BIOG 1105-1106 | Cornell Introductory Biology, Individualized Instruction

Is there a gene for gender?
Sex determination in non-humans (optional):
Honeybee sex gene discovered: Sequencing project reveals two different versions make a female, one a male.
Evolution of Sex Chromosomes: The Case of the White Campion - researchers uncover striking parallels in the details of sex chromosome evolution between mammals and a far more distant group: plants.
Y chromosome sequence completed: DNA readout reveals genetic palindromes safeguard male-defining chromosome. (optional)
Platypus sex is XXX-rated

Objective 17:

Genomic imprinting in humans (17b)
Silent Struggle: A New Theory of Pregnancy - New research on genomic imprinting and its evolution ^(optional)"The most striking case of large-scale genome imprinting involves crosses between horses and donkeys. Cross a female horse and a male donkey and you get a mule. Cross a male horse and a female donkey and you get a hinny, altogether a different creature. Clearly, the same genes act out different roles, depending on whether they come from mom or dad."
The Maternal Grandsire Effect: Secretariat, perhaps the greatest thoroughbred of all time was not matched by his direct offspring, who by and large were unremarkable. His greatness was passed on through his daughters, many of whom went on to produce great performers. ^(optional)Genomic imprinting (optional): geneimprint.com
Genome biology: She moves in mysterious ways - The human X chromosome is a study in contradictions. The detailed sequence of the X, and a survey of inactivated genes in females, help to illuminate this unique 'evolutionary space'.

Molecule Genetics of the ABO Blood Group System

The ABO blood group system involves three major alleles, I^A, I^B, and i, which are located on the long arm of chromosome 9. The product of the I^A and I^B alleles are transferase enzymes that attach a specific sugar to a short chain of sugars known as H substance (see figure below). The enzyme coded for by theI^A allele adds AS (N-acetyl-galactosamine), and the enzyme coded for by the I^B adds Gal (galactose). The i allele codes for a protein, but this protein has no enzymatic activity.

Thus there are three carbohydrate antigens (A, B, and H). A, B, and AB individuals have transferases that convert the H substance into A and/or B antigens, whereas O individuals lack such enzymes and express only the H substance. The molecular basis for ABO genotypes is now understood. The DNA sequence of the I^A and I^B alleles differs in four nucleotide bases, changing four amino acids that cause differences in A and B transferase specificity. A critical single-base deletion was found in the sequence of the i allele, which results in an entirely different, inactive protein incapable of modifying the H substance.

The ABO antigens are expressed on the surface of cells other than the red blood cells. This means that in any tissue transplant, it is necessary to match the ABO type of donor and recipient.