base sequence of the specific DNA sample. The length of these pieces can be analysed and compared with other DNA samples.

Question 6

Will the shorter or longer lengths of DNA travel the greatest distance during electrophoresis? Explain your answer.

Answer 6

Answer: The shorter lengths will travel further. They encounter less resistance from the agarose gel.

Question 7

List three methods of visualising DNA after electrophoresis.

Answer 7

• Ethidium bromide is added and an ultraviolet light is shone over the gel to see the DNA fluoresce.
• Methylene blue binds to the DNA and stains it a deep blue.
• DNA probes with a radioactive or fluorescent molecule that binds to the DNA.

Question 8

Draw a simplified structure of:
a deoxynucleotide triphosphate

dideoxyribonucleotide triphosphate.

Answer 8

textbook 275

Question 9

Explain why temperatures of approximately 96°C are sufficient to denature the DNA.

Answer 9

96°C is hot enough to break the hydrogen bonds holding the two strands together without disrupting the individual strands.

Question 10

DNA sequencing makes it possible for suitable primers to be chosen for PCR.’ Discuss this statement.

Answer 10

DNA sequencing has allowed the determination of the precise order of nucleotides in a sample of DNA. Primers need to be specific to a sequence of DNA to allow the DNA segment to be copied. Knowing the precise order of nucleotides allows for the primers to be made so they can attach to the segment needed to be copied.

Question 11

Identify two situations when it may be unethical to use genetic information. For each situation, discuss the reasons for and against its use.

Answer 11

Applying for a job. It is unethical to access genetic information to determine if applicants have any genetic disease that may make one person more suited than another. This does not allow everyone equity to the job. The employer may want to know if their desired candidate will have good health.
Insurance. It is unethical for insurance companies to access genetic information prior to approving health insurance of life insurance. The insurance companies may want to access this information to increase premium rates, but this breaches confidentiality.

Question 12

Define ‘genome’. Describe how sequencing the genome can be used to provide evidence for evolution

Answer 12

The complete set of DNA in each cell of an organism is called the genome. Sequencing the genome and comparing sequences of human genome with the genome of other organisms, researchers are able to identify regions of similarity and difference. This provides evidence for evolution because the more similar the sequences, the organisms are more closely related.

Question 13

Define ‘endogenous retrovirus’ and ‘non-coding DNA’.

Answer 13

Endogenous retroviruses are viral sequences that have become part of an organism’s genome. Non-coding DNA are sequences of nucleotides that have no apparent function and appear to serve no purpose.

Question 14

Describe how endogenous retroviruses are used as evidence for evolution.

Answer 14

Endogenous retroviruses appear in the non-coding sections of DNA. As they are inherited, they will appear in the same location of DNA in different species that share a common ancestor. The more aligned the location of the ERVs are, the more similar the two species are.

Question 15

What do the genes on mtDNA code for

Answer 15

: Mitochondrial DNA contains 37 genes. 24 genes contain the code for making transfer RNA molecules and 13 genes have instructions for making some enzymes needed for the reactions of cellular respiration.

Question 16

Explain why not all retroviruses are endogenous retroviruses, and why only endogenous retroviruses are useful in providing evidence for evolution.

Answer 16

Answer: Retroviruses copy their DNA or RNA into the host cell through reverse transcription. The retroviruses will only become endogenous when the DNA or RNA is reverse transcribed into the gametes. When retroviruses become endogenous, the viral sequence will be passed on to the offspring from the common ancestor, so when comparing different species that share a common ancestor, the ERV would be found at the same location in the chromosome of both species.

Question 17

Compare and contrast mitochondrial DNA and nuclear DNA.

Answer 17

Compare: Both are composed of nucleotides and hold the code to build proteins (genes).
Contrast: Mitochondrial DNA is inherited maternally whereas nuclear DNA is inherited from both parents. Nuclear DNA contains tens of thousands of genes, whereas mitochondrial DNA contains only 37 genes

Question 18

State the relationship between DNA, RNA, amino acids and proteins.

Answer 18

: DNA contains the code for building proteins. The DNA is transcribed into mRNA and tRNA is used to translate the code into a sequence of amino acids at the ribosome. Amino acids are the building blocks of proteins. Determining the sequence of amino acids can allow for the determination of the sequence of nucleotides in a DNA molecule.

Question 19

Define ‘ubiquitous protein’.

Answer 19

Answer: A ubiquitous protein is one of a group of proteins that appears to be in all species. It performs the same function in each species it is found in.

Question 20

Give an example of a ubiquitous protein.

Answer 20

Answer: Cytochrome C.

Question 21

5 What is bioinformatics?

Answer:

Answer 21

Bioinformatics is the use of computers to describe the molecular components of living things. It uses biochemical analysis to gain information about DNA and proteins and computer software to store and analyse it.

Question 22

Briefly outline the steps in building a DNA sequence.

Answer 22

• DNA is extracted from cell nuclei.
• DNA is broken into pieces and the pieces copied many times.
• Double-stranded DNA separated into single strands.
• Primer added and binds to one strand.
• The second DNA strand is recreated by adding nucleotides in the correct sequence.
• A terminator nucleotide stops the nucleotide sequence.
• Strands can then be compared to determine the nucleotide sequence.

Question 23

Outline the steps in the polymerase chain reaction•

Answer 23

DNA is heated to 96°C to separate the two strands of the molecule (denaturation).

Cooling occurs so that the
• Primers are added and attach to each strand (annealing)

The enzyme DNA polymerase is used to join new complimentary nucleotides to the section or originating with the primers. It is not a full length of original DNA as it starts at the primer and not at the end of the DNA. taq ploymerase used now as heat resistant

• Heating occurs to separate the strands of the new DNA molecules and the process is repeated.

Question 24

Describe how mtDNA has been used to provide evidence for evolutionary relationships between species.

Answer 24

: mtDNA is inherited only from the mother. The mtDNA is a copy of that which was in the female parent’s egg cell. mtDNA mutates more often than nuclear DNA, and the amount of mutation of mtDNA is roughly proportional to the amount of time that has passed. Similarities and differences in the mtDNA of species can thus show evolutionary relationships.

Question 25

List the key areas that need to be ethically considered when deciding whether to gain or use genetic information.

Answer 25

• Confidentiality
• Autonomy
• Privacy
• Equity

Question 26

Define ‘gene flow’.

Answer 26

: Gene flow is the movement of genetic material from one population to another.

Question 27

List four barriers to gene flow.

Answer 27

Answer: Geographical barriers include oceans, mountain ranges, large lake systems, deserts and expansive ice sheets. Sociocultural barriers include economic status, educational background and social position

Question 28

Define ‘natural selection’.

Answer 28

Answer: The process by which a species becomes better adapted to its environment; those individuals with favourable characteristics have a survival advantage and so pass on those characteristics to subsequent generations.

Question 29

List the steps involved in evolution through natural selection.

Answer 29

• Variation exists in the species
• More offspring are produced than can possibly survive to maturity
• There is a struggle for existence
• Individuals with characteristics best suited to the environment have a better chance of surviving and reproducing
• Favourable characteristics are passed on to the next generation

Question 30

Describe what a selective agent is, and give an example.

Answer 30

Answer: A selective agent is the environmental factor acting on the population. Examples include malaria or tuberculosis.

Question 31

genetic drift

Answer 31

Answer: The occurrence of characteristics in a small population as a result of chance rather than natural selection.

Question 32

founder effect

Answer 32

Answer: A type of genetic drift where a new population is formed by a small number of individuals. The founding population shows marked allele differences from the original population.

Question 33

bottleneck effect.

Answer 33

Answer: An extreme form of genetic drift that occurs when the size of a population is severely reduced due to a sudden event such as a natural disaster. The allele frequencies of the survivors may not reflect that of the original population.

Question 34

List the steps involved in speciation.

Answer 34

• Variation
• Isolation
• Selection
• Speciation