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Questions and Answers
What are the building blocks of DNA and RNA?
What are the building blocks of DNA and RNA?
What is the Law of Complementary Pairs in DNA structure?
What is the Law of Complementary Pairs in DNA structure?
Which enzymes are responsible for maintaining DNA integrity by repairing damage?
Which enzymes are responsible for maintaining DNA integrity by repairing damage?
What is the structure formed when DNA winds around histones?
What is the structure formed when DNA winds around histones?
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What role does the kinetochore play during cell division?
What role does the kinetochore play during cell division?
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What type of sugar is found in deoxyribonucleic acid (DNA)?
What type of sugar is found in deoxyribonucleic acid (DNA)?
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Which base is unique to ribonucleic acid (RNA)?
Which base is unique to ribonucleic acid (RNA)?
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What is the average number of nucleotide bases in a DNA molecule?
What is the average number of nucleotide bases in a DNA molecule?
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How many nucleotide chains does DNA have?
How many nucleotide chains does DNA have?
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Where does the primary function of RNA occur within the cell?
Where does the primary function of RNA occur within the cell?
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What role does a gene play in relation to DNA?
What role does a gene play in relation to DNA?
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What accounts for genetic variation among humans?
What accounts for genetic variation among humans?
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Which chromosomes are identified as gene-rich in humans?
Which chromosomes are identified as gene-rich in humans?
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What is the primary function of white/yellow fat in the body?
What is the primary function of white/yellow fat in the body?
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Which type of cartilage provides the most flexibility?
Which type of cartilage provides the most flexibility?
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What primarily occupies the space between adipocytes in adipose tissue?
What primarily occupies the space between adipocytes in adipose tissue?
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Which feature distinguishes compact bone from spongy bone?
Which feature distinguishes compact bone from spongy bone?
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What role do canaliculi serve in bone tissue?
What role do canaliculi serve in bone tissue?
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What structure serves as the base for epithelial tissue?
What structure serves as the base for epithelial tissue?
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Which type of epithelial tissue consists of multiple layers of cells?
Which type of epithelial tissue consists of multiple layers of cells?
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What is the primary function of goblet cells found in epithelial tissue?
What is the primary function of goblet cells found in epithelial tissue?
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Which type of connective tissue is primarily collagen-based and provides strength and flexibility?
Which type of connective tissue is primarily collagen-based and provides strength and flexibility?
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What characterizes loose connective tissue?
What characterizes loose connective tissue?
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Which type of connective tissue is responsible for transporting nutrients and oxygen?
Which type of connective tissue is responsible for transporting nutrients and oxygen?
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What function does keratinized stratified squamous epithelium primarily serve?
What function does keratinized stratified squamous epithelium primarily serve?
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Which type of fibrous connective tissue resists unpredictable stress due to its random fiber orientation?
Which type of fibrous connective tissue resists unpredictable stress due to its random fiber orientation?
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What is the primary function of blood in the body?
What is the primary function of blood in the body?
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Which type of muscle is both striated and involuntary?
Which type of muscle is both striated and involuntary?
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What structure forms gap junctions between cells?
What structure forms gap junctions between cells?
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Which type of blood cell is primarily responsible for immune response?
Which type of blood cell is primarily responsible for immune response?
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What characteristic defines smooth muscle tissue?
What characteristic defines smooth muscle tissue?
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What is a key feature of neurons?
What is a key feature of neurons?
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What is the role of desmosomes in tissues?
What is the role of desmosomes in tissues?
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What type of connective tissue produces blood cells?
What type of connective tissue produces blood cells?
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Study Notes
DNA & RNA Structure and Function
- Nucleic acids (DNA & RNA) are nucleotide polymers, each nucleotide consisting of a sugar, phosphate group, and a nitrogenous base.
- Pyrimidines (single-ringed): cytosine (C) and thymine (T)
- Purines (double-ringed): adenine (A) and guanine (G)
- DNA's double helix structure features alternating deoxyribose and phosphate groups forming the sides, with nitrogenous bases forming the "steps."
- Complementary base pairing: A with T, and G with C (purine always with pyrimidine). This maintains the consistent 2nm width of the helix.
- Watson and Crick determined DNA structure, based partly on Rosalind Franklin's work.
- The human genome contains approximately 22,300 genes (only 2% of DNA); the remaining 98% plays a role in gene activity.
Chromatin and Chromosomes
- Chromosomes are composed of DNA and proteins (chromatin). DNA winds around histone proteins.
- DNA damage (10,000-100,000 instances daily) is repaired by enzymes.
- Chromosomes occupy specific territories within the nucleus, allowing for regulated chemical access. Their locations can change during cell development.
- During cell division, chromosomes become visible under light microscopy.
- The centromere joins sister chromatids and contains kinetochores for spindle fiber attachment.
RNA vs. DNA
- Sugar: DNA uses deoxyribose; RNA uses ribose.
- Nitrogenous Bases: DNA uses A, T, C, G; RNA uses A, U, C, G.
- Number of Bases: DNA averages 108 base pairs; RNA averages 70-10,000 bases (mostly unpaired).
- Number of Nucleotide Chains: DNA has two (double helix); RNA has one.
- Location of Action: DNA primarily acts in the nucleus; RNA acts in the cytoplasm.
- Function: DNA codes for RNA and protein synthesis; RNA carries out DNA instructions and participates in protein synthesis.
Genes and Their Actions
- A gene is a DNA segment that codes for RNA.
- Amino acid sequence is determined by the nucleotide sequence of a gene.
- Single Nucleotide Polymorphisms (SNPs) account for human genetic variation.
- Humans have 46 chromosomes (23 pairs), inheriting one genome from each parent. Humans are 99.9% genetically identical, differing by ~3 million base pairs.
- Gene density varies across chromosomes, with some being gene-rich and others gene-poor.
- The human genome comprises approximately 3.1 billion nucleotide pairs, with individual genes ranging from 3,000 to 2.4 million base pairs in length.
Connective Tissues: Overview
- Connective tissues are abundant, widely distributed, and highly variable in structure and function. Types include fibrous, adipose, cartilage, bone, and blood.
- Functions include binding organs, providing support and protection (physical and immune), facilitating movement, storage, heat regulation, and transport.
- Connective tissue cells typically occupy less space than the extracellular matrix (ECM), and cells generally don't directly touch each other.
Fibrous Connective Tissue
- Collagenous: Tough, flexible, and resistant to stretching; found in tendons and ligaments.
- Reticular: Thin collagen fibers with a glycoprotein coat; forms supportive frameworks in organs.
- Elastic: Thin, branching fibers that stretch and recoil; found in tissues requiring elasticity.
- Loose: More ground substance than fibers; examples include areolar tissue (abundant blood vessels, provides nutrition) and reticular tissue (mesh-like framework).
- Dense: More fibers than ground substance and cells; includes dense regular (parallel fibers, tendons/ligaments) and dense irregular (randomly arranged fibers, resists stress).
Adipose Connective Tissue
- Primarily composed of adipocytes.
- White/yellow fat: most abundant in adults; provides insulation, cushioning, and energy storage.
- Brown fat: generates heat, especially important in infants; contains more mitochondria.
Cartilage
- Relatively stiff and flexible; provides shape and support.
- Chondroblasts produce the matrix and become chondrocytes (within lacunae).
- Avascular (lacks blood capillaries); nutrients diffuse through the matrix, resulting in slow metabolism.
- Three types: hyaline, elastic, and fibrocartilage.
Bone Tissue
- Hard, calcified connective tissue.
- Composed of osseous tissue, cartilage, marrow, etc.
- Spongy bone fills the ends of long bones and interiors of flat bones; compact bone forms the outer surface.
- Osteons (Haversian systems) are cylindrical units containing concentric lamellae around a central canal. Osteocytes reside in lacunae within the lamellae and communicate via canaliculi.
- Covered by the periosteum (a fibrous membrane).
Blood Connective Tissue
- Fluid connective tissue; transports cells and substances.
- Components: plasma (ground substance), erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.
- Formed elements include plasma and the cellular components.
- Produced in the bone marrow and lymphoid organs.
Excitable Tissues: Nervous Tissue
- Specialized for communication via electrical and chemical signals.
- Composed of neurons (transmit signals) and neuroglia (support cells).
- Neurons have a cell body, dendrites (receive signals), and an axon (transmits signals).
- Neuroglia protect and assist neurons.
Excitable Tissues: Muscle Tissue
- Specialized for contraction; generates force.
- Three types:
- Skeletal muscle: long, cylindrical fibers; voluntary control; striated.
- Cardiac muscle: branched fibers; involuntary control; striated; intercalated discs.
- Smooth muscle: spindle-shaped fibers; involuntary control; not striated.
Cell Junctions
- Tight junctions: Completely encircle cells near the apical surface, preventing passage of substances between cells.
- Desmosomes: Patch-like junctions that hold cells together; prevent separation under stress.
- Gap junctions: Connexons (protein channels) allow for direct passage of ions and small molecules between cells.
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Description
Explore the fundamental concepts of DNA and RNA structure, including nucleotide composition and the double helix model. Learn about the roles of pyrimidines and purines in base pairing, as well as the significance of chromatin and chromosomes in DNA organization. Dive into the insights offered by Watson, Crick, and Franklin about DNA's intricate design.
