Biotech, Mutations and Evolutionary Mech

Question 1

Dna sequencing steps, uses

Answer 1

-dna is amplified by pcr
-dna is denaturedto separate strands
-primer is added to the 5 end
-primed dna is added equally among test tubes
-dna polymerase is added to test tubes
-all four dNTPs into each test tube
-specifically modified ddNTPs is added into each only one type into each tube
-dna polymerase attaches dNTPs to template strand until ddNTP is paired
-once the ddNTP is paired, sequence terminates ass ddNTP lacks a hydroxyl group at the 3’ carbon
-dna fragments of different lengths are formed
-gel electrophoresis is used to sequence DNA
-dna moves from negative to positive poles as its negatively charged
-smaller dna move further through the plate
-sequence is read from bottom to top
-process results in complementary sequence of dna
Uses: identify faulty alleles, paternity/maternity tests

Question 2

Electrophoresis steps, uses

Answer 2

-pipette is used to insert dna into the wells (making sure all dna being sequenced use different dyes)
-buffer solution is added to the electrophoresis machine
-machine is then turned on
-the dna moves from the negative to the positive pole as its negatively charged
-smaller strands of dna move further through the plate
-the sequence is read from the bottom to the top
Gel electrophoresis is used for paternity testing, dna testing, forensics
Uses: forensic science, paternity/maternity tests

Question 3

Polymerase chain reaction, uses

Answer 3

Denaturing: high temp break hydrogen bonds and separates strands at 96 degrees
Annealing: cooling at 55 degrees attach primer which adds free nucleotides onto dna strands
Elongation: heated at 72 degrees, add taq polymerase and nucleotides, new dna strand is synthesized which is complementary to DNA template strand
Uses: identify genetic disorders, identify viral disease, blood/fingerprint found at crime scene

Question 4

Recombinant dna steps, uses

Answer 4

-isolate gene and cut it with restriction enzyme
-isolate a plasmid from a bacterial cell and cut it using same enzyme
-splice human dna into the plasmid using dna ligase enzymes to join sticky ends
-treat bacterium so it takes up recombinant plasmid. Once successful, bacterium will multiply so that either the human gene or the product of the gene can be used
Uses: replace faulty genes, treatment of some disease eg CF, identify mutations

Question 5

Gene mutations

Chromosomal mutations

Answer 5

Changes to a single gene so that the trait normally produced are changed or destroyed. Occurs when dna is replicating
Chromosomal mutations affect all or part of a chromosome

Question 6

Somatic mutations

Germline mutations

Answer 6

Somatic mutations occur in the body cells. Only the individual is affected. Reproductive cells are not affected

Germline muatations occur in the gamete meaning it can be passed down into coming generations. Individual is not affected but produces gametes with changed dna.

Question 7

Mutagens

Answer 7

Mutagenic agents increase the rate of mutations, include formaldehyde and mustard gas

Question 8

Chromosomal mutations types

Answer 8

Deletion-part of chromosome is lost
Duplication-section of chromosome occurs twice
Inversion-breaks occur in a chromosome and the broken piece joins back in but the wrong way around
Translocation-part of a chromosome breaks off and joins wrong chromosome
Non disjunction-chromosome pair does not separate so daughter cell has one extra and the other has one less

Question 9

Gene therapy

Answer 9

Aims to treat or cure genetic abnormalities by replacing faulty genes with healthy ones. Focuses on single gene disorders like CF, HD, sickle cell etc

Question 10

Causes of variation

Answer 10

Random assortment of chromosomes-huge number of possible combinations of the chromosomes
Crossing over of chromatids-pieces of chromatid breaking off and attaching to different chromatid
Non disjunction-members of chromosome pair fail to separate during meiosis resulting in gamete have more or less than correct number of chromosomes
Random fertilization-large number of sperm or eggs with different alleles, any sperm can fertilize any egg meaning infinite amount of combinations
Mutations-changes in dna of a chromosome which may result in new characteristics

Question 11

Natural selection

Answer 11

Natural selection is a process where the most preferable phenotype survives. If for example there were 2 types of people which lived in the desert long legged and short legged, the long legged people would be able go run faster to catch food. The short legged people would not be able to catch food as fast and their population would decrease and the population of the long legged people would increase. Nature is favoring the long legged allele at the expense of others

Question 12

Random genetic drift

Answer 12

In small populations random genetic drift occurs. For example if you had 100 balls, 50 red and 50 black then put in a bag and you took out 50 balls you would expect that there are 25 red and 25 black. However your sample could have 30 red and 20 black. After reproducing you would have 60 red balls and 40 black. If 50 balls then were pulled out of the bag then you would expect red to favoured. Occurs in the dunkers population in Pennsylvania, their religion does not let the, marry outside their group. Small interbreeding population allowed for certain characteristics to be more common by chance

Question 13

Founder effect

Answer 13

When a small population from an original population moves into a new location. The new population does not represent the alleles from the original population. The new population therefore shows features which are not typical from the original population. For example the Pitcairn population descended from about 6 men and 12 women from polynesians. With little to no introduction of new alleles the descendant of the pitcairn islander show less genetic diversity than the original parent populations as they descended from a small number of settlers

Question 14

Barriers to gene flow

Answer 14

Geographical-include oceans, mountains, deserts

Sociocultural-religion, different language, economic status

Question 15

Tay sachs disease

Answer 15

• lipid metabolism disorder which occurs frequently in people of jewish descent
• caused by a missing enzyme which results in accumulation of fatty substance in nervous system
• persistent in population as those who are heterozygous have a resistant to tuberculosis
• those who are heterozygous have an advantage over those who aren’t in places where TB is present
• individuals with 2 tay sachs alleles would die at early age
• due to discrimination, ashkenazi jews would be in ghettos under conditions which increase threat of TB

Question 16

Thalassaemia

Answer 16

• occurs in people with Mediterranean descent
• anemia occurs from defects in formation of heamoglobin
• have to take frequent blood transfusions and remove excess iron in their blood through drugs
• decreased o2 carrying capacity, fatigue
• more mutations in gene pool increases mortality
• resistant to malaria meaning a survival advantage

Question 17

Sickle cell anaemia

Answer 17

-occurs in africans or people with african descent
-caused by anopholes mosquito which transmits the malarial parasite
-symptoms include clogged blood vessels, pneumonia, anaemia
Inherited by 2 parent with allele produce offspring or 1 parent with allele and 1 parent with normal parent produces carrier
-heterozygous individual are resistant to malaria
-increases frequency in populations where malaria is present as it gives a survival advantage

Question 18

principles of evolution

Answer 18

1. Variation in a species
2. More offspiring produced than can survive to maturity
3. Because if excessive birth rate and limited resources, struggle for existence occurs
4. Individuals with characteristics best suited for environment have higher chance of surviving and reproducing
5. Favourable characteristics are passed on to next generation
6. Proportion of alleles that produce favourable characteristics increases

Question 19

Speciation

Answer 19

Variation: variation of characteristics exist in a population
Isolation: due to barriers, no interbreeding occurs creating 2 separate gene pools
Selection pressures: different selection pressures means each population will change in allele frequencies
Speciation: over a long period of time, changes in allele frequency may be enough to prevent production of fertile offspring between the 2 population. 2 species now exist