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title: "2.4 The transfer from chromosomes and genes from parent to offspring"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/270893223/2.4%20The%20transfer%20from%20chromosomes%20and%20genes%20from%20parent%20to%20offspring"
format: markdown
---
To understand the genetic relationships among related animals it is necessary to know what happens in the creation of sperm cells, oocytes and zygotes as the start of a new animal. In mammals and birds all body cells of an individual are diploid: all chromosomes in the nucleus of a cell are present in twofold, grouped in pairs.

> ℹ️ ### Definitions
> ℹ️ 
> ℹ️ *A  ****chromosome ****is a discrete block of   DNA and is one of the basic structures of the genome. All nuclear DNA is organized into chromosomes with the number varying between animal species. Genes on a chromosome are linked and tend to be inherited together*
> ℹ️ 
> ℹ️ ***DNA**** is Deoxyribonucleic Acid, which is a macromolecule in the form of a double-stranded helix that carries the genetic information in all cells in higher organisms*
> ℹ️ 
> ℹ️ *A ****gene**** is the hereditary unit, a region of DNA on a chromosome containing genetic information that is transcribed into RNA that is translated into a polypeptide chain with a physiological function. A gene can mutate to various forms called alleles*
> ℹ️ 
> ℹ️ *An ****allele**** is a version of the sequence of DNA nucleotides at a locus. Not all individuals carry exactly the same sequence of DNA nucleotides at a locus. This allelic variation is the source of genetic variation*
> ℹ️ 
> ℹ️ *A ****locus**** is a position on a chromosome, for example of a gene. The plural is loci*

To illustrate these definitions: The MC1R-locus (Melanocortin 1 receptor gene) has been identified on chromosome 5 in dogs. From this gene, 2 alleles E and e are known. The original, so-called wild type allele E (non-mutated allele) causes the black color in dogs, the allele e created by mutation causes the loss of gene function and is responsible for bright red or yellow coat color in genotype e/e.