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dominant-appears in first generation recessive-seems to dissapear
Two recessive alleles (homozygous) will result in the recessive trait being expressed as a phenotype.
In diploid organisms (those with two copies of each gene carried on separate chromosomes), one of the copies of a given gene may differ from the other copy of the same gene on the twin chromosome. In some cases one version of the gene (the dominant allele) has the effect of 'masking' the activity of the other (the recessive allele); that is, the presence of the dominant allele negates the effect of the recessive allele on the organism's phenotype. There are many mechanisms which can cause this phenomena, and it depends on the particular genes involved, but a simple model is one where the recessive allele is a biochemically inactive version of the dominant allele. In this case the dominant allele would mask the effect of the recessive allele by providing an active version of the gene. The dominant phenotype would be the one which shows the downstream effects of this activity, and the recessive phenotype one which shows the downstream effects of a lack of activity. The dominant allele is said to 'mask' the recessive allele because only one copy is required to result in an elimination of the recessive phenotype, whereas all copies of the gene must be the recessive allele to result in the recessive phenotype.
Yes
The dominant form of the trait shows. -Gradpoint
dominant-appears in first generation recessive-seems to dissapear
A 3:1 phenotypic ratio (Mendelian inheritance).
Two recessive alleles (homozygous) will result in the recessive trait being expressed as a phenotype.
If both alleles are recessive, then you will haev a case where contrasting alleles that do not have dominance. Neither allele has the power to be dominant so they will both have equal power of genetics.
The genotype AA represents a homozygous dominant genotype. The capital letter "A" represents the dominant allele, while the lowercase letter "a" would represent the recessive allele. If both dominant alleles are present in a genotype (homozygous dominant) then the phenotype is "A" phenotype. If one dominant allele and one recessive allele are present (heterozygous dominant) then the phenotype is "A". Finally, if both recessive alleles "a" are present (homozygous recessive) then the phenotype is "a". Therefore, the answer to your question is the genotype AA would result in an "A" phenotype because the genotype is homozygous dominant.
By "test cross" you can know whether it homozygous dominant or heterozygous dominant...in homozygous both alleles code for the dominant trait, in heterozygous one allele is recessive (what you called a "hidden factor"). To perform the test cross, cross a homozygous recessive with the first generation. Lets suppose tall pea tree in the first generation is hetrozygous dominant (Xx) and has alleles X (dominant) and x (recessive). When we cross it with homozygous recessive (xx) X x x :Xx xx x :Xx xx we get half offspring showing dominant trait (Xx) and half showing recessive (xx). If the first generation was homozygous (which is not possible) the result would be X X x: Xx Xx x: Xx Xx all the offspring showing dominant trait and it doesn't really happen when we cross the first generation with homozygous recessive. It means that the genotype of first generation is heterozygous (has a hidden factor or a recessive allele x). Note:You must know what the recessive and dominant allele means...In presence of a dominant allele, recessice character is not expressed but it is present is heterozygous. If both alleles are recessive (homozygous recessive) then the recessive trait is expressed. If both the alleles are dominant (homozygous dominant) obviusly the dominant trait is showed by the individual.
It depends on the gene in question, and the type of dominance of the trait.For monogenetic traits (those controlled by a single gene), the dominant trait(s) will be expressed when two different alleles are present.For example, if B leads to black fur and b leads to white fur:Complete dominance would result in a rabbit with Bb having black fur.Incomplete dominance - Bb would result in grey furCodominance - Bb would result in black and white patches/spots/etc.
An Aa genotype can result in the same phenotype as either an AA or AA genotype, if one of the alleles acts in a dominant fashion. If the A allele is dominant over the a allele, then the phenotype of a heterozygous (Aa) individual will be the same as the phenotype of a homozygous dominant (AA) individual.
Sickle cell anemia is an autosomal recessive disorder. It can result from two carriers having a child together.
In diploid organisms (those with two copies of each gene carried on separate chromosomes), one of the copies of a given gene may differ from the other copy of the same gene on the twin chromosome. In some cases one version of the gene (the dominant allele) has the effect of 'masking' the activity of the other (the recessive allele); that is, the presence of the dominant allele negates the effect of the recessive allele on the organism's phenotype. There are many mechanisms which can cause this phenomena, and it depends on the particular genes involved, but a simple model is one where the recessive allele is a biochemically inactive version of the dominant allele. In this case the dominant allele would mask the effect of the recessive allele by providing an active version of the gene. The dominant phenotype would be the one which shows the downstream effects of this activity, and the recessive phenotype one which shows the downstream effects of a lack of activity. The dominant allele is said to 'mask' the recessive allele because only one copy is required to result in an elimination of the recessive phenotype, whereas all copies of the gene must be the recessive allele to result in the recessive phenotype.
All the offspring will be heterozygous with a phenotype showing the dominant trait. Let the alleles be H (dominant) and h (recessive). All the gametes from the first individual will be H, and from the other, h. Thus all the offspring must be Hh.
In classic genetics: AA or Aa for autosomal dominance; for sex-linked dominance, females will need XX or Xx, while males will need Xy It gets more complicated with epistasis and other factors that modulate the genes.