What is an example of homozygous recessive?

A homozygous recessive allele combination contains two recessive alleles and expresses the recessive phenotype. For example, the gene for seed shape in pea plants exists in two forms, one form (or allele) for round seed shape (R) and the other for wrinkled seed shape (r).

Why is homozygous recessive bad?

Homozygous genes and disease. Some diseases are caused by mutated alleles. If the allele is recessive, it’s more likely to cause disease in people who are homozygous for that mutated gene. This risk is related to the way dominant and recessive alleles interact.

Is a genetic disease homozygous?

Narration. Homozygous describes the genetic condition or the genetic state where an individual has inherited the same DNA sequence for a particular gene from both their biological mother and their biological father. It’s often used in the context of disease.

Is Down syndrome a dominant or recessive disorder?

Like cystic fibrosis, Down’s Syndrome is autosomal recessive. This means that the condition is genetic and passed down by the mother and/or the father but the condition is not shown in the parents. An autosomal recessive disorder requires two copies of the abnormal gene for the disease or trait to develop.

Are blue eyes homozygous recessive?

Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb. Of these three genotypes, only bb, the homozygous recessive genotype, will produce a phenotype of blue eyes.

Are freckles homozygous recessive?

Freckles are recessive and no freckles are dominant. Mom is heterozygous dominant (Ff) and dad is homozygous recessive (ff).

Why are most diseases caused by recessive alleles?

One gene in each pair comes from the mother, and the other gene comes from the father. Recessive inheritance means both genes in a pair must be abnormal to cause disease. People with only one defective gene in the pair are called carriers. These people are most often not affected with the condition.

Is cystic fibrosis dominant or recessive?

Cystic fibrosis is an example of a recessive disease. That means a person must have a mutation in both copies of the CFTR gene to have CF. If someone has a mutation in only one copy of the CFTR gene and the other copy is normal, he or she does not have CF and is a CF carrier.