AP Bio - Ch 10

Characteristics of DNA

-double stranded -Deoxyribose -Thymine is the pairing for Adenine

Characteristics of RNA

-single stranded -ribose -Uracil (U) because A=U

Just like DNA polymerase, RNA polymerase performs a template directed synthesis in the:

5'---->3' direction

An mRNA transcript is composed of the following nucleotide sequence: 5'-AAUGCGUA-3' What is the template strand for this transcript?

5'-TACGCATT-3'

Of the ____ different possible codons, ____ specify amino acids and ____ signal stop.

64, 61, 3

Ribonucleic Acid (RNA)

A nucleic acid that uses information from DNA to synthesize proteins.

Transfer RNA (tRNA)

A single strand of RNA that temporarily carries a specific amino acid on one end.

anticodon

A three-nucleotide sequence on tRNA that is complementary to an mRNA codon.

What is the start codon?

AUG

exon

An exon is any nucleotide sequence encoded by a gene that remains present within the final mature RNA product of that gene after introns have been removed by RNA splicing. The term exon refers to both the DNA sequence within a gene and to the corresponding sequence in RNA transcripts.

What is heterochromatin?

DNA that cannot be transcribed. Heterochromatin is "dark" chromatin that represents DNA that is not active in transcription. The fact that it is "dark" implies that it is condensed and inaccessible by polymerases. Heterochromatin is created when DNA is tightly wound around histones. This tight winding prevents transcription proteins from interacting with the DNA. Heterochromatin is most common in the nucleus during mitosis, when no transcription is taking place.

Overall Process

DNA→Transcription→RNA→Translation→ Protein

Step 2 of Translation

Elongation: A new tRNA+amino acid enters the ribosome, at the next codon downstream of the AUG codon. If its anticodon matches the mRNA codon it basepairs and the ribosome can link the two aminoacids together.(If a tRNA with the wrong anticodon and therefore the wrong amino acid enters the ribosome, it can not basepair with the mRNA and is rejected.) The ribosome then moves one triplet forward and a new tRNA+amino acid can enter the ribosome and the procedure is repeated.

What is the 5' cap?

GTP added to increase stability & point of attachment to a ribosome

A cell builds it's proteins from the instructions encoded in its _________?

Genome

Eukaryotic DNA is packed in a chromatin structure, making it hard for DNA to be Transcribed. What proteins are associated with the packing of DNA?

Histones specifically the acetylation of these histones allow for DNA transcription.

Step 1 of Translation

Initiation: When a small subunit of a ribosome charged with a tRNA+the amino acid methionine encounters an mRNA, it attaches and starts to scan for a start signal. When it finds the start sequence AUG, the codon (triplet) for the amino acid methionine, the large subunit joins the small one to form a complete ribosome and the protein synthesis is initiated.

Where does Translation occur?

Occurs in the cytoplasm of the cell

During translation, the ____ site within the ribosome hold the growing amino acid chain while the ____ site holds the next amino acid to be added to the chain.

P, A

Step 1 of Transcription

RNA Polymerase binds to a gene's promoter

Ribosomal RNA (rRNA)

RNA molecules that are part of the structure of ribosomes.

What is the basics of Translation?

RNA to protein

What process occurs before the other? (a way to remember?)

Transcription and then Translation (Translation is like changing languages whereas transcription is just complementary base pairs.)

What are the stop codons?

UAA, UAG, UGA

A gene is ____________.

a section of DNA that codes for a protein or RNA molecule.

promoter

a sequence of DNA that acts like a start signal

In transcription, the promoter is _________.

a sequence of DNA that designates the starting point for RNA polymerase

Messenger RNA (mRNA) can be best described as:

a short lived RNA molecule that carries encoded information, transcribed from DNA.

What is the Poly A Tail?

added to 3' end, 200 adenine molecules

Step 3 of Transcription

adds and links complementary RNA nucleotides together.

Alternative Splicing

allows for different mRNA to be produced with one transcript

Which of the following is directly produced during gene transcription by RNA polymerase?

htRNAWhy? When RNA polymerase binds to the template strand of DNA it recruits complementary ribonucleotides to form a strand of RNA. this strand of RNA however, it is incomplete and must undergo post-transcriptional modification to become a mature mRNA product. The initial RNA transcript is known as heteronuclear RNA or htRNA.... Introns are removed for the htRNA and a 5' cap and poly-Atail are added to convert it to mRNA.

A protein that ultimately functions in the plasma membrane of cell is most likely to have been synthesized ______.

in the rough endoplasmic reticulum. Why? The primary function of the ribosomes bound to the rough ER is to synthesize proteins for transport to the cell exterior or the extracellular matrix. These ribosomes produce polypeptides that are packaged into vesicles by the Golgi apparatus and transported to the membrane. Nuclear ribosomes synthesize replication and transcription proteins into the nucleus while cytoplasmic ribosomes produce cytoplasmic proteins.

What is the Poly A Tail's function?

increases stability as mRNA leaves nuclues

RNA splicing

introns are removed and then the exons are spliced together

Which molecule contains the genetic code?

mRNA

An antibiotic interferes with the ability of the ribosome to move. What affect would exposure to this chemical have on a bacterial cell?

no proteins will be produced

introns

noncoding sections of an RNA transcript, or the DNA encoding it, that are spliced out before the RNA molecule is translated into a protein.

The amino acid sequence of a polypeptide chain comprises the ____ structure of the protein.

primary

Messenger RNA (mRNA)

produced during transcription passes the "message" from DNA to ribosomes.

snRNP

small nuclear ribonucleoproteins that deletes & splices the RNA

What is the ribosome made up of?

small subunit and the large subunit which contains the P and A sites

What is the definition of Transcription?

the instructions are transferred from a gene to RNA (occurs in the nucleus of the cells)

Where does mRNA processing take place?

the nucleus

E-site

the ribosomal site harboring decylated tRNA on transit out from the ribosome.

A-site

the ribosomal site most frequently occupied by aminoacyl-tRNA. The aminoacyl-tRNA in the A-site functions as the acceptor for the growing protein during peptide bond formation.

P-site

the ribosomal site most frequently occupied by peptidyl-tRNA, i.e. the tRNA carrying the growing peptide chain. The P-site is also referred to as the puromycin sensitive site.

codons

three-nucleotide sequences

____ regulate which genes or subsets of genes are transcribed in a particular cell type.

transcription factors

Step 2 of Transcription

unwinds the double helix, exposing DNA nucleotides

Step 3 of Translation

Termination: When the ribosome reaches one of three stop codons, for example UGA, there are no corresponding tRNAs to that sequence. Instead termination proteins bind to the ribosome and stimulate the release of the polypeptide chain (the protein), and the ribosome dissociates from the mRNA. When the ribosome is released from the mRNA, its large and small subunit dissociate. The small subunit can now be loaded with a new tRNA+methionine and start translation once again. Some cells need large quantities of a particular protein. To meet this requirement they make many mRNA copies of the corresponding gene and have many ribosomes working on each mRNA. After translation the protein will usually undergo some further modifications before it becomes fully active.

Step 4 of Transcription

The RNA instructions are written in a series of codons.

Step 5 of Transcription

The amino acids are linked together to form a protein.