set a Flashcards
Mitosis is involved in growth and repair of tissues.
State two other roles of mitosis in multicellular organisms.
- body plan
- asexual reproduction
- producing gametes from haploid cells
- production of new stem cells
A ratio that is different from the expected 9:3:3:1, in a cross such as this, can be the
result of epistasis.
Suggest and explain one reason, other than epistasis, why the phenotype ratio might
not be 9:3:3:1.
- autosomal linkage
- both alleles will be on the same chromosome. they will be inherited together. they will not be separated during independent assortment during meiosis
The yellow colour in peas is the result of an enzyme that breaks down chlorophyll, which is
green.
* The Y allele codes for the production of an enzyme that breaks down chlorophyll.
* The y allele is the result of a mutation in the Y allele.
* The y allele codes for an inactive form of this enzyme.
(i)* Outline how the Y allele codes for the production of this enzyme and explain why the y
allele codes for an enzyme with a different primary structure.
- a gene that codes for the enzyme is expressed
- translation occurs before transcription
- in translation, the dna and rna bases pair up via complemntary base pairing catalysed by rna polymerase, forming the mrna
- the mrna moves out of the nucleus and attatches to the ribosome
- in transctiption, the codon on the mrna pairs with the anticodon on the trna
- the trna is specific to amino acid
With reference to the proteins coded for by the seed colour gene, explain why the y
allele is recessive
- the enzyme will be synthesised even if you have one dominant allele
DNA is a polymer made from monomers called nucleotides.
(a) Describe how nucleotides join together to form DNA.
- it undergoes a condensation reaction whereby, dna nucleotides form phosphodiester bonds catalysed by dna polymerase
Compare and contrast the structure of ATP and a DNA nucleotide.
- both contain a pentose sugar, a base and a phosphate group
- atp contains 3 and dna contains 1 phosphate group
- dna has a deoxyribose sugar and rna has a ribose sugar
- atp has only A and dna has C,T or G
Succession occurs in natural ecosystems. Describe and explain how succession
occurs.
- pioneer species colonise land
- this causes the enviornment to become more suitable to new species
- biodiversity is increased
- climax community is reached
Maltose and lactose both contain the same number of atoms of each element, C, H and O.
(i) State two other structural similarities between lactose and maltose.
- they both contain CH2OH
- both have 1.4 glycosidic bonds
identify differences between the structures of lactose and maltose.
- lactose, alpha glucose and maltose is beta glucose
- lactose has beta glucose bonds and maltose has alpha glucose bonds
- lactose has the sugars flipped and maltose has both monomers in the same direction
- lactose has one glucose monomer and one galactose
monomer and maltose monomers are both glucose
Explain how the structure of galactose allows it to be used as a respiratory substrate.
- soluble so can move
- bonds contain energy and are broken by respiratory enzymes
Suggest and explain why lactose is unable to cross membranes.
- its too big and so unable to pass between phospholipids
In order for lactose to enter the cytoplasm of E. coli a protein is required. The E. coli living in the digestive system of young mammals are more likely to contain this protein than E�.coli living in the digestive system of old mammals.
Suggest an explanation for this observation.
- mammal diet high in lactose concentration
- gene for protein channel transcribed
- lactose permease
Lactose is a reducing sugar. Benedict’s reagent can be used to detect the presence of lactose in a solution. A colorimeter can be used to measure the concentration of lactose.
The colorimeter first needs to be calibrated. Describe how a method that uses Benedict’s reagent and a colorimeter could be calibrated to measure the concentration of lactose in an unknown sample.
- zero the colorimeter
- use red filter
- using blank
- use a known concentration
Human papilloma virus (HPV) is the main cause of cervical cancer. A vaccine
has been developed to protect girls and women from HPV.
Describe how giving this vaccine leads to production of antibody against HPV.
- the vaccine contains antigens
- specific t cells stimulates specific b cells
- b cells divide to give plasma cells
- plasma cells produce antibody
