Central Dogma of Molecular Biology
Gene Expression How does a cell control the timing and choice of synthesizing a particular protein? A gene is expressed when it is transcribed (a.k.a. turned on or activated)
Ch. 10, Sect. 4 – Protein Synthesis RNA – single stranded –Uracil instead of thymine –Ribose instead of deoxyribose –Shorter than DNA –Folds to form some double-stranded regions (A-U, C-G)
Types of RNA Messenger RNA – carries DNA’s message Ribosomal RNA – makes up ribosomes Transfer RNA – transfers amino acids to a growing protein
Transcription – in the nucleus 1.Initiation – RNA polymerase binds to promoter on DNA; DNA unwinds 2.Elongation – RNA polymerase moves along the DNA, adding complementary free-floating nucleotides 3.Termination – RNA polymerase reaches STOP signal and falls off
Ch. 11, sect. 1: Turning genes on Promoter Region (on DNA) = RNA polymerase binding site (TATA box) Transcription Factors (proteins) – help to position RNA polymerase Transcription process results in a pre- mRNA strand complementary to gene sequence
Pre-mRNA RNA Pre-mRNA contains introns and exons – introns are not translated – exons are translated Spliceosomes cut out the introns and bond the exons together – ** exons are the parts that exit the nucleus as mRNA **
Genetic Code Base sequence determines the protein made Each 3-nucleotide sequence in mRNA = codon –Codes for one particular amino acid (there are 20) or the STOP signal tRNA has a strategically placed anticodon (complementary to codon) –each tRNA holds one particular amino acid
Translation – in cytoplasm Initiation – tRNA+methionine and ribosome attach to mRNA Elongation – Ribosome moves 3 base pairs down the mRNA and docks the next tRNA+AA [peptide bond] –polypeptide grows as the ribosome moves along mRNA Termination – ribosome reaches STOP –All components separate
From DNA to a Physical Trait Scientists mapped DNA Knowing location and sequence of gene can help with cure or treatment
Ch. 12 sect. Genetic Disorders Carcinogen = cancer-causing agent – chemical (components in tobacco smoke) – radiation (UV rays, X-rays) – viral (Human papilloma virus) Mutation = change in base sequence of DNA – germ [passed on to offspring], autosomal [affects organism], lethal [death pre-birth], beneficial [phenotypic change helps organism]
Chromosomal Mutations – During Cell Division Deletion Inversion Translocation Nondisjunction
Point Mutations – occur on a single gene –Substitution (wrong nucleotide) may or may not change the corresponding amino acid –Deletion or insertion results in a frameshift Codons are grouped incorrectly Gene Mutations – During DNA Replication or transcription
Prenatal Genetic Testing Looks for gene markers Amniocentesis – analyzes cells from amniotic fluid Chorionic Villi – tests fetal cells
- Good genes put into a virus - Virus injected into fetus - Virus infects fetus, giving it the good gene
Genetic Modification GMO or no???