Chapter 17 (Genetic Info Flow) Flashcards
How is info stored in DNA?
nucleotide sequences
How do nucleotide sequences lead to specific traits?
directing protein synthesis
What do the proteins created by nucleotide sequences link together?
phenotype and genotype
What is a gene?
unit of inheritance, region of the chromosome, and nucleotide sequence that will specify the creation of proteins or sequence of RNA
What is gene expression?
a process where DNA directs protein synthesis
What are the stages of gene expression?
transcription and translation
What is transcription?
the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA in the nucleus
What does transcription produce?
raw RNA product called pre-mRNA (messenger)
How are RNA transcripts modified?
RNA processing creates mature messenger RNA
What is translation?
process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins after the process of transcription of DNA to RNA in the cell’s nucleus
What separates the process of transcription and translation?
nuclear envelope
What are the nucleotides found in DNA?
adenine, guanine, thymine, cytosine
What are the nucleotides encoding?
amino acids
What’s the triplet code?
series of non-overlapping, three-nucleotide “words” that have 64 different combos
What is a codon?
the sequence of three nucleotides that form a unit of genetic code
Out of the 64 different combos of three nucleotides, how many codes for amino acids?
61
What do the remaining combos of codons represent?
stop codons
What is the start codon?
AUG
Even though there are 64 different combos of codons, why is there only production of 20 amino acids?
redundancy and non-ambiguity since multiple combos of codons can give you 1 amino acid
Is the genetic code universal?
yes, so that means you can give different genes to different organisms
What happens during transcription?
1 strand of DNA (template/non-coding strand) and makes complementary mRNA strand by replacing T with U
What happens during translation?
reading from 3’ to 5’ in a reading frame that is 5’ to 3’, each codon generates 1 amino acid and multiple amino acids make a protein
What is the first step in DNA replication?
helicase separates/unwinds double helix and separates strands to create semi-conservative template strands
What does helicase create?
a replication fork
What is the second step of DNA replication?
single-strand binding protein stabilizes the single strands of DNA by preventing the bending
What is the third step in DNA replication?
RNA primase places RNA primer segments that allow DNA polymerase to attach to
What is the fourth step in DNA replication?
DNA pol III connects to primer and adds complementary bases
DNA is read in what direction?
3’ to 5’
What is the fifth step of DNA replication?
DNA pol. I remove primers on lagging strands
What is the sixth step of DNA replication?
DNA pol. I add base pairs to lagging strands and DNA ligase joins Okazaki fragments
What are the steps to transcription?
initiation, elongation, termination
Where does transcription happen?
nucleus
What does RNA polymerase II do?
creates pre-mRNA
What are transcription factors?
proteins bind to different sequences of DNA and are named TF#
What is a transcription unit?
the stretch of DNA that is being described
What is the promotor region?
DNA sequence where RNA polymerase attaches
What is the TATA (thiamine adenine) box and where is it found?
type of DNA promoter sequence, which specifies to other molecules where transcription begins
What is the first step of initiation of transcription?
transcription factors bind to promoter regions (TATA box) on double-stranded DNA to form the initiation complex
What is the second step of initiation of transcription?
the initiation complex attracts RNA polymerase II and RNA polymerase unzips DNA strand to form a replication bubble
What is the coding region?
after the promotor region, the part of DNA that will be transcribed into RNA
What are activator and repressor and enhancer regions?
before the promotor regions that control the level of transcription and expression
What happens in the elongation phase of transcription?
extension of transcript
What is the first and only step in elongation in transcription?
RNA polymerase produces a transcript of RNA bases on the DNA template strand (aka the antisense strand, - strand)
What happens in the termination phase of transcription?
the RNA polymerase meets the termination sequence and detaches, creation of pre mRNA
Is there proofreading happening in transcription?
no
What happens in between transcription and translation?
processing of pre-mRNA
Where does the processing of pre-mRNA happen?
the nucleus
What are the steps of mRNA processing?
splicing, 5’ cap, poly A tail
What happens in splicing?
separation of exons (exit the nucleus, will be preserved and EXpressed) and introns (won’t be carried over to protein synthesis leading to a formation of a splicosome
What are introns?
noncoding regions
What are exons?
regions of sequence that are expressed (called domain)
What are spliceosomes?
the complex of short nucleoribonuleoproteins (snRNP) that lassos the introns and joins exons together in different orders (ex: exon 1 with exon 3)
What happens in the 5’ cap?
the sequence of biomolecules that prevents degradation
What happens in the poly-A tail addition?
added to 3’ end that prevents degradation, sequence of adenines
What are ribozymes?
non-proteins that cut the lasso of a splicosome and physically splice the RNA
Why are introns important?
controls where genes are translated and results in the process where multiple genes codes for 1 protein
What are the components involved in translation?
Ribosome that has 2 subunits (small and big) and tRNA
What happens in the first step of initiation in translation?
small subunit joins 5’ end to look for start codon (AUG)
What happens in the second step of initiation in translation?
large subunit joins small subunit, tRNA encodes MET amino acid
In ribosome, what does the P site do?
in the middle, holds the tRNA that carries the growing polypeptide chain (pass peptide site)
In ribosome, what does the A site do?
holds the tRNA that carries the next amino acid
to be added to the chain (arriving site)
In ribosome, what does the E site do?
tRNAs leave the ribosome (exit)
What are the steps of translation?
initiation, translation, termination
What is the first step in elongation for translation?
tRNA binds to next site that arrives at A site and binds with anticodon
What is the second step in elongation for translation?
passing peptide from A site to P site
What is the third step in elongation for translation
tRNA moves to P site with the amino acids attached to make polypeptide chain until termination
What happens in the termination of translation?
translation of mRNA hits a stop codon and DO NOT have a tRNA, the release factor occupies the A site to release polypeptide chain while ribosome separates
What does the release factor add?
water
What is wobble base pairing?
3rd position of the nucleotide has flexibility in pairing, happens in translation (5’ to 3’)
What is spontaneous in DNA?
replication, recombination, repair
What are mutagens?
physical or chemical agents that cause mutations
What are point mutations?
single base pair mutations
What are the types of point mutations?
substitution, deletion, and insertion
What happens in substitution?
Replaces one nucleotide in either stand to make a silent mutation, nonsense mutation, missense mutation
What happens in insertions and deletions?
Additions or losses of nucleotide
pairs in a gene that can have a disastrous effect on a protein and not be able to have a sequence divisible by 3
