1.4 DNA Flashcards
(18 cards)
2 types of nucleotides
purines
pyrimidine
what r purines
a,g
- double ring structure
pyrimidines?
t,c
- single ring structure
how is DNA replicated semi-consevatively
- dna helicase breaks H bonds + unwinds dna molecule into 2 strands - each strand = original strand
- exposed bases act as template and attract free DNA complementary nucleotides bind - as H bonds only form between C-G and A-T
- phosphodiester bonds formed by DNA polymerase bw nucleotides - leading strand = synthesised continuously but lagging strand req DNA ligase to join Okazaki fragments
- new DNA formed - has one og strand + one new strand therefore semiconservative
what is a gene
a sequence of bases on a DNA molecule coding for a
sequence of amino acids in a polypeptide chain
why is genetic code non overlapping rather than overlapping
- bc single mutation in single nucleotide will only aggevt one AA + observations prove this
why is meant by the genetic code being degenerate, why is it good
- a single amino acid may be coded for by more than one codon, how can we tell - bc there exists more triplet codes than AAs
- so mutations less likely to have an effect on organism - so helps maintain structure protein
how is each nucleotide linked, bond name
condensation reaction
phosphodiester bond
whats the 5’ end and whats the 3’ end
5’ = phosphate sticking out
3’ = ribose sticking out
3 dif bw rna + dna
- rna = ss
- rna = ribose not deoxyribose
- rna = uracil not thymine
transcription process
- DNA strands separate - antisense used as template for mRNA
- activated RNA nucleotides bind, H bonds form
- RNA polymerase synthesises mRNA by forming phosphodiester bonds
is mRNA copy of sense or antisense
SENSE
translation process
- mRNA moves out thru nuclear pores + binds to ribosome
- ribosome moves along mRNA strand. it will read codon at a time and then corresponding tRNA attached to specific AA will be selected to bind
- tRNA anticodon binds to mRNA codon
- peptide bonds form between AA
- repeats till stop codon reached
- process involves start/stop codons
structure of TRNA, where’s it found?
FREE IN CYTOPLASM
clover shape held tg by H bonds
- 3 complementary bases at bottom = anticodon
- 3 complementary bases at top = AA bonding sitee
what r 3 gene mutations
base deletions
base insertions
substitutions
what r chromosomal mutations
- changes in pos of genes within c’some
Understand the effect of point mutations on amino acid sequences, as
illustrated by sickle cell anaemia in humans.
sickle cell affects protein chains making haemoglobin - substituition -> alters nature of protein
- haemoglobin molecules stick tg to form rigid rods -> RBC = sickle shape so dont carry O2 efficiently + block smallest blood vessels -> severe pain/death
role of ribosome in protein synthesis
translation - to hold tRNA TO mRNA while peptide bonds form to join AA together
