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Questions and Answers
Which property of muscle refers to its ability to return to its original shape after being stretched?
Osteoarthritis is characterized by the progressive loss of cartilage in the joints.
True
What is the main function of synovial fluid in synovial joints?
To lubricate and reduce friction between joint surfaces
The muscle that opposes the action of another muscle is called the ______.
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Match the following types of joints with their characteristics:
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Which of the following can lead to changes in DNA methylation patterns?
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Maternal nutrition during pregnancy does not influence the epigenetic changes in the developing fetus.
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What kind of environmental factors can cause epigenetic modifications?
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Exposure to environmental toxins can alter DNA _____ patterns associated with diseases.
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Match the environmental factor with its effect on epigenetics:
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Which of the following statements about the epigenome is true?
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All epigenetic modifications occur irreversibly and cannot be changed.
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How does the epigenome respond to environmental changes?
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Environmental factors such as _____ can influence stress-related gene expression.
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Which of the following aspects is influenced by maternal nutrition during pregnancy?
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What is the primary function of tRNA in protein synthesis?
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What component of a nucleotide is responsible for forming the backbone of DNA?
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The start codon AUG signals the termination of protein synthesis.
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What role does RNA polymerase play in transcription?
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DNA consists of a single strand of nucleotides.
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What is the role of histones in the packaging of DNA into chromosomes?
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The genetic code is stored in sequences of nucleotides in DNA, grouped into _____ which correspond to specific amino acids.
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During DNA replication, the enzyme __________ unwinds the DNA strands.
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Match the following molecules with their roles in translation:
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Which of the following modifications to histones usually enhances gene expression?
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Match the following types of RNA with their roles in protein synthesis:
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Which nitrogenous base is found in RNA but not in DNA?
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Epigenetics involves changes to DNA sequences that affect gene expression.
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The two strands of DNA run in the same direction.
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How does tightly packed chromatin affect transcription?
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What is the purpose of DNA ligase in DNA replication?
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Changes in protein shape can affect their _____ and activity.
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In a chromosome, sister chromatids are joined at a region called the __________.
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What influences gene expression according to environmental factors?
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What is the main function of messenger RNA (mRNA)?
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Study Notes
Types of Muscles
- Skeletal muscle (striated): Voluntary, attached to bones, responsible for movement
- Smooth muscle: Involuntary, found in internal organs, responsible for organ function
- Cardiac muscle: Involuntary, found in the heart, rhythmic contractions for blood circulation
Properties of Muscle
- Elasticity: Ability to return to original shape after stretching
- Extensibility: Ability to stretch beyond resting length
- Contractibility: Ability to shorten and generate force
- Excitability: Ability to respond to stimuli, such as nerve impulses
Structure of Skeletal Muscle and Skeletal Muscle Fibres
- Skeletal muscle is composed of bundles of muscle fibres
- Muscle fibres are long, cylindrical cells containing myofibrils
- Myofibrils are made up of actin (thin filaments) and myosin (thick filaments)
Structure of Myofibrils
- Sarcomere: Basic unit of muscle contraction
- Actin and myosin filaments are arranged in repeating units called sarcomeres
- Z-lines: Mark the boundaries of each sarcomere
- A-band: Region containing both actin and myosin filaments
- I-band: Region containing only actin filaments
- H-zone: Region containing only myosin filaments
Sliding Filament Theory
- Muscle contraction: Occurs when myosin filaments slide past actin filaments
- Myosin heads: Pull on actin filaments, shortening the sarcomere
- ATP: Required for the sliding process and muscle contraction
How Muscles and Bones Work Together
- Muscles contract and pull on bones, causing movement
- Joints: Allow movement between bones
- Tendons: Connect muscles to bones
Antagonist and Agonist Pairings and Synergists
- Agonist: Muscle responsible for the main movement
- Antagonist: Muscle that opposes the movement of the agonist
- Synergist: Muscle that helps the agonist perform the movement
Origin and Insertion Points
- Origin: Point where a muscle is attached to a stationary bone
- Insertion: Point where a muscle is attached to a moving bone
- Muscle contraction: Causes the insertion point to move toward the origin
Muscle Tone
- Muscle tone: State of slight tension in muscles even at rest
- Helps maintain posture, stability, and readiness for action
Functions of Skeleton
- Support: Provides framework for the body
- Protection: Protects vital organs
- Movement: Provides attachment points for muscles
- Mineral storage: Stores calcium and phosphorus
- Blood cell production: Red bone marrow produces blood cells
Types of Bone
- Compact bone: Dense, hard outer layer
- Spongy bone: Porous, lighter inner layer
- Cartilage: Flexible, connective tissue: hyaline cartilage (found in joints), elastic cartilage (found in ears), fibrocartilage (found in intervertebral discs)
Bones of the Skeleton
- Axial skeleton: Skull, vertebral column, ribs, sternum
- Appendicular skeleton: Bones of the limbs, shoulder girdle, and pelvic girdle
Macroscopic Structure of Long Bones
- Diaphysis: Shaft of the bone
- Epiphysis: Ends of the bone
- Periosteum: Outer membrane covering the bone
- Medullary cavity: Hollow space within the diaphysis
- Endosteum: Membrane lining the medullary cavity
Structure of Compact Bone
- Osteons: Basic units of compact bone
- Central canal: Contains blood vessels and nerves
- Concentric lamellae: Rings of bone tissue surrounding the central canal
- Lacunae: Small spaces that house osteocytes (bone cells)
- Canaliculi: Tiny channels that connect lacunae, allowing for nutrient and waste exchange
Structure of Spongy Bone
- Trabeculae**: Interconnecting plates of bone tissue
- Red bone marrow: Found within trabeculae, produces blood cells
Joints
- Fibrous joints: Immovable, united by fibrous connective tissue (e.g., sutures in skull)
- Cartilaginous joints: Slightly movable, united by cartilage (e.g., intervertebral discs)
- Synovial joints: Freely movable, characterized by joint capsule, synovial fluid and articular cartilage
Structure of Synovial Joint
- Articular cartilage: Smooth, slippery layer covering the ends of bones
- Joint capsule: Fibrous sac that encloses the joint
- Synovial membrane: Inner lining of the joint capsule, secretes synovial fluid
- Synovial fluid: Lubricates the joint and reduces friction
Types of Synovial Joints
- Ball and socket: One bone fits into a cup-like socket, allows for all types of movement (e.g., shoulder, hip)
- Hinge: Allows for movement in one plane (e.g., elbow, knee)
- Pivot: Allows for rotation around a central axis (e.g., between radius and ulna)
- Saddle: Allows for movement in two planes (e.g., thumb joint)
- Condyloid: Allows for movement in two planes, but with limited rotation (e.g., wrist)
- Gliding: Allows for sliding movement (e.g., between carpal bones)
Flexion/Extension, Abduction/Adduction, Rotation
- Flexion: Decreases the angle at a joint
- Extension: Increases the angle at a joint
- Abduction: Moves a limb away from the midline
- Adduction: Moves a limb towards the midline
- Rotation: Turning movement around an axis
Osteoporosis
- Weakening of bones: Due to loss of bone density
- Increased risk of fractures
- Risk factors: Age, female sex, family history, lack of calcium, vitamin D deficiency, smoking, alcohol abuse
Osteoarthritis
- Degenerative joint disease: Caused by wear and tear on joint cartilage
- Joint pain, stiffness, and swelling
- Risk factors: Age, obesity, injury, overuse, genetics
DNA Structure
- DNA is a double helix composed of two strands running in opposite directions (antiparallel).
- Each strand is made up of nucleotides, which consist of a phosphate group, a deoxyribose sugar, and a nitrogenous base.
- Four nitrogenous bases are present: adenine (A), guanine (G), cytosine (C), and thymine (T).
- Bases pair specifically: A with T, and C with G, forming the steps of the DNA ladder through hydrogen bonds.
Chromosomes
- DNA is packaged into chromosomes through chromatin formation, where DNA wraps around histone proteins.
- This creates nucleosomes, further coiled into the compact structure of chromosomes.
- During mitosis and meiosis, chromosomes condense, becoming visible under a microscope.
- Each chromosome consists of two identical sister chromatids joined at the centromere, crucial for proper chromosome segregation during cell division.
DNA Replication
- DNA replication involves the separation of the two strands by DNA helicase, breaking hydrogen bonds.
- DNA polymerase then adds complementary nucleotides to the template strands, creating new strands.
- DNA ligase seals any gaps between sections, resulting in two identical DNA molecules.
- DNA polymerase has proofreading capabilities, correcting errors during replication.
RNA and Its Types
- RNA differs from DNA in being single-stranded, containing ribose sugar instead of deoxyribose, and having uracil (U) in place of thymine (T).
- Three main types of RNA:
- mRNA (messenger RNA): carries genetic information from DNA to the ribosome for protein synthesis.
- tRNA (transfer RNA): carries specific amino acids to the ribosome, recognizing codons through its anticodons.
- rRNA (ribosomal RNA): combines with proteins to form ribosomes, facilitating translation.
- RNA polymerase transcribes DNA, creating a complementary RNA molecule.
From DNA to Proteins
- Genetic code is stored in DNA as sequences of nucleotides grouped into codons (three-nucleotide sequences).
- Each codon corresponds to a specific amino acid.
- tRNA carries the appropriate amino acid to the ribosome, where anticodons pair with codons to ensure the correct amino acid sequence.
- Start codons (AUG) initiate translation, while stop codons (UAA, UAG, UGA) signal its termination.
Transcription
- Transcription is triggered by chemical messengers entering the nucleus.
- It begins with a DNA strand unzipping by helicase.
- RNA polymerase transcribes the template strand of DNA, copying information and base pairing.
- RNA polymerase joins complementary nucleotides of mRNA to the base pairings on the DNA.
- When a sequence signals the end, RNA polymerase detaches.
Translation
- Translation decodes mRNA into a polypeptide chain by ribosomes.
- tRNA carries specific amino acids based on their anticodons, pairing with codons on mRNA.
- rRNA forms ribosomes, facilitating translation.
- The ribosome ensures correct amino acids are added by matching codon-anticodon pairs.
Gene Expression and Regulation
- Gene expression is influenced by various factors including transcription factors, environmental conditions, and modifications to histones and DNA.
- Protein shape changes affect their function and activity.
- Acetylation, the addition of an acetyl group to histones, relaxes the chromatin structure, making DNA more accessible for transcription, enhancing gene expression.
- Methylation, the addition of a methyl group to DNA or histones, can either restrict access to RNA polymerase, inhibiting gene expression, or relax the chromatin, increasing transcription.
Epigenetics
- Epigenetics studies environmental and non-genetic factors influencing gene expression without altering the DNA sequence.
- Epigenetic mechanisms allow cells to respond to external stimuli and lead to phenotypic variations without modifying the genetic code.
- DNA methylation and histone modification contribute to epigenetic regulation:
- DNA methylation: adding methyl groups to DNA, typically at cytosine residues, can repress gene expression.
- Histone modification: altering chromatin structure through acetylation, methylation, or phosphorylation, affecting gene expression.
- Epigenetic changes can be inherited across generations, impacting offspring health and disease susceptibility.
Chromatin
- Chromatin is the complex of DNA and proteins (histones) forming chromosomes within the nucleus.
- Chromatin packing affects DNA accessibility for transcription:
- Tightly packed chromatin restricts access to transcription machinery.
- Loosely packed chromatin allows for active gene expression.
- Acetylation of histones relaxes chromatin structure, facilitating gene transcription.
- Methylation can activate or repress gene expression depending on the histone and location.
Environmental Impacts on the Epigenome
- Environmental factors like diet, stress, and exposure to toxins influence the epigenome.
- These factors can cause changes in DNA methylation and histone modifications, altering gene expression patterns.
- Examples of environmental changes causing epigenetic modifications affecting health:
- Maternal nutrition during pregnancy can impact metabolic health later in life.
- Toxin exposure can alter DNA methylation patterns associated with diseases like cancer.
- The epigenome responds dynamically to environmental changes, potentially impacting offspring traits through inheritance.
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Description
This quiz covers the different types of muscles including skeletal, smooth, and cardiac muscle. Additionally, it explores the properties of muscles such as elasticity, extensibility, and contractibility, as well as the structure of skeletal muscle and myofibrils. Test your knowledge on the fundamental aspects of muscular anatomy and physiology.
