vet-tech-therio-ch-1

• branch of veterinary science which comprises the study of the normal physiology and anatomy, and the
• pathology and diseases of the male and female reproductive tracts of animals

the basic unit of structure and function of all living things

cells of the body other than germ cells

sex cells

• the genetic material in the nucleus of a cell.
• The DNA is looped and curled to form the chromosome.

the cell must synthesize new DNA before it divides causing a cycle of events in the life of a cell

• 1. cell division that takes place in the gonads (sex glands - ovaries and testes) to produce ova ond spermatozoa (gametes)
• 2. process of cell division by which reproductive cells (gametes) are formed

• carry the genes
• present in a fixed number for each species
• in all the cell nuclei of plants, animals, and humans

the unit or element of a chromosome that carries and transfers an inherited characteristic from parent to offspring and determines the development of some particular character or trait in the offspring

normal amount of DNA

half the normal amount of DNA

present at birth

outward appearance of an animal

genetic makeup of an individual (inherited factors)

ordinary process of cell division, body replaces dead cells

constriction or narrow point on the chromosome where it attaches to the cell spindle during cell division

formed during metaphase (mitosis), microtubules radiating from the centrioles and connecting to the chromosomes of their centromeres

• located in the centrosome
• migrate to opposite poles of the cell during cell division and serve to organize the spindles

a specialized area of cytoplasm containing the centrioles

• protein structure that binds the two homologous chromosomes together along their long axis during meiosis
• helps in pairing or "synapsis"

• homologous chromosomes line up next to each other and fuse at the chiasmata
• genetic material is exchanged
• importance of crossing over is that it produces new combinations of genes on the chromosomes

point at which homologous chromosomes fuse for crossing over

• come from ancestors (related animals), eg eye color, coat color
• not always present at birth, may develop as animal matures eg spots on a dalmatian, color points, some diseases

• caused by environment
• appear in unrelated animals kept in the same manner of subjected to the same circumstances
• eg unsocial feral cats

• science that differentiates between inherited and acquired characteristics
• provides an understanding of how characteristics are inherited

• characteristic present at birth
• not all congenital charateristics are inherited, eg injury in vivo

• science of genetics, mid-19th century, principls of heredity
• 1900 biologists test and confirm Mendel's theory
• 1944 discovery that genetic information stored in DNA
• 1953 Watson and Crick (actually Rosalind Franklin) describe the double-helix structure of DNA

• Mendelian genetics
• population genetics
• Molecular genetics
• cytogenetics

• genetics of individuals and their families
• characteristics governed by a single gene or just a few genes
• describes how genes are passed from one generation to another

• studies genetic makeup of a larger group
• characteristics governed by many genes

study of DNA and gene activity at the molecular level

study of chromosomes

• consists of two parallel chains of atoms joined by cross links
• chains are the same on both sides
• - consist of a sugar molecule (deoxyribose) and a phosphate molecule
• cross links are formed by pairs of the four bases
• - adenine (A) with thymine (T) or
• - guanine (G) with cytosine (C)
• replicates and produces new molecules exactly the same as the first by breaking the link between the bases, then adding new units
• can "store" genetic material because of its structure
• not all DNA codes for something - most is "rubbish"

sequence of bases on one side determines the sequence of bases on the other

lies in the sequence of bases that form the DNA molecule

part of the DNA molecule that codes

non-coding bits of DNA

• two kinds of organisms - prokaryotes and eukaryotes
• two basic varieties of cells - Somatic cells and germ cells

• no cell nucleus
• DNA floats loosely in center of cell
• eg bacteria

• have a well-defined nucleus to house and protect DNA
• eg simple one-celled animals and plants, complex multicellular organisms (people and animals)

• body cells
• produced by mitosis

• sex cells
• produced by meiosis

• formed in the nucleus from molecules of DNA coiled around protein, coiled again to form loops, loops coiled again
• two types - euchromatin, heterochromatin

chromatin that contains most of the functional genes

contains few functional genes ("rubbish")

• separate units of chromatin
• each species has a specific number of chromosomes
• - cat 38 (19 pairs)
• - dog 78 (39 pairs)
• - horses 64 (32 pairs)
• - humans 46 (23 pairs)
• half of the chromosomes (one of each pair) comes from mother, other half from father

paired chromosomes are identcal to one another (according to which genes they carry)

one pair of chromosomes that do not match each other morphologically and do not carry the same genes (X & Y)

• non-sex chromosomes
• any chromosome other than the X & Y

chromosomes elongated and distributed throughout the nucleus

chromosomes condense and disentangle into separate entities

constriction on the chromosome where it attached to the cell spindle during cell division

• end of a chromosome
• made of densely packed DNA
• serves to protect the DNA message that chromosomes carry

• metacentric - centromere is in the middle
• submetacentric - centromere is near the center on one side
• acrocentric - centromere is on one side, closer to the end than the middle
• telocentric - centromere is at the end

• cell must synthesize new DNA before it can divide
• four phases in division - S phase, Lag or G2 phase, M phase, G1 phase

DNA synthesis stage

• rest phase; second growth phase
• growth and preparation for division

• division of the nucleus and cytoplasm
• divided into subphases - PMAT - prophase, metaphase, anaphase, telophase

• daily work
• growth and normal metabolic roles

• G1, S, and Lag or G2 phases
• everything but M phase

• replication or multiplication division
• when cell divides, it produces two new cells which are exact copies of the original
• has diploid amount of DNA
• process of dividing up the newly copied chroosomes to make certain that the new cells each get a full set

• reduction division
• gametes (sperm and ova) each have only half the amount of DNA
• has haploid amount of DNA