Cells And DNA PPQs Flashcards
Circle answer that shows a single base substitution box mutation in DNA that would result in a change from Val to Ala at amino acid number 203 (1)
CAA —> CGA
Can’t be
GUU —> GCA
GUU —> GUC
Because these code for Val but on the mRNA and it’s asking which DNA mutation (so which DNA codon) codes for Val
It’s not CAC —> CGG
Because although CAC as an mRNA codon codes for Val and then CGG as an mRNA codon codes for Ala, it involves TWO bases changing but the question says ‘single base substitution’
Suggest reasons for why a change from Glu to Lys
at amino acid 300 had no affect on the rate of reaction catalysed by the enzyme
but the same change at amino acid 279
significantly reduce the rate of reaction catalysed by the enzyme (3)
Negative charge to positive charge changes
Change at AA300 had no effect so active site same shape
Change at AA279 had effect, it may have been involved in bond so tertiary structure and active site changed
Label Z of prokaryotic cell (wiggly line)
FLAGELLA not Pili
Describe and explain the appearance of chromosome K (2)
Chromosome consists of two sister chromatids connected at centromere
Because DNA replication has occurred
OR
K on equator of spindle
Because attached at centromere
Explain what is happening at point J in cell B (2)
Crossing over
Between non sister chromatids/ homologous chromosomes
Use the information from all three cells to explain how the number of chromosomes in cell D was produced. (1)
Segregation of homologous chromosomes
Explain why the arrows point in opposite directions in the diagram of DNA replication (4)
DNA has antiparallel strands.
So nucleotides are aligned differently.
enzymes haste an active site with a specific shape.
DNA polymerase active site only binds to the 3’ end of strand
The graph shows information about the movement of chromatids in a cell that has just started metaphase of mitosis.
Complete line Y. (2)
Horizontal until 18 minutes (because they are lined up at the equator and not moving yet so distance between them (chromatids) and the pole stays the same)
At 28 minutes decrease to 0 micrometers (because once they have moved to opposite poles of the cell the separated sister chromatids stay there so the distance between them and the poles stays the same)
Describe how DNA is replicated (8)
DNA help case unwinds double helix
Breaking H bonds between complimentary base pairs
Both strands acts as a template
Free DNA nucleotides attracted to exposed nucleotides.
Complimentary base pairing occurs
DNA polymerase joins nucleotides
Hydrogen bonds reform
Semiconservative replication
Calculate the time in which the cells were an interphase during one cell cycle (2)
One cell cycle = 24 hours
Cells in interphase = 82/100
(82/100) x 24 = 19.68
Explain how he recognised the cells were in interphase (1)
No visible chromosomes
No visible nucleus
Explain which tissue is taken from a cancerous tumour (2)
D not C because
Lower % cells in interphase (at a given time)
(So cells must be) dividing more rapidly
Explain why the structure of the organelles can be seen with a TEM but not an optical microscope (2)
TEM has higher resolution
Optical microscope wavelength of light is too long
Why is cell D not on a stage of mitosis or have homologous chromosomes present?
XXX
X
Use the scale bar (5 micrometers) to calculate magnification of the drawing. (2)
XXX
1800 - 2200
