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The only way to have a recessive trait expressed is to have both alleles be recessive (bb, resulting in the blond hair color). Homozygous genotype is defined by ...
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Read the following passage and answer the questions.
Often times, people will refer to a trait or characteristic such as eye color or hair color as being genetic, but what does the word genetic really mean?
Genetics is termed as the study of heredity and how traits in offspring are based upon those of the parents. Heredity is the process in which traits (characteristics that can be passed only from a living thing to its young) are passed from parents to offspring. A Punnett square is a grid system that can be set up and used to predict the possible outcomes that may result from the mating process between two individuals, when their genotypes are known. Each cell within the square is representative of one possible genotypic outcome for any offspring. The term genotype refers to the genetic make-up of an organism. Genotype is represented by using letters of the alphabet to stand for each allele that has been passed from the parents. A capital letter represents the dominant allele and a lowercase letter represents the recessive allele. Alleles are all the forms of a gene for any given trait. There are usually two allele possibilities for every trait. For example: B and b are both alleles for the trait of hair color. Since genotype is the genetic make-up, phenotype is the physical result of a gene combination – what can be observed. Dominance is when one allele can mask the presence of another (B is the dominant gene for brown hair). Recessive refers to a characteristic that is masked by the presence of a dominant allele (b is a recessive gene for blonde hair). The only way to have a recessive trait expressed is to have both alleles be recessive (bb, resulting in the blond hair color).
Homozygous genotype is defined by the occurrence where the paired alleles that are the same for a specific trait, in this case hair color, are identical (BB or bb). If both parents are homozygous, they can each only pass on one allele type to their offspring. This means that all the offspring will have one B and one b allele and will be Bb genotype. This Bb genotype is termed as heterozygous. A heterozygous genotype is when the genes that an offspring receives are different, Bb. In this instance, dominance will also be expressed because the offspring will have the dominant trait of brown hair.
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allele in their genotype.
A Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment. It is named after Reginald C. Punnett who devised the approach. The diagram is used by biologists to determine the probability of an offspring having a particular genotype
Practice Problems Monohybrid Crosses The parent alleles are set up for you and the dominance of the trait described. Complete the Punnett square and summarize the possible offspring genotypes and phenotypes with percentages and characteristic.
The Phenotype is determined as a percent chance of inheriting the trait. It is given as a percentage.
If R = Red and r = is white, then, from this cross you would have a 50% chance of Red and a 50% chance of white.
This is calculated by taking 2 divided by 4 (2 Rr out of 4 boxes), or 50%
The results in the Punnett Square are the Genotypes.
For this square the Genotypes are Rr and rr