70 Questions
Which of the following is a characteristic of prokaryotic cells?
Their genetic material is a single circular molecule of DNA.
Which of the following statements about viruses is correct?
Viruses contain either DNA or RNA as their genetic material.
Which of the following is a characteristic of eukaryotic cells?
They have larger (80S) ribosomes and membrane-bound organelles.
Which of the following statements about bacterial classification is true?
Bacteria are classified as prokaryotic microorganisms.
What is the approximate number of different microbes that can cause diseases in humans?
Nearly 2,000
Which of the following statements about microbial pathogenesis is correct?
Pathogenic microbes can cause diseases by infecting the host.
What is the approximate number of infections caused by microbes worldwide each year?
10 billion
Which of the following is a characteristic of bacterial growth?
Bacteria can undergo binary fission to divide.
What is the approximate number of deaths caused by infections worldwide each year?
13 million
Which of the following statements about the microbial world is correct?
There are more than $5 \times 10^{30}$ types of microbes in the world.
What are the two major classes of chromosomal proteins mentioned in the text?
Histones and nucleosomes
Which group of proteins is specifically complexed with DNA to produce the basic structural subunits of chromatin?
Nucleosomes
What is the first level of condensation that involves packaging DNA into nucleosomes?
Negative supercoil into nucleosomes
Which components make up the octamer involved in the first level of DNA packaging?
H1, H2A, H2B
What is the term used to describe the giant molecule of DNA that extends from one end through the centromere to the other end of a chromosome?
Large DNA molecule
How is chromatin packaged into chromosomes at the first level of condensation?
As 11-nm-diameter interphase chromatin fibers
What are the two types of large organic molecules that chromosomes are composed of?
Proteins and Nucleic Acids
In which type of cells is the genetic information usually encoded in DNA?
Eukaryotic cells
What type of nucleic acid is the genetic material in some viruses?
Ribonucleic Acid (RNA)
Which macromolecule is responsible for storing the genetic information in cells?
Nucleic Acids
What is the level of DNA packaging in eukaryotic chromosomes to ensure efficient storage of genetic material?
Tightly packed around non-histone proteins
Which organic molecule is not a component of chromosomes?
Carbohydrates
In cells, what is the organizational structure of DNA molecules?
Negatively supercoiled domains
How many genes are typically present in the genome of the bacteriophage MS2?
4 genes
What is the functional state of a bacterial chromosome known as?
Highly condensed genome
What is the structure of eukaryotic chromosomes during mitosis and meiosis?
Highly condensed DNA molecules
How many domains are bacterial chromosomes typically segregated into?
About 50 domains
Which part of eukaryotic chromosomes has unique structures?
Centromeres and telomeres
What is the primary function of the shelterin protein complex?
To protect the telomeres from degradation and modification by DNA repair processes
What is the approximate size of the ellipsoidal beads called nucleosomes, into which the DNA of eukaryotic chromosomes is packaged?
11 nm
What is the approximate size of the chromatin fibers that make up the condensed chromosomes present during mitosis and meiosis, as well as carefully isolated interphase chromosomes?
30 nm
Which of the following statements about the structure of eukaryotic chromosomes is correct?
The centromeres and telomeres have unique structures that facilitate their functions.
What is the primary role of the scaffolds composed of nonhistone chromosomal proteins in eukaryotic chromosomes?
To segregate the 30-nm chromatin fibers into domains at metaphase
Which of the following statements about repetitive DNA sequences in eukaryotic genomes is correct?
Repetitive DNA sequences account for 15% to 80% of eukaryotic genomes.
What is the primary role of histone H1 in the packaging of eukaryotic chromosomes?
It condenses the 11-nm nucleosome fiber into the 30-nm chromatin fiber.
What is the primary function of the centromere region in eukaryotic chromosomes?
It serves as the attachment point for spindle fibers during cell division.
What is the primary function of telomeres in eukaryotic chromosomes?
They prevent deoxyribonucleases from degrading the ends of linear DNA molecules.
What is the approximate number of copies of the alpha (alphoid) satellite sequence found in each centromere of human chromosomes?
5,000 - 15,000 copies
What is the approximate length of the TTAGGG repeats found in telomeres of normal (non-cancerous) human somatic cells?
500 - 3,000 repeats
Which of the following statements accurately describes the third level of condensation in eukaryotic chromosomes?
It involves the separation of segments of the giant DNA molecules into independently supercoiled domains or loops.
What property of the two strands of a DNA double helix makes it uniquely suited to store and transmit genetic information?
Complementarity
Which form of DNA, existing as a right-handed helix with 11 nucleotide pairs per turn, is typically found in high salt concentrations or partially dehydrated states?
A-DNA
What type of supercoiling is typically observed in functional DNA molecules within living cells?
Negative supercoil
In RNA, which nucleotide is typically found instead of thymine?
Uracil
What feature of DNA structure allows for the formation of hydrogen bonds between complementary bases?
Opposite chemical polarity of the two strands
Which form of double helical DNA is a left-handed structure that is different from A-DNA and B-DNA?
Z-DNA
What is the molecular composition of DNA in comparison to RNA and proteins?
DNA is more stable than RNA or proteins
Which base pairs are typically found in DNA, according to the text?
Adenine paired with Thymine and Guanine paired with Cytosine
What is the primary difference between DNA and RNA structures?
RNA contains Thymine instead of Uracil found in DNA
Which statement accurately describes the DNA structure presented in the text?
DNA is single-stranded, with Adenine paired with Thymine and Guanine paired with Cytosine
What type of nucleic acid is commonly found in somatic cells of diploid organisms?
Double-stranded DNA
Which enzymes were used to treat highly purified DNA from type IIIS cells in a specific experiment mentioned in the text?
(1) Deoxyribonuclease (DNase), (2) Ribonuclease (RNase), (3) Proteases
What is the primary structural feature that allows DNA to exist as a double helix?
Hydrogen bonding between nitrogenous bases
Which statement accurately describes the process of DNA denaturation?
The hydrogen bonds between complementary bases are broken, separating the two strands.
Which of the following accurately describes the structure of a nucleotide?
A pentose sugar, a nitrogenous base, and a phosphate group
Which of the following statements accurately describes the difference between purines and pyrimidines?
Purines have a double-ring structure, while pyrimidines have a single-ring structure.
Which of the following statements accurately describes the Chargaff's rules governing the base composition of DNA?
The amount of adenine equals the amount of guanine, and the amount of cytosine equals the amount of thymine.
Which of the following statements accurately describes the process of DNA renaturation?
Complementary single strands of DNA re-form base-paired double helices when cooled slowly under appropriate conditions.
Which of the following statements accurately describes the structure of DNA?
DNA is a double-stranded molecule with antiparallel strands held together by hydrogen bonds between complementary nitrogenous bases.
Which of the following statements accurately describes the process of DNA denaturation?
DNA denaturation occurs when the hydrogen bonds between complementary nitrogenous bases are disrupted, causing the double-stranded DNA to separate into single strands.
Which of the following statements accurately describes the structure of RNA?
RNA is a single-stranded molecule composed of nucleotides with ribose sugars and phosphate groups.
Which of the following statements accurately describes the function of nucleic acids in cells?
DNA stores and transmits genetic information, while RNA is responsible for protein synthesis and gene regulation.
Which of the following statements accurately describes the complementary base pairing in nucleic acids?
In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
Which of the following statements accurately describes the role of nucleic acids in viruses?
In some viruses, RNA is the genetic material responsible for storing and transmitting genetic information, while DNA is not present.
Which of the following statements about DNA packaging in eukaryotic chromosomes is correct?
The first level of packaging involves wrapping DNA around histone octamers to form nucleosomes, creating the 11-nm chromatin fiber.
Which of the following statements regarding the structure of eukaryotic chromosomes is correct?
Each chromosome contains a single, giant molecule of DNA that extends from one end to the other.
What is the primary role of histone H1 in the packaging of eukaryotic chromosomes?
Histone H1 is responsible for the further condensation of the 11-nm chromatin fiber into higher-order structures.
Which of the following statements about the structure of RNA is correct?
RNA is a single-stranded molecule composed of nucleotides with a pentose sugar (ribose) and the nitrogenous bases adenine, guanine, cytosine, and uracil.
Which of the following statements about DNA denaturation is correct?
All of the above statements are correct regarding DNA denaturation.
Which of the following statements about nucleic acids is correct?
The pentose sugar found in DNA is deoxyribose, while the pentose sugar found in RNA is ribose.
Study Notes
Cell Structure
- Prokaryotes have a rigid external cell wall containing peptidoglycan, a polymer of amino acids and sugars.
- Eukaryotes lack peptidoglycan in their cell wall; instead, they have a flexible cell membrane or a rigid cell wall with chitin in fungi.
- Sterols are present in eukaryotic cell membranes but not in prokaryotes, except for the wall-less Mycoplasma.
Nucleic Acids
- Eukaryotic cells contain both DNA and RNA, while viruses contain either DNA or RNA but not both.
- Prokaryotic cells replicate by binary fission, whereas eukaryotic cells replicate by mitosis.
- Viruses disassemble, replicate, and reassemble into multiple progeny viruses.
Reproduction
- Prokaryotic cell division involves binary fission, where a single DNA molecule replicates, attaches to different parts of the cell membrane, and then pulls apart to form two identical cells.
- The difference in ribosome structure (70S in prokaryotes vs. 80S in eukaryotes) allows antibiotics to target prokaryotic ribosomes selectively.
Nucleoid
- The nucleoid is the area of the cytoplasm where DNA is located in prokaryotes.
- Prokaryotic DNA is a single, circular molecule containing about 2000 genes, with no introns.
Plasmids
- Plasmids are extrachromosomal, double-stranded, circular DNA molecules capable of replicating independently of the bacterial chromosome.
- They can be transmissible or non-transmissible, carrying genes for antibiotic resistance, heavy metal resistance, and other functions.
Microbiology
- Microbiology is the study of microorganisms, including normal flora and pathogenic microbes.
- There are approximately 5 x 10^30 microorganisms in the world, with 10 billion microbial cells in the human body.
- Microorganisms can cause diseases, with nearly 2,000 different microbes causing infections worldwide.
Eukaryotes vs. Prokaryotes
- Eukaryotic cells have a true nucleus with multiple chromosomes, mitotic apparatus, and organelles, whereas prokaryotes lack these features.
- Eukaryotes contain larger ribosomes (80S) and are mostly diploid, with two complete sets of genes, whereas prokaryotes have smaller ribosomes (70S) and are usually monoploid.
Chromosome Structure
- Eukaryotic chromosomes contain large DNA molecules that are highly condensed during mitosis and meiosis.
- Chromosomes have unique structures, including centromeres, telomeres, and repetitive DNA sequences.
Centromeres and Telomeres
- Centromeres are constricted regions of metaphase chromosomes, with specific DNA sequences repeated many times.
- Telomeres are stable ends of chromosomes, protecting them from degradation and fusion with other DNA molecules.
Cell Composition
- Cells are complex assemblies of molecules that can acquire materials, recruit and store energy, and carry out diverse activities, including reproduction.
- Genetic material is usually located on chromosomes, which are composed of proteins and nucleic acids (DNA and RNA).
- The genetic information is stored in nucleic acids, not proteins.
Explore the differences in cell wall composition between prokaryotes and eukaryotes. Learn about peptidoglycan in prokaryotes and chitin in fungi, as well as the presence of sterols in eukaryotic cell membranes.
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