Genetics

Course CodeBSC207
Fee CodeS1
Duration (approx)100 hours
QualificationStatement of Attainment
Genetics provides a foundation for both
  • Breeding Plants, and
  • Understanding Plant Conservation and Management.
It is an essential area of study for anyone working in horticultural research, botany, environmental management or other areas of applied biological sciences.
 
If you want to understand how to develop new plant cultivars, you will need to have a knowledge of genetics at a level equal to what is in this course.
 

Lesson Structure

There are 10 lessons in this course:

  1. Introduction to Genetics
  2. The Cell and Organelles
  3. Interaction between Chromosomes
  4. Interaction between Genes
  5. Genetic Chemistry (DNA and Chromosomes)
  6. Mutations (Genomes and Mutations)
  7. DNA repair and Recombination
  8. Developmental Genetics
  9. Population Genetics
  10. Applied Genetics

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


Genetics Underpins Plant Breeding and Propagation

It is through a deeper understanding of genetics that you are able to improve anything you do with plant propagation, or plant breeding. Whenever you set out to create new plants, there are many variables in the outcome. Propagated plants may be produced in a way that is either identical or different to the plant you propagate from.

  • The amount and type of difference can be controlled if you wish.
  • To exercise that control though; it is important to properly understand genetics - and what you learn in this courser underpins and improves your capacity to exercise that control.

Plant Breeding

Plant breeding is concerned with improving plants so that they more readily meet our needs. Both horticultural and agricultural crops have been adapted through breeding to increase the range of species and to alter their quality and performance. In many countries, most, if not all, of the main food crops are quite different to those they were developed from. In fact, many food crops did not originate in the countries where they are now grown but they have been selectively bred to withstand that country's growing conditions. In order to understand plant breeding, it is necessary to gain a foothold in genetics.

PLANT GENETICS

The basis of modern plant breeding is genetics – the inheritance of characteristics from one generation to the next.

The foundation of the science of genetics were laid by an Austrian scientist named Gregor Mendel (1822- 1884). The first studies in genetics were carried out by him in the 1860s.  Mendel became a monk and lived and worked at a monastery near the town of Brunn. Modern genetic scientists have checked and verified the work of Mendel but when he first published the results of his experiments the importance of his scientific work was not realised.

He experimented with garden peas which are true-breeding (homozygous) and capable of self-fertilisation. He chose seven well-defined contrasting traits including differences in flower colour and seed shape and, by carrying out large numbers of experimental crosses, he examined how the traits were passed on to subsequent generations.

Mendel observed the traits that appeared in the first generation (the F1), and counted the plants that possessed contrasting traits in the second (F2) and third (F3) generations. He found that all plants of the F1 generation had only one contrasting trait and that both traits appeared in the F2 generation. He called the traits that appeared in the F1 generation dominant traits, while the traits that appeared only in the second generation were called recessive traits. This is known as the 'principle of dominance', where some traits can entirely mask the appearance of another trait.

Mendel found that when plants of the F1 generation were allowed to self-pollinate, the recessive trait appeared in the F2 generation in a mathematical ratio of 3 dominant to 1 recessive. For example, when Mendel crossed round peas (WW) with wrinkled (ww) peas, he obtained the progeny (the F1 generation) produced round peas (Ww). Mendel then crossed one Ww with another Ww to obtain an F2 generation which produced three plants with round peas (WW, Ww, Ww) to every plant with wrinkled peas (ww). This indicated that dominant and recessive genes were active in this characteristic. Those with Ww displayed the dominant feature. Only those with both recessive genes (ww) showed as wrinkled.

Although Mendel was not aware of the mechanisms of heredity, we now know that the process takes place at a cellular level in the plant tissues. The units of heredity are contained in genes within molecules of DNA, located on the chromosomes. Each gene, or several linked genes, is responsible for determining the development of a particular characteristic, such as flower colour or plant height. During fertilisation, genetic material is exchanged, and some characteristics are retained - others may be altered, resulting in new traits in the offspring.

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