TRANSCRIPTION Flashcards
What molecules accomplish transfer of genetic info from the DNA?
RNA (ribonucleic acid) molecules
What is the process of copying DNA info into RNA called?
- Transcription
What are the defining characteristics of DNA?
- part of chromosomes, located in the nucleus
- deoxyribose (5-carbon sugar)
- Double Stranded
- Nitrogenous bases: cytosine, guanine, adenine, thymine
What is the function of DNA?
- Replicates prior to cell divison; contains info for protein synthesis
What are the defining characteristics of RNA?
- Located in the cytoplasm
- Ribose (5-carbon sugar_
- Single-stranded
- Nitrogenous bases: cytosine, guanine, adenine, uracil
What is the function of RNA?
mRNA carries DNA info to the cytoplasm and acts as a template for synthesis of protein molecules; tRNA carries amino acids to mRNA; rRNA provides structure for ribosome
What is mRNA?
- a form of RNA that carries a gene’s info on how to build a specific polypeptide.
- mRNA is synthesized as its nucleotides form complementary base pairs with one of the two strands of DNA that encodes a particular protein
What is the function of RNA polymerase in transcription of mRNA?
- Recognizes the correct strand of DNA that contains the genetic message, as well as the right direction for RNA synthesis.
What base sequence do all mRNA molecules begin with?
- AUG
What are the specific details of mRNA synthesis?
- RNA polymerase binds to a promotor on the DNA sequence that begins a gene
- The DNA strand unwinds and pulls apart exposing parts of the base sequence
- RNA polymerase moves along the strand exposing other sections of the gene
- Molecule of mRNA forms a RNA that is complementary to those along the DNA strand - they join.
- RNA polymerase continues down the DNA strand until it reaches a special DNA base structure (termination signal)
- This indicates that end of the gene
- The RNA polymerase releases the newly formed mRNA molecule
- The mRNA passes thru a pore in the nucleic envelope into the cytoplasm
What is the process of Translation?
- mRNA leaves the nucleus and attaches to a ribosomal subunit, forming a ribosomal complex after the second subunit attaches
- Translation begins as an initial tRNA anticodon recognizes it’s complementary mRNA codon at the start of a gene, and brings the first amino acid into position
- Translation continues as a specific tRNA molecules bring the correct amino acids to the growing polypeptide chain
- As the ribosome moves along the mRNA, more amino acids are added
- At the end of the mRNA, the ribosome releases the new polypeptide chain
Define genetic code
- is a sequence of nucleotides on RNA molecule derived from the DNA template, that specifies the order of amino acids that makes up each protein that a cell synthesizes
how does RNA differ from DNA?
DNA is double-stranded, while RNA is single-stranded. DNA contains the base thymine, while the RNA contains the base uracil. RNA contains the sugar deoxyribose, and RNA contains the sugar, ribose
What is a codon?
- A set of 3 nucleotides of a messenger RNA molecule that specifies a particular amino acid
What do tRNA molecules do?
- align the specific amino acid building blocks in the proper sequence along an mRNA
- Enables enzymes to bond them to each other
What are the two ends of a tRNA molecule?
- Connectors that bring together the mRNA and the growing chain of amino acids
How does tRNA pick up amino acids?
- The amino acids must be activated to be picked up by tRNA
- Special enzymes catalyze this step
- ATP provides energy for an amino acid and its tRNA to bond
What is an anticodon?
- 3 nucleotides of a tRNA molecule that are complementary to a specific mRNA codon
What is an “initiation codon”?
- the mRNA sequence AUG specifying the amino acid methionine and the start of the encoded protein
What is ribosomal RNA
- rRNA is a type of RNA that forms part of the ribosome
What are ribosomes role in translation?
- tRNA and mRNA occur in close association with a ribosome
- The smaller subunit of a ribosome binds to a molecule of mRNA near the first codon
- the tRNA temporarily binds to an adjacent site on the ribosome with its amino acid
- the ribosome moves along the mRNA adding amino acids to the extending polypeptide chain
- The enzymatic activity necessary for bonding of the amino acids comes from ribosomal proteins and some RNA molecules
- The larger subunit of the ribosome holds the growing chain of amino acids
What is a polyribosome?
- A group of ribosomes that form along a singular mRNA strand, that may be at different stages of formation, and can be present at any given moment
- Several copies of the same protein
What are “chaperones?”
- Proteins that fold the polypeptide chain into a unique conformation
- After this, it is released as a functional protein
