Blg1501 Exam Pack 2026

BLG1501
EXAM PACK

,BLG1501 Assignment 2 - Genetics and Cell Biology - Semester 1 2026

EXAM ANSWERS

QUESTION 1 [20 MARKS]

Cross: Purple homozygous flower × White homozygous flower

 Purple is dominant: P
 White is recessive: p
 Purple homozygous = PP
 White homozygous = pp

Parental generation

PP × pp

Punnett square


P P
p Pp Pp
p Pp Pp


F₁ generation

All offspring are:

 Genotype: Pp
 Phenotype: Purple flowers

Therefore:

Genotypic ratio of F₁ = 100% Pp

Phenotypic ratio of F₁ = 100% purple

,F₂ generation

To obtain F₂, cross two F₁ heterozygotes:

Pp × Pp


P p
P PP Pp
p Pp pp


F₂ results

 PP = 1
 Pp = 2
 pp = 1

Genotypic ratio = 1 PP : 2 Pp : 1 pp

Phenotypically:

 PP = Purple
 Pp = Purple
 pp = White

Therefore:

Phenotypic ratio = 3 purple : 1 white

Summary


Generation Genotype Phenotype
P PP × pp Purple × White
F₁ 100% Pp 100% Purple

, Generation Genotype Phenotype
F₂ 1 PP : 2 Pp : 1 pp 3 Purple : 1 White



QUESTION 2

2.1 Differences between prokaryotic and eukaryotic cells [14]


Feature Prokaryotic cells Eukaryotic cells
No true, membrane-bound
Nucleus Have a membrane-bound nucleus
nucleus
Usually circular and located Usually linear chromosomes
DNA
in the nucleoid located in the nucleus
Membrane-bound
Absent Present
organelles
Generally smaller, about Generally larger, about 10–100
Size
0.1–5 µm µm
Ribosomes Smaller, 70S Larger, 80S in the cytoplasm
Cell division Mainly by binary fission By mitosis and meiosis
Examples Bacteria and archaea Plants, animals, fungi and protists



2.2 Structure and function of ribosomes [10]

Structure

1. Ribosomes are small, non-membrane-bound structures found in cells.
2. They consist mainly of ribosomal RNA (rRNA) and proteins.
3. Each ribosome consists of two subunits: a small subunit and a large subunit.
4. In eukaryotic cytoplasm, ribosomes are generally 80S, consisting of a 40S small
subunit and 60S large subunit.