Nucleotides Flashcards
what elements do all nucleotides contain?
C, H, N, O, P
What is the function of DNA?
it is used to store genetic information
What is the function of RNA?
it is used to make proteins from the instructions in the DNA
What are the differences between a DNA nucleotide and a RNA nucleotide?
a DNA nucleotide has a deoxyribose sugar whereas a RNA nucleotide has a ribose sugar
A DNA nucleotide contains the bases, A,C,T,G whereas a RNA nucleotide contains the bases A,C,U,G.
What is the difference between a purine and a pyrimidine?
a purine base contains two carbon-nitrogen rings joined together whereas a pyrimidine base only has one carbon-nitrogen ring.
A and G are purines
C and T and U are pyrimidines
what is a phosphorylated nucleotide?
a nucleotide that has more than one phosphate group
What is the chain of sugars and phosphates known as?
a sugar-phosphate backbone
What is the structure of DNA?
it is composed of two polynucleotide strands joined together to form a double helix shape
the two polynucleotide strands are anti-parallel which means they run in opposite directions
the two strands are joint together by hydrogen bonds between the bases
two hydrogen bonds between A and T
three hydrogen bonds between C and G.
What is complimentary base pairing?
each base can only pair up with one particular partner
How does DNA replicate?
step 1: DNA helicase breaks the hydrogen bonds between bases causing the helix to unzip to form two single strands
Step 2: each original single strand acts as a template for a new strand. Free floating DNA nucleotides join to the exposed bases on each original template strand by complimentary base pairing.
Step 3: the nucleotides on the strand are joined together by the enzyme DNA polymerase. This forms the sugar-phosphate backbone. Hydrogen bonds form between the bases on the original and new strand.
Why is DNA replication called semi conservative?
the new molecule contains one new strand and one original strand.
Why does DNA replication have to be accurate?
to make sure genetic information is conserved each time the DNA is replicated
What is a mutation?
a mutation is any change to the DNA base sequence and can alter the sequence of amino acids in a protein.
What is a gene?
a sequence of DNA nucleotides that codes for a polypeptide
What is the genetic code?
the sequence of codons in mRNA/DNA which codes for a specific amino acid.
What is transcription?
DNA is too large to move out of the nucleus, so a section is copied into mRNA. This process is called transcription.
What is translation?
this is where the mRNA leaves the nucleus and joins with a ribosome in the cytoplasm, where it can be used to synthesize a protein.
What is the structure of RNA?
a single polynucleotide strand that contains uracil as a base instead of thymine.
What are the three types of RNA?
mRNA (messenger)
tRNA (transfer)
rRNA (ribosomal)
What is the structure and function of mRNA?
it is a single polynucleotide strand and is made in the nucleus during transcription
it carries the genetic code from the DNA in the nucleus to the cytoplasm, where it is used to make a protein using translation.
What is the structure and function of tRNA?
it is a single polynucleotide strand that’s folded into a clover shape
hydrogen bonds between specific base pairs hold the shape in this molecule
every tRNA molecule has a specific sequence of three bases at one end called an anti-codon.
they also have an amino acid binding site at the other end
it is found in the cytoplasm where it is involved with translation by carrying the amino acids that are used to make proteins to the ribosome.
What is the structure and function of rRNA?
rRNA forms the two subunits in a ribosome along with proteins. The ribosome moves along the mRNA strand during protein synthesis
the rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids.
Explain the process od transcription.
RNA polymerase attaches to the DNA at the start of a gene causing the hydrogen bonds between the two DNA strands to break. This separates the strands and the DNA unzips. One of the strands is then used to make an mRNA copy
step 2: RNA polymerase lines up free RNA nucleotides alongside the template strand. The mRNA strand ends up being a complimentary copy of the DNA template strand. Once they are all paired up, they are joint together forming a mRNA molecule
step 3: RNA polymerase moves down the DNA strand, separating the strands and assembling the mRNA strand. The hydrogen bonds between the uncoiled strands of DNA re-form once the DNA polymerase has passed by
step 4: When RNA polymerase reaches a stop codon. it stops making mRNA and detaches from the DNA. The mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm.
Explain the process of translation.
the mRNA attaches itself to a ribosome and tRNA molecules carry the amino acids to the ribosome.
step 2; a tRNA molecule, with an anti codon that is complimentary to the start codon on the mRNA attaches to the mRNA by complimentary base pairing. A second tRNA molecule attaches itself to the next codon on the mRNA in the same way.
step 3: rRNA catalyses the formation of peptide bonds between the two amino acids attached to the tRNA molecules. The first tRNA molecule moves away, leaving its amino acid behind.
step 4: a third tRNA molecule binds to the next codon on the mRNA. Its amino acid bionds to the first two and the second tRNA molecule moves away. This process continues, producing a chain of linked amino acids until there is a stop codon on the mRNA molecule.
step 4: the polypeptide chain then moves away from the ribosome and translation is complete.
