Chapter 20: Chromosomes and DNA - Understanding Genetic Material

Chapter 20 Chromosomes And DNA RTS Questions With Answers

1. What is Karyotype? Why is its importance?

A karyotype is the number and visual appearance of chromosomes in the nucleus of a cell. It helps in detecting chromosomal abnormalities such as trisomy or monosomy.

2. What are Nucleosomes?
Nucleosomes are structural units of chromatin, consisting of a segment of DNA wrapped around histone proteins. They help in packaging DNA into a compact structure.

3. Differentiate between Heterochromatin and Euchromatin.

Heterochromatin: Dense, inactive, and tightly packed chromatin, less transcriptionally active.
Euchromatin: Less dense, actively transcribed, and loosely packed chromatin.

4. State Chromosomal Theory of Inheritance.
The Chromosomal Theory of Inheritance states that genes are located on chromosomes, and it is the chromosomes that segregate and assort during meiosis, passing genetic traits from parents to offspring.

5. What is Transformation, and in which bacteria was it discovered?
Transformation is the process by which genetic material is transferred from one bacterium to another. It was discovered in Streptococcus pneumoniae.

6. Explain Phosphodiester Bond with figure.
A phosphodiester bond is the covalent bond that links the sugar of one nucleotide to the phosphate group of another, forming the backbone of DNA.
( bond connects the 3' hydroxyl group of one sugar to the 5' phosphate group of the next nucleotide.)

7. Define Nucleoside and Nucleotide.

Nucleoside: A compound consisting of a nitrogenous base and a sugar.
Nucleotide: A nucleoside with one or more phosphate groups attached.

8. Why is DNA Replication Semi-Conservative?
DNA replication is semi-conservative because each new DNA molecule consists of one old (parental) strand and one new (daughter) strand.

9. Differentiate Leading and Lagging Strand.

Leading Strand: Synthesized continuously in the direction of the replication fork.
Lagging Strand: Synthesized discontinuously in short fragments (Okazaki fragments) opposite to the direction of the replication fork.

10. Describe Structure and Functions of DNA Polymerase III.
DNA Polymerase III is an enzyme responsible for synthesizing the new DNA strand by adding nucleotides to the growing chain during DNA replication. It also has proofreading ability to correct errors.

11. What is the One Gene-One Polypeptide Hypothesis?
The One Gene-One Polypeptide Hypothesis states that each gene encodes a specific enzyme or polypeptide chain, suggesting a direct relationship between genes and proteins.

12. Explain Promoter Briefly.
A promoter is a DNA sequence that initiates the transcription of a particular gene. It is located upstream of the gene and signals RNA polymerase to begin transcription.

13. Give Types of RNA.
The three main types of RNA are:

mRNA (Messenger RNA): Carries the genetic code from DNA to ribosomes for protein synthesis.
tRNA (Transfer RNA): Brings amino acids to the ribosome during protein synthesis.
rRNA (Ribosomal RNA): Combines with proteins to form ribosomes, the site of protein synthesis.

14. Define Genetic Code. Enlist its Properties.
Genetic code is the set of rules by which the information in mRNA is translated into proteins.
Properties:

Triplet code
Degeneracy (more than one codon for an amino acid)
Universality
Non-overlapping

15. What is Nonsense Codon? Give Example.
A nonsense codon is a codon that signals the end of protein synthesis, resulting in a stop. Example: UAA, UAG, UGA.

16. Differentiate Transcription and Translation.

Transcription: The process of synthesizing RNA from a DNA template.
Translation: The process of synthesizing proteins from mRNA at the ribosome.

17. Define Phenylketonuria.
Phenylketonuria (PKU) is a genetic disorder in which the body cannot metabolize phenylalanine, leading to mental retardation and other developmental problems if untreated.

18. Differentiate Point Mutation and Chromosomal Aberration.

Point Mutation: A change in a single nucleotide base pair.
Chromosomal Aberration: A large-scale change involving a segment or entire chromosome, such as deletion, duplication, or translocation.