To Learn General Flashcards
(40 cards)
How do chromosome numbers change during mitosis?
2n->2n
n->n
How do chromosome numbers change during meiosis?
2n-
Daughter cells have half the number of chromosomes as the parent cell
Sickle cell anaemia is an inherited disease in which red blood cells are abnormally shaped, sufferers have two copies of the recessive sickle cell allele and often die prematurely.
A single copy of the sickle cell allele allows for protection against malaria.
The sickle cell is most abundant where malaria is endemic.
Explain the type of selection occurring in areas where the incidence of malaria is high.
Stabilising selection
-loss of recessive sickle cell allele through death of homozygotes, this is balanced by reproductive advantage of heterozygous
Frequency of recessive allele remains constant over generations.
A single copy of the sickle cell allele allows for protection against malaria.
The sickle cell is most abundant where malaria is endemic.
Explain the type of selection occurring in areas where the incidence of malaria is low
Directional selection
-recessive sickle cell allele causes the death of homozygotes , reproductive disadvantages
-frequency of recessive allele decreases over generations
Precautions taken by scientists to avoid contamination during agar plate experiment
Disinfect work surface using ethanol
Use sterile equipment - sterilise glassware in an autoclave
Keep lid of agar plate
Work near Bunsen burner to burn microorganisms
How to calculate the % of genes showing genetic diversity
Number of genes exhibiting genetic diversity / number of genes
X100
Insects cause significant damage to crops and reduce yields
Many crop specie have low genetic diversity
Suggest why the yields of crops with low genetic diversity may decrease in the presence of insects?
Low genetic diversity means only a small number of alleles for particular genes in the population
Limited variation in insect resistance so alleles for resistant to the insect are unlikely to be present
Non-disjunction mutation
During meiosis chromosomes are not separated as they all stay in one cell
This means that they do not form homologous pairs
Apart from mutation explain one way that genetic variation within a species is increased
Random fusion of gamers/ random fertilisation
Produces new allele combinations
How can a gene mutation have no effect on an individual
Genetic code is degenerate meaning an amino acid sequence may not change
Mutation is an intron so is spliced before translation
Functions of lipids
-energy source
-thermal insulation
-waterproofing
-buoyancy
-insulation around neurones
Why are lipids suitable for the function of energy sources ?
-insoluble
-compact
-high energy value
Why are lipids suitable for insulation in mammals?
-poor heat conductor
-low thermal conductivity
-minimise heat loss from body
why are lipids suitable for water proofing?
-non polar
-hydrophobic
-insoluble
What is the induced fit model and how do enzymes act as catalysts ?
The induced fit model is where the active site of an enzyme changes slightly to fit with the substrate. This leads to an enzyme substrate complex forming. When the active site changes it distorts the bonds in the substrate causing the activation energy to be lowered. This leads to more enzyme-substrate complexes forming and a faster rate of reaction
Main polymer in plant cell wall
Cellulose
Main polymer in fungal cell wall
Chitin
How does farming affect biodiversity?
Plant biodiversity is lower on previously farmed land
Plant biodiversity higher on land that has not had crops grown on it
Farming reduces fungal species richness
Less decomposition
For antibiotic resistance what is the antibiotic resistant known as?
The selection pressure
Why is there more antibiotic resistant in hospitals?
More antibiotics used in hospitals compared to elsewhere so high frequency of resistance allele in bacterial population
Role of cholesterol in membranes
-stabilises the membrane
-reduces movement of molecules/phospholipids/fatty acids
How is a virus replicated?
Attachment protein attaches to receptors on host cell
Viral nucleacid enters cell
Nuclei if acid replicated in cell
Reverse transcriptase makes DNA from RNA
Cell produces viral proteins and enzymes
Virus assembled and released from cell
How can two enzymes with different amino acid sequences catalyse the same reaction?
They have active sites with similar tertiary structures
Form enzyme substrate complexes with the same substrate
What control should be used in an experiment involving ph and enzymes
A denatured enzyme (boiled to break bonds)
Same pH buffer and same concentration of substrate
