Video Transcript
Gregor Mendel investigated the
inheritance of genes through breeding experiments using his pea plants. From these experiments, he produced
three laws of inheritance. Which of the following best
explains Mendel’s law of segregation? (A) When gametes combine in
fertilization, the alleles for each gene will come from one parent only. (B) A gamete of an organism will
carry only one allele for each gene. (C) A gamete of an organism will
carry only two alleles for each gene. (D) The alleles for a gene are kept
at separate positions on a chromosome.
This question asks us about the key
contributions of Gregor Mendel to the science of inheritance and heredity. Heredity is the transmission of
characteristics across generations that occurs by genetic processes. Gregor Mendel is considered a
pioneer in this field. Through his experiments with pea
plants, he produced three laws of inheritance that are still used today. Let’s review these three laws of
inheritance in order to answer this question.
Mendel’s first law is the law of
dominance, where he determined that some alleles were dominant over others. You’ll recall that an allele is a
version of a gene that can give a different trait. For instance, seed texture has
traits that are influenced by the wrinkled allele or the smooth allele. With his experiments, Mendel found
that crossing a smooth seed with a wrinkled seed produced more smooth seeds. From this, he concluded that the
smooth allele was dominant to the wrinkled allele.
Mendel’s second law of inheritance
is called the law of segregation. This law stated that only one
allele could exist in each gamete. Remember that a gamete is a haploid
sperm or egg cell that comes together to form a zygote. Zygotes contain two alleles for
every gene, with one allele coming from each the mother and father. Therefore, in the sperm and egg
cells, only one allele can exist. This is the law of segregation.
The last law of inheritance is
called the law of independent assortment. During his experiments, Mendel
realized that the genes he studied were inherited independently of one another. For example, the expression of
flower color, which is indicated by the alleles labeled as the letter T here, are
separate from the alleles for seed texture, indicated by the letter B here. The alleles for these genes
separate independently during gamete formation.
It’s important to differentiate
between the law of segregation and the law of independent assortment. The law of segregation refers to a
single gene and how its alleles separate during gamete formation. On the other hand, the law of
independent assortment refers to two or more genes and how their alleles
independently separate during gamete formation.
Our question asked about the law of
segregation, which states that a sperm or egg cell will only contain one allele for
a particular gene. When these gametes come together in
fertilization, the resulting zygote will contain two alleles for each gene. Therefore, the option that best
describes Mendel’s law of segregation is given by answer choice (B). A gamete of an organism will only
carry one allele for each gene.
