genetic information Flashcards
why does the DNA molecule have to be stable
because it has to pass genetic information from one generation to the next
which nitrogen bases are purines
adenine and guanine
double string structures
which nitrogen bases are pyrimidines
thymine and cytosine
single ring structures
how many different types of amino acids are there in living organisms
20
what determines the number ans sequence of amino acids in each polypeptide
DNA sequence
what are 3 features of DNA in prokaryotic cells
short
circular
not associated with proteins
how is DNA in eukaryotic cells different from prokaryotic
very long
linear
associated with proteins
what 2 molecules make up a chromosome in eukaryotic cells what two types
DNA molecule
associated protein- histones
what is the monomer of DNA
nucleotides
what two molecules do genes code for
amino acid sequence of a polypeptide
a functional RNA
what is a gene locus
position of a gene on a map of a chromosome
what are stop codons
- do not code for an amino acid
- if they appear in polypeptide chain then no amino acid would be added
- chain would stop in this place
what is another name for a stop codon
nonsense codon
what does the genetic code being non overlapping mean
each base is only read once in the code
the genetic code is said to be universal what does this mean
the same DNA triplet codes for the same amino acid in all living organisms
what factors cause DNA to mutate
- mutations can occur spontaneously when DNA replicates
- radiation
- chemicals/metals
- biological agents
what is a frame shift mutation
the insertion or deletion of nucleotide bases in numbers that are not multiples of three
why might a deletion mutation have a greater affect if it is near the start of the gene rather than the end of the gene
- it will change the amino acids after the point of mutations
- may create a stop codon and so terminate the polypeptide chain
what % of DNA codes for polypeptides or RNA?
very small 1-2%
microsatellite
- short tandem repeats that consists of 1 to 9 base pairs monomer repeating sequences
- rich with A and T bases
minisatellite
- tandem repeats with a monomer repeat length of 10 to 100 base pairs
- rich with C and G bases
what are the non coding parts of DNA within genes known as
introns
what is the genome of a cell
genetic material of an organism
consists of DNA
includes both genes and the non- codingsequences of DNA/RNA
what is the proteome of a cell
entire set of proteins expressed by a genome, cell, tissue or organism at a certain time
under defined conditions
which enzyme unzips the DNA
DNA helicase
what enzyme is used to covalently join the RNA nucleotides to make mRNA
RNA polymerase
how is mRNA adapted to its function
- small - fit through pore
- contains a series of nucleotides
- unstable molecule - hydrolysed quickly when it is no longer needed
what is a transcription factor
protein that binds to specific DNA sequences
controlling the rate of transcription
how do transcription factors act
- move from cytoplasm to DNA
- binds to specific gene/ binds to promoter
- allows/ blocks binding of RNA polymerase
what is a promoter
a region of DNA that RNA polymerase and the necessary transcription factors bind to
what is an intron
a region of DNA within a gene that does not code for amino acids within a protein
what is an exon
it is a region of DNA within a gene that codes for the amino acids within a protein
what molecule must be hydrolysed to provide the energy needed for the production of the peptide bond
ATP
what two types of molecules are ribosomes made from
rRNA and protein
three stages of translation
stage 1- initiation
stage 2- elongation
stage 3- termination
stage 1 of translation initiation
- A tRNA brings first amino acid into position- anticodon forms Hydrogen bonds with complementary codon
- start codon is AUG so first amino acid always methionine
- the ribosomes stabilises the binding of the tRNA to the mRNA
stage 2 of translation elongation
- tRNA amino acid complexes are held close together by the ribosome: amino acids joined by a peptide bond formed by a condensation reaction
- once amino acid has been attached to the polypeptide chain, the tRNA that carried it there will now go back to the cytoplasm to pick up another amino acid of the same type
stage 3 of translation termination
when ribosome reaches a stop codon, the ribosome mRNA and completed polypeptide chain
ribosomes are connected in groups called
polyribosomes or polysomes
held together by a thin strand of ribosomal RNA
how is a tRNA molecule adapted to its function
- each tRNA has an amino acid binding site, enabling it to carry a specific amino acid in the cytoplasm
- has anticodon complementary to a codon on mRNA- determines order of amino acids in polypeptides
- more stable than mRNA enabling them to pick up another amino acid
what type of bonds are important in secondary structure
hydrogen bonds
what are the names of the 2 types of secondary structure
alpha helix and beta pleated sheets
what are the names of the 3 types of bond present in a tertiary structure
hydrogen, disulfide and ionic bonds
which bond is least likely to break if a protein is denatured
disulfide bonds
which amino acid is often removed from the beginning of a polypeptide chain after translation
methionine
