8.1 - 8.2 Genes, The Genetic Code, DNA and Chromosomes

Bee Brittain
Mind Map by Bee Brittain, updated more than 1 year ago
Bee Brittain
Created by Bee Brittain about 4 years ago


AS - Level Biology (8 - DNA, Genes and Protein Synthesis) Mind Map on 8.1 - 8.2 Genes, The Genetic Code, DNA and Chromosomes, created by Bee Brittain on 03/16/2016.

Resource summary

8.1 - 8.2 Genes, The Genetic Code, DNA and Chromosomes
1.1 A Gene is a section of DNA that codes for: 1) the amino acid sequence in a poly peptide 2) Functional RNA (inc. tRNA and rRNA)
1.2 A gene occupies a fixed position on the DNA molecule called a locus
2 The Genetic Code
2.1 20 Different A.A
2.2 4 Bases - Adenine and Thymine, Cytosine and Guanine
2.3 Three bases = One amino acid
2.3.1 64 Possible Codes
2.4 The code is DEGENERATE
2.4.1 This means that most amino acids are coded for by more than one triplet
2.5 One Triplet = One animo acid
2.6 The code is UNIVERSAL (mostly)
2.6.1 The same triplet codes for the same amino acid in most organisms
2.7 The code is NON-OVERLAPPING
2.7.1 Each base sequence is only once
2.8 Non-Coding regions
2.8.1 Multiple repeats of base sequences
2.8.2 Within Genes there are: Introns - Non-coding regions Exons - Coding regions
3.1 Prokaryotic
3.1.1 Circular
3.1.2 Shorter
3.1.3 Not associated with protein molecules
3.1.4 Don't have chromosones
3.2 Eukaryotic
3.2.1 Linear
3.2.2 Longer
3.2.3 Associated with proteins called HISTONES
3.2.5 Mitochondria and Chloroplasts of eukaryotic cells also contain DNA This is like DNA of prokaryotes though
4 Chromosome Structure
4.1 1) DNA is a double helix
4.2 2) Helix is wound around histones to fix it in position
4.3 3) This DNA-Histone complex is then coiled further
4.4 4) The coil is the looped and further coiled and packaged into a CHROMOSOME
4.5 Chromosome contains a single molecule of DNA
4.5.1 Single molecule has many genes along it
5 Homologous Chromosomes
5.1 One chromosome from each homologous pair comes from the mother (maternal) and one comes from the father (paternal)
5.1.1 Homologous chromosomes are similar, but not identical They have the same genes in the same order, for example: eye colour then hair colour. However they will have different alleles, so the maternal chromosome may have blue eyes, then blonde hair, where as the dad could have brown eyes and brown hair.
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