Exam Questions Flashcards
Describe how a sample of chloroplasts could be isolates from leaves
Break open cells and filter
In cold, isotonic and buffered solution
Centrifuge and remove nuclei
Centrifuge at higher speeds chloroplasts settle out
Describe how acetylcoenzyme A is formed in the link reaction
Oxidation/hydrogen removed from pyruvate and carbon dioxide released
Addition of co enzyme A
Purification ponds only work efficiently when they are shallow and warm. Explain why
Sufficient light for photosynthesis
Warm leads to faster enzyme activity, so faster bacterial respiration and decomposition
So faster photoynthesis ( as respiration by bacteria produces CO2 used in photosynthesis)
Increased growth
Explain the advantage of having both algae and bacteria in a purification pond
Breakdown organic matter by enzymes from bacteria
Ammonia used by algae to make proteins
Algae photosynthesise
Bacterial respiration uses O2
Respiration allows for growth of bacteria
Explain why a statistical test should be applied to the data obtained in this investigation
To determine the probability of results being due to chance
Give 2 types of factors that cause PHENOTYPIC variation
Environment
Mutation/meiosis/alleles
What is Allopatric speciaton
New species form from different populations
In different areas/isolated populations
What is sympatric speciation
Formation of new species/reproductive isolation
From a population in the same area/ without geographical isolation
Describe one way which scientists could find out whether organisms from 2 diff populations belong to same species
Breed together
If fertile offspring then same species
Explain how sympatric speciation may have occured (in relation to question)
Mutation occurs
Correct e.g. of isolating mechanism
e.g.
temporal − different breeding seasons / feeding times /
ecological / behavioural − different courtship displays / different niches / habitats / feeding areas /
mechanical − mismatch of reproductive parts /
gamete incompatibility − sperm killed in female’s reproductive tract /
hybrid inviability / hybrid infertility;
Ignore references to “genetic isolation” or “reproductive isolation”
Different selection pressures operate / changes in allele frequency / divergence of gene
Explain the advantage of presenting the results as a ratio
•allows for comparison
• sample sizes may vary
Viruses infect only one species. Suggest and explain how the viruses became able to infect other species of frog
Mutation in Viral dna
Altered tertiary structure
Allows attachment proteins to bind to other species
Name techniques scientists use when analysing viral DNA to determine viruses were closely related
Genetic Dna fingerprinting
Gel electrophoresis
Dna sequencing
Polymerase chain reaction
Determining genome of viruses allows scientists to develop vaccine. How?
Scientists could identify proteins
Then identify potential antigens
Describe how B lymphocytes respond to vaccination against virus
Dont include cellular response
B cell divides by mitosis
To produce plasma cells which produce antibodies
B cells also produce memory cells
Genome
All the DNA in an organism
Explain why antibody binds to transcription factor
It has a specific binding site
Complementary to Transcription factor
Suggest how single stranded cDNA could prevent transcription of the question gene
Bind to promoter region
Describe roles of 2 enzymes used to insert DNA fragments into plasmids
DNA LIGASE
joins vector DNA and foreign DNA forming phosphodiester bonds
RESTRICTION endonuclease cut plasmid/ hydrolyse dna?
Suggest 2 features of the structure of different proteins that enable them to be separated by electrophoresis
Primary structure/tertiary structure
R groups
Dna probe
Short single stranded DNA with complementary base sequence to target DNA (radioactive labelled by a fluorescent molecule)
Fertillised egg cell (zygote) is made up of what and what else do they do
Totipotent stem cells
They divide rapidly by mitosis producing genetically identical daughter cells
Can also produce any type of body cells BECAUSE they translate part of their Dna
Which types of cells are vital for growth and repair of damaged tissues
Multipotent and unipotent (1) stem cells
Which types of cells are the only ones which can divide by mitosis
STEM CELLS
Production of IPS
Laboratory grown pluripotent cells produced from human somatic cells using certain protein transcription factors.
Not identical to pluripotent stem cells but capable of self renewal- providing limitless supply in medical research and removes ethical issues of using embryonic stem cells in medical research
Doninant characteristic rules
Affected offspring must have at least one affected parent
Unaffected parents only have unaffected offspring
If both parents are affected and produce an unaffected offspring, both parents must be heterozygous
Suggest how a mutation can spread
Founder effect/migration/interbreeding
DESCRIBE how alterations to tumour suppressor genes can lead to the development of tumours
Increased methylation
Mutation in tumour suppressor genes
Tumour suppressor genes are not transcribed/expressed
Results in uncontrollable cell division
Explain advantage of growing plants in tissue culture
Will be clones and have desired characteristics
Suggest how these type of stem cells( related to the question) can cause harm
Might divide uncontrollably
Leads to formation of a tumour/cancer
What does a large SD suggest (a very wide range)
Not much increase, no better than control
Describe method to find mean number of () per mm2
Measure diameter, calculate area
Using micrometer eyepiece graticule
Count number of () and calculate mean
Epigenetics
Heritable changes to gene function
Without changes to the base sequence of DNA
Explain how increased methylation could lead to cancer
Methyl groups added to tumour suppressor gene
Transcription of tumour suppressor gene is inhibited
Leading to uncontrolled cell division
Give one way in which benign tumours differ from malignant tumours
Cells of benign tumours cannot spread to other parts of the body/metastasise
Whereas cells of malignant tumours can
Codominant alleles
Both alleles expressed within the phenotype
Phenotype
Expression of its genetic constitution and its interaction with its environment
Explain why males are more likely than females to show a phenotype produced by a recessive allele carried on X chromosomes
Males have one allele
Females need two recessive alleles must be homozygous recessive
Sex linked gene
Gene located on the X chromosome
Genes that are linked are on the same chromosome
Describe how behaviour can result in sympatric speciation
If related to a question also talk about
Not geographically isolated
Leads to reproductive isolation
Separate gene pools
Change in allelic frequencies
Cannot breed to produce fertile offspring
(Occurring in the same area)
Mutations causes (whatever question gives e.g diff breeding times/ occupy diff habitat/courtship)
Reproductive isolation
Gene pool
All the alleles in a population
Suggest one reason why DNA replication stops in the polymerase chain reaction
Limited number of nucleotides
Dna polymerase also eventually denatures
Describe two ways in which both types of tumour may cause harm to the body
May damage organ concerned
May cause blockage
