Name the method used to make many copies of a DNA sequence from a very tiny amount of DNA.
Explain why this DNA sequence must be copied many times if embryos are to be tested for $Hb^{S}$ alleles by RFLP analysis.
Using Fig. 3.1, Fig. 3.2 and Fig. 3.3, explain why the enzyme $MstII$ may be used in RFLP analysis to reveal the distinction between these sections of the $Hb^{A}$ and $Hb^{S}$ alleles.
Once cut with $MstII$, the DNA fragments are then separated by gel electrophoresis. Explain how gel electrophoresis separates DNA fragments that have been cut with restriction endonucleases.
Embryos 1, 2, 3 and 4 were tested for the $Hb^{S}$ allele by means of RFLP analysis. Fig. 3.4 shows the DNA fragments separated by gel electrophoresis for these four embryos. The DNA fragments from two individuals with known genotypes, one homozygous for $Hb^{A}$ and one homozygous for $Hb^{S}$, are also included.
State why DNA from individuals homozygous for $Hb^{A}$ and for $Hb^{S}$ is used.
With Fig. 3.4 as reference, fill in Table 3.1 to show the genotypes of embryos 2, 3 and 4.
Discuss the ethical and social issues involved in gene testing embryos for genetic diseases.