Genes & Protein Synthesis

Question 1

How does DNA make Proteins?

Answer 1

Through the process called “Protein Synthesis”. 3 types of RNA

Question 2

Central Dogma of Biology

Answer 2

Describes flow of genetic info in the cell from genes to mRNA to proteins. Genes specify the sequence used to make mRNA by the process of transcription. mRNA is used to synthesize proteins by the process of translation.

Question 3

Steps of Protein Synthesis

Answer 3

Transcription- the process of copying the genetic code of DNA onto a molecule of mRNA. Occurs in the nucleus, DNA stays there.
Translation- the process of converting the code of mRNA into a sequence of amino acids to produce a protein (polypeptide chain).

Question 4

Transcription- 1st step of Protein Synthesis

Answer 4

Like DNA replication. DNA is copied and complementary bases are added in 5’ to 3’ direction.
Unlike DNA replication
-Only small stretch is replicated at a time to make a particular protein, *not an entire strand of DNA.
-RNA polymerase catalyzes nucleotide addition.
-Product is a single strand of RNA.

Question 5

Translation- 2nd step of Protein Synthesis

Answer 5

Occurs in the cytoplasm by the work of all three classes of RNA.
*mRNA, tRNA, and rRNA.
*mRNA after it copies the code from DNA but the process occurs in the cytoplasm.

Question 6

3 classes of RNAs during Protein Synthesis

Answer 6

Messenger RNA (mRNA) *codon
-Carries protein building instruction from the DNA to the cytoplasm.
Transfer RNA (tRNA) *anti-codon
-Delivers amino acids to ribosomes
Ribosomal RNA (rRNA)
-Combines with ribosomes to join amino acids together to make a protein.

Question 7

Promoter

Answer 7

Base sequence in the DNA that signals the start of a gene
-always and only AUG
Transcription, RNA polymerase must mind to a promoter region AUG

Question 8

Pre-mRNA Splicing *Intron vs Exon

Answer 8

Introns- area of pre-mRNA snipped out
Exons- area of pre-mRNA that remains in the genetic transcript and exits the nucleus and be used during protein synthesis.

Question 9

Genetic Code

Answer 9

System enables the 4 nucleotides (A,T,G,C) to code for the 20 different amino acids.
-consists of set of 64 base triplets (codons)
-Anti-codon- a base triplet on the tRNA that carries the correct amino acid,
-Codon-a base triplet on the mRNA that represents a different amino acid.

Question 10

3 Stages of Translation

Answer 10

Initiation, Elongation, Termination

Question 11

Initiation

Answer 11

Initiator tRNA binds to small ribosomal subunit.
Small subunit/tRNA complex attaches to mRNA and moves along it to an AUG “start” codon.
Large ribosomal subunit joins complex.

Question 12

Elongation

Answer 12

mRNA passes through ribosomal subintes
tRNAs deliver amino acids to the ribosomal binding site in the order specified by the mRNA.
Peptide bonds form between the amino acids and the polypeptide chain grows.

Question 13

Termination

Answer 13

Stop codon is reached.
Release factors bind to the ribosome
mRNA and polypeptide chain is released

Question 14

Gene Mutations

Answer 14

Induced- mutation caused by exposure to chemicals or UVA/UVB
Spontaneous-occur from natural reactions in the body
Types:
Base-pair substitutions
Insertions
Deletions

Question 15

Frameshift Mutations

Answer 15

Insertion
-extra base added into gene region
Deletion
-base removed from gene region
Both shift the reading frame
Result in many wrong amino acid