Assume that a recessive autosomal disorder occurs in 1 of 40,000 individuals (0.000025) in the general population and that in this population about 1 percent (0.01) of the individuals are carriers for the disorder.
a) Estimate the probability of this disorder occurring in the offspring of a marriage between first cousins.
b) Compare this probability to the population at large.
_Compare this probability to the population at large.
_Inbreeding increases the likelihood of homozygosity.
_Inbreeding decreases the likelihood of homozygosity.
_Inbreeding does not change the likelihood of homozygosity.
Autosomal recessive:-
Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families.
An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.
Information:
Inheriting a specific disease, condition, or trait depends on the type of chromosome that is affected. The two types are autosomal chromosomes and sex chromosomes. It also depends on whether the trait is dominant or recessive.
A mutation in a gene on one of the first 22 nonsex chromosomes can lead to an autosomal disorder.
Genes come in pairs. 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. However, they can pass the abnormal gene to their children.
CHANCES OF INHERITING A TRAIT
If you are born to parents who carry the same autosomal recessive change (mutation), you have a 1 in 4 chance of inheriting the abnormal gene from both parents and developing the disease. You have a 50% (1 in 2) chance of inheriting one abnormal gene. This would make you a carrier.
In other words, for a child born to a couple who both carry the gene (but do not have signs of disease), the expected outcome for each pregnancy is:
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity.
Inbreeding results in homozygosity, which can increase the chances of offspring being affected by deleterious or recessive traits.
Autosomal recessive disorders occur in individuals who have two copies of an allele for a particular recessive genetic mutation. Since relatives share a higher proportion of their genes than do unrelated people, it is more likely that related parents will both be carriers of the same recessive allele, and therefore their children are at a higher risk of inheriting an autosomal recessive genetic disorder. The extent to which the risk increases depends on the degree of genetic relationship between the parents; the risk is greater when the parents are close relatives and lower for relationships between more distant relatives, such as second cousins, though still greater than for the general population.
Children of parent-child or sibling-sibling unions are at an increased risk compared to cousin-cousin unions. Inbreeding may result in a greater than expected phenotypic expression of deleterious recessive alleles within a population.
Qa) Estimate the probability of this disorder occurring in the offspring of a marriage between first cousins.
The chance of probability increases to 1 in 4 i.e. 25% or 0.25
Qb) Compare this probability to the population at large.
Answer:- Inbreeding increases the likelihood of homozygosity.
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