Question

could someone explaim this question, it is two parts. thanks a lot, im pretty lost in these types. appreciate it

Sam and Pat recently found out they are expecting a child and have come to you very worried. They met while visiting a mutual friend in the hospital who has since died of cystic fibrosis. Sam and Pat know that their friend's parents did not have cystic fibrosis and were unaware that they both carried the allele for this recessive condition before having a child with CF. Now Pat and Sam are worried that they might be carriers too. Sam and Pat were both only children and their parents were also only children. Both Sam and Pat's grandparents were from small families too and there was nothing remarkable about their health. If about 1/25 people are carriers of the CF allele. What is the likelihood that Sam and Pat's child has CF? C

Answer 1

Cystic fibrosis is an inherited disease that affects the glands that make mucus and sweat. Children may be born with cystic fibrosis if each parent carries one faulty gene for the disease. Someone with one normal CF gene and one faulty CF gene is known as a cystic fibrosis carrier. You can be a carrier and not have the disease yourself.

Many women find out they are carriers when they become, or are trying to become, pregnant. If their partner is also a carrier, their child may be born with the disease.

When both the couples are CF carriers and have a baby, there is a 25 percent chance that their baby will be born with the disease and a 50 percent chance that their baby will be a carrier of a CF gene mutation, but not have the disease themselves. One in four children will neither be carriers nor have the disease, therefore breaking the chain of heredity.

Many carrier couples decide to undergo a genetic screening test on their embryos, called preimplantation genetic diagnosis (PGD). This test is done prior to pregnancy on embryos acquired through in vitro fertilization (IVF). In PGD, one or two cells are extracted from each embryo and analyzed to determine if the baby will:

• have cystic fibrosis
• be a carrier of the disease
• not have the defective gene at all

The removal of cells does not adversely affect the embryos. Once we have this information about the embryos, one can decide which to have implanted in the uterus in the hopes that a pregnancy will occur.