Flashcards · Biology · Genetic Inheritance
Inherited Disorders and Family Trees
-
What causes an inherited disorder?
The inheritance of certain alleles from the parents.
-
What is polydactyly?
Having extra fingers or toes, caused by a dominant allele.
-
What is cystic fibrosis?
A disorder of cell membranes caused by a recessive allele.
-
How many copies of the cystic fibrosis allele are needed to have the disorder?
Two.
-
What is a carrier?
A person with one recessive allele who does not have the disorder.
-
Can two parents without cystic fibrosis have a child with it?
Yes, if they are both carriers.
-
What is the chance that two carrier parents have a child with the disorder?
1 in 4, or 25%.
-
What is the chance that two carrier parents have a child who is a carrier?
1 in 2, or 50%.
-
How can you tell from a family tree that a disorder is recessive?
Two unaffected parents have an affected child.
-
What does a shaded symbol on a family tree show?
A person who has the disorder.
-
What do squares and circles mean in a family tree?
Squares are males and circles are females.
-
What is embryo screening?
Testing an embryo for a faulty allele, so only healthy embryos are put in the womb.
-
Name one ethical objection to embryo screening.
Embryos with the faulty allele are destroyed.
-
What is gene therapy?
Modifying the genes in a person's cells to overcome an inherited disorder.
-
Is a dominant disorder always common?
No. A dominant allele can be rare.
-
A family tree shows two unaffected parents with an affected child. Is the allele dominant or recessive, and what are the parents' genotypes?
The allele is recessive. Both parents are carriers, so they are both Nn, and the affected child is nn.