GENETIC CODE, GENES, GENOMIC Flashcards
WHAT ARE THE 4 MOST IMPORTANT ASPECTS OF DNA?
- Lasting and stable
- Capability of change during evolution
- Capability of reproducing
- Easily available for realisation (expression)
WHAT IS GENETIC INFORMATION?
internal information of the cell passed on from parental cell to daughter cell
WHAT IS A GENEOPHORE?
GIVE SOME EXAMPLES.
it is a carrier of genetic information
-prokaryotes and eukaryotes = DNA
-viruses = RNA
-cytoplasm geneophore = plasmids (not vital for the functioning of the cell)
WHAT IS THE FUNCTION OF CHROMOSOMES?
carry large amounts of DNA
WHAT IS THE GENETIC CODE?
RULE = base sequence determines which corresponding amino acid is added
-genetic information is saved as a sequence of individual bases and codes the sequence of amino acids of the protein
-universal
WHAT IS THE GENETIC CODE BASED ON?
triplets
WHAT IS THE CODON?
a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule
HOW MANY COMBINATIONS OF TRIPLETS ARE THERE?
4 bases (A, G, C, T) → 64 (4^3) combinations of triplets (codons)
HOW MANY PROTEOIGENIC AMINO ACIDS ARE THERE?
20 (21 selenocysteine)
WHAT DOES THE GENETIC CODE BEING REDUNANT MEAN?
IS IT GOOD?
the genetic code is redundant as there are more available combinations of triplets than there are coded amino acids
-this is good as it means that there is a lower chance of mistakes occurring
WHAT ARE THE STOP CODONS?
UAA, UAG, UGA
WHAT IS THE INITIATION CODON?
AUG = Methionine
WHAT IS DEGENERACY?
once protein is made one cannot get the amino acid sequence from it
WHAT IS MEANT BY THE READING FRAME?
there are 3 possible ways of reading the sequence of triplets
WHAT IS A GENE?
functional segment of DNA which which encodes a single polypeptide chain or a single strand of RNA
WHAT IS A GENE LOCUS?
the position of the gene on the chromosome or DNA sequence
WHAT IS AN EXON?
coding section
WHAT IS AN INTRON?
non coding section
WHAT ARE PROMOTORS?
regulatory regions of genes
-specific genes regulating gene expression bind to them
-not transcribed and do not encode proteins or RNA
-lay infront of their own gene and contain introns + exons
-binding site is recognised by RNA polymerase and transcription begins
HOW ARE GENES ARRANGED IN DNA?
anti-parallel
WHAT IS THE FUNCTION OF STRUCTURAL GENES?
they encode proteins
WHAT IS THE FUNCTION OF RNA GENES?
encode all types of RNA, except mRNA
HOW MANY BASE PAIRS DOES THE HUMAN GENOME CONSIST OF?
3x10^4
WHAT IS THE STRUCTURE OF THE PROKARYOTIC GENE?
-only uninterrupted DNA sequence which encodes corresponding polypeptide chain
-ORFs are often grouped into a polycistronic operon under the control of a shared set of regulatory sequences. These ORFs are all transcribed onto the same mRNA and so
are co-regulated and often serve related functions, only possible in prokaryotes because their transcription and translation take place at
the same time and in the same subcellular location
-Each ORF typically has its own ribosome
binding site (RBS) so that ribosomes simultaneously translate ORFs on the same mRNA
-The operator sequence next to the promoter is the main regulatory element in prokaryotes. Repressor proteins bound to the operator sequence physically obstructs the RNA polymerase enzyme, preventing transcription
(ORF = open reading frame)
WHAT IS THE STRUCTURE OF THE EUKARYOTIC GENE?
-more regulatory elements to control gene expression compared to prokaryotes
-exon and intron regions
-post-transcriptional modification of pre-mRNAs to produce mature mRNA ready for translation into protein
-Eukaryotic post-transcriptional processing also adds a 5’ cap to the start of the mRNA and
a poly-adenosine tail to the end of the mRNA. These additions stabilise the mRNA and direct its transport from the nucleus to the cytoplasm
GIVE EXAMPLES OF NON-GENE DNA
1: REGULATORY GENES: involved in the regulation of gene expression
2: REPETITIVE SEQUENCE: short repeating sequence of unexplained origin
- highly variable and unique for each individual, are therefore used in DNA fingerprinting
3: MOBILE ELEMENTS: do not have a stable position within the DNA sequence
-transposons
4: PSEUDOGENES: genes which lost their function due to the accumulation of mutations
WHAT IS A RETROTRANSPOSON?
A transposition of sequences in DNA that does not originate in the DNA but rather in an mRNA, that is transcribed back into the genomic DNA by reverse transcription
(COPY AND PASTE MECHANISM)
WHAT IS THE GENOME?
the complete set of DNA in a cell
WHERE IS THE GENOME OF THE PROKARYOTIC CELL?
chromosome and possible plasmids
WHERE IS THE GENOME OF THE EUKARYOTIC CELL?
nuclear chromosomes + mitochondrial chromosomes + chloroplast chromosomes (in plants)
-possible plasmids
HOW MANY PROTEIN CODING GENES DOES THE HUMAN GENOME CONSIST OF?
HAPLOID SET = 20 000 - 25 000
T/F: THE NUMBER OF GENES IN AN ORGANISM CORRELATES WITH THE SIZE OF THE GENOME AND ITS COMPLEXITY
false
HOW MANY PROTEIN CODING GENES DOES ECOLI K12 CONSIST OF?
4,315
