Cell Biology Multiple Choice Questions & Answers (MCQs)on “Genes, Chromosomes and Genomes – 1”.
1. The segregation of alleles on one trait did not have any effect on the segregation of alleles on a different trait. This is based on ____________
A. Mendel’s law of Heredity
B. Mendel’s law of Dominance
C. Mendel’s law of Independent Assortment
D. Mendel’s law of Segregation
Answer: C
Clarification: There are three Mendel’s laws n Heredity. 1. The Mendel’s law of Dominance states that when a dominant individual is crossed with a recessive individual, the F1 generation offspring will exhibit the dominant trait. 2. According to Mendel’s law of Segregation, a pair of allele governing a single trait segregates from each other during the formation of gametes. 3. According to Mendel’s law of Independent Assortment, the segregation of alleles on one trait did not have any effect on the segregation of alleles on a different trait.
2. Genes that show tendency to be inherited together is known as ____________
A. Linkage group
B. Homologous group
C. Co-dependent genes
D. None of the mentioned
Answer: A
Clarification: Some genes are packed together on a chromosome and tend to pass on from parents to offsprings as a group. These genes form a unit during the formation of gametes and are not separated during gamete formation. These genes on the same chromosome act like they are linked to one another and hence, are known as linkage groups.
3. Giant polytene chromosomes are found in ___________
A. Egg of fruit fly
B. Salivary gland of larvae of fruit fly
C. Salivary gland of adult fruit fly
D. All of the mentioned
Answer: B
Clarification: Polytene chromosomes are a type of giant chromosomes which are many times longer in length than normal chromosomes. Polytene chromosomes are found in the salivary gland of a larval fruit fly and show several distinct darkly stained bands.
4. An example of co-dominance is ____________
A. Mouse coat colour
B. Human ABO blood group system
C. Human hand size
D. Human eye colour
Answer: B
Clarification: When two different alleles are crosses and neither of them is dominant and recessive and both get expressed in the phenotype offspring, then such a genetic scenario is known as codominance. In the ABO Blood group system of humans, a person with A protein has blood type A and a person with B protein has blood type B. If a person with blood type A mates with person with blood type B, then the dominant A and B genes will be co-expressed in the offspring and he will have blood type ‘AB’.
5. Loops in lampbrush chromosomes represent site of _____________
A. Replication
B. Transcription
C. Cell division
D. Crossing over
Answer: b
Clarification: Lampbrush chromosomes are a type of giant chromosomes found in the growing oocytes of amphibians. Twin loops arise on either side of the chromosome in meiotic prophase. This is due to the active transcription of many genes.
6. How can it be determined whether the parent progeny is homozygous or heterozygous?
A. Test cross
B. Back cross
C. Monohybrid cross
D. Reciprocal cross
Answer: A
Clarification: Test cross is the cross of a F1 generation offspring with the homozygous recessive parent. If the offspring phenotype is dominant: recessive = 1:1, the F1 offspring is heterozygous dominant. If all the plant exhibits dominant phenotype, the F1 offspring is homozygous dominant. In this way, the genotype of an offspring can be determined.
7. The expression of Holandric genes causes the following genetic trait ______________
A. Haemophilia
B. Colour blindness
C. Down’s syndrome
D. Hypertrichosis
Answer: D
Clarification: Y-linked genes are called Holandric genes. Hypertrichosis is the genetic trait by which hair appears on the earlobe of an individual. The gene for Hypertrochosis is present in the Y chromosome and thus this trait is only expressed in males. This trait is governed by holandric gene.
8. The method of DNA replication is _____________
A. conservative
B. semi-conservative
C. non-conservative
D. disruptive
Answer: B
Clarification: In DNA replication , the two daughter strands unwind and are used as template for the formation of a new DNA strand. As a result, one strand in conserved and a new strand is produced by taking the conserved strand as a template. Thus, DNA replication is a semi-conservative process.
9. The DNA binding proteins bind at the _______________
A. Minor groove
B. Major groove
C. Phosphate molecules
D. Pentose sugars
Answer: B
Clarification: The DNA double strands are present as a double-helix as they wound around each another. Due to base stacking, alternative minor and major grooves are formed in the helix. Major groove provide the site for DNA protein binding.
10. During DNA denaturation, which of the following occurs?
A. Unwinding of DNA double strand
B. Absorbance of UV rays
C. Decrease in hydrophobic interactions of base stacking
D. All of the mentioned
Answer: D
Clarification: DNA denaturation takes place either due to thermal treatment or due to treatment in saline solution. During denaturation, DNA double strands get separated and there is an increase in the absorbance of UV rays by the dissolved DNA. Once the two DNA strands have separated, the hydrophobic interactions that result from base stacking are greatly decreased.
11. Human Genome Project was focused on discovering the details of ___________
A. sNRPs
B. 3D DNA structure
C. Junk DNA
D. VNTRs
Answer: C
Clarification: The Human Genome Project was an international scientific research project with the goal of determining the sequence of nucleotide base pairs that make up human DNA from a period of 1990 to 2003. The main purpose of these projects was to find out the base sequence of human junk DNA which was different for every individual.