Genetics, Variation and Interdependence Flashcards
Describe and explain how a mutation in a tumour suppressor gene could lead to a malignant tumour
(4 marks)
A mutation is a change in the DNA base sequence.
It leads to a different sequence of amino acids.
The protein formed may have a different tertiary structure that prevents it from carrying out its function to control cell division.
This allows a malignant tumour to form as there is no control of cell division (cells divide uncontrollably).
Describe and explain what is meant by a frameshift and how this may affect the protein made
(2 marks)
A frameshift occurs when there is a deletion or addition of a base in the DNA which results in all of the bases shifting position.
As a result the amino acid coded for can change which leads to a different 3D shape (change in tertiary structure).
Describe the structure of transfer RNA which is involved in the process of translation
(4 marks)
- single stranded molecule
- made up of RNA nucleotides
- ribose sugar
- uracil nitrogenous base
- amino acid binding site is at the 3’ end
- there is an anticodon in the middle loop
- it forms a clover leaf loop shape structure
Distinguish between the genome and proteome of a cell
(2 marks)
Genome is the complete set of genes in a cell.
Proteome is the full range of proteins that a cell can produce.
All cells with a nucleus have the same genome
The expression of the proteome varies between tissues
Explain why there is a difference between transcription in eukaryotic and prokaryotic cells
(3 marks)
DNA of eukaryotic cells have introns (non coding regions)
A prokaryotic cell does not have introns
Eukaryotic pre-mRNA contain non-coding regions
After transcription these regions are removed from the pre-mRNA
Explain the processes of meiosis and how they lead to genetic variation
(5 marks)
Homologous chromosomes pair up which can lead to the formation of a chiasma and crossing over can occur.
Crossing over results in a new combination of alleles.
The chromosomes can also align randomly which can produce varying combinations of chromosomes (independent segregation)
Describe how independent segregation results in genetic variation
(2 marks)
There is a random alignment of homologous pairs of chromosomes along the equator of the cell.
This happens in metaphase I of meiosis and results in a different combination of alleles in daughter cells.
Describe the similarities and differences between homologous chromosomes
(3 marks)
SIMILARITIES
- they carry the same genes
- the genes are in the same loci
- they are the same size
DIFFERENCES
- they contain different alleles
Describe a base substitution and explain its possible effects
(5 marks)
A base substitution is when a single base is substituted in a DNA sequence.
This leads to a change in the triplet code and so a different amino acid can be coded.
This changes the primary structure of the protein coded by the gene.
Due to the degenerate nature of DNA the triplet code can still code for the same amino acid.
The substitution can also lead to a premature stop codon which causes the mRNA transcribed to be shorter.
Describe and explain 3 ways in which the scientist would ensure they used aseptic techniques when preparing the inoculated agar plates
(3 marks)
- flame the equipment to sterilise it in order the remove microbes and prevent contamination
- wash hands to remove microbes
- disinfect work areas to kill microbes
- lift the lid slightly to prevent the entry of microbes
Explain how courtship behaviour prevents mating between different species
(2 marks)
Each species has a unique courtship ritual which allows individuals to recognise a member of their own species
Explain how genome sequencing can be used to deduce evolutionary relationships between organisms
(3 marks)
Determining the sequence of bases in DNA.
Comparing multiple regions of the genome allows for more representative data so conclusions can be drawn.
The greater the differences between the gene sequences the less closely related the species are.
Explain how DNA sequencing has led to a better understanding of biodiversity
(2 marks)
It allows….
- direction comparison of DNA sequences
- more precise comparison than phenotypic variation
- more accurate classification
Explain why biological sampling of an ecosystem must be free of bias, and how this can be achieved
(3 marks)
Bias is a prejudice towards or against a specific outcome.
To avoid bias sampling must be random in order to be representative of the population
