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Chapter 17 Gene Expression - Coggle Diagram
Chapter 17 Gene Expression
flow of genetic information
traits are determined by genes
albinism is determined by a recessive allele of a pigmentation gene
genes come in a specific form of nucleotides called genetic material
faulty versions of key proteins are what cause defects like albinism, because the information the gene contains is incorrect
the DNA in an organism leads to specific traits by dictating the synthesis in protein synthesis
proteins are links between genotypes and phenotypes
gene expression is when DNA directs the synthesis of proteins
expression of genes that code for proteins are in both transcription and translation
transcription- synthesis of RNA complementary to a template strand of DNA
translation- synthesis o fa polypeptide who's amino acid sequence is specified by the nucleotide sequence in mRNA
codon s are encoded genetic information as a sequence of non overlapping nucleotide triplets
if it is in mRNA it is either translated into amino acid or 0serves as a stop signal
1902- Archibald was first to suggest genes dictate phenotypes through enzymes
Beadle and Tatum found studies that mutant strains of neurospora led to the one gene to one polypeptide hypothesis
Transcription is a DNA directed synthesis of RNA
RNA synthesis is categorized into. RNA polymer
links together RNA nucleotides complementary to a DNA template strand
follows same base pairs as DNA replication , except that in RNA uracil subs for thymine
transcription has three stages:
initiation, elongation, and termination
promoter, includes TATA box in eukaryotes establishes where RNA synthesis is initiated
transcription factors help eukaryotic RNA polymerase recognize promoter sequences forming a transcription initiation complex
termination differs in bacteria and eukaryotes
most eukaryotes are split based on whether they have introns interspersed among the exons
in DNA splicing, introns are removed and exons are joined, splicing is carried out by spliceosomers, but in this case RNA alone catalyzes its own splicing
the catalytic ability of some RNA molecules called ribosomes derive from the inherent properties of RNA
tne presence of introns allows for alternative RNA splicing
Translation is the RNA directed synthesis of a polypeptide
cells translate an mRNA message into protein with the help of transfer RNA
after being bound to specific amino acids with aminoacyl-tRNA synthetase, tRNA lines up using anticodon at the complementary codon on mRNA
ribosomes are made of ribosomal RNA and proteins, facilitates this coupling with binding sites for mRNA and tRNA
ribosomes coordinate the three stages of translation (initiation, elongation, and termination)
formation of peptides bonds between amino acids is catalyzed by rRNA as tRNA move through the A and P sites and leave through the E site
after translation, proteins may be modified by cleavage or by attachment sugars, lipids, phosphates, or other chemicals
free ribosomes in the cytosol initiate synthesis of all proteins, however proteins with signal peptides are synthesized inside of the ER
genes can be transcribed by multiple RNA polymerases simultaneously
single mRNA molecule can be translated by a miner of ribosomes forming a polyribosome
in bacteria. these processes are copied but in eukaryotes they separate in space and time by nuclear membrane
mutation of one or less nucleotides can affect protein structure and function
small scale mutations such as point mutations can change one DNA nucleotide pair
this can lead to production of non functional proteins
nucleotide pair substitutions can cause missense or nonsense mutations
nucleotide pair insertions or deletions may produce era,eshift mutations
spontaneous mutations can occur during DNA replication and recombinations
chemical and physical mutagens cause DNA damage that can alter genes