TY - CHAP M1 - Book, Section TI - Organization and Structure of Human Chromosomes A1 - Hogge, W. Allen A1 - Rajkovic, Aleksandar PY - 2015 T2 - Practical Genetics for the Ob-Gyn AB - The human genome is comprised of nuclear DNA sequences, tightly packed into distinct subunits called chromosomes and hundreds to thousands of circular DNA molecules within the mitochondrion. DNA sequences that encode for proteins account for few percent of the total genome, and the rest of the genome is involved in coding for various RNA molecules that do not code for protein (noncoding RNA) as well as regulatory function. DNA packed into chromosomes is coated with histone and nonhistone proteins, and these proteins play an important role in the regulation of gene expression. There are a total of 22 autosomal chromosomes (1–22) and the sex-determining X and Y chromosomes (Figure 2-1). The gametes, eggs and sperm, each contain a haploid set of 23 different chromosomes that upon fertilization gives rise to the diploid set, 46 chromosomes. In a normal diploid human cell, 23 chromosome pairs are present: 22 pairs of autosomes and two sex chromosomes—XX in females and XY in males. In each individual, each member of a pair is derived from either the father or the mother. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/20 UR - obgyn.mhmedical.com/content.aspx?aid=1115992832 ER -