Test 3-dna replication, protein synthesis, gene mutations

Question 1

Whatre the four enzymes in dna replication, what do they do

Answer 1

Helicase unzips (breaks h bonds between bases)
Rna primase lays down a primer (origin of replication, dna polymerase cannot replicate without it), dna polymerase positions and joins compliemtary bases with h bonds, replaces rna primer with dna primer, proofreads codes, checking for errors, ligase joins sugar phosphate together by dehydration synthesis and okazaki fragments

Question 2

Are primers removed in dna replication

Answer 2

Yes, replaced with dna nucleotides (Doesnt become dna primer)

Question 3

What way does dna polymerase read and add nucleotides

Answer 3

Read: 3’ to 5’
Add: 5’ to 3’

Question 4

Which starting strand is the leading and lagging strand (with respect to the direction helicase is unzipping in)

Answer 4

Leading: 3’ to 5’
Lagging: 5’ to 3’

Question 5

Which form faster: the hydrogen bonds or covalent bonds in dna, why

Answer 5

Hydrogen bonds, formed by dna polymerase, while covalent ones are formed after with ligase

Question 6

Whats a gene, what is gene expression also called and why

Answer 6

A segment of dna found on the chromosome that specifies the amino acid sequence of a polypeptide
Also called gene expression, since transcribing the gene means its activated/ expressed (proteins are being made from that gene)

Question 7

Does rna polymerase need a primer, why

Answer 7

No, because it attaches to the promoter site and begins to unwind/unzip dna

Question 8

Which strand is the template strand for rna polymerase

Answer 8

3’ to 5’, leading

Question 9

What is around the gene being transcribed

Answer 9

Promoter and termination site

Question 10

Whatre the three post transcriptional modifications of pre mrna

Answer 10

Capping: adds cap (modified guanine) on 5’ end
Tail: poly a tail (Adenine) added to 3’ end
Splicing: spliceosomes take/splice out introns

Question 11

What does the cap and poly a tail do, where are they found on the mrna

Answer 11

Cap: 5’, turns the 5’ end into the leading end and prevents degradation
Tail: 3’: prevents damage/degradation

Question 12

Whatre introns, what happens to them in splicing

Answer 12

Noncoding regions of mrna, get spliced out

Question 13

Whatre the three steps of translation, give a brief definition

Answer 13

Initiation: small ribosomal subunit binds to mrna at start codon aug, large subunit and anticodon arrives
Elongation: trna brings the next amino acid to a site, peptide bonds between the amino acids form, elongation continues until the ribosome reaches a stop codon
Termination: stop codon reached, release factor (which doesnt contain amino acid) enters a site, trna released and polypeptide chain released from trna while ribosome dissociates

Question 14

Whats a polyribosome

Answer 14

When there are multiple ribosomes reading one strand

Question 15

Whatre the three sites of ribosome and what do they do

Answer 15

A: accepting/amino acid site: where trnas with amino acids enter from
P: peptide/ peptidal site: trna releases amino acid (polypeptide chain grows here)
E: exit site, exit for trna after amino acid is released

Question 16

Where does aug codon start at, where does the polypeptide chain grow from

Answer 16

Starts at p site
Grows from p site

Question 17

When do large and small subunits separate

Answer 17

To release mrna

Question 18

Whats another name for the ribosome

Answer 18

Initiation complex

Question 19

What does the stop codon do

Answer 19

Doesnt code for amino acid, but is recognized by the release factor, a protein that stops translation

Question 20

Whats a mutation

Answer 20

A permanent change in the sequence of bases that make up a particular gene

Question 21

What can cause mutations

Answer 21

Errors in replication (rare), mutations/carcinogens (ex. Radioactivity, x rays, uv radiations), organic chemicals in cigarettes (tar), pesticides, and environmental factors, transposons

Question 22

Whatre transposons

Answer 22

Specific dna sequences that can “jump” within and between chromosomes, disrupting gene expression (Ex. Causes frameshift mutation)

Question 23

Whatre the two types of mutations (just names are okay)

Answer 23

Point mutation
Frameshift mutation

Question 24

Whats a point mutation, what does it change, whatre the three point mutations

Answer 24

When one nucleotide in a gene sequence is accidentally paired with the wrong nucleotide during replication or transcription
Changes one nucleotide (one amino acid)
Silent mutation: no effect, code changed results in same amino acid
Missense: one amino acid is changed, possibly results in alteration/ loss of protein function
Nonsense: stop codon (or start) changes, protein function is completely lost

Question 25

Whats a frameshift mutation and whatre the two types

Answer 25

Occurs when an extra base is inserted/ deleted from gene sequence, affecting all amino acids after it
Insertion: shifts entire code of gene to right
Deletion: shifts entire code of gene to left

Question 26

Whats the chance of developing cancer (Generally and in canada)

Answer 26

1/3 general, 1/2 in canada

Question 27

What is cancer caused by

Answer 27

A series of mutations of the tumor supressor genes and proto oncogenes

Question 28

What do proto oncogenes do

Answer 28

Controls cell growth and division

Question 29

Whatre characteristics of cancer cells

Answer 29

Genetically unstable (continues growing), doesnt follow checkpoints in cell cycle, ignores apoptosis, and can survive and proliferate in other parts of the body

Question 30

Whats a tumor

Answer 30

Abnormal mass of tissue that occurs when cells grow/ divide too much/ dont die when they should

Question 31

Whatre the two types of tumors

Answer 31

Benign: abnormal growths that remain in one place
Malignant: cancerous and start in one area, but invate nearby tissues, possibly spreading to other parts of the body

Question 32

how many nucleotides is a primer made of

Answer 32

aprox 20