DNA GENES AND PROTEIN SYNTHESIS Flashcards
Polypeptide
A chain of amino acids coded by nucleotides that make up the primary structure of a protein.
Nucleotides
Monomers that make up DNA. Contain: pentode sugar, phosphate group and an organic base.
Chromosome
Collection of DNA that codes for a specific part of you, organised in 23 pairs.
Gene
Section of DNA on a chromosome codes for Amino Acids
Allele
Alternative form of the same gene
Locus
Genes fixed position on a chromosome.
Triplet code
3 bases = 1amino acid
There are around 20 amino acids and 4 bases so the actual number of codes are around 64.
Degenerate code
Most amino acids are coded for by more than 1 triplet, this protects against point mutations. Only a few have 1 code (Methionine ATG)
Non overlapping
Each base is only in 1 triplet so it is only read once. This protects against mutation as it would only affect one triplet not 3.
Features of the dna code.
- triplet code
- degenerate code
- non overlapping
Ribosomes in eukaryotes
BIG 80s
Ribosomes in Prokaryotes
Small 70s
DNA in prokaryotes
Shorter and forms a circle, not associated with proteins (histones) so no chromosomes.
DNA in eukaryotes
Longer and linear, associated with proteins (histones) so make chromosomes.
DNA in sub cellular organelles?
Mitochondria and chloroplasts have dna like prokaryotes
Super coiling 1/4
Bundles of tightly coiled dna are found in the nucleus of almost every cell. These are chromosomes.
Super coiling 2/4
Only visible as distinct structures during mitosis/meiosis.
Super coiling 3/4
When they are first visible at the start of division they appear as two threads called CHROMATIDS joined by the CENTROMERE.
Super coiling 4/4
Each thread is called a chromatid as the dna molecule has already replicated to give 2 identical molecules.
Chromosome structure
Each chromosome has 2 short (p) arms and 2 longer (q) arms. The ends of each arm are protected by telomeres.
What is a NUCLEOSOME?
DNA wrapped many times around a histone protein
What is a homologous pair?
different alleles of the same gene
What is diploid and what is Haploid?
Diploid = 2 copies of each chromosome Haploid= 1 copy of each
