Nucleotides And Nucleic Acids Flashcards
DNA replication
correct statements:
- DNA molecule unwinds
- Hydrogen bonds between base pairs break
- Hydrogen bonds form between conplementary bases
- DNA plymerase links the new nucleotides
- Covalent bonds form between the phosphates of one nucleotide and the pentose sugar of the next nucleotide
Intraspecific
Variation between individuals of same species
No of DNA nucleotide bases that code for a single amono acid
3
Max of 64 different bas combinations in DNA that could each code for an amino acid
How is this no of combinations calculated
4^3
20 different amino acids commonly used for protein synthesis
In theory–> 20 different base combinations
Explan uses of remaining 44 combinations
Several truplets/codons code for one amino acid
Some are used as start/stop/termination
Mutation may not result in change in amino acid/have a neutral effect/ result in silent mutation
Which nucleitide bases are common to DNA and RNA
Adenine
Cytosine
Guanine
Describe how a nucleotide base sequence in a gene is used to synthesise a polypeptide
Transcription:
- DNA transcribed/copied into mRNA
- free/activated RNA nucleotides
- line up bu complementary base pairing
- to template DNA strand
- catalyses by RNA polymerase
Translation:
- mRNA moves to ribosomes
- tRNA molecules bind to mRNA
- anticodons bind to codons
- specific amino acid attached to tRNA
- formation of peptide bond between amino acids
Cytosine and guanine
3 hydrogen bonds
Adenine and thymine
2 hydrogen bonds
Purines
2 rings
Adenine
AND
Guanine
Pyrimidines
1 ring
Thymine
AND
Cytosine
Gene
Section of DNA that codes for the production of a polypeptide
RNA
Molecule that copies gene and carries the information to a ribosome
2 ways in which diagram of RNA molecule would differ from DNA molecule
- RNA usually single stranded
2. Uracil instead of Thymine
Explain why DNA replication is considered to be semi-conservative
One strand from original DNA
AND
one strand form newly formed DNA strand
An original strand/polynucleotide,acts as template (for new strand)
Explain why complementary base pairing is important in DNA replication
DNA can be replicated witjout error/same sequence if nucleotides is produced
Reduces occurence of mutations
Allows reformation of hydrigen bonds
Bands
Bacteria griwn in food source that contained heavy isotope of 15N. After long time, bacterial DNA contained only the heavy form of nitrogen.
Some of bacteria transferred to another food source containing only normal,lighter form of nitrogen 14N
15N–>14N
DNA extracted from bacteria and centrifuged (heavier, more dense molecules tend to settle nearer the bottom of tube)
R1- DNA ectracted from bacteria that had been transferred form 15N to 14N and left ling enough for DNA to replicate once only.
R2-left long enough for DNA to replicate twice
Rings-after centrifuging
Band in tube R1 higher than band in 15N and lower than band in 14N tube
One band in R2 clearly at same height as that in tube R1 and one band in R2 clearly at same height as that in the 14N tube.
3 precautions that meselson and stahl would have taken in order to ensure that the centrifugation part of their investigation produced valid results
- same concentration of sugar solution in each tube
- Same volume of mixture/solution/sugar solution in each tube
- Spin all tubes at same speed
- spin all tubes for same length of time
Group of carbohydrate molecules of which glucose is a part of
Monosaccardides
Syate and explain 2 ways in which glucose molecule is well-suited to its function in living organism
- Soluble so can be easily transported/carried around organism
- small molecule so can be transported/diffuse across cell membranes
- easily/quickly respired
- molecules can join to produce disaccharides (condensation)
Describe structural relationship between deoxyribose and the other components of the DNA molecule
- part of nucleotide
- bonded to nitrogenous base e.g.adenine and phosphate group
- phosphate jpined to C5 and C3
- Deoxyribose is part of backbone of DNA
- linking with second phosphate on adjacent nucleotide
- nucleotide is monomer of polynucleotide/DNA
Cellulose structure
Cellulose molecule is insolubel
It contains only the elements carbon, hydrogen and oxygen
It is made up of b-glucose subunits
Glucose subunits linked by 1-4 glycosidic bonds formed by condensation readctions
Many long chains
Branches/straight chains
