47, XX,+16 is a chromosomal abnormality in which there are three copies of chromosome 16 rather than two. It is the most common chromosomal cause of miscarriage during the first trimester of pregnancy. It is impossible for an infant to take birth with an extra copy of this chromosome present in all cells.

The presence of a Y-chromosome predicts that testes will develop. Differentiation of external genitalia is controlled by the androgen derivative (5-alpha-dihydrotestosterone) and a defect in the androgen receptor which results in androgen insensitivity means that external male genitalia will not be stimulated to differentiate. Thus, this individual will look phenotypically female but will have undescended testes.

Huntington disease displays age-dependent penetrance. Her risk is now less than 50%, though it is still possible that she will develop the disorder. 

Fragile X syndrome is characterized by expansion of a CGG triplet repeat in the first exon of the FMR-1 gene on the long arm of the X chromosome, with the total chromosome number not being affected i.e. still euploid.

DNA replication is a semiconservative process. Helicase is responsible for unwinding DNA.

The lagging strand is synthesized by DNA polymerase α. Polymerase δ is used for the leading strand.

It is the only correct statement. In RNA, uracil is present instead of thymidine in DNA.

The sequence at the 3' end is the splice acceptor (which includes AT preceded by a consensus sequence).

TATA box is located in the promoter and is involved in gene regulation.

A single base insertion would cause a frameshift and usually leads to premature termination of translation.

The anticodon is present on the tRNA and recognizes the codon sequence on the mRNA.

It is the correct statement that it is associated with methylation of cytosines 5' to guanosines.

If they produced anti-A antibodies, it would destroy their own blood. However, they do normally produce anti-B antibodies since B type blood would be alien to them.

Since type O blood normally lacks both A and B antigens, it will not be recognised as an alien type by the blood of anyone. As a result, anyone usually can be transfused with O blood without concern about rejection for this blood group.

The rules of dominance for the ABO system is that both A and B are dominant over O (i.e. O is recessive) and A and B are codominant.

Prader-Willi Syndrome (PWS) is caused by genomic imprinting, defined as the differential expression of maternal and paternal alleles. When the information in region 15q11-q13 is derived only from a mother (either via uniparental disomy (both chromosomes from a single parent) or deletion on the paternal chromosome), the maternally imprinted chromosome is unable to express its genetic information and the result is PWS.

Karl Landsteiner discovered the ABO system in 1900 and 1901 while trying to understand why blood transfusions sometimes saved lives and at other times caused death.

The most life threatening problem is the result of a Rh blood type incompatibility between a mother and her developing fetus.

In most cases, these alleles are totally responsible for determining blood type phenotypes. The inheritance usually follows simple Mendelian patterns. However, there are rare exceptions such as Bombay Phenotype.

All the above statements are correct.

Due to Bombay Phenotype and other possible exceptions, the ABO blood type system is not conclusive in determining whether or not someone could be a parent of a particular child. The other two kinds of evidence are much more reliable.

The Rh blood factor is a dominant trait. Therefore, both DD and Dd people have Rh antigen on the surface of their red cells which make them Rh positive.

In order for the fetus to be Rh positive, the father must also be Rh positive. As a result, when the mother is Rh negative and the father is Rh positive (or his Rh type is unknown), doctors usually assume that there will be a serious medical problem.

If the father is homozygous dominant (DD), the chances of the fetus being Rh positive and an incompatibility problem occurring will be 100%. If the father is heterozygous (Dd), the chances are 50%. There will be no problem if the fetus is Rh negative.

Europeans have the highest frequency of Rh negative people (40%), which puts them at the highest risk for this problem. About 13% of newborn Europeans are at risk, but we can now prevent the life threatening complications in most cases.