gene expression

the process of conerting archived information into moelcules that actually do things in our cell

according to beadly and tatum genes...

-can discover what genes do by making them defective

-one gene one exyme hypthothesis

knockout,null, or loss-of-function alleles

alleles that do not function

one gene one enzyme hypothesis

each gene contains the information needed to make an enzyme

metabolic pathways

an ordered series of chemical rsns that build up or break down a particular molecule

-often each rxn catalyzed by a different enzyme

Genetic Screen

technique for picking certain types of mutants out of many thousands of randmonly generated mutants

Genetic Code Hypothesis

-the sequence of the bases in DNA is a code

-a gene contains the information to specify the s.s. sequence of a protein

Intermediary between Genes and Proteins

RNA

(acts as a link btwn genes and the protein manufacturing center-MANUFACTURING CENTER)

mRNA

carries information from DNA to the site of protein synthesis

RNA polymerase

polymerizes ribonucleotides into strands of RNA (enzyme that catalyzes the synthesis of RNA)

Primers-RNA vs DNA

RNA polymerase does NOT require primer to begin connecting ribonucleotides together to produce a strand of DNA

-DNA does

central dogma

summarizes the flow of information in cells

DNA (codes for) RNA (codes for) protiens

motor/contractile proteins

move the cell itself or cellular cargo

 structural proteins

provide support for the cell or tracks for transporting cargo

peptide hormones

carry signals from cell to cell

membrane transport proteins

conduct specific ions or molecules across the plasma membrane

antibodies/other immune system proteins

provide defense by recognizing and destroying invading viruses and bacteria

Transcription

the process of copying hereditary info in DNA to RNA

(by RNA polymerase)

Translation

process of using the info in nucleic acids to synthesize proteins

-mRNA is translated to protiens (in the ribosomes)

genotype

-determined by the sequence of bases in DNA

phenotype

the product of proteins it produces

How do gene's alleles differ?

-gene's alleles differ in their DNA sequence

(proteins produced by diff alleles of the gene may differ in their a.a. sequence)

2 exceptions to the Central Dogma

-many proteins code for RNA molecules that do not function as mRNAs (they are not translated into proteins)

-Reverse Transcriptase

REverse Transcriptase

enzyme of RNA viruses that can synthesize double stranded DNA from a single stranded RNA template

Genetic Code

-the rules that specify the relationship btwn a sequence of nucleotides in DNA or RNA and the sequence of a.a. in a protein

triplet code

3 base code

Reading Frame

the division of a sequence of DNA or RNA into a particular series of 3 nucleotide codons

(3 possible reading frames for any sequence)

start codon

(AUG)

signals that protein synthesis should begin at the point on the mRNA moleuce

AUG codes for the a.a.-methionine

Stop Codons

UAA, UAG, UGA

-signal that the protein is complete and end the translation process

4 characteristice of the genetic code

1-redundent

2-unambiguous

3-nearly universal

4-is convservative

Redundancy in the genetic code

-all a.a. expet methionine and trypotophan are coded by more than one codon

Unambiguitity in the genetic code

a single codon never codes for more than 1 a.a.

(mult diff codons can code for the same a.a. thought)

universal nature of the genetic code

with a few minor exception all codons specify the same a.a. in all organisms

Conservative nature of the genetic code

when several codons specify the same a.a.

the 2st and 2nd bases in those codons are almost always identical

Mutation

any permanent chainge in an organisms DNA

-modification in a cells info archive (change in genotype)

-creates new alleles

mutation-change in genotype-affect

changes in genotype can change the mRNA codons that are transcribed and the a.a. that are translation

-mutations may lead to changes that affect the primary structure of proteins and thus organism's phenotype

point mutations

-single base change

Beneficial mutations

mutations that INC fitness of the organism

(fitnes=ability to survive and reproduce)

Neutral mutations

if a mutation has no affect on fitness

(normally silent mutations)

Deleterious Mutations

mutations that lower fitness

(most mutations since organisms tend to already be well adapted to its environment)

Silent mutations 

change in nucleotide that does not change a.a. specified my codon

Missense (replacement) mutations

change in nucleotide that changes a.a. specified by codon

-will cause change in primary structure of protein

Nonsense Mutations

change in nucleotide that results in early stop codon (UAA UGA UAG)

-will cause premature termination 

-usually deleterious

Frameshift mutation

-addition or deletion of a nucleotide

-will cause reading frame to be shift massive missive

usually delterious

polyploidy chromosome mutation

change in the number of each type of chromosome present

Aneuploidy Mutation

addition/deletion of a chromasome

Inversion mutation

when chromosome segments become flipped and rejoin

Translocation Mutation

when chromosome segments become attached to a different chromosome

karyotype

the complete set of all chromosomes in a cell