DNA, Genes and Chromosomes
- Created by: jessicawarren
- Created on: 10-05-16 19:30
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- DNA, Genes and Chromosomes
- Nuclear Eukaryotic DNA
- 1) Eukaryotic cells contain linear DNA that exists as chromosomes- one long molecule of DNA. Found in nucleus
- 2) DNA molecule really long, has to be wound up to fit into nucleus
- 3) DNA wound around proteins called histones
- 4) Histone proteins help to support DNA
- 5) DNA coiled up tightly to make compact chromosome
- 6) Mitochondria and chloroplasts have own DNA. Circular/ shorter, not associated with histone proteins
- Genes
- 1) Sequence of DNA bases that codes for a polypeptide/ functional RNA
- 2) Sequence of amino acids forms primary structure of protein
- 3) Different polypeptides have different order/ number of amino acids. Order of bases determines order of amino acids in polypeptide
- 4) Each amino acid coded for by sequence of three bases: triplet
- 5) To make polypeptide, DNA first copied into mRNA. First stage of protein synthesis
- 6) Genes that don't code for polypeptides code for functional RNA- RNA molecules other than mRNA. Perform special tasks during protein synthesis e.g. tRNA and rRNA
- Genome: Complete set of genes. Proteome: Full range of proteins cell able to produce
- Coding
- 1) Some genes dont code for polypeptides, code for functional RNA
- 2) Eukaryotic DNA- genes that do code for polypeptides contain sections that dont code for amino acids
- 3) These sections are introns. Several within a gene
- 4) Genes that do code for amino acid are exons
- 5) Introns removed during protein synthesis- don't affect amino acid order. Prokaryotic DNA doesnt have introns
- 6) Eukaryotic DNA contains multiple repeats outside genes
- 7) DNA sequences that repeat e.g. CCTTCCTTCC
- 8) These areas dont code for amino acids- non- coding repeats
- Alleles
- 1) Different forms of same gene
- 2) Order of bases in alleles different- code for slightly different versions of same polypeptide
- E.g. Gene that determines blood type has three alleles: O, A and B
- In eukaryotic cell, DNA stored as chromosomes. Humans have 23 homologous pairs
- Homologous pairs- both chromosomes same size/have same genes- could have different alleles.
- Alleles coding for same characteristic found at same fixed position: locus on chromosome
- Nuclear Eukaryotic DNA
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