Human Chromosome Inheritance
We inherit 23 chromosomes from each parent, for a total of 46 chromosomes in normal human cells. 1
Chromosome Composition
Human cells contain a total of 46 chromosomes organized as 23 pairs 1, 2:
- 22 pairs of autosomes (non-sex chromosomes numbered 1-22)
- 1 pair of sex chromosomes (XX in females, XY in males) 3
Parental Contribution
Each parent contributes exactly half of our chromosomal complement 3:
- 23 chromosomes from the mother (including one X chromosome)
- 23 chromosomes from the father (including either an X or Y chromosome)
This equal contribution occurs through the process of meiosis, where parental germ cells (egg and sperm) each contain 23 chromosomes (haploid), which combine during fertilization to restore the diploid number of 46 3.
Clinical Relevance
The normal inheritance pattern of one chromosome from each parent is critical for genetic health 3:
- Deviations from normal inheritance can result in chromosomal abnormalities
- Uniparental disomy (UPD) occurs when both copies of a chromosome are inherited from one parent instead of one from each, which can lead to genetic disorders depending on which chromosome is affected 3
- Chromosomes with imprinting effects (such as chromosomes 6,7,11,14,15, and 20) are particularly sensitive to abnormal parental inheritance patterns 3
Sex Chromosome Considerations
Males have one X and one Y chromosome, which means they cannot have homozygosity (identical copies) at most loci on these chromosomes outside of small pseudoautosomal regions where X and Y share sequences 3.