(7) Nucleic Acids Flashcards
Describe the initiation of transcription, including the role of the promoter, transcription factors and RNA polymerase
Transcription is the proccess by which a DNA sequence (gene) is copied into a complementary RNA sequence by RNA polymerase. The promoter (a short sequence of base pairs that are not transcribed) located on the antisense binds with mRNA and tells it to begin transcription
Describe the elongation of transcription, including the role of the nucleotide, triphosphates and the direction of transcription
Transcription is the process by which a DNA sequence (gene) is copied into a complementary RNA sequence by RNA polymerase. Free nucleotides exists in the cells as nucleotide triphosphates (NTPs) which line up opposite their complementary partner.
describe termination of tranoscription including the role of the terminator
RNA polymerase transouilres until told to stop. The terminator is a sequence of DNA that acts as this signal
list two major differences in gene expression between prokaryotic and eukaryotic cells
A) Pro: control of gene expression taken place during transcription
EUK: intracellular organelles add to complexity
B) PRO: transcription + translation occur simultaneously in cytoplasm
EUK: transcription in nucleus
state the effect of DNA methylation on gene expression
DNA methylation regulates gene expression by recruiting protein involved in gene expression or by initiating the trending of transcription factors to DNA. IT essentially blocks the promoter site.
Outline the effect of methylation on nucleosome tails of gene expression
chemical modification of tritone tails can either activate/deativate or increase/decrease gene expression
outline two examples of environmental influence on gene expression
- drugs and chemicals
- temperature and light
outline gene expression
the processes by which information from a gene to synthesize a functional gene product that enables it to produce non-coding RNA
Outline the process of translation initiation.
- The small subunit of the ribosome binds to the 5’ end of the mRNA
- The anticodon of the initiator tRNA binds to the start of the codon on the mRNA by hydrogen bonds
Outline the process of translation elongation
- charged tRNA binds to the A site
- to bind, the anticodon of the tRNA must be complimentary to the codon of the mRNA by hydrogen bonds
- a peptide bond forms between the amino acids at the P and A sites
- the tRNA at the P site detaches from the amino acid
- the ribosome moves one codon along the mRNA (5’-3’)
- The tRNA with the growing polypeptide chain is now in the P site
- the tRNA with no amino acid is now in the E site and exits the ribosome
- a newly changed tRNA can now enter the A site
State the direction of movement of the ribosome along the mRNA molecule
5’ → 3’ direction
Outline the process of translation termination
- The ribosome moves down the mRNA until the stop codon is in the A site, tRNA can’t bond to the stop codons
- Proteins called release factors bind to the A site
- This causes the polypeptide chain to be released from the tRNA in the P site. The ribosome separates from the mRNA and splits into subnuits
State the difference between free and bound ribosomes
free= synthesize proteins for use primarily within the cell
bound= synthesize proteins primarily for secretion or use in lysosomes
list destinations of proteins synthesized on free ribosomes
cytoplasm, mitochondria, chloroplasts
compare the timing and location of transcription and translation between prokaryotes and eukaryotes
once transcription is complete in euk, the transcript is modified in several ways before exiting the nucleus. thus, there is a delay between transcription and translation. in pro, as soon as the mRNA is transcribed, translation begins
describe the primary structure of a protein
the number and sequence of amino acids that make up the linear polypeptide. the number and sequence is determined by the base sequence of the gene. the primary structure will determine how the polypeptide will fold up following translation. shape of protein determines function.
describe the secondary structure of a protien
secondary strucutre represents the first level of protein folding. hydrogen bonds form between polar C-O and N-H groups within the polypeptide backbone. these groups are positioned on either side of each peptide bond.
there are 2 types of folding that can contribute to secondary structure:
a) alpha helix- polypeptide forms a helic with hydrogen bonds between the turns of the helix
b) beta plated sheets- sections of the polypeptide align parallel to each other, hydrogen bond form between them.
In both, a and b, hydrogen bonds stabilize structure
describe the tertiary structure of protien
tertiary structure = final shape
R groups determine the way the polypeptide chain folds up. there are 4 types of interactions between R groups that hold the structure
a) hydrogen bonds form between amino acids with polar R groups
b) ionic bonds form between amino acids with the oppositely charged R groups
c) disulfide bridges form between 2 amino acids containing sulfur in the R group
d) hydrophilic interactions form between amino acids with non polar R groups
outline the quaternary structure of a protien
some protiens are comprised of more then one polypeptide. intermolecular bonds gold different polypeptide chains together. the number and position of the polypeptide chain is called the quaternary structure
outline the process of attaching an amino acid to the tRNA by the tRNA activating enzyme
- ATP is hydrolosized and the amino acids is covalently linked to the AMP
- the amino acid is covalently linked to the tRNA and AMP is released
- charged tRNA is released from the active site
describe the structure of ribosomes
ribosomes = rRNA & protiens
2 subunits: small (rRNA binding site)
large (tRNA binding sites with A,P,E)
outline the structure of tRNA molecules
the tRNA molecule has a distinctive folded structure with 3 hairpin loops that form the shape of a 3 leaf clover
outline the structure of a polysome
a single mRNA and several attaches ribosome. 1 ribosome per abt 100 nucleotides
what is the difference between a peptide, polypeptide and a protein
peptide: 2+ amino acids joined by peptide bonds
polypeptide: chain of amino acids
protein: contains 1+ polypeptide
