AS-348 August, 1966
This publication is designed as a teaching aid for the intensified cattle breeding schools conducted by the Indiana Cooperative Extension Service. The purpose of this publication is to help producers more clearly understand how characteristics, or traits observed in cattle are affected by segregation of genes in gamete (sperm and egg) formation and recombination of these genes at fertilization (union of egg and sperm).
Body growth, tissue repair, and body metabolism systems are controlled by the genes located within the cell.
Two processes govern and insure the continuation of species from generation to generation. These two processes are (1) mitosis and (2) mieosis.
Mitosis
Introduction
The basis of all living matter is the cells. Each body cell contains a certain number of paired, threadlike bodies called chromosomes, and the number of pairs is typical for the species. Cattle, horses and sheep have 30 pairs of chromosomes, swine have 19 pairs and humans have 23 pairs. Hundreds and possibly thousands of genes are located in special positions on each chromosome.
Hence, both the chromosomes and the genes are in paired condition in the cell.
Mitosis is the process whereby the cell divides to give two daughter cells having the same chromosome complement. This is the process whereby all animals grow from a "one-celled" zygote to the "multicellular" (many celled) adult. Consequently, it is an aspect of growth and is generally accompanied by enlargement and differentiation of the cells. Mitosis is shown in Figure 1 with one pair of chromosomes and one pair of genes.
Beef Section • Animal Sciences Department Cooperative Extension Service, PURDUE UNIVERSITY, Lafayette, Indiana
Basic Genetics i
K. J. Drewry, W.M. Dillon, and L. L. }Vilson j:l Animal Sciences Department '
Selection  Beef