Lecture 2 Flashcards
What are the three main functions of DNA
- Store info
- Replicate faithfully (preserve info)
- Ha s ability to mutate (variability of info)
Gene
Entire dna sewuence needed to make a functional protein or RNA (the info neccessary to do this)
DNA carries
1) coding for proteins and rna
2) regulatory sequences: act as signals or binding sites
Gene expression
Process by which info in gene is turned into a fucntion unit
What is another name of the template strand
Antisense strand
What is another name ofr the coding strand
RNA like strand or sense strand
What is special about DNA shape
it is a double helix
strands have polarity
-5’ end has a phosphate group
3’ end has a hydroxyl group )oh)
they are complimentary (bases pair up)
they are antiparallel (one runs 5’ to 3’, other 3’to 5’)
What does it mean by dna replicates faithfully
2 parent strands of the helix seperate and each serve as a template for synthesis of a new daughter strand by complimentary base pairing
Is repliaction of dna conservative or semi conservative
Semi conservative:
because one strand remains the same (is conserved, the parent one) and one is newly synthesized
Semiconservaative model vs conservative vs dispersive
Semiconserivative was proved by meselson and stahl in 1958 that this was what dna did
outcome means each of the two new helixes have one new and one parent
conservative:
theory that the og strand will remain in tact after replication resulting in one helix that is the same as parent (consists of boht og strands )and the other would be made up of two newly syntehsized strands
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Dispersive:
Suggests that og dna is broken into pieces and the newly synthesized material is disperesed randomly throughout the og strands so new daughter strands will be a mix of 2 strands with both the new and old on each strand
How did they test for this
1) Replicated ecoli in heavy nitrogen (N15)
2) moved it to a contaoner of N14 which was lighter in density
3) allowed for growth
4) put into centrifuge to seperate the strands
After the first one they found that all the dna was at a single band level of an intermediate density (N14 and N15) so ruled out conservative theory cuz then it would have two bands, one at 15 and one at 14, no intermediate
replicated again and seperated and found that some were at N14/N14 while a second band was at N14/N15, so ruled out dispersive since dispersive would only still have. a mix at n14/15 (only a single band)
So what kind of replication is dna
Semiconservative: two parents dna strands seperate and become a template for the daughter strands, and make new daugher strand from complimentary vase pairing
OUTCOME: information is preserved
What are the types of mutations
1) Missense: a base is swapped for another base
2)Nonsense: A base is swapped for another, leading to the production of a stop codon
3) Frameshift: A base is added in or taken out resulting in a change of frme
4) Silent mutation: BAse is changed but results in same amino acid
What is the importance of mutations
1) Formation of new alleles
-results in either an altered product
-no product
-altered regulation of product expression
All of this + selection leads to evolution
What leads to evolution
Mutations + Selection
