# The Human Genome **Human Genetics** - Replication results in ~1 mistake per billion bp - Due to the long generation time of humans and the limited # of offspring during reproduction, it would be difficult to map out the entire human genetic map using these methods (and would instead require modern biotechnology in the 1980s) ## Humans vs Other Primates - The loss of hair and the gain of sweat glands provided us with an extremely efficient cooling system, allowing humans to be active for longer before overheating/becoming exhausted - Gene regulation and gene splicing appear to be used more extensively in the human genome than in genomes of msot organisms - ### The X Chromosome - Most beneficial mutations are recessive - Because females have two copies of the X chromosome, so a recessive mutation could hide throughout their female progeny - true, we also have two copies of all of the autosomal chromosomes, but the difference between females (XX) and males (XY) is what makes the sex chromosomes a good “testing ground” or “screening process" for new mutations - Relates back to the concept of ### The Y Chromosome - 0.5% of men have Ghengis Khan’s Y chromosome **Sex-Determining Region Y (SRY)** - The SRY protein is the male specific transcription factor - SRY+ → Testis - SRY- → Ovaries - The Y chromosome has pseudoautosomal regions (PARs) homologous to the X chromosome which recombine during *meiosis* --- **The Human Genome** - 23 unique chromosomes - 3 billion base pairs in our genome - Autosomal (Chromosomes 1-22) - Sex Chromosomes (X and Y, 23) - The initial numbering of the human chromosomes was meant to be from largest (1) → smallest (23) - [[Mitochondria|Mitochondrial DNA]] - Has overlapping exon regions - There are thousands of mitochondria per cell, each containing multiple copies of their genome - We are *organizationally* similar identical to 92% of other mammals at the sequence level, but not organizationally