DNA and Protein Synthesis

Question 1

Hershey & Chase

Answer 1

DNA, not protein, is the genetic material that a virus infects a bacteria with.

DNA is the hereditary material of bacteriophage viruses (blender experiment).

Used radioactive labeling and a centrifuge to determine this.

Question 2

Chargaff’s Rules

Answer 2

In DNA, the amount of guanine (G) equals cytosine (C), and adenine (A) equals thymine (T).

1:1 ratio of pyrimidine and purine bases.

Analyzed the base composition of DNA from various organisms.

Question 3

Watson-Crick-Wilkins-Franklin (& Pauling)

Answer 3

Discovered the double-helix structure of DNA.

Used X-ray diffraction data from Rosalind Franklin and Maurice Wilkins.

Constructed a model of DNA as a double helix.

Question 4

5’ (Methyl) cap

Answer 4

Helps the RNA strand bind to the ribosome.

Question 5

Poly-A tail

Answer 5

Added to the 3’ end; protects RNA from degradation.

Question 6

Introns

Answer 6

Removed so only exons leave the nucleus.

Question 7

How can the human genome produce 100,000 polypeptides but only have 24,000 genes?

Answer 7

Different RNA is created based on what is treated as an exon vs. an intron.

Question 8

Parts of nucleotide

Answer 8

Deoxyribose sugar, phosphate, nitrogenous base.

Question 9

Chromatin

Answer 9

Composed of histones (proteins) and DNA.

Question 10

Replication fork

Answer 10

Y-shaped region where new DNA elongates.

Question 11

Origin of replication

Answer 11

Where replication begins.

Question 12

Replication bubbles

Answer 12

Where the 2 strands of DNA separate.

Question 13

Helicase

Answer 13

Untwists the double helix of DNA.

Question 14

Ligase

Answer 14

Joins fragments together.

Question 15

Primase

Answer 15

Adds short RNA primers onto DNA strands.

Question 16

DNA polymerase

Answer 16

Builds a new strand from 5’ to 3’; cannot initiate replication.

Question 17

Leading strand

Answer 17

Forms towards the replication fork continuously.

Question 18

Lagging strand

Answer 18

Forms away from the replication fork non-continuously in Okazaki fragments.

Question 19

DNA vs. RNA

Answer 19

DNA has Thymine; RNA has Uracil.

DNA has deoxyribose sugar; RNA has ribose sugar.

DNA is double-stranded; RNA is single-stranded.

Question 20

How is DNA replication semi-conservative?

Answer 20

When it finishes replicating it consists of one old strand and one new strand

Question 21

DNA replication takes place where in a Eukaryotic cell? Prokaryotic cell?

Answer 21

Eukaryotic: nucleus
Prokaryotic: cytoplasm

Question 22

how does DNA become a protein?

Answer 22

The triplet code in DNA is transcribed into a codon sequence in mRNA in the nucleus. The RNA leaves the nucleus and is translated into a polypeptide in the ribosome

Question 23

What is the start codon?

Answer 23

AUG which codes for methionine

Question 24

What is the stop codon?

Answer 24

UAA, UGA, UAG

Question 25

Anticodon

Answer 25

sequences of nucleotides that are complementary to codons

Question 26

What are the 3 stages of translation?

Answer 26

Initiation, elongation, termination

Question 27

Initiation

Answer 27

When the strand starts. RNA polymerase recognises and binds to DNA in a promoter region Promoter tells RNA polymerase where to start transcription

Question 28

Elongation

Answer 28

The strand get bigger. RNA polymerase adds nucleotides to 3’ end of chain

Question 29

Termination

Answer 29

The strand ends. Release factor breaks the bond between tRNA and the last amino acid Ends shortly after stop sequence (AAUAAA)

Question 30

Translation

Answer 30

Codons of mRNA become an amino acid sequence

Question 31

Why can new strands only grow 5’ to 3’?

Answer 31

The enzyme responsible for building the strand, DNA polymerase, can only add nucleotides to the 3' end of an existing strand

Question 32

Point mutations

Answer 32

The simplest mutation. A base-pair substitution where there is a change in one base pair in a single gene. Ex. THE FAT CAT SAW THE DOG → THE FAT CAT SAW THE HOG

Question 33

Frame-shift mutations

Answer 33

Caused by one singular nucleotide being inserted or deleted. The insertion or deletion results in a frameshift, where the reading frame changes Deletion: Ex. THE FAT CAT SAW THE DOG → THF ATC ATS AWT HED OG Insertion: Ex. THE FAT CAT SAW THE DOG → THE FTA TCA TSA WTH EDO G

Question 34

Why do some insertions and deletions not result in a frameshift?

Answer 34

Because the insertion/deletion can cause a mutated polypeptide to form, or no polypeptide to form

Question 35

Silent mutations

Answer 35

mutations that don’t alter the amino acid sequence of a protein.

Question 36

Nonsense mutations

Answer 36

mutations that create a premature stop codon, leading to a shorter, nonfunctional protein.

Question 37

Missense mutations

Answer 37

Mutations that replace one amino acid with another, which may or may not affect protein function.