The pairs of autosomal chromosomes, one from the father and one from the mother, carry basically the similar information. That is, each of them has the same genes, but there are slight variations in DNA sequence of nucleotide bases in each gene. These slight variations appear in less than one percent of the DNA sequence and produce different variants of a particular gene that are called alleles.
The primary concern witth incest is that the family members are too genetically linked. Breeding between siblings can lead to genetic disorders. It can have ill effects like mortalities and slow growth rate. Inbreeding increases the frequency of homozygotes, that is, the same allele at the same locus on both meembers of a chromosome pair (the location of the gene is called the locus). This means that they carry two copies (alleles) of the same gene (if both alleles are different, the organism is called heterozygous). This happens because close relatives are more likely to share alleles more than nonrelated individuals. This is especially important for deleterious recessive genes, that are inactive and harmless in a heterozygous pairing, but when homozygous can cause developmental defects. Such offspring have much higher chance of death before reaching at the reproduction age, leading to what biologists call inbreeding depression. Recessive genes which may contain various genetic problems have a tendency to appear more frequently if joined with someone who has the same gene. Genetic traits can be influenced by more than one gene, sometimes interactions between multiple genes are involved, which makes the process of inheritance rather complicated.
First-generation inbred individuals will more likely to show physical and health defects, including:
• Increased genetic disorders
• Reduced fertility both in litter size and sperm viability
• Fluctuating facial asymmetry
• Lower birth rate
• Higher infant mortality
• Smaller adult size
• Slower growth rate
• Loss of immune system function