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Practice with Monohybrid Punnett Squares
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.
Use a different color font when filling in with google doc
1. Genetics is the study of
2. Traits are characteristic that can be passed only from a to its .
3. The process in which traits are passed from parents to offspring is .
4. Each cell of a Punnett square represents one possible outcome for any offspring
of two specific parents.
5. Genotype refers to the make-up of an organism.
6. is the physical trait that is expressed in an individual.
7. are the different forms of a gene for any given trait.
8. For each trait, there are allele possibilities.
9. When the expression of one allele is masked by the presence of another, it is said to be
.
