Summary
Summary Unit 2 Summarized
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- University Of South Africa (Unisa)
Extensive step-by-step summary of the textbook (Brooker) and Study Guide combined. All outcomes are covered in this summary of Unit 2.
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GNE2601 SUMMARY | Fransché BeukesLearning Unit 2: Basic concepts in genetics
TRANSMISSION OF TRAITS FROM GENERATION TO GENERATION
MENDEL’S USE OF PEA PLANTS FOR HIS EXPERIMENTS
CROSS: A mating between two distinct
individuals. An analysis of their offspring
may be conducted to understand how
traits are passed from parent to
offspring.
HYBRIDIZATION: The mating of two
organisms of the same species with
different characteristics; the
phenomenon in which two single-
stranded molecules renature together to
form a hybrid molecule.
Figure 2.2 Flower structure and
Hybrid: an offspring obtained from a pollination in pea plants The pea flower
hybridization experiment; a cell can produce both pollen and egg cells.
The pollen grains are produced within the
produced from a cell fusion experiment
anthers, and the egg cells are produced
in which the two separate nuclei have within the ovules that are contained within
fused to make a single nucleus. the ovary. A modified petal called a keel
encloses the anthers and ovaries.
SELF-FERTILIZATION: Fertilization that
involves the union of male and female gametes derived from the same parent.
- : It requires that the male and female gametes come from separate individuals.
True-breeding line: A strain of a particular species that continues to produce the same trait after
several generations of self-fertilization (in plants) or inbreeding. (AKA True-breeding strain)
SEVEN CHARACTERISTICS THAT BREAD TRUE
Height (tall or dwarf) Seed shape (round or wrinkled)
Flower colour (purple or white) Pod colour (green or yellow)
Flower position (axial or terminal) Pod shape (smooth or constricted)
Seed colour (yellow or green)
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, GNE2601 SUMMARY | Fransché Beukes
SINGLE TRAIT INHERITANCE (MONOHYBRID CROSS)
MONOHYBRID CROSS: A cross in which an experimenter is observing only one character. This cross
will produce single character hybrids – monohybrids.
Parental generation: The first generation in the experiment. In Mendel’s studies, the parental
generation was true-breeding with regard to particular traits.
F1-generation: The offspring produced from a cross of the parental generation.
F2-generation: The offspring produced from cross of the F1 generation.
Monohybrid crosses always have the dominant gene in F1 generation. Eg. Length was
investigated. All offspring will be tall.
Monohybrid crosses – F2 generation will always have the ratio of 3:1 (3 dominant: 1 recessive)
Gene: A unit of hereditary that may influence the outcome of an organism’s traits. At the molecular
level, a gene contains the information to make a functional product, either RNA or protein.
Allele:
An alternative form of a specific gene. (One allele from father one from mother)
Gamete:
Genotype: The genetic composition of an individual.
Phenotype: The observable characteristics of an organism.
Dihybrid cross: A cross in which an experimenter follows the outcome of two different traits.
Mendel’s law of segregation: The two copies of a gene segregate from each other during
transmission from parent to offspring.
EXPERIMENT 2A
Two pea plants are crossed. The one plant a tall and the other a dwarf plant.
STEPS TO DETERMINE F1 AND F2 GENERATIONS
Capital letters are used to represent the DOMINANT allele
Small letters are used to represent the RECESSIVE allele
Identical copies of the specific gene – HOMOZYGOUS (possessing two identical copies of a
particular gene)
Segregation must occur before the genes are separated.
Prepare a punnet square with the genes. (columns male and rows female)
Describe the genotype of F1 generation.
Describe the phenotype of F1 generation.
Repeat steps to determine F2 generation.
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