longer answers PAPER 1

Question 1

how do pregnancy tests work?

Answer 1

• the part you wee on has mobile antibodies to HCG with blue beads attached
• the test strip has stationary antibodies as they are stuck onto the strip
• HCG binds to the antibodies on the blue beads
• the urine moves up the stick carrying the hormone and the beads
• the beads and HCG bind to the antibodies on the strip
• the beads get stuck on the strip making it have 2 blue lines

Question 2

how are monoclonal antibodies made?

Answer 2

• inject a mouse with the chosen antigen
• B-lymphocytes are taken from the mouse
• B-lymphocyte is fused with a tumour cell to form a hybridoma
• this divides quickly to produce lots of clones that produce monoclonal antibodies

Question 3

what is the lytic pathway?

Answer 3

• virus binds to a host cell and injects its genetic material
• virus is replicated using the host cells resources
• to produce more viral genetic material
• produced viral proteins
• new virus assemble
• host cell is lysed

Question 4

what is the lysogenic pathway?

Answer 4

• the injected genetic material is incorporated into the DNA of the host cell
• viral genetic material gets replicated along with the host cell
• virus is dormant and no new virus is made
• a trigger causes the virus to leave the genome and enter the lytic pathway

Question 5

describe how an electrical impulse is transmitted between 2 neurones

Answer 5

• the electrical impulse travels to the end of the neurone
• this triggers the release of neurotransmitters in vesicles across a synapse
• they bind to the receptor molecule at the post synaptic neurone
• a new electrical impulse is generated

Question 6

describe how a doctor might determine if a baby is growing as expected

Answer 6

• measure head circumference every month
• find the percentile on percentile chart for their age
• measurements shouod increase along or around the same percentile

Question 7

describe how changes in DNA sequence can affect the individuals and how the sequencing of a person’s genome could influence medical treatments

Answer 7

• DNA has 4 bases
• changes in DNA are mutations which results in different alleles for these genes
• affects the phenotype of a person causing variation
• by sequencing DNA you can identify genetic diseases and the risk of developing them
• by knowing a disease can develop it allows the person to modify their lifestyle to reduce the risk
• HGP determined the location of the genes which lead to a better understanding of diseases
• so people can take preventative medicines and doctors can provide personalised medicines

Question 8

some antibiotics are no longer effective in killing pathogens, using natural selection explain why

Answer 8

• there is VARIATION in pathogen population of the trait that is resistant to antibiotics
• causes pathogen to be immune due to RANDOM MUTATIONS
• antibiotics being used is a selective pressure so some die but some survive as they have the RESISTANT allele
• these pathogens reproduce and multiple where they pass on the GENE to their offspring

Question 9

Explain how DNA can be extracted from fruit

Answer 9

• mix cold water, a teaspoon of salt, 10ml of detergent in a beaker
• mash fruit with skin off and add it to the solution in the beaker
• the detergent breaks down cell membrane to release DNA
• the salt will make DNA stick together
• add enzyme protease to mixture as protease breaks down proteins in cell membrane
• filter mixture using filter paper and funnel to get big insoluble bits of cell out
• add cold ethanol to the solution as DNA is insoluble in ethanol and wait 10 mins
• DNA will start to appear as a white precipitate that can be fished by a glass rod

Question 10

Describe the stages of protein synthesis

Answer 10

• RNA polymerase binds to non-coding DNA located in front of gene
• RNA polymerase produces complementary mRNA strand from coding DNA of the gene
• mRNA attaches to reibosome
• the coding by base triplets (codons) in mRNA for a specific amino acid
• transfer of amino acids to ribosome by tRNA
• amino acids link together to form polypeptides and fold in a specific shape for its function

Question 13

Explain why a bomb calorimeter gives a more accurate value than the normal equipment for burning food

Answer 13

• because the system is sealed as it has a life
• there is less heat loss
• and the stirrer distributes the heat evenly
• and all of the food burns