Question

QUESTION 1: Explain what is wrong (and how it is inherited) if you have the genetic defect of hemophilia. What specific types of cells in the circulatory system would be involved with hemophilia.

QUESTION 2: A researcher is preparing to insert a gene of interest into a bacterial plasmid in order to clone a gene. Explain why the researcher would genetically engineer the plasmid to carry two useful genes, ampR conferring resistance to the antibiotic ampicillin and GEP encoding the green fluorescent protein.

Please answer each part of the questions!  

Answer 1

Haemophilia is an X-linked recessive disorder which impairs the ability of body to make clots (required for stopping bleeding in case of injury). Human females who are homozygous for the allele are haemophilic while as human males need only one copy of allele to be haemophilic (because males carry only one chromosome). The females which are heterozygous for the allele are carriers for the disease. generally haemophilic females have higher mortality as they reach puberty ( due to menstrual cycle and their inability to blood clotting). Haemophilic individuals bleed for a longer time and have increased chances of internal bleeding in joints or brain making it a more complicated problem. As you know blood clotting requires the participation of blood platelets or thrombocytes and clotting factors. Haemophilia A affects the clotting Factor VIII or AHF (Antihaemophilic factor) while as Haemophilia B affects clotting factor IX. The low amounts of these clotting factors hampers the process of blood clotting by thrombocytes. Therefore blood platelets are involved with this disorder.

As far as its inheritance is concerned, let us take an example of cross between carrier female and a normal male

XXh x XY

Gametes -----> X Xh    X Y

offsprings -------> XX XY XXh XhY

(Normal female)   (Normal male) (Carrier female) (Haemophilic male)

Now consider the case of Normal female and haemophilic male

XX x XhY

Gametes-----------> X X Xh Y

Offsprings---------> XXh XY XXh XY

(carrier female) (Normal male)   (carrier female) (Normal male)

Q2) In order to genetically engineer a plasmid, ampicillin resistance genes act as selectable marker gene which enables the selection of recombinant plasmids against the non-recombinant ones. The GEP encoding green flurescent protein will act as scorable gene which will help in monitoring the expression of the transgene in the recombinant plasmid.