Ch 10 from DNA to Protein

Question 0

Steps of Gene Expression

Answer 0

Production of protein from instruction on the DNA

TRANSCRIPTION = production of mRNA 
TRANSLATION= production of protein using mRNA, tRNA, and. rRNA 

Folding of the protein into the active 3D form

Question 1

Gene Expression Human Genome

Answer 1

Human Genome contains about 20,000 protein-encoding genes this is only a small part of the genome

Human genome controls protein synthesis
Time speed and location

Question 2

Central Dogma

Answer 2

Refers to the directional flow of genetic information

Replication
Transcription
Translation
Protein

Viruses have a reverse rRNA it works from RNA to DNA

Question 3

Nucleic Acids

Answer 3

Two types of nucleic Acids
RNA
DNA

Both consist of sequences of N-containing bases joined by sugar phosphate backbones

Question 4

DNA

Answer 4

Usually double stranded 
Thymine as the base 
Deoxyribose as the sugar (more stable sugar) 
Maintains proteins-encoding information
Cannot function as an enzyme 
Persists

Question 5

RNA

Answer 5

Usually single stranded (helix not linear can fold up on it self more variety with shape)

Uracil as a base

Ribose as the sugar (presence of hydrogen makes it more stable)

Carries protein-encoding information and controls how information is used

Can function as an enzyme

Transient

Question 6

Types of RNA

Answer 6

3 major types

mRNA - messenger RNA

rRNA - ribosomal RNA A Polypeptide made up of ribosomal DNA + protein it is the site that link Amino Acids together

tRNA -transfer RNA brings the amino acids to the ribosome subunit

Other classes of RNA control gene expression

Question 7

mRNA

Answer 7

Carries information that specifies a particular protein

Produced in the nucleus

Transported to the ribosome

3 nucleotide Codon specifies a particular amino acid

Most mRNA are 500 - 4500 bases long

Question 8

rRNA

Answer 8

Associated with proteins to make up ribosomes

Ribosomes consist of two subunits that join during protein synthesis

rRNA provides structural support -some are a catalyst (ribozymes)

Question 9

tRNA

Answer 9

Only 75-80 bases long

The 2-D shape is a clover leaf

The 3-D shape is an inverted L

Has two business ends:
The anticodon forms hydrogen bonds with the mRNA codon

The 3’ end binds the amino acid specified by the mRNA codon

Question 10

Transcription

Answer 10

RNA is the bridge between DNA and protein

RNA is synthesized from one strand of the DNA double helix, which is called the template strand

The complementary strand is called the coding strand of DNA

Requires the enzyme RNA polymerase

Question 11

Transcription Factors

Answer 11

In bacteria, operons control gene expression.

In more complex organisms transcription factors control gene expression and link genome to environment

These contain DNA-binding domains

About 2000 in humans

Mutations in transcription factors may cause a wide range of effects

Question 12

Steps if Transcription

Answer 12

Initiation a cascade of transcription factors bind to the promoter region of a gene

These open a pocket allowing the RNA polymerase to bind just in front of the start of the gene sequence

Elongation RNA polymerase reads the nucleotides on the template strand from 3’ to 5’ and creates an RNA molecule that looks like the coding strand

Termination occurs when sequences in the DNA prompt the RNA polymerase to fall off ending the transcript

Question 13

RNA Processing

Answer 13

In Eukaryotes mRNA transcripts are modified before they leave the nucleus

1. A methylated cap added to 5’ end
   - recognition site for protein synthesis
2. A poly-A tail is added to the 3’ end
   - stabilizes the mRNA

3 splicing occurs

• introns are removed (they code for sequence we don’t need)
• Exons are spliced together expressing sequence (code for sequence we need so they are spliced together )

Finally the mature mRNA is sent out of the nucleus

3’ end folds up on itself

Question 14

Translation (3 steps)

Answer 14

The process of reading the mRNA base sequence and creating the amino acid sequence of a protein

Divided into 3 steps

Initiation The start codon (AUG) attracts an initiator tRNA that carries methionine (initiation complex completes) The A-site is where the new amino acid will enter tRNA forms hydrogen bond

Elongation the second tRNA binds to next mRNA codon first peptide bond forms bet. The two amino acids

tRNA bring in more amino acids as the ribosome moves down the mRNA

A-site holds the newest tRNA
P-site bears the polypeptide chain

Termination occurs when a stop codon enters the A-site of the ribosome
A protein release factor frees the polypeptide
The ribosomal subunits separates and are recycled

E-site is the exit area of subunit

Question 15

The Genetic Code

Answer 15

It is a triplet code -3 successive mRNA bases form a codon

There at 64 codons including (AUG) one start signal
3 stop signals (UAA,UAG,& UGA)

It is non-overlapping

It is degenerate
-two or more codons may specify the same amino acid

It is universal
-evidence that all life evolved from a common ancestor

Question 16

Reading frame

Answer 16

A sequence of amino acids encoded for a certain starting point in a DNA/RNA sequence

One or two base added causes a frameshift everything after that added bases is wrong and alters the sequence making it invalid

Question 17

Polypeptide

Answer 17

Polypeptide can be a couple thousand codons long
Anything after stop codon does not get copied to polypeptide chain and release factor are used to release mRNA and last created tRNA

Multiple copies of a protein can be made simultaneously the closer to the end of the gene the longer the polypeptide

Question 18

Protein Structure

Answer 18

Protein fold into one or more 3-D shapes or conformations

There are four levels for protein structure

Primary (1) structure is the single polypeptide chain

Secondary (2) structure due to hydrogen bonds are helix or beta pleated sheets doesn’t have to be all one or the other

Tertiary (3) structure interaction with R-groups and determine the shape of the eternal structure

Quaternary (4) structure if made up of multiple polypeptide chain hemoglobin made up of 4 polypeptide chains

Polypeptide is just one chain
Protein can be multiple polypeptide chains linked together

Question 19

Protein folding

Answer 19

Protein folding begins as translation proceeds
Enzymes and chaperone proteins assist

Should a protein midfield an “unfolded protein response” occurs
-protein synthesis slows or even stops

Question 20

Protein Misfolding

Answer 20

Misfolded proteins are tagged with ubiquitin

Then, they are escorted to a protea some, a tunnel-like multi protein structure

As the protein moves through the tunnel it is straightened as dismantled

Protea some also destroy properly-folded proteins that are in excess or no longer needed

Question 21

Prions

Answer 21

Prion protein (PrP) can fold into any several conformations

One conformation is aberrant
-moreover it can be passed on to other prions upon contact, propagating like an “infectious” agent

Prion Misfolded proteins that cause many infection disease no nucleic acids unique ability when come in contact when come in contact with normal protein they change its shape. They cluster together
Prions do not denature even when you cook it still stays alive

Question 22

Splicing

Answer 22

Introns are intervening sequences of RNA that do not code for a polypeptide and must be spliced/cut out.