Recessive gene and dominant gene

  • Thread starter thorium1010
  • Start date
  • Tags
    Gene
In summary: This way, some people will be resistant to malaria and some people will be resistant to sickle cell anemia. However, people with two copies of the recessive allele (i.e., AA or BB) will have sickle cell anemia and are at risk for malaria.In summary, recessive gene genetic variations of a dominant gene(or normal gene) arise when one allele is non-functional due to a mutation. These mutations can be bought on by genetic mutations.
  • #1
thorium1010
178
6
Like the title,
1)Are recessive gene genetic variations of a dominant gene(or normal gene).
2)What is the origin of a recessive gene?
3)Are recessive genes bought on by genetic mutations ?

I know the questions are trivial, but I am not able to clear these concepts.
 
Biology news on Phys.org
  • #4
thorium1010 said:
Like the title,
1)Are recessive gene genetic variations of a dominant gene(or normal gene).
2)What is the origin of a recessive gene?
3)Are recessive genes bought on by genetic mutations ?

I know the questions are trivial, but I am not able to clear these concepts.
These questions are far from trivial.

The molecular basis of gene dominance has a lot to do with the chemical pathways that lead to a particular phenotype being expressed. Here are links to review article on the mechanisms of gene dominance.

http://en.wikipedia.org/wiki/Dominance_(genetics)#Molecular_mechanisms
“Dominance typically occurs when one of the two alleles is non-functional at the molecular level, that is, it is not transcribed or else does not produce a protein product. This can be the result of a mutation that alters the DNA sequence of the allele. An organism homozygous for the non-functional allele will generally show a distinctive phenotype, due to the absence of the protein product. For example, in humans and other organisms, the unpigmented skin of the albino phenotype[8] results when an individual is homozygous for an allele that prevents synthesis of the skin pigment protein melanin. It is important to understand that it is not the lack of function that allows the allele to be described as recessive: this is the interaction with the alternative allele in the heterozygote.”

http://jmg.bmj.com/content/31/2/89.full.pdf
“The molecular basis of genetic dominance
Abstract

"This review draws on the rapid expansion in knowledge of molecular and cellular biology to classify the molecular mechanisms of dominant mutation. The categories discussed include (1) reduced gene dosage, expression, or protein activity (haploinsufficiency); (2) increased gene dosage; (3) ectopic or temporally altered mRNA expression; (4) increased or constitutive protein activity; (5) dominant negative effects; (6) altered structural proteins; (7) toxic protein alterations; and (8) new protein functions.”

http://www.pearsonhighered.com/sanders1einfo/assets/images/other/sanders-C04.pdf
“Gene Interaction
Interactions between Alleles Produce Dominance Relationships”
 
Last edited:
  • #5
Drakkith said:
I don't believe the gene itself is recessive or dominant, but the traits that arise because of the genes are dominant or recessive. See here: http://en.wikipedia.org/wiki/Recessive_gene#Nomenclature
You are right. This is an important distinction when one allele controls two phenotypic features.
The expression of a particular phenotypic feature is dominant or recessive. However, one allele can control several different phenotypic features, each of which has a different ranking.
For example, consider the allele that usually determines sickle cell anemia.
The allele (i.e., chromosome locus) that controls sickle cell anemia has two genes. Gene A is associated with both sick cell anemia and malaria resistance. Gene B is associated with being free of sickle cell anemia and malaria predisposition.
Gene A is dominant with respect to malaria resistance but recessive with respect to sickle cell anemia. Gene B is recessive with respect to malaria predisposition but dominant with respect to freedom from sickle cell anemia.
If you do the arithmetic (Punnet squares), you find that this means the following. The heterozygous AB person with both genes A and B has no sickle cell anemia and is resistant to malaria. However, a homozygous AA is resistant to malaria but has sickle cell anemia. A homozygous BB person is not resistant to malaria but doesn't have sickle cell anemia.
In an area with lots of mosquitoes and the malaria parasite, natural selection favors a mixed population with both A and B genes.
 

1. What is the difference between a recessive gene and a dominant gene?

A recessive gene is one that is only expressed when there are two copies present in an individual's genetic makeup. On the other hand, a dominant gene is one that is expressed even if there is only one copy present. This means that the dominant gene will override the recessive gene if they are present together in an individual.

2. How do recessive and dominant genes affect inheritance patterns?

Inheritance patterns are determined by the presence of dominant and recessive genes. If both parents have the same dominant gene, their offspring will inherit that gene and exhibit its traits. If both parents have the same recessive gene, their offspring will also inherit that gene and exhibit its traits. However, if one parent has a dominant gene and the other has a recessive gene, the dominant gene will be expressed in the offspring.

3. Can a recessive gene ever be expressed?

Yes, a recessive gene can be expressed if an individual inherits two copies of it, one from each parent. This is known as homozygosity. In this case, the recessive gene will be expressed because there is no dominant gene to override it.

4. How can we determine if a gene is recessive or dominant?

The determination of whether a gene is recessive or dominant can be made through genetic testing. By studying the patterns of inheritance in a family, scientists can determine if a gene is dominant or recessive. Additionally, experiments with breeding and observing the offspring can also help in identifying the dominant and recessive genes.

5. Do all traits have a recessive and dominant gene?

No, not all traits have a recessive and dominant gene. Some traits are determined by multiple genes, while others may be influenced by environmental factors. Additionally, some traits may not have a clear dominant or recessive gene, but rather have a blend of both genes that are expressed in the individual.

Similar threads

  • Biology and Medical
Replies
7
Views
1K
Replies
2
Views
2K
Replies
10
Views
1K
  • Biology and Medical
Replies
1
Views
1K
  • Biology and Medical
Replies
8
Views
1K
  • Biology and Medical
Replies
7
Views
1K
Replies
12
Views
1K
  • Biology and Medical
Replies
6
Views
1K
Replies
3
Views
1K
Replies
3
Views
2K
Back
Top