Veterinary Genetics and Genetic Engineering

Veterinary Genetics & Genetic Engineering Notes

• Veterinary genetics is the study of heredity and variation in animals, covering how traits are passed between generations and the differences between species.
• Areas of veterinary genetics include classical genetics (Mendellian), cytogenetics, molecular genetics, population genetics, radiation genetics and microbial genetics.
• Classical genetics is also known as transmission genetics, and focuses on Mendel's laws of inheritance.
• Cytogenetics studies chromosome number and structure, including changes observed.
• Molecular genetics examines the genetic material (DNA and RNA) at a biochemical level.
• Population genetics investigates gene and genotypic frequencies within a population.
• Radiation genetics studies the effects of radiation on chromosomes and genes.
• Microbial genetics examines inheritance in microorganisms.

Chromosomes and Cell Cycle

• Chromosomes are thread-like structures in the nucleus packaging DNA and carrying genetic information.
• Each chromosome is a complex of DNA and histone proteins.
• DNA is wrapped around histone proteins to form a structure.
• There are two types of proteins involved in chromosome structure, histones (DNA is wrapped around them), and non-histone proteins (enzymes involved in various DNA processes, proteins that bind other proteins, and motor proteins that drive life's processes.)
• Chromatin, composed of DNA and proteins (histones), are stringy fibers called nucleosomes.
• The function of nucleosomes is to compact DNA for storage in the nucleus and gene regulation.
• The cell cycle is a series of events leading to cell duplication and daughter cell separation.
• Interphase (95% of cell cycle) includes G1 (growth and metabolic activity), S (DNA synthesis), and G2 (growth and metabolic activity).
• Mitosis (division phase) involves nuclear (mitosis) and cytoplasmic (cytokinesis) division.
• There are regulatory factors that govern the cell cycle, including external factors.
• Internal factors include Cyclin-dependent kinases (CDKs), which modify target proteins via cyclin-CDK modifications.
• Cell cycle checkpoints ensure accurate cell division by halting the cycle when conditions aren't right for continuing.

Types of Chromatin

• Heterochromatin contains inactive genes, is dark staining, and is tightly packed.
• Euchromatin contains active genes, is light staining, and is loosely packed.

Cell Cycle Checkpoints

• G1 checkpoint controls if a cell is ready for DNA synthesis.
• G2 checkpoint controls DNA and other cell factors for mitosis and cell division.
• Metaphase checkpoint detects if chromosomes properly attached to the spindle fibers.

Chromosomal Structure

• Chromosomes consist of two arms (p - short, q - long) and a centromere.
• Chromatids are two symmetrical structures forming a chromosome during replication.
• Telomeres are caps at the ends, preventing chromosome fusion.
• Secondary constriction is a specific region on some chromosomes, useful in chromosome identification.
• Nucleolar organizer regions (NORs) contain genes coding for ribosomal RNA (rRNA).
• Satellites are rounded bodies separated from the rest of the chromosome.
• The terms of chromosome structure such as chromatids, centromere, telomeres, secondary constriction, and satellites are defined.

Types of Chromosome Structure

• Telocentric (centromere at end)
• Acrocentric (centromere near end)
• Submetacentric (centromere in the middle; unequal arms)
• Metacentric (centromere in the middle)
• Monocentric, Holocentric, Acentric and Dicentric chromosomes are discussed; differences are highlighted.

Chromosomal Aberrations

• Chromosomal aberrations are changes in chromosomal structure or number.
• Numerical aberrations concern changes in chromosome numbers (e.g.: monosomy, trisomy, polyploidy).
• Structural aberrations involve changes in normal chromosome arrangement (e.g.: deletions, duplications, inversions, translocations, ring chromosomes).
• Specific examples of chromosomal diseases associated with defects in chromosome and autosomes are discussed.
• The various types of numerical chromosomal aberrations like triploidy, various types of trisomy are discussed (Klinefelter, Triple X, Mosaicism, etc.,).
• The phenotypic consequences of these aberrant chromosome aberrations are discussed, and associated features are described.

Chromosome types

• Various chromosomal types (e.g. telocentric, acrocentric, submetacentric, metacentric) are differentiated.
• Different types of chromosome banding (Q-banding, G-banding, R-banding, C-banding, T-banding, NOR-banding) are discussed, along with advantages/disadvantages and uses.

Karyotyping

• The study and analysis of chromosomes are described, and it is stated that this involves the systematic arrangement of metaphase chromosomes by their size and morphology.