Module 2:Nucleotides and Nucleic Acids Flashcards
What does DNA do ?
DNA holds genetic
information
What does RNA do ?
RNA transfers genetic information from DNA to the ribosomes
Deoxyribonucleic and ribonucleic acid are both what?
polymers of nucleotides
What do nucleotides consist of?
-a pentose sugar
-a nitrogenous organic base
-a phosphate group
What are the components of a DNA nucleotide?
-deoxyribose
-a phosphate group
-one organic base( A T C G )
What are the organic bases ?
adenine , cytosine , guanine , thymine , uracil
What are the components of a RNA nucleotide?
-ribose
-a phosphate group
-one organic base( A U C G )
How do nucleotides join together?
by phosphodiester bonds formed in condensation reactions
What is the structure of DNA?
-its a double helix
-there are 2 polynucleotide chains that are joined together by H bonds between complementary bases
What is the structure of RNA?
-its a relatively short single polynucleotide chain
What is ATP and what does it consist of ?
-adenosine triphosphate is a nucleotide derivative
-consists of ribose , adenine and three phosphate groups
What happens when ATP is hydrolyzed and which enzyme catalyses this reaction?
-energy is released and ATP is broken down into ADP and a phosphate molecule
-ATP hydrolase
What can the inorganic phosphate molecule do ?
-it can phosphorylate other compounds and make them more reactive as a result
What happens when ADP and the inorganic phosphate undergo a condensation reaction and which enzyme catalyses this reaction?
-produces ATP during photosynthesis and respiration
-catalysed by ATP synthase
Why is DNA replication known as semi-conservative?
-because 2 DNA molecules are formed and they each have one original strand and one new strand
What does semi-conservative replication ensure?
-it ensures genetic continuity between generations of cells meaning genetic info is passed on from one generation to the next
What is the first stage of DNA replication?
-the double helix unwinds and the hydrogen bonds between complementary bases break
-this is catalysed by DNA helicase which runs along the back bone of the strands.
-this separates the two strands
What is the second stage of replication
-both strands are used as templates and complementary base pairing occurs between the template strands and free nucleotides in the cytoplasm
What is the final stage of DNA replication
adjacent nucleotides are joined by phosphodiester bonds formed in condensation reactions
-this process is catalysed by DNA polymerase
What is the genetic code?
What is a triplet known as ?
What does each triplet of bases do?
the order of bases on DNA
-consists of triplets of bases
-a codon
-code for a particular amino acid
What type of bonding occurs between amino acids
What do amino acids form?
peptide bonds
long polypeptide chains
What is a gene?
a sequence of bases on a DNA molecule coding for a sequence of amino acids in a
polypeptide chain
NOT ALL OF THE GENOME CODES FOR PROTEINS
what are the non-coding sections of DNA called?
what are the coding sections called?
Introns
Exons
What are the features of the genetic code?
-its NON-OVERLAPPING , meaning each triplet is only read once and triplets don’t share bases
-its DEGENERATE meaning that more than one triplet codes for the same amino acid, this reduces the phenotypic effect of mutations
What is meant by a mutation?
when a mistake in the base sequence occurs
What else does the genetic code contain?
start and stop codons that control protein synthesis
What are the 2 stages of protein synthesis?
transcription
translation
Where does transcription occur and what does it involve?
in the nucleus
involves DNA and mRNA
during transcription a molecule of mRNA is made in the nucleus
What does translation involve?
(name the 2 molecules , where it happens and what is synthesised
mRNA tRNA and ribosomes
during translation amino acids join together to form a polypeptide chain
What is the first two stages of transcription?
What is the name given to the strand that acts as a template?
H bonds between the complementary bases break and the DNA uncoils separating the two strands
One of the DNA strands is used as a template by RNA polymerase to make the
mRNA molecule
the template is called the antisense strand
What are the last two stages of transcription?
Free nucleotides line up by complementary base pairing and adjacent nucleotides
are joined by phosphodiester bonds
This forms a single stranded molecule of mRNA
mRNA then moves out of the nucleus through a pore and attaches to a ribosome in
the cytoplasm
What are the first two stages of translation?
mRNA attaches to a ribosome and transfer RNA collects amino acids from the
cytoplasm and carries them to the ribosome
tRNA attaches itself to mRNA by complementary base pairing( 2 molecule attach to mRNA at a time)
What are the last two stages of translation?
the AA attached to two tRNA molecules join by a peptide bond and the tRNA molecules detach themselves from the AA leaving them behind
the process is repeated which forms a polypeptide chain until a stop codon is reached on mRNA
