DNA and protein synthesis Flashcards
gene
base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functioning RNA
genome
complete set of genes present in a cell
where is a full genome present
every cell of an organism
where is a genome expressed
not every gene is expressed in every cell, which genes are expressed depends on the type of cell
what controls what genes are expressed
the type of cell
proteome
full range of proteins a cell is able to produce
is genome or proteome typically larger
proteome
why is proteome typically larger than the genome
-large amount of post-transnational modification of proteins
-each gene is also capable of producing multiple different proteins by alternative splicing
similarities of DNA and RNA
-both polynucleotide as made of many nucleotide together in a long chain
-both contain nitrogenous bases adenine, guanine and cytosine
what is similar about chain of DNA and RNA
both polynucleotide as made of many nucleotide linked together in a long chain
similarities of bases in DNA and RNA
both have adenine, guanine and thymine
differences in DNA and RNA
-DNA contains nitrogenous thymine by RNA contains nitrogenous uracil
-RNA has pentose sugar ribose and DNA has pentose sugar deoxyribse
difference in nitrogenous based of DNA and RNA
DNA has thymine and RNA has uracil
difference of pentose sugars of DNA and RNA
DNA has deocyribose and RNA has ribose
strand of DNA
double-stranded
strand of RNA
single-stranded
structure of RNA
-ribose (pentose sugar)
-phosphate group
-nitrogenous base of A,U,C,G
structure of DNA
-deoxyribose (pentose suagr)
-phosphate group
-nitrogenous base A,T,C,G
what is each RNA polynucleotide strand made of
alternating ribose sugars and phosphate groups linked together, with the nitrogenous bases of each nucleotide projecting out sideways from the single-stranded RNA molecule
phosphodiester bonds
the sugar-phosphate bonds between different nucleotides in the same strand are covalent bonds
what do phosphodiester bonds between nucleotides form
the sugar-phosphate backbone of the RNA polynucleotide strand
what do the phosphodiester bonds link
link the 5-carbon of one ribose sugar molecule to the phosphate group from the same nucleotide, which itself is kinked by another phosphodiester bond to the 3-carbon of the ribose sugar of the next molecule in the strand
strand of mRNA
single stranded
what is mRNA made of
sugar-phosphate backbone and exposed unpaired bases (A,U,C,G)
tRNA strands
single-stranded
what is tRNA made of
sugar-phosphate backbone
tRNA shape
folded or clover leaf shape as hydrogen bonds between some complementary base pairs
where do amino acids bind to tRNA
specific region of the molecule
what is the anticodon in tRNA complementary to
specific codon on mRNA molecule
what is a gene
base sequence of DNA that codes for the amino acids sequence of a polypeptide or functional RNA molecule
what 2 stages do protein synthesis occurs in
transcription and translation
what is transcription
DNA is transcribed and an mRNA molecule if produced
where does transcription occur
in nucleus of the cell
outline transcription
-occurs in nucleus of the cell
-part of the DNA molecule unwinds (breaks hydrogen bonds between complementary base pairs break) this is catalysed by DNA helicase
-this exposes the gene to be transcribed
-a complementary copy of the code from the gene is made by building a single-stranded nucleic acid molecule know as mRNA
-free activated RNA nucleotides pair up via hydrogen bonds with their complementary bases on one strand of the unzipped DNA molecule
-the sugar-phosphate bonds of these RNA nucleotides are then bonded together by enzyme RNA polymerase to form sugar-phosphate backbone of mRNA molecule
-when the gene has been transcribed (when the mRNA molecule is complete) the hydrogen bonds between the mRNA and DNA strand break and double-stranded DNA molecule re-forms
-the mRNA molecule leaves the nucleus via pores in the nuclear envelope
unwinding of DNA
Part of DNA molecule unwinds breaking hydrogen bonds between complementary base pairs which is catalysed by DNA helicase
what does unwinding of DNA expose
exposes the gene to be transcribed
what happens once gene is exposed in transcription
complementary copy of code from gene is made by building a single-stranded nucleic acid molecule known as mRNA
what do the free floating RNA nucleotides do
free activated RNA nucleotides pair up via hydrogen bonds with complementary bases on one strand of the unzipped DNA molecule
how is sugar-phosphate backbone form
-the sugar-phosphate groups of these RNA nucleotides are then bonded together by enzyme RNA polymerase to form the sugar-phosphate backbone of the mRNA molecule
what happens in translation when the gene has been transcribed
when the gene has been transcribed the hydrogen bods between the mRNA and DNA strands break and the double-stranded DNA molecule re-forms
what happens once the mRNA molecule is done
the mRNA molecule leaves the nucleus via pores in the nuclear envelope
what is the DNA molecule not transcribed called
non-template strand
what is the unzipped strand called
template strand
where can non-coding DNA be found
-between genes as non-coding repeats
-within genes as introns
what type of DNA has non-coding regions
eukaryotic
what of the gene is transcribed and what does it make
pre-mRNA which contain all introns and exons
what happens when pre-mRNA has splicing
-non-coding sections are removed
-coding sections are joined together
-the resulting mRNA molecules carriers only the coding sequences of the gene
-mRNA contains only exons and exists the nucleus before joining a ribosome for translation
what is another way exons can be spliced
through alternative splicing
what does alternative splicing mean
single eukaryotic gene can code for more than one polypeptide chain, this is part of the reason why proteome is much bigger than the genome
what is translation
mRNA is translated and an amino acid sequence is produced
where does translation occur
cytoplasm of the cell
outline translation
-occurs in cytoplasm of the cell
-after leaving nucleus, the mRNA molecule attaches to a ribosme
-in cytoplasm there are free molecules of tRNA
-these tRNA molecules have a triplet of unpaired bases at one end (anticodon) and a region where a specific amino acid can attach to the other
-there are at least 20 different tRNA molecules, each with a specific anticodon and specific amino acid binding site
-the tRNA molecules bind with their specific amino acids (in cytoplasm) and bring them to the molecule in the ribosome
-the triplet of bases (anticodon) on each tRNA molecule pairs with a complementary triplet (codon) on mRNA molecule
-two tRNA molecules fit onto the ribosome at any one time, bringing the amino acid they are carrying side by side
-a peptide bond is formed between the 2 amino acids, the formation of a peptide bond between amino acids requires energy in the form of ATP, the ATP needed for translation is provided by the mitochondria within the cell
-this process continues until a stop codon on the mRNA molecule is reached, this cats as a signal for translation to stop and at this point the amino acid chain coded for by the mRNA molecule is complete
-this amino acid chain then form the final polypeptide
what happens to mRNA molecule after leaving nucleus
mRNA attaches to a ribosome
what RNA is free floating in cytoplasm
free molecules of tRNA
tRNA molecules binding sites
have a triplet of unpaired bases at one end (anticodon) and a region where a specific amino acids can attach at the other
how many different tRNA molecules are there
at least 20
tRNA binding
tRNA molecules bind with their specific amino acids (in cytoplasm) and bring them to the mRNA molecule on the ribosome
tRNA anticodon binding
the triplet of bases (anticodon) on each tRNA molecule pairs with complementary triplet (codon) on the mRNA molecule
how many tRNA molecules can fit onto the ribsome at any one time
2, bringing the amino acid they are carrying side by side
peptide bond formed between amino acids requires
-formation of a peptide bond between amino acids requires energy in the form of ATP
-the ATP needed for translation is provided by the mitochondria within the cell
when does translation stop
when as stop codon is reached
what is a stop codon a signal for
signal for translation to stop and at this point the amino acids chain coded for by the mRNA molecule is complete
what does the amino acid chain formed from translation form
the final polypeptide
what is a triplet
sequence of 3 DNA bases that codes for a specific amino acid
what is a codon
sequence of 3 mRNA bases that codes for a specific amino acid
where is codon transcribed from
triplet
what is codon complementary to
the triplet
what is an anticodon
sequence of 3 tRNA bases that are complementary to a codon
how many codons can the 4 bases in RNA form
64
what does genetic code is degenerate mean
-multiple mRNA codons can encode the same amino acid
what 3 features does DNA have
-degenerate
-non overlapping
-universal
what does degenerate code mean for mutations
change in genetic code doesn’t necessarily result in a change the amino acid sequence
what do START codons do
mark the start if the protein and therefore initiate the process of translation from the right location (AUG which is methionine in eukaryotic cells)
what do STOP codons do
casue translation to terminate at the ends of the protein and do not code for any amino acids
what does non-overlapping genetic code mean
each base is only read once in the codon its part of
how can number of amino acids be determined from number of coding mRNA nucleotides
divide by 3 and -1 (for stop codon)
how to work out number of mRNA nucleotides from number of amino acids
multiply by 3 and add 3 (for stop codon)
