UNIT 4
4.1 DNA, genes and chromosomes
Nucleotides are made out of 3 components
- phosphate group
- pentose sugar (deoxyribose = DNA and ribose = RNA )
- base (ATCG/AUCG) (AT= 2 H bonds) (CG = 3 H bonds)
DNA = stores RNA = transfers
STRUCTURE (differences)
- Made out of deoxyribose sugars - Made out of ribose sugars
- ATCG bases - AUCG bases
- Single stranded
- Double stranded, LONG CHAIN
- Shorter significantly (for mRNA to
- Double helix shape, pass through the nuclear pores)
- anti parallel
ROLE
ROLE - mRNA transfers genetic information
- carries genetic information and (transcription) from DNA to
determines inherited ribosomes for protein synthesis
characteristics - tRNA translation to supply
complementary amino acids and
base pair anticodon to codon to
make a polypeptide chain
(similarities for both no matter)
- Made out of many nucleotides as monomers to form a polymer chain
- Hydrogen bonds in between the bases weak to break
- Phosphodiester bonds between adjacent nucleotides
DIFFERENCES OF DNA
EUKARYOTIC (animal) PROKARYOTIC (include chloroplast/mito)
- Long and linear + larger - shorter and circular DNA
- Associated with proteins like - Not associated with any proteins
histones and chromatin to form like histones and chromatin as
chromosomes there is not enough DNA to coil
- Found in nucleus - Found free in the cytoplasm
- Introns found (non coding) so - No introns
splicing is needed - Additional DNA like plasmids
- Additional DNA like mitochondrial
/chloroplast DNA (= prokaryotic)
, CONDENSING/PACKAGING DNA to fit into the nucleus (4m)
1. DNA WRAPS around histones (proteins) and form nucleosomes
2. Nucleosomes are COILED to form chromatin
3. Chromatin is SUPER-COILED to form chromosomes
CHROMOSOME STRUCTURE
- Two replicated copies of the DNA join at the centre by the CENTROMERE
- CHROMATID is each of the thread/arm of chromosome and are identical =
SISTER chromatids
- Diploid cells = paired chromosomes in cells like (somatic body cells which are
homologous chromosomes since one of each comes from a parent) (46)
- Haploid cells = single chromosomes (gametes: sperm, egg cells) (23)
DEFINITIONS FOR THE SECTION
GENE – is the base sequence of DNA that codes for a sequence of amino acids to
make a specific polypeptide, and also code for a functional RNA (tRNA, rRNA)
LOCUS – fixed position on a DNA molecules that a gene occupies
ALLELE – different versions of the same gene, found at the same locus
TRIPLET – a sequence of three DNA base and codes for specific amino acids
(4x4x4 = 64 triplet code gives 64 combinations for a.a)
4.1 DNA, genes and chromosomes
Nucleotides are made out of 3 components
- phosphate group
- pentose sugar (deoxyribose = DNA and ribose = RNA )
- base (ATCG/AUCG) (AT= 2 H bonds) (CG = 3 H bonds)
DNA = stores RNA = transfers
STRUCTURE (differences)
- Made out of deoxyribose sugars - Made out of ribose sugars
- ATCG bases - AUCG bases
- Single stranded
- Double stranded, LONG CHAIN
- Shorter significantly (for mRNA to
- Double helix shape, pass through the nuclear pores)
- anti parallel
ROLE
ROLE - mRNA transfers genetic information
- carries genetic information and (transcription) from DNA to
determines inherited ribosomes for protein synthesis
characteristics - tRNA translation to supply
complementary amino acids and
base pair anticodon to codon to
make a polypeptide chain
(similarities for both no matter)
- Made out of many nucleotides as monomers to form a polymer chain
- Hydrogen bonds in between the bases weak to break
- Phosphodiester bonds between adjacent nucleotides
DIFFERENCES OF DNA
EUKARYOTIC (animal) PROKARYOTIC (include chloroplast/mito)
- Long and linear + larger - shorter and circular DNA
- Associated with proteins like - Not associated with any proteins
histones and chromatin to form like histones and chromatin as
chromosomes there is not enough DNA to coil
- Found in nucleus - Found free in the cytoplasm
- Introns found (non coding) so - No introns
splicing is needed - Additional DNA like plasmids
- Additional DNA like mitochondrial
/chloroplast DNA (= prokaryotic)
, CONDENSING/PACKAGING DNA to fit into the nucleus (4m)
1. DNA WRAPS around histones (proteins) and form nucleosomes
2. Nucleosomes are COILED to form chromatin
3. Chromatin is SUPER-COILED to form chromosomes
CHROMOSOME STRUCTURE
- Two replicated copies of the DNA join at the centre by the CENTROMERE
- CHROMATID is each of the thread/arm of chromosome and are identical =
SISTER chromatids
- Diploid cells = paired chromosomes in cells like (somatic body cells which are
homologous chromosomes since one of each comes from a parent) (46)
- Haploid cells = single chromosomes (gametes: sperm, egg cells) (23)
DEFINITIONS FOR THE SECTION
GENE – is the base sequence of DNA that codes for a sequence of amino acids to
make a specific polypeptide, and also code for a functional RNA (tRNA, rRNA)
LOCUS – fixed position on a DNA molecules that a gene occupies
ALLELE – different versions of the same gene, found at the same locus
TRIPLET – a sequence of three DNA base and codes for specific amino acids
(4x4x4 = 64 triplet code gives 64 combinations for a.a)
