IUPUI K101 Exam 4

RNA is ____ from DNA

transcribed

RNA is __________ into protein

translated

How do genes direct the synthesis of proteins?

transcription and translation

Where does transcription occur?

the nucleus

Where does translation occur?

the cytoplasm

______ in the link between DNA and protein

RNA

What are the components of RNA?

1 ribose, a phosphate group, and a nucleotide base

RNA typically function as ______________ but can bind to themselves to provide 3D structure

single-stranded polymers

What are the 3 types of RNA involved in protein synthesis?

mRNA, tRNA, rRNA

What is the function of mRNA?

provides the genetic instructions to make proteins

What is the function of tRNA?

carry amino acids to ribosomes on one end and bind mRNA on the other end

What is the function of rRNA?

form the body of the ribosome and provide a physical link between mRNA and tRNA

What happens in transcription?

1. DNA of one gene unwinds
2. RNA polymerase transcribes a copy of DNA into RNA
3. Codon is read and translated into amino acids and proteins in the ribosome

What enzyme translates a copy of DNA into RNA?

RNA polymerase

A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

codon

RNA polymerase binds to a promoter, where the helix unwinds and transcription starts

initiation

RNA polymerase moves 5' to 3', unwinding the DNA and elongating the RNA transcript

elongation

RNA polymerase reaches a terminator sequence and detaches from the template, separating RNA and DNA

termination

What are the three stages of transcription?

initiation, elongation, termination

mRNA is complementary to the _____________

template strand of DNA

What are attached to the end of mRNA in processing?

5' guanine cap and poly-A tail

What is the function of the 5' cap and poly-A tail?

to protect the RNA and help it to exit the nucleus safely

What makes up the poly-A tail?

50-250 adenine nucleotides

What happens in RNA splicing?

introns are cut out and eons are spliced together

The ________ complex of proteins and RNAs helps splice RNA

spliceosome

What must occur before the mRNA can leave the nucleus?

Processing and Splicing

What is the product of translation?

a protein

How many start codons are there?

1

How many stop codons are there?

3

How many possible codons are there?

64

What are the two main features of the genetic code?

universal and redundant

What is the Wobble Hypothesis?

There is some wiggle room in the 3rd nucleotide in a codon, allowing many codons to code for the same amino acid if they have the same first 2 bases

A tRNA contains ___ base-paired regions

4

Where does the amino acid bind to the tRNA?

3' end

group of three bases on a tRNA molecule that are complementary to an mRNA codon

anticodon

When is a tRNA charged?

when an amino acid is attached

How is tRNA activated?

The active site binds an amino acid and ATP, ATP loses 2 phosphates and joins amino acids as AMP, appropriate tRNA binds to amino acid, displacing AMP, then the activated amino acid and AMP is released by the enzyme

What enzyme helps activate tRNA?

aminocyl-tRNA synthetases

structure made of rRNA and proteins

ribonucleoprotein

eukaryotic ribosomes are ________ than prokaryotic ribosomes

bigger

When does tRNA fit into a binding site on a ribosome?

its anticodon is base-paired with an mRNA codon

what are the 3 sites in a ribosome?

A, P, E

What is the function of the A site?

holds incoming activated tRNA

what is the function of the P site?

holds the tRNA that carries the growing polypeptide chain

What is the function of the E site?

Holds un-activated tRNS

How is translation initiated?

Small ribosomal subunit binds to mRNA, large ribosomal subunit completes the initiation complex, charged tRNA binds to mRNA by complementary base-pairing and then the large subunit comes over the top to complete initiation

How many ribosomal subunits are there?

2

What are the stages of the elongation cycle?

Codon recognition, peptide bond formation, translocation

What happens during codon recognition?

a tRNA is recruited into the A site

What happens in peptide bond formation?

The enzyme peptidyltransferase detaches the aa at the P site
and joins it to the aa at the A site

What happens in translocation?

The ribosome shifts down the mRNA, moving the protein
chain into the P site

What signals the termination in translation?

The ribosome reaches a stop codon

Wehn translation is terminated a release factor promotes _____________, and uses ________

hydrolysis, 2 GTP

Why do polyribosomes form?

Because the half-life or mRNA is so short, many ribosomes cluster on the same mRNA at the same time so the many proteins can be made at the same time

What is the purpose of the signal peptide KDEL?

To be recognized by a signal recognition particle, which pulls the protein t the ER and threads it through the ER lumen

What is the difference in gene expression in prokaryotes and eukaryotes?

In prokaryotes polyribosomes stay attached to DNA via DNA polymerase. In eukaryotes ribosomes are in the cytoplasm. In prokaryotes transcription and translation occur simultaneously, and in eukaryotes mRNA processing occurs in between.

What type of mutation causes SCD?

point mutation

In sickle cell anemia hydrophobic --- is inserted instead of hydrophilic ----

valine, glutamic acid

3 Types of base-pair substitution

silent mutation, missense mutation, nonsense mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

silent mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

missense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

nonsense mutation

What gene is a common example of a frameshift causing an immediate nonsense?

BRCA1

What diseases are associated with insertions causing missense?

Huntington's and Fragile X Syndrome

What disease is associated with the insertion or deletion of 3 nucleotides causing a missing or extra amino acid?

cystic fibrosis

What did Garrod discover?

inborn errors of metabolism

What scientists had the one-gene, one-enzyme hypothesis in the 1940s?

Beadle and Talum

Who won the Nobel Prize in 1954 for prosing a genetic relationship between sickle-cell hemoglobin and the sickle-cell trait?

Linus Pauling

Why do cells switch genes on and off?

to conserve resources

DNA unpacking involving histone acetylation and DNA demethylation

chromatin modification

Histone tails form a(n) ___________

Octomer

histone tails protrude outward from a ________

nucleosome

chromatin that is methylated is _______________

inactive

chromatin that is acetylated is ____________

active

a functional group containing a carbonyl and a methyl

acetyl group

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

epigentic inheritance

The TATA box is a ___________

promoter

the binding site for RNA polymerase

TATA box/ promoter

What are proximal control elements needed for?

accurate transcription initiation

What do proximal control elements do?

bind the transcription initiation complex

What do distal control elements do?

Increase the rate of transcription

proteins that bind to enhancer sequences in eukaryotes to increase transcription

activator proteins

What brings the bound activators closer to the promoter?

DNA bending protein

Where do activators bind to other transcription factors?

the promoter

DNA that is densely packed around histones

Heterochromatin

loosely packed chromatin

euchromatin

What factors affect transcription during chromatin modification?

DNA methylation and acetylation, epigenetic regulation

What regulates the initiation of transcription?

DNA control elements in promoters and enhancers binding specific transcription factors

Cell type specific expression begins with the ____________

zygote

miRNA

Micro RNA

enzyme that cleaves and processes double stranded RNA to produce miRNAs

Dicer

An miRNA that is bound to proteins can base pair with ________________ that contains the complementary sequence

any target mRNA

What do miRNAs do?

block translation

A protein that attaches itself to faulty or misfolded proteins and thus targets them for destruction by proteasomes

ubiquitin

A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.

proteasome

small infectious particle consisting of nucleic acid enclosed in a protein coat and sometimes a membranous envelope

virus

the protein shell that encloses the viral genome

capsoid

_______ use host cell materials to self-assemble

viruses

protein subunits that make up capsids

capsomeres

A virus that infects bacteria

Bacteriophage