Protein synthesis and DNA replication

Question 1

Fredrick Griffith Oswald Avery

Answer 1

Transformation is a change in the genotype caused from cells taking up foreign genetic material

Question 2

Hershey and Chase

Answer 2

they used new technology to show that genes are made up of DNA

Question 3

Chargaffs rule

Answer 3

Found that the amount of A in any sample of DNA is always approxiamately equal to the amount of R, and the amount of C is always approxiametely equal to G

Question 4

Rosalind Franklin

Answer 4

used X-ray photography to analyze the structure of DNA her observations provides crucial information about the molecular structure of DNA

Question 5

Watson & Crick

Answer 5

provides a structural model of DNA(Double helis-twisted ladder)

Question 6

What happens during transcription

Answer 6

During transcription the information in a segment of DNA is copied into mRNA. RNA polymeraseDNA unwinds and unzips at the gene that needs to be used.

RNA polymerase binds to the promoter region on the DNA.

Using the sense strand of DNA as a template, RNA polymerase matches RNA nucleotides:

A (in DNA) → U (in RNA)

T → A

C → G

G → C

This builds a single-stranded mRNA molecule.

When a stop signal is reached, transcription ends.

The mRNA leaves the nucleus through a nuclear pore and enters the cytoplasm.

Question 7

What happens during translation

Answer 7

The ribosome attaches to the mRNA at the start codon (AUG).

tRNA molecules carry specific amino acids to the ribosome.

Each tRNA has an anticodon that matches the mRNA codon.

The ribosome reads the mRNA three bases at a time (codon).

tRNA brings the correct amino acid, and the ribosome connects it using a peptide bond.

The ribosome moves down the mRNA, adding more amino acids.

When a stop codon (UAA, UAG, or UGA) is reached, the ribosome releases the polypeptide.

Question 8

Initiation

Answer 8

Replication begins at specific places on the DNA called origins of replication.
➤ In eukaryotes (like humans), there are many origins to speed up the process.

Helicase enzyme unwinds and unzips the DNA double helix by breaking the hydrogen bonds between the base pairs (A-T, G-C).

This creates a replication bubble with a replication fork at each end.
➤ A replication fork is a Y-shaped structure where the DNA is being separated.

Single-strand binding proteins (SSBs) attach to the now-separated DNA strands to keep them from snapping back together.

Question 9

Elongation

Answer 9

An enzyme called primase builds a short RNA primer to start the process.
➤ This gives DNA polymerase something to attach to.

DNA polymerase:

Adds new DNA nucleotides to the template strand

Matches A with T, and C with G

Builds in the 5′ to 3′ direction only

Because DNA strands are antiparallel, the two strands are built differently:

Leading strand: Built continuously toward the replication fork.

Lagging strand: Built in short fragments (Okazaki fragments) away from the fork.

DNA ligase joins (or “glues”) the Okazaki fragments together on the lagging strand.

Question 10

Termination

Answer 10

Once the entire DNA strand is copied, the replication process wraps up.

DNA rewinds back into its double helix form.

All the replication enzymes detach, and the replication complex breaks down.

You are left with two identical DNA molecules, each with:

One original strand

One new strand
➤ This is why we call it semi-conservative replication.