replication and protein synthesis Flashcards
example of a nucleotide not DNA or RNA
ATP
ATP strucure
ribose adenine and 3 phosphates
DNA structure
sugar base and phosphate
features of DNA molecules
2 strands antiparallel to eachother
double helix
each chain has sugar phosphate backbone with bases at right angles
each chain is a right handed helix
how many rings in purines
2
how many rings in pyrimidines
1
which bases are purines
adenine and guanine
which bases are pyrimidines
cytosine thymine and uracil
which bases make 3 hydrogen bonds
Cytosine and guanine (CGP=CG3)
which bases make 2 hydrogen bonds
adenine thymine and uracil
true or false purines pairs with a purine
false purines always pair with pyrimidines (think about which one shave 2 vs 3 hydrogen bonds)
which enzymes breaks complementary hydrogen bonds in the first step of DNA replication
DNA helicase
which way does leading strand unwind
5’ to 3’
which way does DNA polymerase work
5’ to 3’
how does DNA polymerase work
attaches to single strand and adds one new nucleotide at a time
how does DNA polymerase work on laggin strand
works in opposite direction to unwinding. Copies unwound pieces then goes back to copy next piece creating small fragments called Okazaki fragments
what enzyme sticks nucleotides together and how
DNA ligase makes covalent phosphodiester bonds between nucleotides
how are strands held together before DNA ligase
hydrogen binds between complementary bases
semi conservative replication
DNA molecule is copied to form 2 identical molecules each containing one strand from the original molecule and one newly synthesised strand
how many amino acids are there
20
how many possible combinations of 3 bases are there
4^3 64
different codons can code for the same amino acid what is this called
degenerate/redundant code
first step of protein synthesis
transcription (you must write a speech before you say it)
transcription takes place in the
nucleus
what enzyme is used in transcription
RNA polymerase
how does transcription work
RNA polymerase attaches to beginning of gene, it unwinds the DNA of the gene
DNA helicase unzips the DNA
complementary RNA copy of the template strand is made from free nucleotides and hydrogen bond
RNA polymerase attaches them to each other with phosphodiester bond and hydrogen bond is broken
mRNA leaves through nuclear pore in nuclear envelope
another name for template strand
transcribed strand
which direction does RNA polymerase work in
5’ to 3’
do RNA and DNA polymerase work in the same direction
yes 5’ to 3’
what step is in between transcription and translation
modification/ splicing
how is mRNA modified
RNA splicing. Removing introns from primary transcript and exons are joined together
translation
tRNA transfers amino acids to the ribosome and mRNA is converted/translated into a polypeptide chain
where does translation take place
ribosome
what are ribosomes made out of
small and large subunit made of rRNA and protein
when an mRNA molecule arrives at a ribosome where doe sit enter
groove between 2 subunits
how many tRNA can fit on ribosome at any time
2
what bond is formed between amino acids
peptide bond (before the anticodon and codon were hydrogen bonded)
2 types of mutations
gene and chromosome
chromosome mutation
a random and unpredictable change in the structure or number of chromosomes in a cell
gene mutation
change in base sequence in part of a DNA molecule
substitution
base replaced by a different base
deletion
base is lost and not replaced
insertion
base is added
deletion and insertion are
frame shift mutations- incorrect reading of the sequence of triplets in the genetic code due to a frame shift in the reading frame
