L.5 Transription, Translation & DNA Repair

Question 1

Cancer cells

Answer 1

Cancer cells are cells that divide relentlessly, forming solid tumors or flooding the blood with abnormal cells.

Cell division is a normal process used by the body

for growth and repair.

Question 2

Oncogene

Answer 2

Mutated genes that cause cancer by affecting the cell-cycle.

Question 3

Metastasis

Answer 3

Migration of affected cell to distant locations, through the bloodstream or lymphatic system.

Question 4

Protooncogenes

Answer 4

Oncogenes before they become mutated

Question 5

Tumor suppressor genes

Answer 5

Genes that create tumor suppressors genes,

by

genes that regulate cell cycle and

participate in DNA Repair

also known as

antioncogenes.

Mutation in tumor suppressor genes can also cause cancer

Question 6

How do the alleles of the oncogenes and antioncogenes, explain their function.

Answer 6

oncogenes are esentially dominant, only one affected allele is needed to change a protooncogene to an oncogene.

Tumor supressor genes also only need one alle to work

Question 7

What are the 4 types of repair mechanisms of DNA?

Answer 7

1. Proofreading
2. Mismatch pair
3. Nucleotide excision repair
4. Base excision repair

Question 8

Proofreading happens in what phase of the cell cycle and what key enzymes/genes aid.

Answer 8

S pahse, DNA polymerase

Durring replication , DNA polymerase proffreadsits work and excises incorectly matched bases.

Daughter strand is ID by lack of methylation.

Question 9

Mismatch Pair happens in what phase of the cell cycle and what key enzymes/genes aid.

Answer 9

G2, genes MSH2 MLH1

Detect and remove errors in replication that were missed during S phase.

Question 10

Nucleotide excision repair happens in what phase of the cell cycle and what key enzymes/genes aid.

Answer 10

Excision endonuclease, G1 & G2

UV —> thymine dimers

Thymine dimers —–> distort double helix

NER—-> cut and patch process, removing affected oligonucleotide and DNA ligase seals

Question 11

Base Pair Excision Repair happens in what phase of the cell cycle and what key enzymes/genes aid.

Answer 11

G1, G2 & Glycosylase enzymes and AP endonuclease

Thermal energy —-> C to U by loss of amino group

Small non-helix-distorting mutations system recognize

Glycosylase enzymes remove this U

and

replaces with AP site

AP site recognized by AP endonuclease

which removes it, then

DNA polymerase and ligase fill the gap

Question 12

Central dogma?

Answer 12

DNA —-> RNA —-> Protein

Question 13

What is a degenerate code?

Answer 13

A code that allows multiple codons to encode

for the same Amino Acid.

Question 14

What are the initiation and Stop Codons?

Answer 14

Initiation: AUG

Stop: UAA, UGA, UAG

Question 15

What do redundancy and Wobble (third base codon) do?

Answer 15

Allow mutationa to occur without effects in protein

Question 16

What are the three-point mutation?

Answer 16

1. Silent
2. Nonsense
3. Missense

Silent: mutations with no effect on protein synthesis

Nonsense: Mutation that inserts a stop codon

Missense: Mutation that produces a codon that codes for different Amino Acid

Question 17

Describe frameshift mutations

Answer 17

A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.

Question 18

Difference between RNA and DNA

Answer 18

RNA

Ribose vs deoxyribose

Uracil vs Thymine

Single-stranded vs Double-stranded

Question 19

What are the 3 types of RNA and their function?

Answer 19

Messenger RNA (mRNA)

Carries the message from DNA in the nucleus via transcription of the gene; it travels into the cytoplasm to be translated. 1 mRNA = 1 protein

Transfer RNA (tRNA)

Brings amino acids and recognized the codon on the mRNA using it anticodon

Ribosomal RNA (rRNA)

Makes up ribosome and is enzymatically active, catalyzes the formation of peptide bonds and aids in splicing

Question 20

In transcription what is the role of Helicase?

Answer 20

Helicase unwinds DNA

Question 21

What polymerase in transcription binds to TATA BOX?

Answer 21

Polymerase II binds to TATA BOX or promotor region to begin synthesis of hnRNA

Question 22

What are 5 post-transcriptional modification

Answer 22

1. A 7-methylguanylate triphosphate CAP to the 5’ end
2. A Polyadenosyl (Poly-A) tail is added to the 3’ end
3. Splicing is done by spliceosomes, introns are removed in a lariat structure.
4. polycistronic genes in prokaryotes, different gene products from one gene.
5. Alternative splicing by combining different exons

Question 23

What RNA translates codon into correct amino acid?

Answer 23

tRNA

Question 24

How are ribosomes useful?

Answer 24

Ribosomes are the location where translation happens.

Question 25

What are the 3 stages of translation?

Answer 25

1. Initiation
2. Elongation
3. Termination

Question 26

Describe what happens in the initiation stage

Answer 26

Eukaryotes

40S Ribosome attaches to the 5’ cap and scans for a start codon: it lays down methionine in the P site of the ribosome.

initiation Factors

Charged initiators bind to start codon

Question 27

What happens in elongation?

Answer 27

Involves the addition of a new aminoacyl-tRNA

into the A site of the ribosome and transfer of the growing polypeptide chain from the tRNA

in the P site to the tRNA in the A site of the ribosome.

Question 28

What happens in termination?

Answer 28

Occurs when the codon in the A site is a stop codon, a release factorplaces a water molecule on the polypeptide chain and thus release the protein.

Question 29

What are the 4 types of posttranslational modifications?

Answer 29

1. Folding by chaperones
2. Formation of quartenary structures
3. cleave of proteins or signal sequences
4. Covalent addition of other biomolecules
   
   • phosphorylation
   • carboxylation
   • gycolylation
   • prenylation

Question 30

Describe covalent posttstranslational modifications i detail.

1. Carboxylation
2. glycosylation
3. phosphorylation
4. prenylation

Answer 30

1. Carboxylation; addition of carboxylic acid groups, usually serve as calcium-binding sites
2. Gycosylation: addition of oligossacharides as proteins as they pass through the ER and golgi apparatus to determine cellular destination
3. Phosphorylation: addition of phosphate PO₄^2- by protein kinases to activate or deactivate proteins; most common seen in serine, threonine and tyrosine.
4. Prenylation: addition of lipid groups to certain memebrane bound enzymes