Cells and molecular bio
You are a structural biologist working in the lab and your aim is to crystalize the extracellular domain of epidermal growth factor (EGF), a type I transmembrane protein. Using molecular biology tools, you modify the gene to remove the transmembrane α-helix, however you keep the native signal sequence. Which ONE answer best describes where you expect the protein to be?
A. In the nucleus
B. In the cytoplasm
C. In the endoplasmic reticulum
D. In the plasma membrane
E. Secreted outside the cell
E. Secreted outside the cell
The tropical forest biome: (Select TWO answers.)
A. Is only found where soils are deep
B. Has more carbon in its above ground vegetation than does the boreal forest biome
C. Is the most productive biome on the planet
D. Supports more large herbivores per unit area than savannah
E. Contains many sclerophyllous plants
B. Has more carbon in its above ground vegetation than does the boreal forest biome
C. Is the most productive biome on the planet
If gene A is epistatic to gene B then: (Select TWO answers)
A. Gene A must act upstream of gene B in the same pathway
B. An allele at locus A masks the effects of another allele at locus B
C. Gene B must act upstream of gene A in the same pathway
D. Gene B masks the expression of the phenotype of all alleles at gene A
E. Gene A could be acting upstream of gene B in the same pathway
B. An allele at locus A masks the effects of another allele at locus B
E. Gene A could be acting upstream of gene B in the same pathway
Suppose a diploid population undergoes a population bottleneck. Which TWO of the following are true?
A. The population is expected to increase in genetic diversity
B. Some rare alleles are expected to become common following the bottleneck
C. Many alleles are expected to become fixed following the bottleneck
D. The rate of genetic drift is expected to increase as the population size recovers
E. The population is expected to be in mutation-drift equilibrium following the bottleneck
B. Some rare alleles are expected to become common following the bottleneck
C. Many alleles are expected to become fixed following the bottleneck
Some animal viruses are specific to a single host species whereas others are not. Which ONE of the following statements are true?
A. Polio virus has a rodent reservoir
B. Ebola virus has a fruit-bat reservoir
C. HIV-1 likely originated in chimpanzees, whereas HIV-2 likely originated in gorillas
D. Marburg virus only infects humans
E. Influenza virus can infect humans, pigs, and mosquitos
B. Ebola virus has a fruit-bat reservoir
Transcription has an error rate of about 10−4 nt−1. What is the probability of an RNA polymerase making a eukaryotic mRNA that is 10 000 nucleotides long without making a single error? (Select ONE answer.)
A. 0.0001
B. 0.3679
C. 0.5000
D. 0.6321
E. 0.9999
B. 0.3679
Which TWO of the following parameters are required to predict extinction rates from habitat loss?
A. z
B. K
C. c
D. Snew
E. Aorig
A. z
E. Aorig
Select THREE of the following to complete the sentence to make it true. A genetic distance of 1 centimorgan (cM) or map unit (m.u.) between two loci indicates:
A. That the expected average number of crossovers between them is 0.01 per generation
B. That in a cross approximately 10% of the progeny would be expected to be recombinant for these loci
C. That the two loci are linked
D. That the two loci are non-syntenic
E. That in a cross approximately 1% of the progeny would be expected to be recombinant for these loci
A. That the expected average number of crossovers between them is 0.01 per generation
C. That the two loci are linked
E. That in a cross approximately 1% of the progeny would be expected to be recombinant for these loci
Suppose there are two populations. Population A has an effective population size of 1000, and Population B has an effective population size of 10000. Both populations have the same mutation rate μ, and both populations are in mutation-drift equilibrium. Which TWO of the following are true about neutral evolution in these populations?
A. The substitution rate for Population A will be greater than for Population B
B. The substitution rate for both populations will be equal
C. Population A will have more genetic variation than Population B
D. The amount of genetic variation in both populations will be equal
E. Population B will produce more mutations each generation than Population A
B. The substitution rate for both populations will be equal
E. Population B will produce more mutations each generation than Population A
Integrated lysogenic phages and endogenous retroviruses (retroviruses that have integrated into germ line cells) have which THREE of the following properties in common?
A. Both can persist for multiple generations of the host organism or host cell
B. Both integrate randomly into the host genome
C. Both excise themselves before starting their lytic cycle
D. Both can be activated in response to host DNA damage
E. An integrated retrovirus is termed a provirus, whereas an integrated lysogenic phage is termed a prophage
A. Both can persist for multiple generations of the host organism or host cell
D. Both can be activated in response to host DNA damage
E. An integrated retrovirus is termed a provirus, whereas an integrated lysogenic phage is termed a prophage
Which ONE organelle is directly targeted by a signal sequence characterized by a positive N-terminus followed by a short stretch of hydrophobic then polar amino acids?
A. Mitochondrion
B. Endoplasmic reticulum
C. Golgi body
D. Lysosome
E. Nucleus
B. Endoplasmic reticulum
Which TWO of the following statements regarding competition are true?
A. Both inter- and intra-specific competitions are important in shaping community structures
B. Inter-specific competition helps define an organism's fundamental niche
C. Competition between species can be of either a direct or indirect (apparent) nature
D. Scramble competition usually has a stabilising influence on community dynamics
E. Mutualisms can be considered a special case of inter-specific competition
A. Both inter- and intra-specific competitions are important in shaping community structures
C. Competition between species can be of either a direct or indirect (apparent) nature
A testcross of plants with an AaBb genotype results in the following number of offspring in four phenotype classes:Â AB = 50, ab = 52, Ab = 21 and aB= 23. These data indicate that the distance in map units between the genes is which ONE of the following?
A. 2.1
B. 2.3
C. 4.4
D. 30.1
E. 69.9
D. 30.1
A diploid population has a mutation rate of μ and an effective population size of Ne. Which THREE of the following are true?
A. If the population size is increasing μ will also increase
B. If the population size is decreasing the genetic diversity will decrease
C. If the population is at mutation drift equilibrium the amount of genetic diversity is only dependent upon Ne
D. The number of new mutations expected every generation is 2Neμ
E. If the population is at mutation drift equilibrium the number of variants that are expected to go extinct every generation is 2Neμ
B. If the population size is decreasing the genetic diversity will decrease
D. The number of new mutations expected every generation is 2Neμ
E. If the population is at mutation drift equilibrium the number of variants that are expected to go extinct every generation is 2Neμ
Which ONE of the following statements about B cell development are true?
A. A single B cell receptor typically recognizes multiple, unrelated antigens
B. Antibodies are an insoluble form of the B cell receptor
C. The heavy chain of the B cell receptor is produced following V, D and J DNA segment rearrangement
D. The light chain of the B cell receptor is produced following V, D and J DNA segment rearrangement
E. Mature B cells exit the lymph nodes and encounter antigen in the bone marrow
C. The heavy chain of the B cell receptor is produced following V, D and J DNA segment rearrangement
Which THREE of the following statements about the extracellular matrix are true?
A. Basal lamina ECM contains type IV collagen
B. Fibronectin binds integrins
C. Collagen is a glycosaminoglycan
D. Metastatic cancer cells have abnormal interactions with the ECM
E. Hyaluronan is a highly branched protein with many N-linked oligosaccharide side-chains
A. Basal lamina ECM contains type IV collagen
B. Fibronectin binds integrins
D. Metastatic cancer cells have abnormal interactions with the ECM
Nitrogen: (Select THREE answers.)
A. Is always more limiting for plant growth than is phosphorus
B. Can be acquired as a mineral nutrient as well as through biological fixation of N2
C. Is an important component of many plant membranes
D. Is more likely to be limiting for plant growth in younger soils
E. Is often a factor limiting ecosystem productivity in colder environments
B. Can be acquired as a mineral nutrient as well as through biological fixation of N2
D. Is more likely to be limiting for plant growth in younger soils
E. Is often a factor limiting ecosystem productivity in colder environments
Mendel continued his famous monohybrid cross investigating seed shape inheritance in peas beyond the F2 generation. He grew plants from F2 round seeds. Upon selfing these F2 plants, what proportion of them produced F3 offspring with a phenotype ratio of 3 round seeds to 1 wrinkled seed? (Select ONE answer.)
A. One quarter
B. One third
C. One half
D. Two-thirds
E. All
D. Two-thirds
The coefficient of relatedness (r) between individuals is thought to be important in kin selection. Which one of more of the following statements are true? (Select THREE answers.)
A. r between sisters of haplodiploid species is 0.75
B. Hamilton's rule suggests that an allele promoting altruism will only spread in a population if rB-C < 0, where B is the benefit of the altruist act to the recipient and C is the cost to the actor.
C. Co-operatively breeding birds may help each other without gaining genetic benefits
D. Inclusive fitness consists of direct and indirect fitness
E. Kin selection increases direct fitness
A. r between sisters of haplodiploid species is 0.75
C. Co-operatively breeding birds may help each other without gaining genetic benefits
D. Inclusive fitness consists of direct and indirect fitness
Many cells can defend themselves against viral infection. In particular, which TWO of the following are true?
A. Interferon can stimulate cells to produce antiviral proteins
B. The T.I.P. protein works by inhibiting viral transcription
C. APOBEC prevents viral uncoating
D. TRIM 5 works by blocking viral integration
E. Virus maturation inhibitors work at a late stage of the viral life-cycle
A. Interferon can stimulate cells to produce antiviral proteins
E. Virus maturation inhibitors work at a late stage of the viral life-cycle
Which THREE of the following statements about the cell cycle are accurate?
A. The mitotic checkpoint checks whether chromosomes are correctly aligned on the mitotic spindle
B. The number of cells in G1 phase can be estimated using a flow cytometer
C. DNA damage leads to rapid loss of P53 protein, which triggers arrest of the cell cycle
D. Interphase is the shortest phase of the cell cycle
E. Cultured cells in M phase can be directly distinguished from cells NOT in M phase using phase contrast microscopy
A. The mitotic checkpoint checks whether chromosomes are correctly aligned on the mitotic spindle
B. The number of cells in G1 phase can be estimated using a flow cytometer
E. Cultured cells in M phase can be directly distinguished from cells NOT in M phase using phase contrast microscopy
The diagram below was used to infer the population dynamics of a harvested fish population. The rate of recruitment of new individuals into the fishery is shown as the dashed line, and the rate of mortality (solid line) is assumed to be due solely to harvesting activity. Which ONE of the following statements are true?
A. The point marked with arrow 1 is an unstable equilibrium point
B. The point marked with arrow 2 is an unstable equilibrium point
C. This is an example of a fixed-effort harvesting strategy
D. The harvesting strategy used here assumes there is no density dependence in the fish population
E. The Maximum Sustainable Yield (MSY) is at arrows 1 and 2
A. The point marked with arrow 1 is an unstable equilibrium point
During pachytene in meiosis: (Select THREE answers.)
A. Condensation has stopped
B. Chromosomes in the homologous pair are visible
C. Bivalents/tetrads have been formed
D. The synaptonemal complex has broken down
E. Crossing over between non-sister chromatids occurs
B. Chromosomes in the homologous pair are visible
C. Bivalents/tetrads have been formed
E. Crossing over between non-sister chromatids occurs
Which TWO of the following statements about molecular evolution and phylogeny reconstruction are accurate?
A. Transversions are more likely than transitions
B. Synonymous changes are more likely than non-synonymous changes
C. Molecular distances tend to underestimate the age of older divergences
D. Gene duplication always results in gene copies that maintain the same function
E. The number of possible phylogenetic trees increases linearly with the number of species
B. Synonymous changes are more likely than non-synonymous changes
C. Molecular distances tend to underestimate the age of older divergences
Viruses have a variety of mechanisms of infecting cells. Which TWO of the following statements are true?
A. HIV-1 can either fuse with the host cell membrane or enter via endocytosis
B. Poliovirus enters via fusion at the cell surface
C. Influenza enters a cell via endocytosis followed by pH-dependent fusion
D. Adenovirus extrudes its genome through a pore at the cell surface
E. HIV-1 attaches to a single cell receptor on the host cell whereas adenovirus, poliovirus and influenza viruses attach to more than one
A. HIV-1 can either fuse with the host cell membrane or enter via endocytosis
C. Influenza enters a cell via endocytosis followed by pH-dependent fusion