Homozygous dominant and heterozygous organisms for a specific trait have different genotypes
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In general, humans have the same genes. A number of genes are varied. These control our physical traits and health. Show
Each variation is called an allele. You inherit two alleles for each gene. One comes from your biological mother and one comes from your biological father. If the alleles are identical, you’re homozygous for that specific gene. For instance, it could mean you have two alleles for the gene that causes brown eyes. Some alleles are dominant, while others are recessive. The dominant allele is expressed more strongly, so it masks the recessive allele. However, in a homozygous genotype, this interaction doesn’t occur. You either have two dominant alleles (homozygous dominant) or two recessive alleles (homozygous recessive). Read on to learn about the homozygous genotype, along with examples and disease risks. The term “heterozygous” also refers to a pair of alleles. Unlike homozygous, being heterozygous means you have two different alleles. You inherited a different version from each parent. In a heterozygous genotype, the dominant allele overrules the recessive one. Therefore, the dominant trait will be expressed. The recessive trait won’t show, but you’re still a carrier. This means you can pass it on to your children. It’s the opposite of being homozygous, where the trait of the matching alleles — either dominant or recessive — is expressed. A homozygous genotype can appear in various ways, such as: Eye colorThe brown eye color allele is dominant over the blue eye allele. You can have brown eyes whether you’re homozygous (two alleles for brown eyes) or heterozygous (one for brown and one for blue). This is unlike the allele for blue eyes, which is recessive. You need two identical blue eye alleles in order to have blue eyes. FrecklesFreckles are tiny brown spots on the skin. They’re made of melanin, the pigment that gives color to your skin and hair. The MC1R gene controls freckles. The trait is also dominant. If you don’t have freckles, it means you’re homozygous for a recessive version that doesn’t cause them. Hair colorRed hair is a recessive trait. A person who is heterozygous for red hair has one allele for a dominant trait, like brown hair, and one allele for red hair. They can pass the red hair allele to their future children. If the child inherits the same allele from the other parent, they’ll be homozygous and have red hair. 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. If you were heterozygous for that mutated recessive allele, the normal dominant allele would take over. The disease may be expressed mildly or not at all. If you’re homozygous for the recessive mutated gene, you have a higher risk of the disease. You don’t have a dominant allele to mask its effect. The following genetic conditions are more likely to affect people who are homozygous for them: Cystic fibrosisThe cystic fibrosis transmembrane conductance regulator (CFTR) gene makes a protein that controls fluid movement in and out of cells. If you inherit two mutated copies of this gene, you have cystic fibrosis (CF). Every person with CF is homozygous for this mutation. The mutation causes thick mucus to build up, resulting in:
Sickle cell anemiaThe hemoglobin subunit beta (HBB) gene helps produce beta-globin, which is part of hemoglobin in red blood cells. Hemoglobin makes it possible for red blood cells to deliver oxygen throughout the body. In sickle cell anemia, there are two copies of an HBB gene mutation. The mutated alleles make abnormal beta-globin, which leads to low red blood cells and poor blood supply. PhenylketonuriaPhenylketonuria (PKU) occurs when a person is homozygous for a phenylalanine hydroxylase (PAH) gene mutation. Normally, the PAH gene instructs cells to produce an enzyme that breaks down an amino acid called phenylalanine. In PKU, the cells can’t create the enzyme. This causes phenylalanine to accumulate in the tissues and blood. A person with PKU needs to limit phenylalanine in their diet. Otherwise, they can develop:
Methylenetetrahydrofolate reductase (MTHFR) gene mutationThe MTHFR gene instructs our body to make methylenetetrahydrofolate reductase, an enzyme that breaks down homocysteine. In a MTHFR gene mutation, the gene doesn’t make the enzyme. Two notable mutations include:
While scientists are still learning about MTHFR mutations, it’s been associated with:
We all have two alleles, or versions, of each gene. Being homozygous for a particular gene means you inherited two identical versions. It’s the opposite of a heterozygous genotype, where the alleles are different. People who have recessive traits, like blue eyes or red hair, are always homozygous for that gene. The recessive allele is expressed because there isn’t a dominant one to mask it. What is the difference of the genotype of a homozygous and heterozygous trait?We all have two alleles, or versions, of each gene. Being homozygous for a particular gene means you inherited two identical versions. It's the opposite of a heterozygous genotype, where the alleles are different. People who have recessive traits, like blue eyes or red hair, are always homozygous for that gene.
How are homozygous and heterozygous genotypes for a particular trait in plants different?An organism that has the same two copies of a gene is considered homozygous for that trait, while an organism that has different copies of a gene for a particular trait is considered heterozygous for that trait. In plant and animal breeding, such organisms can be called homozygotes and heterozygotes.
What is the difference between organisms that are heterozygous dominant and homozygous dominant?Homozygous and heterozygous are terms that are used to describe allele pairs.
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Homozygous vs Heterozygous.. Can two organisms have different genotypes but the same phenotype?The answer is yes, two different genotypes can result in the same phenotype. Remember, the recessive phenotype will be expressed only when the dominant allele is absent, or when an individual is homozygous recessive (tt) (Figure below).
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