What is the differences between RNA & DNA nucleotides?
ribose in RNA, deoxyribose in DNA. Thymine in DNA, uracil in RNA
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What bonds can be found in a nucleotide?
covalent between pentose and phosphate group. hydrogen between bases.
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Which base pairs are 'complementary'?
A&T/U C&G
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Who discovered the structure of DNA?
Crick & Watson. They used cardboard shapes to represent bases, metal rods and sheeting.
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What is semi-conservative replication?
When the DNA strands are separated, new nucleotides are assembled based on the bases of the 'template strand'. One new strand is made and one old strand is kept.
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What where the 2 alternate theories of DNA replication that were rejected?
conservative replication (2 new created from the 2 old) and dispersive replication (each strand has 'bits' of old and new)
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Summarise Meselson and Stahl's evidence for DNA semi-conservative replication
Cultured E.Coli bacteria in 'heavy' 15N nitrogen isotope so the N in bacterial DNA bases was also 15N. Bacteria transferred to lighter 14N isotope. Spun in centrifuge w/ caesium chloride solution (24 hrs). More 'light' band over time & less 'dark'.
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What are histones?
Proteins in eukaryotes that DNA wraps itself around forming the structure known as a nucleosome. DNA is negatively charged & histones are +vely
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What is an exon and intron in DNA?
exon= part of DNA that codes for proteins (less than 2% of DNA). intron= non-coding ('junk' DNA)
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Outline DNA replication (3 stages)
1: Helicase 'unzips' double helix & separates 2 strands by breaking H bonds. 2: DNA polymerase links free nucleotides to template strand via complemetary base pairing. 3: Daughter DNA molecules/ strands each rewind into double helix
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What is transcription?
the copying of a base sequence of a gene, making an RNA molecule that will later code for a protein
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What is translation?
the synthesis of polypeptides on ribosomes using mRNA and tRNA.
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Outline the stages (5) of transcription
1: RNA polymerase separates DNA into 2 strands 2:RNA nucleotides are assembled along 1 strand via complementary base pairing (but uracil -instead of T- with A). 3:nucleotides linked together w/ covalent bonds 4:(m)RNA strand separates 5:DNA rewinds
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Outline the stages (4) of translation
1:mRNA leaves nucleus via pores & binds to site on ribosome 2:complementary anticodons of 2 tRNAs can bind to codons of mRNA at once via H bonds. 3:AAs carried by tRNA bind together (peptide). 4:tRNA moves along until full polypeptide is formed
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What is the genetic code & how is it involved in translation?
The genetic code is a triplet code (3 bases -called a codon- for 1 amino acid). The complementary base pairing of the codons of mRNA & anticodons of tRNA ensure that the correct amino acid sequence is coded for.
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What is the 'sense' strand?
The strand that was not copied from in transcription and that is therefore identical to the mRNA strand produced from the template strand (the ANTISENSE strand)
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What is the benefit of the genetic being universal?
e.g. it means that insulin can be produced in E.coli bacteria and then used to treat diabetes in humans
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Why is the genetic code 'degenerate'?
Because more than 1 codon exists for the coding of most AAs
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What is the polymerase chain reaction (PCR) used for?
Amplifying DNA for forensic analysis (semen, blood, body tissues) or for gene transfer procedures
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Outline the polymerase chain reaction (3 steps, repeated many times)
1: DNA heated to 95 degrees; seperates strands. 2:cooled to 55 degrees. Primers added which tells Taq DNA polymerase where to add bases. 3:Heat to 72 degrees; encourages Taq DNA pol. to begin replication. REPEAT STEPS many times.
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What is Taq DNA polymerase and why must it be used in PCR?
PCR is carried out at high temps to speed up the reaction. Therefore a heat-stable version of DNA polymerase (links free nucleotides to template strand) must be used (Taq DNA pol.). It is obtained from bacterium that lives in hot springs.
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Other cards in this set
Card 2
Front
What is the differences between RNA & DNA nucleotides?
Back
ribose in RNA, deoxyribose in DNA. Thymine in DNA, uracil in RNA
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