Question

gregor mendel crossed homozygous tall plants (tt) with homozygous short plants (tt). all the resulting offspring were tall. from these results, what conclusion did mendel draw?
tallness is a dominant trait.
the word homozygous always means dominant.
only dominant alleles are passed on to offspring.
the alleles of the offspring were recessive.

Explanation:

• Tallness is a dominant trait: In Mendelian genetics, when a homozygous dominant (TT - tall) and homozygous recessive (tt - short) are crossed, the \(F_1\) generation (\(Tt\)) shows the dominant trait (tall). This is because the dominant allele (\(T\)) masks the recessive allele (\(t\)).
• The word homozygous always means dominant: Homozygous refers to having two identical alleles. It can be homozygous dominant (e.g., \(TT\)) or homozygous recessive (e.g., \(tt\)). So, homozygous does not always mean dominant.
• Only dominant alleles are passed on to offspring: In the cross \(TT\times tt\), each parent passes one allele. The \(TT\) parent passes \(T\) and the \(tt\) parent passes \(t\). Offspring get one allele from each parent (\(Tt\)), so both dominant and recessive alleles can be passed (but the dominant one is expressed in this case).
• The alleles of the offspring were recessive: The offspring genotype is \(Tt\). They have a recessive allele (\(t\)) but also a dominant allele (\(T\)). Since the dominant allele (\(T\)) determines the phenotype (tall), the statement is wrong.

Answer:

Tallness is a dominant trait.