Biology Overview Quiz

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Questions and Answers

Why is replication faster in prokaryotes compared to eukaryotes?

Eukaryotes utilize more complex replication proteins.

Prokaryotes have larger genomes that replicate more quickly.

Eukaryotes replicate in the cytoplasm instead of the nucleus.

Prokaryotes have a simpler structure with circular DNA. (correct)

What role do telomeres play in eukaryotic DNA replication?

They are involved in the proofreading mechanism.

They speed up the replication process.

They allow replication to occur at multiple origins.

They protect the ends of chromosomes from degradation. (correct)

What is a key difference in the replication machinery between eukaryotes and prokaryotes?

Prokaryotes have multiple origins of replication.

Eukaryotes require histones and complex proteins for chromatin remodeling. (correct)

Prokaryotes need telomerase for their chromosomes.

Eukaryotes employ circular DNA for replication.

Which of the following statements is true regarding eukaryotic DNA replication?

It involves multiple origins and occurs in the nucleus. Signup and view all the answers

In what way is the structure of DNA in prokaryotes significant during replication?

Prokaryotic DNA is circular, allowing for a faster replication process. Signup and view all the answers

What is the correct sequence of processes in the Central Dogma of Molecular Biology?

Replication → Transcription → Translation Signup and view all the answers

Which property of life specifically describes the ability of an organism to maintain stable internal conditions?

Homeostasis Signup and view all the answers

What distinguishes prokaryotic cells from eukaryotic cells regarding their DNA structure?

Eukaryotes contain multiple chromosomes while prokaryotes contain one circular chromosome. Signup and view all the answers

Which statement about viruses is true?

Viruses require a host cell to reproduce. Signup and view all the answers

Which of the following is NOT a property of life?

Immortality Signup and view all the answers

What is the main mode of reproduction for Paramecium?

Binary fission Signup and view all the answers

What size range differentiates prokaryotic cells from eukaryotic cells?

Prokaryotic cells range from 0.5-10 µm in size. Signup and view all the answers

Which of the following cellular structures is found in eukaryotic cells but absent in prokaryotic cells?

Nucleus Signup and view all the answers

What primarily determines the host specificity of a virus?

The affinity of capsid proteins to host cell receptors Signup and view all the answers

Which of the following correctly describes prions?

They are infectious proteins that cause other proteins to misfold. Signup and view all the answers

How does mitochondrial DNA (mtDNA) differ from nuclear DNA (nDNA)?

mtDNA is circular and varies in copy number with cell function. Signup and view all the answers

What key characteristic differentiates eukaryotic somatic cells from germ cells?

Somatic cells have two copies of genetic information, while germ cells have one. Signup and view all the answers

Which nitrogenous base is found in RNA but not in DNA?

Uracil Signup and view all the answers

What role does the major groove of DNA play?

It binds to proteins that are essential for DNA replication. Signup and view all the answers

Which type of RNA is primarily responsible for the actual synthesis of proteins?

tRNA Signup and view all the answers

What structural feature characterizes both DNA and RNA?

Both are made of nucleotides consisting of a sugar, phosphate, and base. Signup and view all the answers

How do plasmids contribute to bacterial genetic diversity?

Plasmids can transfer genetic material between different bacteria. Signup and view all the answers

What is a primary function of ribosomal RNA (rRNA)?

Forming part of the ribosome and catalyzing peptide bonds. Signup and view all the answers

What is the composition of a nucleotide?

A pentose sugar, a phosphate group, and a nitrogenous base. Signup and view all the answers

Which type of cell lacks a cell wall and has a liquid-like structure?

Animal cells Signup and view all the answers

The double-stranded nature of DNA allows for what primary function?

Stabilization of genetic information. Signup and view all the answers

What is one of the roles of non-coding RNAs in cells?

They regulate gene expression and epigenetics. Signup and view all the answers

What enzyme is responsible for unwinding the DNA double helix during replication?

Helicase Signup and view all the answers

Which DNA polymerase is primarily responsible for synthesizing the leading strand in eukaryotic cells?

DNA polymerase ε Signup and view all the answers

What problem arises during the replication of the lagging strand?

Lack of free 3' OH group Signup and view all the answers

Which of the following enzymes is responsible for sealing the gaps between Okazaki fragments?

DNA ligase Signup and view all the answers

During the termination phase of DNA replication, what occurs to telomeres with each cell division in eukaryotes?

They shorten Signup and view all the answers

What type of RNA component is part of the telomerase enzyme?

Integral RNA Signup and view all the answers

How do eukaryotic cells differ from prokaryotic cells in terms of origins of replication?

Prokaryotes have a single origin, eukaryotes have multiple. Signup and view all the answers

What specific role does RNase H perform during DNA replication?

Removes RNA primers Signup and view all the answers

Which strand of DNA is synthesized continuously during replication?

Leading strand Signup and view all the answers

Which of the following best describes the main difference in DNA structure between eukaryotes and prokaryotes?

Eukaryotes have linear DNA complexed with histones, while prokaryotes have circular DNA. Signup and view all the answers

What is the primary energy source for the polymerization of DNA during replication?

Pyrophosphate hydrolysis Signup and view all the answers

What is the direction of synthesis for all newly added nucleotides during DNA replication?

5' to 3' Signup and view all the answers

During DNA replication, what is the role of topoisomerase?

To prevent supercoiling of the DNA Signup and view all the answers

What defines the semi-conservative nature of DNA replication?

Each new DNA molecule contains one old and one new strand. Signup and view all the answers

The flow of genetic information follows the order DNA → RNA → ______.

Protein Signup and view all the answers

Paramecia are surrounded by small hairs called ______ that allow them to move.

cilia Signup and view all the answers

Eukaryotes have a ______ and membrane-bound organelles, unlike prokaryotes.

nucleus Signup and view all the answers

Viruses must infect a ______ to grow and reproduce.

host-cell Signup and view all the answers

Life is organized into ______, which are the basic units of life.

cells Signup and view all the answers

The primary reproduction method for Paramecium is ______.

fission Signup and view all the answers

Prokaryotes are generally ______ in size compared to eukaryotes.

smaller Signup and view all the answers

Both eukaryotes and prokaryotes contain ______ as their genetic material.

DNA Signup and view all the answers

Eukaryotes have ______ DNA, while prokaryotes have circular DNA.

linear Signup and view all the answers

In eukaryotes, replication occurs in the ______.

nucleus Signup and view all the answers

Eukaryotic cells need the enzyme ______ to maintain telomeres.

telomerase Signup and view all the answers

Eukaryotes require a more complex set of replication ______ due to the chromatin structure.

proteins Signup and view all the answers

Prokaryotes replicate their DNA ______ than eukaryotes due to their simpler structure.

faster Signup and view all the answers

The infectious particles made of nucleic acids are surrounded by a protein coat called a ______.

capsid Signup and view all the answers

Bacteriophages specifically infect ______.

bacteria Signup and view all the answers

Prions can cause neuro-degenerative disorders by misfolding ______ proteins.

normal Signup and view all the answers

In prokaryotes, DNA is typically ______ and located in a structure called the nucleoid.

circular Signup and view all the answers

Plasmids are small, circular ______ that can provide advantages like antibiotic resistance.

molecules Signup and view all the answers

Nuclear DNA (nDNA) is linear and ______-stranded.

double Signup and view all the answers

Chloroplast DNA (cpDNA) is typically ______ and involved in photosynthesis.

circular Signup and view all the answers

Animal cells lack a cell wall, whereas plant cells have cell walls made of ______.

cellulose Signup and view all the answers

MRNA delivers copied information to the ______ for protein synthesis.

cytoplasm Signup and view all the answers

Transfer RNA (tRNA) binds activated amino acids and delivers them to ______.

ribosomes Signup and view all the answers

In DNA, A pairs with T and G pairs with ______.

C Signup and view all the answers

RNA is typically ______-stranded and can form loops and folds.

single Signup and view all the answers

The ______ groove of DNA binds to specific proteins and is crucial for transcription initiation.

major Signup and view all the answers

Non-coding RNA molecules are involved in ______ regulation, influencing cellular processes.

epigenetic Signup and view all the answers

Viruses and proviruses consist of nucleic acid molecules; they have ______ structure.

no cell Signup and view all the answers

RRNA forms the core of ______, catalyzing peptide bonds in proteins.

ribosomes Signup and view all the answers

In eukaryotic cells, DNA replication occurs in the ______ phase of the cell cycle.

S Signup and view all the answers

During DNA replication, helicase uncoils the double-helix by breaking ______ bonds.

hydrogen Signup and view all the answers

The leading strand is synthesized in the ______ direction.

5’ to 3’ Signup and view all the answers

The RNA component of telomerase serves as a ______ to synthesize the single-stranded telomere cap.

template Signup and view all the answers

In prokaryotic cells, DNA replication occurs in the ______ since they lack a nucleus.

cytoplasm Signup and view all the answers

Okazaki fragments are formed during the synthesis of the ______ strand.

lagging Signup and view all the answers

DNA polymerase β is responsible for filling in gaps left after the removal of ______ primers.

RNA Signup and view all the answers

The enzyme ______ connects newly added nucleotides by sealing the DNA backbone.

DNA ligase Signup and view all the answers

The telomeres in humans consist of repeated nucleotide sequences known as ______.

TTAGGG Signup and view all the answers

In eukaryotic DNA replication, multiple ______ of replication speed up the process along linear chromosomes.

origins Signup and view all the answers

During the elongation phase, DNA polymerase epsilon (ε) synthesizes the ______ strand.

leading Signup and view all the answers

DNA polymerase III primarily performs the bulk of DNA synthesis in ______ cells.

prokaryotic Signup and view all the answers

The end-replication problem in eukaryotes is primarily associated with ______.

telomeres Signup and view all the answers

Study Notes

Central Dogma of Molecular Biology

Describes the flow of genetic information in organisms.
DNA replicates itself.
DNA is transcribed into RNA.
RNA is translated into proteins.
Information flows from DNA to RNA to protein.

Properties of Life

Life is organized into cells.
Genetic information is stored in DNA and expressed through RNA.
Organisms synthesize proteins.
Metabolism involves chemical reactions for life maintenance.
Homeostasis maintains internal conditions.
Reproduction ensures the transmission of genetic material.

Eukaryotes vs. Prokaryotes

Both have DNA, ribosomes, and plasma membranes.
Eukaryotes:
- Have a nucleus, membrane-bound organelles, 80s ribosomes, and are larger (10-100 µm).
Prokaryotes:
- Lack a nucleus (naked DNA), have a different cell wall composition (peptidoglycan), no membrane-bound organelles, 70s ribosomes, and are smaller (0.5-10 µm).

Viruses and Prions

Disease-causing agents without cellular structure.
Cannot grow or self-reproduce, lack metabolism.
Require a host cell to grow and reproduce.
Viruses are cell (species) specific.
Viruses are infectious particles containing nucleic acids (DNA or RNA) encased in a protein coat (capsid).
Viruses require a host cell for replication.
Bacteriophages are viruses that infect bacteria.
Prions are infectious proteins that misfold normal proteins, causing diseases like Creutzfeldt-Jakob disease.
Prions lack nucleic acids and infect cells in the nervous system.

Storage of Information in Cells

Prokaryotes:
- DNA is circular and located in the nucleoid, a region with no surrounding membrane.
- DNA is not attached to histone proteins.
- Prokaryotes are haploid, having only one copy of genetic information.
- Plasmids are small, circular DNA molecules containing extra genetic information.
Eukaryotes:
- nDNA (nuclear DNA):
  - Linear and double-stranded.
  - Found in somatic (diploid) and germ (haploid) cells.
- mtDNA (mitochondrial DNA):
  - Circular and double-stranded.
  - Contains information for mitochondrial function.
- cpDNA (chloroplast DNA):
  - Circular and double-stranded.
  - Contains information for chloroplast function.

Types of Eukaryotic Cells

Animal Cells:
- Lack cell walls.
- Have mitochondria.
- Possess centrosomes for cell division.
Plant Cells:
- Have cell walls composed of cellulose.
- Contain chloroplasts for photosynthesis.
Fungal Cells:
- Have cell walls containing chitin.
- Lack chloroplasts.
Somatic Cells:
- Form the body (tissues, organs).
- Not involved in sexual reproduction.
- Diploid, having two sets of genetic information.
Germ Cells:
- Responsible for sexual reproduction.
- Include primordial cells and mature gametes.
- Haploid, having one set of genetic information.

Chemical Composition of Nucleic Acids

Nucleic Acids are polymers of nucleotides (DNA and RNA).
They contain nitrogenous bases (adenine, guanine, cytosine, thymine in DNA, uracil in RNA), a pentose sugar (deoxyribose or ribose), and a phosphate group.

Structure of DNA and RNA

DNA:
- Double-helix structure with complementary base pairing (A-T, G-C).
- Antiparallel strands running in opposite directions (5' to 3' and 3' to 5').
RNA:
- Single-stranded, capable of forming loops and folds.
- Contains uracil instead of thymine.
The double helix is stabilized by hydrogen bonds between bases and stacking interactions of aromatic rings.
DNA grooves (major and minor) allow protein binding and DNA unwinding.

Biological Roles of DNA and RNA

DNA:
- Stores genetic information.
RNA:
- mRNA: Carries information for protein synthesis from DNA to ribosomes.
- tRNA: Transfers amino acids to ribosomes during protein synthesis.
- rRNA: Forms the core of ribosomes and catalyzes peptide bond formation.

DNA Replication

Occurs in the S phase of the cell cycle in eukaryotes and during binary fission in prokaryotes.
DNA polymerase catalyzes the process.
Steps:
- Initiation:
  - Starts at the origin of replication.
  - Requires initiation proteins.
  - Helicase unwinds the double helix.
  - Topoisomerase prevents supercoiling.
  - Single-strand binding proteins stabilize the separated strands.
  - Primase synthesizes RNA primers.
- Elongation:
  - DNA polymerase adds nucleotides to the 3' end of the primer.
  - Synthesizes in the 5' to 3' direction.
  - Leading strand: Continuous synthesis.
  - Lagging strand: Discontinuous synthesis in Okazaki fragments.
  - RNase H removes RNA primers.
  - DNA polymerase fills gaps.
  - DNA ligase seals the DNA strands.
- Termination:
  - Telomeres shorten with each replication in eukaryotes.
  - Telomerase adds telomere sequences to maintain telomere length.
Replication of Leading and Lagging Strands:
- Leading strand: Continuous synthesis in the same direction as the replication fork movement.
- Lagging strand: Discontinuous synthesis opposite to the replication fork movement, producing Okazaki fragments.

Differences in DNA Replication between Eukaryotes and Prokaryotes

Location:
- Eukaryotes: Nucleus.
- Prokaryotes: Cytoplasm.
Origins of Replication:
- Eukaryotes: Multiple origins.
- Prokaryotes: Single origin.
DNA:
- Eukaryotes: Linear and complexed with histones.
- Prokaryotes: Circular and not complexed with histones.
DNA Polymerase:
- Eukaryotes: Multiple DNA polymerases.
- Prokaryotes: Primarily DNA polymerase III.
Speed:
- Eukaryotes: Slower.
- Prokaryotes: Faster.
Telomeres:
- Eukaryotes: Have telomeres.
- Prokaryotes: Lack telomeres.
Replication Machinery:
- Eukaryotes: More complex.
- Prokaryotes: Simpler.

Central Dogma of Molecular Biology

Describes the flow of genetic information in living organisms
Information flows in this order: DNA → RNA → Protein
DNA replication: DNA makes an exact copy of itself
Transcription: DNA is transcribed into RNA
Translation: RNA is translated into a protein

Properties of Life

Life is organized into cells
Life stores genetic information in DNA and realizes it through RNA
Life synthesizes proteins
Metabolism: Chemical reactions that maintain life (e.g., ATP production)
Homeostasis: Regulation of internal conditions (e.g., body temperature)
Reproduction: Life reproduces to pass on genetic material

Paramecium Example

Paramecium is a heterotrophic, eukaryotic organism
Paramecia are surrounded by cilia, which allow them to move
Paramecia have a cytostome (feeding groove), through which they engulf food
Food particles are digested in vacuoles containing enzymes
Solid waste is removed through an anal pore, and liquid waste is pumped out through contractile vacuoles
Gases enter and exit the cell via diffusion
Paramecia divide asexually (fission), but can also share genetic information via conjugation

Eukaryotes and Prokaryotes

Both have DNA, ribosomes, and plasma membranes
Eukaryotes have a nucleus, membrane-bound organelles, 80s ribosomes, and are larger (10-100 µm)
Prokaryotes lack a nucleus (have naked DNA, one circular chromosome), their cell walls are made of peptidoglycan, they lack membrane-bound organelles, have 70s ribosomes, and are smaller (0.5-10 µm)

Viruses and Prions

Disease-causing agents without cell structure
Cannot grow or reproduce independently, they must infect a host cell
Viruses are cell (species) specific, some can infect multiple species
Viruses are composed of nucleic acids (DNA or RNA) surrounded by a protein coat called a capsid
Bacteriophages are viruses that specifically infect bacteria
Prions are infectious proteins that cause diseases by misfolding normal proteins
Prions lack nucleic acids
Prions infect cells in the nervous systems
A prion is a misfolded version of a normal protein found in nerve cells
When a prion infects a nerve cell, it promotes the misfolding of healthy proteins, leading to a self-propagating cascade of misfolded proteins

Storage of Information in Cells

Prokaryotes: DNA is circular and located in a structure called the nucleoid
Nucleoid is a complex of DNA and RNA with nucleoproteins and lacks a membrane
Bacteria are haploid organisms, meaning they have one copy of genetic information
Prokaryotes often have plasmids: small, circular molecules containing a small part of genetic information
Plasmids can contribute to antibiotic resistance, and some are mobile, allowing them to transfer between bacteria
Eukaryotic cells store genetic information in nDNA, mtDNA, and cpDNA
Nuclear DNA (nDNA): linear and double-stranded, found in somatic cells (diploid) and germ cells (haploid), contains information for organism development
Mitochondrial DNA (mtDNA): circular and double-stranded, the number of copies varies depending on cell function, contains information essential for mitochondrial function
Chloroplast DNA (cpDNA): circular and double-stranded, contains information for chloroplast function

Types of Eukaryotic Cells

Animal Cells: lack cell walls, have mitochondria, and centrosomes for cell division, are flexible
Plant Cells: have cell walls (cellulose), chloroplasts, and are immobile
Fungal Cells: have cell walls made of chitin, lack chloroplasts, and are immobile
Somatic Cells: form the body (tissues, organs), are not involved in sexual reproduction, are diploid
Germ Cells: responsible for sexual reproduction (include all stages from primordial cells to gametes), are haploid

Chemical Composition of Nucleic Acids

Nucleic acids are polymers of nucleotides (DNA and RNA)
Nucleotide components:
- Nitrogenous Base: purines (Adenine, Guanine) and pyrimidines (Cytosine, Thymine in DNA, Uracil in RNA)
- Pentose Sugar: Deoxyribose (in DNA), Ribose (in RNA)
- Phosphate Group: Forms the backbone of the nucleic acid

Structure of DNA and RNA

DNA: double-helix structure formed by complementary base pairing (A-T, G-C), strands run antiparallel (5' to 3' and 3' to 5')
RNA: single-stranded, can form loops and folds (secondary structure), and complex tertiary structures, contains Uracil instead of Thymine
The DNA double-helix is stabilized by hydrogen bonds between the bases and by stacking interactions of the aromatic rings of the bases in the center of the helix

Biological Roles of DNA and RNA

DNA: stores genetic information
RNA: realizes DNA information
- mRNA: carries copied information for protein synthesis from DNA to ribosomes
- tRNA: transfers amino acids to ribosomes during protein synthesis
- rRNA: forms the core of ribosomes, catalyzes peptide bond formation in proteins
Regulatory RNAs:
- snRNA: involved in RNA splicing
- ncRNA: regulates gene expression
- miRNA: regulates gene expression by binding mRNA and causing its breakdown
- siRNA: regulates gene expression by binding mRNA and causing its breakdown
- lncRNA: long non-coding RNA, involved in various functions
Key Mnemonic: "DNA Stores, RNA Realizes and Delivers"

DNA Replication

DNA replication is the process of making a duplicate of the DNA molecule (semiconservative)
Replication is catalyzed by enzymes
Replication ensures that each daughter cell receives a complete set of chromosomes during cell division
In eukaryotic cells, replication occurs during the S phase of the cell cycle
In prokaryotes, replication starts with binary fission
Steps:
- Initiation:
  - Starts at the origin of replication, a specific DNA sequence
  - Requires initiation proteins
  - Helicase unwinds the double-helix by breaking hydrogen bonds
  - Topoisomerase prevents supercoiling of the DNA
  - Single-strand binding proteins prevent the reformation of the double helix
  - Leading vs. Lagging Strand:
    - Leading strand: continuous synthesis of new DNA (5' to 3')
    - Lagging strand: discontinuous synthesis in short sections called Okazaki fragments (3' to 5')
  - Primers and Primase:
    - RNA primers (10-12 nucleotides long) are synthesized by primase
    - The polymerase complex starts working from the primer added
  - Polymerization:
    - DNA polymerase adds free dNTPs (deoxyribonucleotide triphosphates) to the 3' OH end of the primer
    - Synthesis always proceed in the 5' to 3' direction
    - Energy for Polymerization: the breaking of the bond between phosphate groups in dNTPs releases energy, driving the polymerization process.
- Elongation:
  - DNA polymerase epsilon (ε) synthesizes the leading strand
  - DNA polymerase delta (δ) synthesizes the lagging strand
  - Both polymerases have repair activity to fix mistakes
  - RNA Primer Removal: RNase H recognizes and degrades RNA primers
  - Filling Gaps: DNA polymerase beta (β) fills in the gaps
  - Sealing the DNA: DNA ligase connects the newly added nucleotides
- Termination:
  - The end of replication occurs at telomeres (ends of chromosomes)
  - Telomeres are made of repeated nucleotide sequences and are species-specific (TTAGGG repeats in humans)
  - The 3' end of the telomere is single-stranded and forms a protective cap
  - End-Replication Problem: due to the lagging strand, the ends of chromosomes can not be fully replicated
  - Telomerase: enzyme that adds telomere sequences to the end of DNA
Key Points:
- Polymerase ε: Leading strand
- Polymerase δ: Lagging strand
- RNase H: Removes RNA primers
- Polymerase β: Fills in gaps
- Ligase: Seals the DNA strands

Differences in Replication of Leading and Lagging Strands

DNA strands are antiparallel, meaning that one strand runs 5' to 3' and the other runs 3' to 5'
DNA polymerase can only synthesize new DNA in the 5' to 3' direction
Leading strand: synthesized continuously in the same direction as the replication fork moves
Lagging strand: synthesized discontinuously in short fragments called Okazaki fragments
- Each Okazaki fragment is initiated by an RNA primer
- The RNA primers are removed by RNase H
- The gaps are filled by DNA polymerase
- The fragments are sealed by DNA ligase

Differences in DNA Replication between Eukaryotes and Prokaryotes

Eukaryotes:
- Replication occurs in the nucleus
- Multiple origins of replication on linear chromosomes
- Linear DNA complexed with histones, resulting in telomere shortening
- Multiple types of DNA polymerases (e.g., α, δ, ε) with specialized roles
- Slower replication due to chromatin structure and larger genome size
- Telomeres are maintained by telomerase
- More complex replication machinery due to chromatin structure and larger genome size
Prokaryotes:
- Replication occurs in the cytoplasm
- Single origin of replication on circular DNA
- Circular DNA, no telomeres
- Primarily uses DNA polymerase III for synthesis and DNA polymerase I for primer removal and gap filling
- Faster replication due to smaller genome and simpler structure
- Lack telomeres
- Simpler replication machinery due to absence of chromatin and smaller genome

Memorization Tips:

Central Dogma: (DNA → RNA → Transcription)
Prokaryotes vs.Eukaryotes: "Euks have Nucs, Proks don't!"
Viruses and Prions
DNA vs. RNA: (DNA = Double-stranded, RNA = Single-stranded)
DNA Replication Process: "Helicase Opens, Polymerase Copies, Ligase Seals!"

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Description

Test your knowledge on key concepts in biology, including the Central Dogma of Molecular Biology, properties of life, and the differences between eukaryotes and prokaryotes. Additionally, explore the unique characteristics of viruses and prions. This quiz encompasses fundamental biological principles that are crucial for understanding life.