Humans with the genotype XX are female, as females get two X chromosomes (one from the mother, one from the father). On the other hand, humans with the genotype XY are male, as males get a Y chromosome from the father and an X chromosome from the mother.

Sex linked disorders are carried mutations on the X-chromosome. Men are more likely to be affected by sex-linked disorders because of their genetic makeup. Men contain one X-chromosome and one Y-chromosome. Therefore, if there is a mutation on the X-chromosome, it is likely to be passed to the male and expressed. On the other hand, women have two X-chromosomes. They are less likely to express the mutated X-chromosome because they have two copies.

A Barr body is an inactivated X-chromosome found in females. Females have two X chromosomes (XX) while males have one X-chromosome and one Y-chromosome (XY). Only one X-chromosome is expressed in females, and the other is "unexpressed". The inactivated X-chromosome in females is termed a Barr body.

X-linked disorders are inherited when a parent passes on his or her X-chromosome. Since females have two X-chromosomes, they are less likely to exhibit symptoms of a recessive disorder than males, who have only one. Females are capable of carrying a recessive X-linked trait without expressing it, while males are not. A male must inherit his Y-chromosome from the father and an X-chromosome from the mother, while a female must inherit X-chromosomes from both parents.

If a genotypically healthy mother and a colorblind father have a son, then this child must inherit an X-chromosome from the mother and a Y-chromosome from the father. The mother's chromosome are both genotypically normal, and do not possess the colorblind allele. This means that the son cannot possibly inherit a colorblind allele if the mother is genotypically normal.

All other presented answer represent scenarios that are possible.

XIST stands for X-inactivation specific transcript, which acts in the inactivation process in females since only one X will be active. The nuclei of cells in females contain the barr body. Female heterozygotes are mosaics. Calico cats are almost always female.

Achondroplasia is a gain of function, because the gene is always active, therefore you are gaining more than you normally would. In loss of function, you are losing the ability to use that gene/protein, so it is under active — such as in marfan syndrome. Porphyria refers to not having enough enzymes to breakdown products, leading to a build up of the substrate. Abnormal multimeric complex is when you have a structure that involves multiple components to combine to make one; i.e. collagen type I in osteogenesis imperfects.

Sickle cell anemia is a heterozygous genotype. Having this genotype protects against malaria, which is describing the heterozygous advantage (where having the heterozygote genotype is more favorable than being homozygous dominant or recessive). Heteroplasmy is when there is more than 1 type of organelle genome in a cell like mitochondria. Founder effect is a sudden decrease in population size. Continuous variation is a range of phenotypes from allelic variation in multiple genes.

Genomic imprinting is when certain genes are expressed in a parent-of-origin inheritance pattern. In the example, angleman syndrome goes to the offspring if the mother has a deletion in chromosome 15. Mitochondrial inheritance is only from the mother and refers to the number of defective mitochondria that may have been inherited. Trinucleotide repeat is the expansion of 3 nucleotide repeats usually associated with Huntington's. Multifactorial inheritance has to do with polygenic (genes & environment), co inheritance, risk factors, and environmental influence. 

Pleitrophy occurs when a single mutation causes different systems that are unrelated to be affects. A modifier gene is something that can make a gene worse or better. One example are single nucleotide polymorphisms. Frameshift is an example of one of the mutations that could occur. Lionization is X inactivation that occurs in females.

The correct answer here is autosomal dominance. This means that if at least one of the child's allele's is a Huntington allele, they will have the disease later in life. This is the opposite of autosomal recessive. If you chose this option, it may have been because you know the disease is not sex-linked or has anything to with co-dominance (because you can't exhibit and not exhibit the disease at the same time). Autosomal recessive means that you'd need two Huntington alleles to have the disease. Remember that Huntington's disease only needs one of the two alleles to exhibit the disease.