SASS Bio Molecular Genetic Notes

6093 Biology (2022) Chapter 20 Molecular Genetics SASS_PJY 1 ST ANDREW’S SECONDARY SCHOOL Secondary 4 Biology (6093) Chapters 20: Molecular Genetics Name: _______________________ ( ) Class: _________ Date: __________ 14. Molecular Genetics Content • The Structure of DNA • The Role of DNA in Protein Synthesis • Genes • Genetic Engineering and Medical Biotechnology Learning Outcomes Candidates should be able to: (a) outline the relationship between DNA, genes and chromosomes (b) state the structure of DNA in terms of the bases, sugar and phosphate groups found in each of their nucleotides (c) state the rule of complementary base pairing (d) explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny (e) state that DNA is used to carry the genetic code, which is used to synthesise specific polypeptides (details of transcription and translation are not required) (f) state that each gene is a sequence of nucleotides, as part of a DNA molecule (g) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same species or different species – transgenic plants or animals (h) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology (i) discuss the social and ethical implications of genetic engineering, with reference to a named example (k) state that variation and competition lead to differential survival of, and reproduction by, those organisms best fitted to the environment Use the knowledge gained in this section in new situations or to solve related problems.

6093 Biology (2022) Chapter 20 Molecular Genetics SASS_PJY 2 20.1 DNA Organisation of DNA Basic units of DNA • DNA is made up of basic units known as nucleotides. A nucleotide is made up of: o a sugar called deoxyribose, o a phosphate group, and o a nitrogen-containing bases (also referred to as nitrogenous base) • The four types of bases found in a DNA molecule are: o adenine (A) o thymine (T) o cytosine (C) o guanine (G) • Nucleotides join together to form polynucleotides. • The DNA molecule is made up of two anti-parallel polynucleotide chains that run in opposite directions.

6093 Biology (2022) Chapter 20 Molecular Genetics SASS_PJY 3 • A polynucleotide consists of: • The bases from one strand form hydrogen bonds with the bases on the other strand according to the rule of complementary base pairing. This rule states that: • As a result of this, the ratio of A-T and C-G is 1:1 • The two antiparallel polynucleotide strands twist and coil about each other to form a double helix. 20.2 Genes How proteins are made from genes ______________ Sugar phosphate backbone polynucleotide withbonds adenine withbonds Nitrogenous bases thymine cytosine guanine

6093 Biology (2022) C