SAMPLE APA PAPER FOR STUDENTS 2. Abstract. You may not have to include an abstract with your paper; if in doubt, ask your instructor. The. abstract is a single paragraph in block format (without paragraph indentation) and should be. between 150 and 250 words. Be sure to understand the difference between the abstract (a.
In the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively. Hormone levels in the male parent affect the sex ratio of sperm in humans.
The final pair is called the sex chromosomes. Sex chromosomes determine an individual's sex: females have two X chromosomes (XX), and males have an X and a Y chromosome (XY). The mother and father each contribute one set of 22 autosomes and one sex chromosome. Top of page. How do scientists study chromosomes?