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Replace your entire `question.php` with this:
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Genetics Questions
Q.
Assuming Hardy-Weinberg equilibrium, the genotype frequency of heterozygotes, if the frequency of the two alleles at the gene being studied are 0.6 and 0.4, will be:
0.64
0.8
0.32
0.48
Explanation:
The Hardy-Weinberg equation for heterozygote frequency is 2pq. With p = 0.6 and q = 0.4, the frequency is 2 * 0.6 * 0.4 = 0.48.
Q.
Familial hypercholesterolaemia is caused by mutations in the gene which encodes what?
High density lipoprotein
HMG-CoA reductase
Low density lipoprotein
Low density lipoprotein receptor
Explanation:
Familial hypercholesterolaemia is most commonly caused by mutations in the LDLR gene, which encodes the low-density lipoprotein receptor.
Q.
A cross between two true breeding lines one with dark blue flowers and one with bright white flowers produces F1 offspring that are light blue. When the F1 progeny are selfed a 1:2:1 ratio of dark blue to light blue to white flowers is observed. What genetic phenomenon is consistent with these results?
epistasis
incomplete dominance
codominance
inbreeding depression
Explanation:
The 1:2:1 phenotypic ratio in the F2 generation, with an intermediate phenotype in the heterozygote, is characteristic of incomplete dominance.
Q.
Which of the following conditions shows anticipation in paternal transmission?
Fragile X syndrome
Marfan syndrome
Huntington disease
Cystic fibrosis
Explanation:
Huntington disease is a trinucleotide repeat disorder that exhibits anticipation, particularly when transmitted through the paternal line.
Q.
A homeotic mutation is one which
substitutes one body part for another in development
results in development of a tumor
is present in only one form in an individual
is wild type at one temperature and abnormal at another
Explanation:
Homeotic mutations cause one body part to develop in place of another, such as legs growing where antennae should be.
Q.
Severe anaemia at birth is a feature of what?
Sickle cell disease
Hereditary persistence of fetal haemoglobin
Alpha-thalassaemia
Beta-thalassaemia
Explanation:
Alpha-thalassaemia major can present with severe anaemia at birth due to the absence of alpha-globin chains.
Q.
Tay-Sachs disease is caused by deficiency of _________________?
Alpha-L-iduronidase
Hexosaminidase A
Glucose-6-phosphatase
Homogentisic acid oxidase
Explanation:
Tay-Sachs disease results from a deficiency of the enzyme hexosaminidase A, leading to the accumulation of GM2 ganglioside in neurons.
Q.
A nonsense mutation involves:
the creation of a stop codon.
a regulatory sequence.
the creation of a different amino acid.
an AG splice acceptor site.
Explanation:
A nonsense mutation changes a codon that specifies an amino acid into a stop codon, prematurely terminating translation.
Q.
The polymerase chain reaction or PCR is a technique that
uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
measures the ribosome transfer rate during translation
is used to determine the content of minerals in a soil sample
was used to demonstrate DNA as the genetic material
Explanation:
PCR uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Q.
The maternal serum level of alpha-fetoprotein (AFP) is lower than average in which situation?
Exomphalos
Twin pregnancies
Neural tube defects
Down syndrome
Explanation:
Low maternal serum AFP is associated with Down syndrome (trisomy 21), whereas high levels are associated with neural tube defects.
Q.
The proportion of genes shared by first cousins is on average ___.
1.0/4
1.0/16
1.0/2
1.0/8
Explanation:
First cousins share, on average, 1/8 of their genes because they share one set of grandparents.
Q.
Which of the following is not a tumour suppressor gene?
RET
RB1
NF1
APC
Explanation:
RET is a proto-oncogene, while APC, NF1, and RB1 are tumor suppressor genes.
Q.
Which of the following is a feature of X-linked dominant inheritance?
Transmitted by males only to females
Transmission only by females
Parental consanguinity
Male to male transmission
Explanation:
In X-linked dominant inheritance, affected males transmit the trait to all their daughters but none of their sons.
Q.
On average, how many fragments would a restriction enzyme which recognizes a specific 4 base sequence in DNA be expected to cleave a double-stranded bacteriophage with a genome size of 5,000 bp into?
about 50
about 4
about 2
about 20
Explanation:
A 4-base recognition site occurs on average every 4^4 = 256 bp. For a 5,000 bp genome, the expected number of cuts is approximately 5,000 / 256 ≈ 20.
Q.
Positional cloning refers to
mapping a gene to a chromosomal region and then identifying and cloning a genomic copy of the gene from the region
cloning a portion of a gene using PCR
isolating a gene by PCR using primers from another species
using a selection procedure to clone a cDNA
Explanation:
Positional cloning is the process of mapping a gene to a chromosomal region and then identifying and cloning a genomic copy of the gene from that region.
Q.
The coding sequences of genes are called:
codons.
exons.
extrons.
introns.
Explanation:
Exons are the coding sequences of a gene that are retained in the mature mRNA and translated into protein.
Q.
The epigenetic inheritance system has been described as ______ (Mayr and Provine, 1980).
soft inheritance
genotype inheritance
RNA inheritance
hard inheritance
Explanation:
The epigenetic inheritance system is often described as 'soft inheritance' because it involves changes in gene expression that are not due to changes in the DNA sequence.
Q.
If an X-linked recessive disorder is in Hardy-Weinberg equilibrium and the incidence in males equals 1 in 100, then the expected incidence of affected homozygous females would be _______.
1 in 40 000
1 in 1000
1 in 4000
1 in 10 000
Explanation:
For an X-linked recessive trait, the frequency of affected males equals q (the allele frequency). If q = 1/100, then the frequency of affected homozygous females is q^2 = (1/100)^2 = 1 in 10,000.
Q.
Which of the following is not a familial cancer syndrome
Von Hippel-Lindau syndrome
adenomatous polyposis
Li-Fraumeni syndrome
Waardenburg syndrome
Explanation:
Waardenburg syndrome is a genetic condition characterized by hearing loss and changes in pigmentation, not a familial cancer syndrome.
Q.
Arabidopsis is advantageous for plant genetic research because:
it is the closest to humans of any existing plant
it is a small plant with a small genome size which can be raised inexpensively
it is an endangered species
it is commercially important as a food crop
Explanation:
Arabidopsis is a small plant with a small genome size that can be raised inexpensively, making it an ideal model organism for plant genetics.
Q.
______ has been described as the phenomenon by which one genotype can give rise to a range of different physiological or morphological states in response to different environmental conditions during development (West-Eberhard, 1989).
Fetal plasticity
Developmental plasticity
The fetal origins hypothesis
Environmental plasticity
Explanation:
Developmental plasticity is the ability of a single genotype to produce different phenotypes in response to environmental conditions during development.
Q.
Vectors that can generally accommodate larger inserts than phage vectors are:
plasmids
viral vectors only
cosmids and BACs
phagemids
Explanation:
Cosmids and BACs (bacterial artificial chromosomes) can accommodate larger DNA inserts than standard phage vectors.
Q.
Which of the following is an autosomal dominant disorder?
Cystic fibrosis
Phenylketonuria
Tay-Sachs disease
Huntington disease
Explanation:
Huntington disease is a classic example of an autosomal dominant disorder, as are Marfan syndrome and familial hypercholesterolaemia.
Q.
A nucleotide is composed of which three components?
Phosphate, ribose sugar, and nitrogenous base
Phosphate, sugar, and nitrogenous base
Phosphate, deoxyribose sugar, and amino acid
Sugar, nitrogenous base, and protein
Explanation:
A nucleotide consists of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.
Q.
Which of the following is NOT found within DNA?
Phosphodiester bonds
Amino acids
Complementary base pairing
Thymine
Explanation:
Amino acids are the building blocks of proteins, not DNA. DNA contains nucleotides with nitrogenous bases, phosphodiester bonds, and complementary base pairing.
Q.
If 30% of the bases within a DNA molecule are adenine, what is the percentage of thymine?
25%
20%
35%
30%
Explanation:
According to Chargaff's rules, adenine pairs with thymine. If adenine is 30%, thymine must also be 30%.
Q.
Which pyrimidine base is found in RNA but not in DNA?
Cytosine
Guanine
Uracil
Thymine
Explanation:
Uracil is a pyrimidine base found in RNA but not in DNA. DNA contains thymine instead.
Q.
Purines found in nucleic acids include:
Adenine and guanine
Adenine and thymine
Guanine and uracil
Cytosine and thymine
Explanation:
Adenine and guanine are the purines, which have a double-ring structure. Cytosine, thymine, and uracil are pyrimidines.
Q.
The process of making an RNA strand from a DNA template is known as:
Translation
Replication
Transcription
Transformation
Explanation:
Transcription is the synthesis of RNA from a DNA template, catalyzed by RNA polymerase.
Q.
Which of the following statements is FALSE about DNA gel electrophoresis?
Agarose is commonly used as the gel matrix.
DNA is visualized using fluorescent dyes.
DNA migrates toward the negative electrode.
Smaller DNA fragments migrate faster than larger ones.
Explanation:
In DNA gel electrophoresis, DNA fragments migrate toward the positive electrode (anode) because DNA is negatively charged due to its phosphate backbone.
Q.
Which one of the following statements is correct as per 'Central Dogma of Molecular Biology'?
Protein is transcribed into RNA and then translated into DNA
RNA is transcribed into DNA and then translated into protein
The code on DNA is 'Transcribed into RNA' and 'Translated into Protein'
DNA is translated directly into protein without RNA
Explanation:
The Central Dogma states that genetic information flows from DNA to RNA (transcription) and then to protein (translation).
Q.
mRNA generation from primary RNA transcripts involves the removal of intron sequences. This process is called:
Splicing
Capping
Editing
Polyadenylation
Explanation:
Splicing is the process by which introns are removed from the primary RNA transcript and exons are joined together.
Q.
The semi-conservative mode of DNA replication was experimentally proved by:
Meselson and Stahl
Watson and Crick
Hershey and Chase
Griffith
Explanation:
The Meselson-Stahl experiment demonstrated that DNA replication is semi-conservative, where each new DNA molecule consists of one original and one newly synthesized strand.
Q.
These RNAs act as sponges for miRNAs.
siRNA
lncRNA
hnRNA
mRNA
Explanation:
Long non-coding RNAs (lncRNAs) can act as molecular sponges for miRNAs, sequestering them and preventing them from regulating their target mRNAs.
Q.
Which of the following DNA sequences is likely to form a left-handed Z-DNA?
Alternating GC repeats
AT-rich sequences
Random sequences
Poly-A tracts
Explanation:
Z-DNA is favored by alternating purine-pyrimidine sequences, particularly those rich in guanine and cytosine, such as (GC)n repeats.
Q.
In theory, what is the minimum number of PCR cycles required in order to amplify more than 100 copies from one double-stranded DNA molecule?
12
7
5
10
Explanation:
Each PCR cycle doubles the number of DNA molecules. Starting from 1 copy, after n cycles, you have 2^n copies. To exceed 100, 2^7 = 128, so a minimum of 7 cycles is required.
Q.
Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. The bacterium is probably which of the following?
An Aerotolerant Anaerobe
An Obligate Aerobe
A Facultative Anaerobe
An Obligate Anaerobe
Explanation:
Pseudomonas aeruginosa is an obligate aerobe, meaning it requires oxygen to grow, which is relevant in the oxygen-rich environment of cystic fibrosis airways.
Q.
The spoilage of canned foods is caused by Geobacillus stearothermophilus. This organism is:
A mesophilic virus
A thermophilic spore-former
A halophilic fungus
A psychrophilic pathogen
Explanation:
Geobacillus stearothermophilus is a thermophilic, spore-forming bacterium that can survive commercial canning processes and cause spoilage, particularly in low-acid canned foods.
Q.
Decreasing order of resistance to sterilization is: