Notes, summaries, assignments, exams, and problems for Biology

Constructing Recombinant DNA

The following steps are involved in the construction of recombinant DNA:

1. Preparation of the Gene: Gene cloning in bacteria is achieved by cleaving DNA with enzymes called restriction endonucleases, which create small fragments. Each fragment often has a "sticky end." Since eukaryotic genes contain introns that are not processed in bacteria, the DNA for cloning is usually obtained from relevant mRNA through the process of reverse transcription. In cases where nucleotide or amino acid sequences are known, synthetic DNA may also be produced.
2. Insertion into a Vector: The vector is a vehicle, such as a plasmid or bacteriophage, used to transfer DNA into a host cell. The vector is cut with the same restriction endonuclease

Direct DNA Transfer: Vectorless Gene Introduction

The term direct or vectorless transfer of DNA is used when foreign DNA is introduced directly into the host genome, bypassing biological vectors.

Key Direct Gene Transfer Methods

1. Electroporation

   Electroporation involves using high field strength electrical impulses to reversibly permeabilize cell membranes, allowing the uptake of DNA. This technique can be used for the delivery of DNA into intact plant cells and protoplasts. Nowadays, intact cells, callus cultures, and immature embryos can be used with suitable pre- and post-electroporation treatments. Electroporation has been successfully employed for producing transgenic plants of many cereals, such as rice, wheat, and maize.

2. Particle Bombardment

Define Callus and Describe Procedure For Callus Culture

A callus culture is a mass of irregular undifferentiated parenchymatous and totipotent cells. These cells have the ability to divide and differentiate to form an entire organism. It is formed in culture media due to active mitotic division of the cells of the explant. Callus culturing is used in the production of secondary metabolites for plant regeneration.

Types of Callus Culture

• Compact Callus
• Friable Callus

1) Compact Callus

It shows densely aggregated cells.

2) Friable Callus

It shows loosely associated cells, and the callus becomes soft and breaks easily.

Stages of Callus Culture

There are three stages of callus culture:

1) Induction

Cells in the explant dedifferentiate and begin to divide.

2)

Biology Concepts

Cellular Processes and Structure

• 1-A) Ev against abiogenesis.
• 3-C) Cannot maggots developed.
• 4-B) Life forms from non-living matter.
• 5-C) Cells contain organelles.
• 6-B) Move through phospholipid bilayer quickly.
• 7-A) Endocytosis.
• 8- Vacuole: 3, Nucleus: 7, Cytoplasm: 2, Rough ER: 4.
• 9- Synthesize lipids: 5, Convert glucose: 8, Convert sunlight: 1, Modify lipids: 6.
• 10-B) None.
• 11-D) Glucose and Oxygen.
• 12-C) Makes ATP.
• 13-B) Cells, tissues, systems.
• 14-C) Tissues.

Microscopy and Molecular Biology

• 15- 2) Internal structures: Transmission electron microscope (TEM), 3) 2 more lenses: Compound microscope, 4) 3D image: Scanning electron microscope (SEM), 5) Highest magnification: Scanning tunneling microscope (STM).
• 16-D) Mitch.
• 17-A) Starch molecule.

Steps in Root End Surgery

• Local anesthesia and hemostasis
• Management of soft tissue
• Management of hard tissue
• Surgical access (visual and operative)
• Access to root structure
• Periradicular curettage
• Root end resection
• Root end preparation
• Root end filling
• Soft tissue repositioning and suturing
• Post-surgical care

Root End Preparation

Preparing a cavity to receive root end filling.

According to Carr and Bentkover, this involves a Class I preparation at least 3mm into root dentin with walls parallel to and coincident with the anatomic outline of the pulp space.

Key requirements:

1. The apical 3mm of the root canal must be freshly cleaned and shaped.
2. The preparation must be parallel to and coincident with the anatomic outline of the pulp space.
3. Adequate retention form

Spina Bifida: Definition, Symptoms, and Complications

Spina bifida is a neural tube defect (NTD) that occurs when the spinal column does not close completely during early fetal development, usually within the first month of pregnancy. This condition can lead to physical and neurological complications, depending on the type and severity.

Definition of Spina Bifida

Spina bifida is a congenital defect in which the vertebrae fail to close around the spinal cord, leading to an opening in the spine. It can result in the exposure or protrusion of the spinal cord and membranes, depending on the form.

Types of Spina Bifida

1. Spina Bifida Occulta:

   • Mildest form
   • Small gap in the spine, with no protrusion of the spinal cord or membranes
   • Often asymptomatic

2. Meningocele:

Early Foundations and Key Milestones in Plant Tissue Culture

The science of plant tissue culture originates from the discovery of the cell, followed by the postulation of cell theory. In 1838, Schleiden and Schwann proposed that the cell is the basic structural unit of all living organisms. They envisioned that a cell is capable of autonomy and, therefore, it should be possible for each cell, if given the right environment, to regenerate into a whole plant. Based on this premise, in 1902, German physiologist Gottlieb Haberlandt for the first time attempted to culture isolated single palisade cells from leaves in Knop’s salt solution enriched with sucrose. The cells remained alive for up to one month, increased in size, accumulated starch,... Continue reading "Milestones in Plant Tissue Culture Development" »

Basement Membrane Structure & Function

Covering & Lining Epithelia

Knee Joint Anatomy and Function

This document provides a detailed look at the structure, mechanics, and common clinical aspects of the knee joint.

Type of Joint

• The knee is classified as a synovial hinge joint.
• It primarily allows flexion and extension.
• A small degree of medial/lateral rotation is possible when the knee is flexed.

Bones Involved

1. Femur (thigh bone)
2. Tibia (shin bone)
3. Patella (kneecap)

The fibula is nearby but does not participate in the primary knee joint articulation.

Articulating Surfaces

• The medial and lateral femoral condyles articulate with the tibial condyles.
• The patella articulates with the femoral trochlear groove.

Main Ligaments

1. Anterior Cruciate Ligament (ACL) – Prevents anterior displacement of the tibia relative to the femur.

Plasmids pBR322 and pUC18/19

pBR322

pBR322, developed in 1977, is a foundational plasmid in molecular biology. Key features include:

• Size: ~4,361 base pairs (bp)
• Origin of Replication: Allows independent replication within bacteria.
• Selection Markers:
  • ampR: Confers ampicillin resistance.
  • tetR: Confers tetracycline resistance.
• Cloning Sites: Multiple sites for inserting foreign DNA.
• Applications: Gene cloning, expression, and manipulation.

pUC18/19

pUC18/19, derived from pBR322 in the early 1980s, simplifies cloning. Key features include:

• Size: ~2,686 bp
• Origin of Replication: High-copy-number pMB1 ori for increased yield.
• Selection Marker:
  • lacZ: Beta-galactosidase gene; enables blue/white screening for insert identification.
• Cloning Sites: Multiple cloning