Podcast
Questions and Answers
What is the approximate length of a DNA double helix in a typical mammalian cell?
What is the approximate length of a DNA double helix in a typical mammalian cell?
- 10–6 m
- 0.34 nm
- 1.36 mm
- 2.2 metres (correct)
What components primarily hold E.coli DNA in a defined region within the cell?
What components primarily hold E.coli DNA in a defined region within the cell?
- Proton carriers
- Nucleosomes
- Histones
- Proteins with positive charges (correct)
Which amino acids are primarily found in histones that contribute to their positive charge?
Which amino acids are primarily found in histones that contribute to their positive charge?
- Cysteine and Methionine
- Tyrosine and Serine
- Aspartic acid and Glutamic acid
- Lysine and Arginine (correct)
How many base pairs does a typical nucleosome contain?
How many base pairs does a typical nucleosome contain?
The beads-on-string structure observed in chromatin is mainly composed of what?
The beads-on-string structure observed in chromatin is mainly composed of what?
What structural organization is formed when nucleosomes are further coiled and condensed during cell division?
What structural organization is formed when nucleosomes are further coiled and condensed during cell division?
What is the primary role of histone proteins in the packaging of DNA?
What is the primary role of histone proteins in the packaging of DNA?
Which characteristic of DNA contributes to its organization in prokaryotes like E.coli?
Which characteristic of DNA contributes to its organization in prokaryotes like E.coli?
What is the function of the lac operon in bacteria?
What is the function of the lac operon in bacteria?
What phenomenon does DNA Fingerprinting rely on?
What phenomenon does DNA Fingerprinting rely on?
What would happen if 20% of cytosine is present in a double-stranded DNA?
What would happen if 20% of cytosine is present in a double-stranded DNA?
What did Watson and Crick's hypothesis about DNA replication rely on?
What did Watson and Crick's hypothesis about DNA replication rely on?
During the Hershey and Chase experiment, what was used to differentiate between DNA and protein?
During the Hershey and Chase experiment, what was used to differentiate between DNA and protein?
What occurs to the lac operon after lactose is added to the E. coli medium?
What occurs to the lac operon after lactose is added to the E. coli medium?
Which type of nucleic acid polymerase synthesizes RNA from a DNA template?
Which type of nucleic acid polymerase synthesizes RNA from a DNA template?
Which type of DNA is specifically associated with repetitive sequences in the genome?
Which type of DNA is specifically associated with repetitive sequences in the genome?
What are Non-histone Chromosomal proteins primarily required for?
What are Non-histone Chromosomal proteins primarily required for?
Which type of chromatin is considered transcriptionally active?
Which type of chromatin is considered transcriptionally active?
What was the key observation made by Frederick Griffith in his experiments?
What was the key observation made by Frederick Griffith in his experiments?
Why did mice injected with heat-killed S strain bacteria remain healthy?
Why did mice injected with heat-killed S strain bacteria remain healthy?
What is the primary difference between S strain and R strain bacteria?
What is the primary difference between S strain and R strain bacteria?
Which scientist conducted experiments that contributed to the understanding of genetic material?
Which scientist conducted experiments that contributed to the understanding of genetic material?
What observation did Griffith make upon injecting mice with a mixture of heat-killed S strain and live R strain bacteria?
What observation did Griffith make upon injecting mice with a mixture of heat-killed S strain and live R strain bacteria?
What is the typical outcome for mice infected with R strain bacteria?
What is the typical outcome for mice infected with R strain bacteria?
What was completed in May 2006 related to human chromosomes?
What was completed in May 2006 related to human chromosomes?
What is the estimated total number of genes in the human genome?
What is the estimated total number of genes in the human genome?
What percentage of the human genome is known to code for proteins?
What percentage of the human genome is known to code for proteins?
Which chromosome has the most genes?
Which chromosome has the most genes?
What is a significant feature of repetitive DNA sequences in the human genome?
What is a significant feature of repetitive DNA sequences in the human genome?
What percentage of nucleotide bases are exactly the same in all human beings?
What percentage of nucleotide bases are exactly the same in all human beings?
What is the function of the ribosome during protein synthesis?
What is the function of the ribosome during protein synthesis?
What is the largest known human gene?
What is the largest known human gene?
What signifies the beginning and end of a translational unit in mRNA?
What signifies the beginning and end of a translational unit in mRNA?
Which of the following is NOT a level at which gene expression can be regulated in eukaryotes?
Which of the following is NOT a level at which gene expression can be regulated in eukaryotes?
What is indicated by the identification of approximately 1.4 million locations of SNPs in humans?
What is indicated by the identification of approximately 1.4 million locations of SNPs in humans?
What occurs during the elongation phase of protein synthesis?
What occurs during the elongation phase of protein synthesis?
Why are untranslated regions (UTRs) important in mRNA?
Why are untranslated regions (UTRs) important in mRNA?
What happens when a release factor binds to the stop codon during translation?
What happens when a release factor binds to the stop codon during translation?
How does beta-galactosidase contribute to the metabolism of E. coli?
How does beta-galactosidase contribute to the metabolism of E. coli?
Which component of the ribosome acts as an enzyme during peptide bond formation?
Which component of the ribosome acts as an enzyme during peptide bond formation?
Study Notes
Packaging of DNA Helix
- DNA is a very long molecule
- In a typical mammalian cell, the DNA helix is 2.2 meters long.
- This is much longer than the typical nucleus, which is only about 10^-6 meters in diameter.
- To fit inside the nucleus DNA is tightly packaged with proteins
- In prokaryotes like E. coli, DNA is organized into large loops held by proteins in a region called the nucleoid
- In eukaryotes, DNA is packaged with proteins called histones, positively charged proteins that are rich in lysine and arginine
- Histones form an octamer, a unit of eight molecules around which DNA wraps to form a nucleosome
- A typical nucleosome contains 200 base pairs of DNA
- Nucleosomes are the repeating units of a structure called chromatin, which is visible under an electron microscope as "beads-on-a-string"
- The chromatin fibers can be further coiled and condensed to form chromosomes during cell division
E. coli DNA
- E. coli DNA is 1.36 millimeters long, and has 4.0 x 10^6 base pairs.
Chromatin Structure
- Chromatin fibers are further coiled and condensed to form chromosomes
- The packaging of chromatin at higher levels requires a set of proteins called nonhistone chromosomal (NHC) proteins
Euchromatin and Heterochromatin
- Euchromatin is loosely packed and stains lightly
- Heterochromatin is densely packed and stains darkly
- Euchromatin is transcriptionally active, meaning it is actively being used to produce proteins
- Heterochromatin is inactive and is not being transcribed.
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Description
Explore the intricate packaging of DNA within cells, focusing on the differences between prokaryotic and eukaryotic DNA structures. Learn about histones, nucleosomes, and how chromatin condenses into chromosomes. This quiz covers key concepts regarding the organization of DNA in E. coli as well.
