G6pd deficiency is an x-linked recessive disorder. when people who have this disorder eat fava beans, they have a dangerous acute reaction in which a large number of their red blood cells rupture. a mother has the disorder; the father does not. what is the chance that any child of this union will have the trait?

In case   mother carries an X-linked recessive disease and father does not, the risk for each offspring is dependable upon the offspring is male or female. In case of male child, there is a 50% chance to be disease free, and a 50% chance to be affected by this disorder.

Explanation:

G6PD deficiency is an X-linked recessive disorder. The coding gene for G6PD is in the distal long-arm of the X chromosome (Xq28). The gene is 18 kb of length. It has 13 exons. The G6PD enzyme consists of  515 amino acids.

There are over 60 mutations detected in the G6PD gene. The majority of them are single-base changes (amino acid substitution). The X-linked disease is a disease caused by mutation of a gene on the X chromosome. In X recessive disorder male children most commonly manifest the abnormality. The female children are carriers and asymptomatic in case of homozygous or if there is an inactivation of their normal X chromosome.

In case   mother carries an X-linked recessive disease and father does not, the risk for each offspring is dependable upon the offspring is male or female. In case of male child, there is a 50% chance to be disease free, and a 50% chance to be affected by this disorder.

In case of a female offspring, there is a 50% chance to be unaffected, and a 50% to be a carrier.

If a father has G6PD deficiency, while the mother is a carrier all male offspring will be healthy. In this case, the female offspring will be carriers.

In case of  G6PD deficiency, reactive oxygen molecules accumulate and lead to the damage of red blood cells. Certain factors (fava beans, certain medicaments, infections etc. ) may lower the reactive oxygen molecules and lead to acute episodic hemolytic anemia.  In that case, red blood cells are damaged faster than they may be replaced in the human body. There are signs of hemolytic anemia in case of G6PD deficiency. Thus, chronic hemolysis may occur with a significantly lower level of enzyme.  In case of symptomatic patients there is a neonatal jaundice and acute hemolytic anemia. Kernicterus may be a neonatal complications in G6PD deficiency.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.