Molecular basis of inheritance important questions
Answers
Answer:
Q.1. State the role of histones in DNA packaging.
A.1.
The basic histone proteins neutralize the acid nature of DNA.
They play a role in gene regulation.
They help the DNA to wind around itself.
Also Read: DNA packaging.
Q.2. What is the difference between heterochromatin and euchromatin?
A.2. Heterochromatin is that part of the chromosomes which is tightly packed and is genetically inactive, whereas euchromatin is the part that of chromosomes which is uncoiled or loosely packed and is transcriptionally active.
More Details: Difference between heterochromatin and euchromatin
Q.3. Name any three viruses with RNA as the genetic material.
A.3. Human Immunodeficiency Virus, Influenza Virus, Tobacco Mozaic Virus.
Explore More: Viruses
Q.4. What is the reason for the discontinuous synthesis of DNA on one of the parental strands?
A.4. The DNA synthesis occurs in 5’-3’ direction. The DNA strands act as templates. One of the strands is synthesized in the 3’-5’ direction. The other strand is synthesized in the opposite direction producing small stretches of DNA known as Okazaki fragments. That is why DNA synthesis is discontinuous.
Q.5. The sequence of the coding strand of DNA in a transcription unit is mentioned below.
3’ AATGCAGCTATTAGG 5’
Write the sequence for:
Its complementary strand
It’s mRNA
A.5.
5’ TTACGTCGATAATCC 3’
5’ CGAUUAUCGACGUAA 3’
Q.6. What is DNA polymorphism?
A.6. DNA polymorphism is the variation in the DNA sequence arising due to mutation at non-coding sequences.
Q.7. Comment on the statement “Retroviruses do not follow central dogma.”
A.7. Retroviruses have RNA as genetic material. That is why they do not follow the central dogma. Instead, the RNA is converted into DNA by the enzyme reverse transcriptase.
Q.8. Sometimes the young ones born have an extremely different set of eyes or limbs. Give a relevant explanation for the abnormality.
A.8. This happens due to non-coordination in the regulation of expression in the set of genes associated with the development of organs.
Q.9. Discuss the dual polymerase present in E.coli.
A.9. DNA polymerase III is found in E.coli that helps in the replication process. It performs the 5’-3’ polymerase activity as well as 3’-5’ exonuclease activity. It has the ability to proofread the wrong nucleotides and substitutes it with the correct one.
Q.10. Mention the functions of:
Methylated guanosine cap
poly-A tail
A.10.
Methylated guanosine cap- It attaches the mRNA to the smaller sub-units of the ribosome during translation initiation.
Poly-A tail- It increases the length of the mRNA and provides longevity to the mRNA.
Short Answer Type Questions
Q.1. Define the following:
Promoter
tRNA
Exons
A.1.
Promoter– The promoter serves as the binding site for RNA polymerase for transcription. It helps in transcription initiation.
tRNA– tRNA or transfer RNA is involved in the translation of proteins. It reads the genetic code on the RNA and transfers specific amino acids to mRNA on the ribosomes.
Exons– Exons are the coding regions present in a DNA sequence in eukaryotes.
Q.2. Describe the role of the ribosome in translation.
A.2. Ribosomes are made up of rRNA. It performs the following functions during translation.
The two ribosomal sub-units sandwich around the mRNA.
It provides bing site for tRNA.
With each triplet codon of mRNA moving through the ribosome, a specific tRNA with its own anticodon is recruited and a polypeptide is synthesized.
When the ribosome encounters a stop codon, it dissociates and no more polypeptides are synthesized.
Q.3. What is cistron? Differentiate between monocistronic and polycistronic transcription units.
Answer:
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