This set of Cell Biology Questions and Answers for Freshers focuses on “Genes, Chromosomes and Genomes – 2”.
1. In FISH technology, which fluorescence confirms a BCR/ABL translocation?
a) Red signal
b) Green signal
c) Yellow signal
d) Orange signal
Explanation: In FISH, the green signal indicates presence of the BCR gene and the red signal indicate the presence of the ABL gene. The red-green fusion (yellow) signal confirms a BCR/ABL translocation.
2. The nucleosome is composed of how many histone proteins?
Explanation: The nucleosome is composed of 8 histone proteins known as Histone Octamer and a separate H1 protein. The histone proteins present are two H2A, two H2B, two H3 and two H4 proteins along with a single H1 protein. The DNA strand wounds around the DNA Octamer to produce a nucleosome unit.
3. An example of polyploidy is _________
a) Xenopus laevis
b) Xenopus tropicalis
c) Xenopus amieti
d) Xenopus andrei
Explanation: Polyploidy is the phenomenon by which the entire genome is duplicated in an organism. The organism becomes triploid (3n), tetraploid (4n) etc in place of the normal diploid (2n). Xenopus laevis has double the set of chromosome as Xenopus tropicalis is an example of polyploidy.
4. Hybrid vigour is referred to __________
a) superior phenotype of a hybrid
b) increased fertility of a hybrid
c) increased mortality of a hybrid
d) decreased function of a hybrid
Explanation: Hybrid vigour is the phenomenon of increased vigour in the hybrids as compared to both of its parents. This phenomenon came to light in the 20th century in corn F1 hybrids. The resulting hybrid plant had a higher growth rate, was phenotypically superior and had increased yield as compared to both the parents.
5. Hybrid vigour results from ____________
c) over dominance
d) incomplete dominance
Explanation: In case of dominance, the expression of dominant allele masks the expression of recessive allele. In co-dominance, both the alleles are equally expressed. In over dominance, the combination of genotypes from two different parents leads to supplementing the effect of each other and thus the effects lead to increased vigour.
6. Application of non-ionizing ultraviolet radiation causes _________
a) formation of pyrimidine dimers
b) deletion of pyrimidine bases
c) formation of methyl guanine
d) formation of methyl thymine
Explanation: During application of UV rays, as photons are absorbed by DNA molecules, an excited state is produced which allows for the rearrangement of electrons resulting in the formation of photoproducts.These photoproducts are cyclobutane pyrimidine dimer (CPD) and 6-4 pyrimidine –pyrimidone, both of which are pyrimidine dimers.
7. During translation of proteins, the aminoacyl tRNA arrives at ____________
a) Ribosomal A site
b) Ribosomal P site
c) Ribosomal T site
d) Ribosomal S site
Explanation: During translation, the aminoacyl tRNA carrying the desired amino acid approaches the A site on the ribosome. It then further moves to the P site and becomes peptidyl tRNA, which initiates the formation of a peptide bond between the amino acid and the growing peptide chain. The peptidyl tRNA leaves through the E site of ribosome.
8. Which of the following is a consensus sequence?
a) Promoter sequence
b) Enhancer sequence
c) Terminator sequence
d) All of the mentioned
Explanation: Consensus sequence is the most common version of conserved gene sequence which has minute variations from gen to gene. A promoter sequence, enhancer sequence and terminator sequence of a particular gene is conserved and are consensus sequences.
9. Which of the following is the start codon in protein translation?
Explanation: The start codon indicates the start of protein translation after the 5’-untranslated region (UTR) and the ribosome binds to the start codon in the mRNA. AUG is the sole start codon and codes for the amino acid Methionine. UAA, UAG and UGA are the three stop codons that indicate the termination of protein translation.
10. What is the approximate fraction of genetic variation in the nuclear genome that is expected to have a harmful effect on gene function?
Explanation: Genetic variation due to mutation causes harmful effects on gene function. Ad low as 1% genetic variation can cause noticeable harmful changes the expression and function of genes. It may lead to congenital diseases or may be fatal.
11. Which of the following statements is correct according to Chargaff’s rules?
a) All DNA molecules contain the same proportions of A, C, G and T
b) Single-stranded RNA molecules contain the same amount of A and U
c) In double-stranded DNA, the amount of T equals the amount of C
d) In double-stranded DNA, the amount of G equals the amount of C
Explanation: Chargaff rule states that the amount of A is equal to the amount of T whereas the amount of C is equal to the amount of G. This is because during base pairing, A binds with T with two hydrogen bonds and C binds with G with three hydrogen bonds.
Sanfoundry Global Education & Learning Series – Cell Biology.
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