Mendel took garden pea plants with different characteristics, such as height to study the inheritance pattern of factors (genes). He crossed tall pea plant with short pea plant and obtained all the tall plants in the $\mathrm{F}_{1}$ generation. Answer the following questions: (a) Why only tall pea plants were observed in $\mathrm{F}_{1}$ progeny? (b) By which method did Mendel obtain $\mathrm{F}_{2}$ progeny? (c) (i) Write one difference between dominant and recessive trait. OR (c) (ii) Write two observations made by Mendel about $\mathrm{F}_{1}$ progeny.

This case grounds itself directly in the chapter's account of Mendel's monohybrid cross: 'He took pea plants with different characteristics – a tall plant and a short plant, produced progeny by crossing them... In the first place, there were no halfway characteristics in this first-generation, or F1 progeny – no medium-height plants. All plants were tall... This led Mendel to propose that two copies of factor (now called genes) controlling traits are present in sexually reproducing organism.'

Part (a) tests understanding of dominance: the chapter states 'In this explanation, both TT and Tt are tall plants, while only tt is a short plant... a single copy of T is enough to make the plant tall, while both copies have to be t for the plant to be short.' Since the tall parent is TT and the short parent is tt, every F1 individual necessarily receives one T and one t, becoming Tt, and because T is dominant the plant appears tall.

Part (b) directly uses the chapter's description of the experimental method: 'Mendelian experiments test this by getting both the parental plants and these F1 tall plants to reproduce by self-pollination... the second-generation, or F2, progeny of the F1 tall plants are not all tall.' This confirms self-pollination of F1 as the method used.

Part (c) offers an internal choice. Choice (i) asks for a difference between dominant and recessive traits, which follows directly from the TT/Tt/tt logic above — dominant traits need only one copy to show, recessive traits need both copies to be the recessive form. Choice (ii) asks for two observations Mendel made about F1, which the chapter states explicitly: no intermediate/blended phenotypes appeared, and only one parental trait (the dominant one) was visible, with the recessive trait remaining hidden (later shown in F2 to still be present, since F2 gives a 1:2:1 ratio of TT:Tt:tt, i.e., 3 tall : 1 short).