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created 6 months ago by molly2490
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biology
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1

Name the 2 major steps in protein synthesis? where does it occur ?

  • Transcription: This is like copying a recipe from a cookbook. The DNA's instructions are transcribed into a temporary copy called mRNA. This happens in the nucleus for eukaryotic cells and in the cytoplasm for prokaryotic cells.
  • Translation: Think of this as following the recipe to make a dish. The mRNA is read by ribosomes in the cytoplasm, and they assemble amino acids in the correct order to build a protein, just like putting together ingredients to make a meal.

2

Compare replication and transcription?

  1. Purpose:
    • Replication: Makes a copy of the entire DNA.
    • Transcription: Makes a copy of a specific gene to produce RNA.
  2. Enzyme:
    • Replication: Uses DNA polymerase.
    • Transcription: Uses RNA polymerase.
  3. Template:
    • Replication: Both DNA strands are used as templates.
    • Transcription: Only one DNA strand is used as a template.
  4. Product:
    • Replication: Produces two identical DNA molecules.
    • Transcription: Produces a single-stranded RNA molecule.
  5. Location:
    • Replication: Occurs in the nucleus (eukaryotes) or cytoplasm (prokaryotes).
    • Transcription: Also occurs in the nucleus (eukaryotes) or cytoplasm (prokaryotes), but the RNA might need further processing.

3

How much of a molecule of DNA is untwisted during replication? during transcription?

During DNA replication, a significant portion of the DNA molecule is untwisted. In contrast, during transcription, only a small portion of the DNA molecule is untwisted at a time.

4

The DNA triplet CGA is transcribed into which RNA codon?

GCU

5

Which enzyme reads MRNA?

Ribosome and it is an enzyme

6

Explain the role played by each of the following in protein synthesis. template strand of DNA, RNA codon, enzymes, mRNA, tRNA

  1. Template Strand of DNA:
    • It's like a recipe book. It provides the instructions for making RNA (the recipe) during transcription.
  2. RNA Codon:
    • These are like the words in the recipe. They are groups of three RNA letters (nucleotides) that tell the cell which amino acid to add to the growing protein chain.
  3. Enzymes:
    • They're like the chefs in the kitchen. Enzymes help carry out the steps of protein synthesis. For example, RNA polymerase is like the chef who reads the recipe (DNA) and makes the RNA copy (mRNA).
  4. mRNA (Messenger RNA):
    • It's like a messenger carrying the recipe (instructions) from the recipe book (DNA) to the kitchen (ribosomes) where the protein is made.
  5. tRNA (Transfer RNA):
    • These are like the delivery trucks. Each tRNA molecule carries a specific amino acid to the ribosome, where it matches its amino acid to the correct spot on the mRNA recipe, ensuring that the protein is made correctly.

7

What is the first codon word of any polypeptide

AUG (start codon)

8

for the DNA triplet CGT, write the complementary mRNA codon and the tRNA anticodon

mRNA codon GCA would be CGU.

mRNA codon to the DNA triplet CGT would be GCA.

9

what would be the effect on translation if the stop codon were changed by mutation

  • Premature Termination: Translation may stop too early, resulting in a shortened or incomplete protein.
  • Readthrough: The stop signal may be ignored, causing translation to continue beyond its normal endpoint. This could result in a longer-than-normal protein.
  • No Effect: Sometimes, the mutation may not affect translation at all, especially if the stop codon is changed to another stop codon or if it occurs far from where the protein ends.

10

What types of mutations are there what happens if a start codon is mutated?

  • Point mutations: A single nucleotide is changed, inserted, or deleted.
  • Frameshift mutations: Nucleotides are inserted or deleted, shifting the reading frame of the genetic code.
  • Insertions: One or more nucleotides are added to the DNA sequence.
  • Deletions: One or more nucleotides are removed from the DNA sequence.
  • Substitutions: One nucleotide is replaced with another.
  • if a start codon (usually AUG) is mutated:
    1. Premature Start Codon: If changed, translation may start at a different point, possibly making a shorter or altered protein.
    2. Loss of Start Codon: If deleted or changed too much, translation may not start properly, leading to no protein or a non-functional one.
    3. Readthrough: Sometimes, a nearby AUG may be used instead, causing translation to start at the wrong place, making a protein with errors.