2.1.3- Nucleotides + Nucleic Acids Flashcards
what is a nucleotide?
a monomer from which nucleic acids are made?
what are the 5 elements are nucleic acids made from?
- carbon
- oxygen
- hydrogen
- nitrogen
- phosphorus
what are nucleotides made up of?
- phosphate group
- sugar
- base
what are the two different types of nucleic acids?
- DNA
- RNA
what are the 4 differences between DNA + mRNA?
- DNA=double-stranded, while mRNA= single-stranded
- dna contains deoxyribose, while mrna contains ribose
- dna contains thymine, whereas mrna contains uracil
- mrna is less stable than dna due to having exposed bases + the fact that uracil is easier to degrade.
what type of pentose sugar is found in DNA + mRNA?
- DNA= deoxyribose
- mRNA= ribose
what is a purine?
a class of nitrogenous bases that are made up of 2 rings that Adenine + Guanine are members of.
what is a pyramidine?
a class of nitrogenous bases made up of a single ring, cytosine, thymine and uracil are members.
what bond is formed between 2 nucleotides (polynucleotides)?
- PHOSPHODIESTER BOND
- between the phosphate group (5th carbon) +the hydroxyl group (3rd carbon)
- condensation reaction builds, while hydrolysis reaction breaks them down.
how do you write the numbers of a phosphodiester bond?
5”,3”
what is a phosphorylated nucleotide?
The process of introducing one or more phosphate groups into a nucleotide to produce a phosphorylated nucleoside.
what are the 2 examples of phosphorylated nucleotides?
- ADP
- ATP
what is the structure of ATP?
- adenine base
- ribose sugar
- 3 phosphate groups
what does ATP do?
- provides energy, so that cells can synthesise, transport + move
- it is released through hydrolysis
what does ATP break down into?
- inorganic phosphate ion
- ADP
- energy
what is the structure of ADP?
- base
- sugar
- two phosphate groups
what is the structure of DNA like?
- very long, so can store increased amounts of info
- base-pairing rules, easy to replicate info
- double helix, stable molecule, where info is stored safely.
how is DNA formed?
-hydrogen bonding between complementary base pairs on 2 anti-parallel DNA polynucleotides
what are the two complementary base pairs in DNA, and how many hydrogen bonds do they form?
- Adenine + Thymine = forms 2 hydrogen bonds
- Cytosine + Guanine = forms 3 hydrogen bonds
what bases are purines?
- adenine
- guanine
what bases are pyramidines?
- cytosine
- thymine
what is a double-stranded/double helix DNA?
- 2 single strands of DNA twist around each other forming a double-helix
- this helix is held by hydrogen bonds between nitrogenous bases on different strands
- it is anti-parallel
how many bases are in DNA and how many codons does this then make?
- 4 bases = A-T, C-G
- makes 64 different codons
what is the function of DNA?
- holds genetic info
- codes for the primary structure of proteins
- store these codes, called genes
what is the definition of GENES?
a sequence of nucleotides that code for a polypeptide.
what is single-stranded DNA?
a long chain of nucleotides
what is SEMI-CONSERVATIVE DNA REPLICATION?
when half of the parent strand is conserved
what is the first stage of semi-conservative replication?
- DNA helicase unzips DNA by breaking hydrogen bonds between complementary bases.
- helicase = enzyme
what is the second stage of semi-conservative replication?
- the free DNA nucleotides become attracted to the exposed bases by complementary base pairing
- the free strands act as templates
what is the third stage of semi-conservative replication?
-free nucleotides join by phosphodiester bonds by DNA polymerase (enzyme) to form a phosphate sugar backbone.
what is the fourth stage of semi-conservative replication?
-each DNA molecule is then made up of one OLD strand, and one NEW strand of DNA.
what is the importance of semi-conservative replication?
- it conserves genetic information with accuracy.
- prepares cells for mitosis
what are the 3 types of mutations in the base sequence?
- base deletion (the loss of genetic material)
- insertion (the addition of genetic material)
- substitution (where one base pair is replaced with another base pair)
what does generate coding mean?
when amino acids have more than one corresponding codon
what does degenerate coding mean?
when amino acids have more than one corresponding codon
what are INTRONS?
the non-coding sections of DNA
what are EXONS?
the coding regions of DNA.
what are the 3 features of the genetic code?
-it is non-overlapping (each triplet is read only once, with triplets not sharing bases)
-it is degenerate (more than one triplet codes for the
same amino acids, reducing phenotypic effect of mutations).
-contains start and stop codons (which start/stop protein synthesis).
what can mutations cause?
phenotypic effects
what can mutations cause?
phenotypic effects
- production of sticky mucus and causes cystic fibrosis
- sickle cell anaemia
what do mutations of the base sequence of DNA cause?
- alters the amino acid sequence
- alters the proteins, so has many effects.
what is nucleic acid transcription?
the process of copying + transporting genes out of the nucleus and into the ribosomes, to produce RNA
what is the first stage of transcription?
-part of the DNA that contains the genes unzips when hydrogen bonds between two strands break
what are the 2nd and 3rd stages of transcription
- complementary free RNA nucleotides line up opposite the anti-sense strand, acting as a template.
- these then join by phosphodiester bonds to create a single-stranded mRNA
what is the last stage of transcription?
- it stops at the end of the gene, with mRNA then moving out of the nucleus through a pore and attaching to a ribosome in the cytoplasm
- double helix reforms
what is an anti-sense strand?
a complementary copy of the sense strand that doesn’t code for a protein but acts as a template.
what happens during translation?
amino acids join together to form polypeptide chains
what is the first stage of translation?
-mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carries them to the ribosome.
what is the second stage of translation?
- tRNA attaches itself to mRNA by complementary base pairing
- two molecules attach to mRNA at a time
what is the third stage of translation?
-the amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach themselves from the amino acids, leaving them behind
what is the last stage of translation?
-this process is repeated, leading to the formation of a polypeptide chain until a stop codon is reached on mRNA and ends the process of protein synthesis
what is a sense strand?
a strand that contains a code for protein to be synthesised.
what does the condensation of nucleotides form?
- a long/strong phosphate-sugar backbone
- base that is attached to sugars
