DNA Is a Molecule That Contains Genetic Information for Heritable Traits and Directs The
DNA
DNA is a molecule that contains genetic information for heritable traits and directs the structures and functions of the cell. DNA is the “stuff of life”; it is the blueprint for what you look like and to an extent – you we are. The DNA is the material that is passed down from parent to offspring.
The nucleus is the control centre of the cell. It contains the genetic material (DNA) of the cell.
DNA has a library of four letters! The different sequences and arrangements of these four letters produces the genetic code – which is responsible for your traits. DNA can be stretched out to a distance of 3 000 000 km. 97% of the letters are junk!
A gene is a section of DNA. A gene may contain thousands of the “four letters”, and the unique arrangement of these letters, directs the cell to carry out specific functions (ie. Produce blue eyes). On one strand of DNA there may be 1000’s of genes. In the human there are 30, 000 genes.
DNA is coiled up and compacted into chromosomes (see diagram). So chromosomes are strands of DNA that look like an X. (Humans have 46 chromosomes; 23 from each parent).
BLM 1-15.
Why do cells divide?
-growth
-repair
-replace
There are 2 types of cell division
1)Mitosis - A cell divides into 2 identical copies (like binary fission)
-each daughter cell has the same number of chromosomes as the original parent. See diagram
The life span of cells in the human body:
Brain cells30-50 years
Red Blood cells120 days
Stomach lining2 days
Skin cells20 days
2)Meiosis
A form of cell division that leads to the formation of sex cells (gametes). Human sperm cells contain 23 chromosomes, and human egg cells contain 23 chromosomes. When the two gametes unite, a zygote is formed with 46 chromosomes. The final result of meiosis is that the gametes have only half the original number of chromosomes as the parent cell.
Unlike mitosis, meiosis results in genetic variation – what chromosomes do you get from each parent creates 8.4 million possible chromosome combinations! Therefore sexual reproduction and the process of meiosis increases the variation within a species!
Genetics and technology (a form of biotechnology)
Genetic engineering involves moving pieces of DNA from one species to another.
Example – a gene from the firefly that produces bioluminescence can be moved into a tobacco plant causing the tobacco plant to grow. Another example is moving the human gene for insulin into bacteria, which has allowed the bacteria to produce insulin as a waste product.
Concerns with genetic engineering:
-create a genetic “monster” that might spread to the environment which might compete with and displace native species, interbreed with and change the genetics of a native species, or grow out of control in the absence of natural predators.
-It is not morally acceptable to change organisms in such fundamental ways. These ethical considerations supersede all others such as economic considerations
-Has become valuable for studying the genetic bases of disease. By manipulating DNA researchers can learn which genes are important to disease and how they have their effects.
Read page 53.
Biotechnology is currently used in medicine – the production of proteins, such as insulin and hormones and vaccines, by genetically engineered organisms can be much less costly than producing these proteins chemically in a lab.
Biotechnology is currently used in food production – we have inserted genes for rapid growth and disease resistance, and even antifreeze genes into fish, and are currently harvesting these fish (aquaculture). 25% of the fish consumed are produced in fish farms.
Some crops such as corn and tomatoes, are resistant to diseases and drought, and are tastier and more nutritious. (One concern is that we are creating monocultures – all the same species with little variety).
2) Page 56 #1-8
3) Page 57 #1-14