The Grade 12 Agricultural Sciences Paper 2 Note Set is the perfect study companion for students preparing for their paper 2 examination. These comprehensive study notes are filled with colorful explanations and diagrams to help students grasp difficult concepts quickly and easily. From genetics to ...
, AGRICULTURAL GENETICS
= study of heritable traits: the innate differences and
similarities between successive generations (offspring /
offspring)
= determine how the organism will look and function.
= coiled DNA chains wrapped = observable characteristics an allele expressed in the
around histones or characteristics of an phenotype when found in the
• HISTONE : special organism > organism's heterozygous and homozygous
proteins in the cell morphology or physical state
FENOTYPE
CHROMOSOME nucleus that package + form and structure, its
control DNA developmental processes, its
• Recruiting information biochemical and
stored in chromosome physiological characteristics
DNA DOMINANT = relationship between two versions of a gene > alleles of a gene
= segment of DNA in a ALLELE differ, one allele will be expressed; it is the dominant gene
chromosome that the RECESSIVE = variety of genetic code that does not create a phenotype
contain code for a ALLELE when a dominant allele is present
particular characteristic DEPICTION OF GENO & PHENOTYPE:
GENE • First letter of the dominant characteristic
LOCUS : exact position • Allele for dominant property = capital letter
(location) of a gene on a • Allele for recessive property = lowercase
chromosome
= variant of a gene = organism with two
[chromosome located] > dominant alleles looks the
conveys information about same as an organism with
the same characteristics only one functioning allele
HETEROZYGOTIC
2 ALELLE : one of mother & = combination of NON-
ALELLE IDENTICAL ALLELLES
one of father
dominant allele (L) – tall = none and allele is NOT
plant IDENTICAL [hybrid]
recessive allele (L) – short = individual inherits the
plant same alleles for a specific
gene from both parents
= complete set of genetic
[identical gene + allele]
material [GENETIC MAKEUP] HOMOZYGOUS
= where an individual
> refers to the alleles or
GENOTYPE inherits identical forms of
variants carried by an
a particular gene from each
individual in a particular
parent
gene or genetic location
, VARIATION TERMS
= differences in the
characteristics of organisms
Genetic variation > result:
• Crossing over and random segregation
CROSSING ILLUSTRATIONS
VARIATION belonging to the same type of chromosomes during meiosis
• arbitrary fusion of gametes during
fertilisation
MONOHYBRID only 1 feature or With : Complete dominance
CROSSING trait is described in the
genetic intersection
Shown
[JUST 1 PAIR OF GENES]
= 2 individuals with 1 pair of Punnett square
contrasting traits [single
traits]
Schematic Genetic diagrams
representation
Steps in solving monohybrid crosses:
u Determine the dominant characteristic
u Determine the key i.e. symbol / letter to be used
u Determine the phenotypes and genotypes of the parents
With: Incomplete dominance u Determine the alleles of each gamete after meiosis
u Determine the alleles of the zygote after fertilization – F1 – genotype
u Describe the F1 generation phenotypes
LAW OF SEGREGATION : MENDEL'S FIRST LAW :
Mendel's first law (Law of Segregation) states that the alleles for a particular trait
(such as flower color) separate during the process of meiosis. Their alleles recombine
With : co-dominance RANDOMLY during fertilisation and result in various genotype combinations.
, Please explain.?
= two different
characteristics
found in
genetic cross
DIHYBRID CROSSING be shown
= 2x individuals >
different alleles for
2x properties
LAW OF INDEPENDENT VARIETY / INDEPENDENT
RECOMBINATION : MENDEL'S SECOND LAW :
= that there > independent reassorting and recombination of features simply means
that two unrelated features function separately from each other
Qualitative Quantitative
characteristics properties
• Traits are by 1 gene control • More than 1 gene eg. growth rate
• eye colour or gender and milk production
• height, weight or milk production
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