These notes will help you feel very prepared for your final examinations with their in-depth notes on this very important section of Life Sciences in Matric. Helped me to get an A throughout Matric.
Genetics
The scientific study of how physical, biochemical, and behavioural traits are
transmitted from parents to their offspring.
Terminology
Genes – a section of DNA that controls a hereditary characteristic (trait)
Herdeity – passing on of traits/characteristics from one generation to the
next
Alleles – Genes responsible for controlling different versions of a
trait/characteristic found on the same locus (position) on a chromosome
eg: for the gene determining coat colour, one allele could determine a
black coat (B) and another allele a white coat (b)
Haploid – (n) half the number of chromosomes. One of a pair of
homologous chromosomes. One of each pair of alleles. Eg: Sex cells
(gametes)
Diploid – (2n) full set of chromosomes. A pair of homologous
chromosomes. Two alles. Eg: Somatic
Homozygous – if the pair of alleles at a locus are the same. Eg: BB or bb
Heterozygous - if the pair of alleles at a locus are different. Eg: Bb
Genotype- Made up of all the genes an organism carries on its
chromosomes, which is inhertited from its parents.
Phenotype- Physical appearance of an organism (tallness, hair colour
etc.). This is partly programmed by the its genotype AND by external
factors.
Human genome - the entire genetic blueprint of a human beings
Gene locus – the position of a particular gene on a chromosome.
Homologous pair - chromosmes of the same length, have the
centromere in the same position and carry the same the same genes and
the same alleles in identical positions.
Karyotype – all the chromosomes in a cell, showing their size, number
and shape.
, Who was the ‘Father of Genetics’
Gregor Mendel (1822-1884), an Austrian monk often called the ‘Father of
Genetics’ was responsible for the first major breakthrough in the study of
heredity by investigating the transfer of characteristics from one
generation to the next.
He realised that something is passed on from parent to offspring and that
sexual reproduction combines these ‘somethings’ from each parent to
produce offspring which are unique, yet the same.
Gregor Mendel developed the principes of heredity while studying seven
pairs of inherited characteristics in pea plants. Although the significance
of his work was not recognised during his life time, it has become the
basis for the present-day field of genetics
Chromosomes
Each chromatid is made up of one DNA Nearly all somatic cells have an exact
molecule. Each DNA molecule is made up copy of all the genes in that organism.
of a series of genes.
Because there are two kind of each kind
A gene is a section of DNA that controls a of chromosomes (paternal and
hereditary characteristic (trait). maternal), each cell contains two of
each kind of gene. These versions of a
gene are known as alleles
, Genes
Each chromatid is made up of one, helical DNA molecule. Each DNA
molecule is made up of a series of genes.
What is a gene? HEREDITY - the passing on of
A gene can be defined as a section of DNA physical or mental
(series of nucleotides/bases) that controls characteristics genetically fro
a hereditary characteristics (trait), ie. It is the m one generation to another.
basic unit of heredity in living organisms.
Nearly all somatic cells (body cells) have an exact copy of all the genes in
that organism. Mature red blood cells have no nuclei, therefore no
chromosomes nor genes.
This is because there are two of each kind of chromosomes (paternal and
maternal), each cell contains two of each kind of gene (before
replication). These versions of a gene are known as alleles.
What is a gene pool?
A gene pool refers to the set of all genes, or genetic information, in a
population of sexually reproducing organisms. A large gene pool indicates
high genetic diversity and increased chances of survival.
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