Biology Chapter: DNA and Chromatin Structure

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Questions and Answers

What are the proteins that facilitate the higher-level packaging of chromatin called?

Nuclear scaffold proteins

Transcription factors

Non-histone chromosomal proteins (correct)

Histone proteins

Which type of chromatin is known for being transcriptionally inactive?

Open chromatin

Euchromatin

Heterochromatin (correct)

Condensed chromatin

What was the significant discovery made by Frederick Griffith in his experiments?

Antigenic variation occurs in bacteria

Heat-killed pathogens were ineffective

Bacteria can transform from one strain to another (correct)

DNA is the genetic material

Which strain of Streptococcus pneumoniae is associated with severe pneumonia in mice?

S strain (B) Signup and view all the answers

What characteristic distinguishes the S strain bacteria from the R strain bacteria?

Presence of a polysaccharide coat (A) Signup and view all the answers

What was the outcome when Griffith injected mice with a mixture of heat-killed S strain and live R strain?

Mice died and living S bacteria were recovered (C) Signup and view all the answers

Which researchers significantly contributed to the understanding of genetic material in the early 20th century?

Gregor Mendel and Walter Sutton (D) Signup and view all the answers

How does euchromatin appear in a typical nucleus compared to heterochromatin?

It is loosely packed and lighter in stain (A) Signup and view all the answers

What process did RNA perform in early life that DNA does not perform as effectively?

Catalysis (C) Signup and view all the answers

What is one reason why DNA evolved from RNA?

DNA is more stable than RNA. (A) Signup and view all the answers

According to Watson and Crick's model, what happens to the two DNA strands during replication?

They separate and both serve as templates. (A) Signup and view all the answers

What term describes the type of replication that results in each DNA molecule containing one parental and one new strand?

Semiconservative replication (C) Signup and view all the answers

Which of the following is a key feature of DNA that aids in its stability compared to RNA?

Double-stranded structure (B) Signup and view all the answers

What did Watson and Crick predict about the pairing of nucleotides during DNA replication?

Specific pairing suggests a copying mechanism. (C) Signup and view all the answers

Which process is NOT described in the context of DNA replication?

Catalysis by RNA molecules (C) Signup and view all the answers

Which of the following statements about RNA in early life processes is accurate?

RNA acted mainly as a genetic material. (C) Signup and view all the answers

What was the primary goal of the Human Genome Project?

To identify all human genes. (D) Signup and view all the answers

In what year was the Human Genome Project officially launched?

1990 (C) Signup and view all the answers

What was the estimated total cost of the Human Genome Project based on initial predictions?

9 billion US dollars (B) Signup and view all the answers

Which organizations coordinated the Human Genome Project?

U.S. Department of Energy and National Institute of Health (B) Signup and view all the answers

What significant area in biology developed alongside the Human Genome Project?

Bioinformatics (B) Signup and view all the answers

How many books would be required to store the DNA sequence information from a single human cell?

3300 (B) Signup and view all the answers

What is one of the ethical considerations addressed by the Human Genome Project?

Ethical issues regarding genetic testing (B) Signup and view all the answers

How long did the Human Genome Project take to complete?

13 years (C) Signup and view all the answers

What is the primary reason that only one strand of DNA is copied during transcription?

It prevents the formation of double stranded RNA. (A) Signup and view all the answers

Which of the following statements about the role of vectors in recombinant DNA procedures is correct?

Vectors provide an origin of replication for DNA. (B) Signup and view all the answers

Which of the following best describes the process of transcription?

The copying of genetic information from DNA to RNA. (D) Signup and view all the answers

What phenomenon occurs if cell division does not follow DNA replication?

Polyploidy. (A) Signup and view all the answers

How does the process of transcription differ from that of DNA replication?

Only a segment of DNA is copied during transcription. (D) Signup and view all the answers

Which base pairs with adenosine during transcription?

Uracil. (B) Signup and view all the answers

Why is it important for transcription to define boundaries for the segment being copied?

To avoid producing two RNA molecules with different sequences. (D) Signup and view all the answers

What is a potential consequence of having both strands of DNA act as templates during transcription?

Disruption in amino acid sequences of proteins. (C) Signup and view all the answers

What was completed in May 2006?

The sequencing of chromosome 1 (A) Signup and view all the answers

What is the estimated number of genes in the human genome?

30,000 (A) Signup and view all the answers

Which gene is identified as the largest known human gene?

Dystrophin (D) Signup and view all the answers

What percentage of nucleotide bases are identical across all humans?

99.9 per cent (B) Signup and view all the answers

What fraction of the human genome is known to code for proteins?

Less than 2 per cent (D) Signup and view all the answers

Which chromosome has the most genes?

Chromosome 1 (C) Signup and view all the answers

What are repetitive sequences thought to contribute to?

Chromosome structure and evolution (D) Signup and view all the answers

What are SNPs commonly referred to as?

Single nucleotide polymorphisms (C) Signup and view all the answers

Study Notes

Chromatin Structure

Chromatin is organized into euchromatin and heterochromatin
Euchromatin is loosely packed and stains light, associated with active transcription
Heterochromatin is densely packed and stains dark, associated with inactive transcription
Non-histone chromosomal (NHC) proteins are required for higher-level chromatin packaging

Genetic Material Discovery

DNA was identified as the genetic material after a series of experiments
Frederick Griffith's experiments with Streptococcus pneumoniae demonstrated transformation: the change of a living organism's physical form
Griffith found that heat-killed S-strain bacteria, which are virulent (cause disease), could still transform living R-strain bacteria into the virulent S-strain

DNA Replication

Watson and Crick proposed a semi-conservative model of DNA replication
Replication involves separating the two strands of DNA and using each strand as a template for synthesis of a new complementary strand
Each new DNA molecule contains one parental strand and one newly synthesized strand
Replication requires an origin of replication, provided by vectors in recombinant DNA procedures

Transcription

Transcription copies genetic information from DNA to RNA
The process follows base complementarity rules, with uracil replacing thymine in RNA
Only a segment of DNA, and only one strand, is transcribed into RNA
Both strands are not copied because they would produce RNA molecules with different sequences, leading to ambiguity in the genetic code

Human Genome Project (HGP)

HGP aimed to sequence the entire human genome, approximately 3 billion base pairs
The project was completed in 2003, with the sequence of chromosome 1 being completed in 2006
HGP revealed several key features of the human genome:
- The human genome contains 3,164.7 million base pairs.
- The estimated number of genes is 30,000-25,000, significantly lower than previous estimates.
- Less than 2% of the genome codes for proteins.
- Repetitive sequences make up a large portion of the genome.
- Scientists have identified about 1.4 million single nucleotide polymorphisms (SNPs) in humans.

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Description

Explore the fascinating concepts of chromatin organization, the discovery of DNA as genetic material, and the process of DNA replication. This quiz covers key experiments and models that have shaped our understanding of genetics. Test your knowledge on euchromatin, heterochromatin, and the semi-conservative replication model.