biology Homework help??????

1. which of the following might result in a human zygote with 45 chromosomes?

A) fertilization of a 23 chromosome human egg by a 22 chromosome sperm of a closely related species

B) an error in the alignment of chromosomes on the metaphase plate

C) failure of the egg nucleus to be fertilized by the sperm

D) lack of chiasmata in prophase I

E) an error in either egg or sperm meiotic anaphase

2. women (and all female mammals) have one active X chromosome per cell instead of two. what causes this?

A) the removal of methyl (CH3) groups from the X chromosome that will remain active

B) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive

C) crossover between the XIST gene on one X chromosome and a related gene on an autosome

D) inactivation of the XIST gene on the X chromosome derived from the male parent

E) activation of the Barr gene on one of the two X chromosomes that then inactivates

3. What is a syndrome?

A) a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation

B) a characteristic that only appears in conjunction with one specific aneuploidy

C) a characteristic facial appearance

D) a group of traits, all of which must be present if an aneuploidy is to be diagnosed

E) a characteristic trait usually given the discoverer's name