Nucleic acids and protein synthesis
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NUCLEIC ACIDS AND PROTEIN SYNTHESIS. QUESTION 1. DNA. QUESTION 2. To store and transmit the genetic information that tells cells which proteins to make and when to make them. QUESTION 3. They form the structural units of cells and help control chemical processes within cells.

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To store and transmit the genetic information that tells cells which proteins to make and when to make them


They form the structural units of cells and help control chemical processes within cells.

Question 4

The nucleotide. They are arranged in two long complementary chains.

Question 5

A nitrogen-containing base, a sugar molecule called deoxyribose, and a phosphate group.

Question 6

Adenine, abbreviated A

Guanine, abbreviated G

Cytosine, abbreviated C

Thymine, abbreviated T

Purines: Adenine and Guanine. Have two carbon rings

Pyrimidines: Cytosine and Thymine. Have a single carbon ring.

Question 8

James Watson and Francis Crick in 1953.

Question 9

The alternating deoxyribose sugar and phosphate molecules which are linked together by covalent bonds.

Two Views of the DNA backbone



The backbone is shown in yellow in this diagram. Notice that there are two backbones, one for each of the strands of nucleotides

Question 10

They are covalently bonded to the deoxyribose sugar and then to the complementary nitrogen base in the other strand by hydrogen bonds.


Covalent bonds

Hydrogen bonds

Question 11

Guanine from one nucleotide strand will always pair with cytosine from the other strand using three hydrogen bonds and adenine from one strand will pair with thymine from the other using two hydrogen bonds.


Two Three

Question 12

The process of copying DNA in a cell.

Question 13

The two nucleotide chains separate by unwinding, and each chain serves as a template for a new nucleotide chain.

Red color is the new strand.Blue color is the original strand.

The point at which the two nucleotide chains separate

Replication Fork

Question 14

Question 15

They separate the two complementary chains of nucleotides in the DNA molecule by moving along the molecule and breaking the hydrogen bonds between the complementary bases.

DNA Helicase

Question 16

Bind to a separated chain of nucleotides, move along the separated chain and assemble a new chain using free nucleotides in the nucleus and the separated chain as a template.

DNA Helicase



Question 17

The complementary nature of the two chains of nucleotides that make up the DNA molecule. If the original chain of nucleotides has a nitrogen base sequence of CATCAA the other assembled beside it would be GTAGTT.

Red color is the new strand,blue color the original strand. The red box is showing the complementary bases mentioned in the last slide.

DNA Helicase



Question 18

It proceeds in opposite directions on each original strand. Replication begins simultaneously at many points along one original strand and at just one point on the other original strand.

DNA Helicase


Direction of Replication





Question 19

Two new exact copies of the original DNA molecule. Each molecule has one original strand of nucleotides and a copied complementary strand.

Original DNA strands opened up

Original DNA

Two new molecules of DNA each with one old and one new strand

Practice making a copy of DNA

Question 20

Replication is very accurate, only about one error in every 10,000 paired nucleotides.

Question 21

A mutation

Question 22

Enzymes that proofread DNA and repair errors

Question 23

A variety of agents, including chemicals, ultraviolet radiation and other forms of radiation.

The transfer of genetic information from the DNA in the nucleus to the site of protein synthesis on the ribosomes.

Question 24

Question 25

The nucleotide.

The sugar in RNA is ribose in DNA it’s deoxyribose. RNA has the nitrogen base Uracil (U) instead of Thymine as in DNA

Question 26

Question 27

Messenger RNA (mRNA) - carries genetic information from DNA in the nucleus to the ribosome.

Ribosomal RNA (rRNA), combines with proteins to make up the two subunits of a ribosome

Question 27 (continued)

Transfer RNA (tRNA) -each binds to a particular amino acid and brings it to the ribosome

Question 28

The process by which genetic information is copied from DNA to mRNA

Question 29

RNA polymerase. Makes RNA copies of specific sequences of DNA

A specific region of DNA that marks the beginning of that part of the DNA chain that will be transcribed.

Question 30

The DNA unwinds and the RNA polymerase binds at a particular site on the DNA. The initial binding site is called the "promoter region".

Question 31

That portion of the DNA molecule (only one of the two nucleotide strands) that is copied by RNA polymerase.

Template strand


Question 32

The nitrogen base sequence on the template chain and complementary base pairing by RNA polymerase.

Template strand

Nitrogen base sequence on DNA

Complementary base pairing on mRNA


Template strand


Question 33


The termination signal - a specific sequence of nucleotides on the template that marks the end of a gene.

Template strand


Question 34

Template strand


Question 35

The RNA polymerase

Termination signal

Question 36

Transcripts - different types of RNA molecules including mRNA, tRNA, and rRNA. The mRNA may have further processing occur. Noncoding regions called introns are removed and the remaining coding regions called exons are spliced together.

Question 37

Amino Acids. Twenty different kinds.

Question 38

It’s three dimensional structure, which is determined by its amino-acid sequence.

Levels of protein structure that determine the function of a protein.

Question 39

Triplets of nucleotides in mRNA that determine the sequence of amino acids in proteins

Genetic Code

Question 40

A sequence of three nucleotides on a mRNA molecule. It codes for one specific amino acid. There are 64 codons.

Genetic Code






Question 41

The codon that causes a ribosome to start translating an mRNA molecule into a protein. It is always the nitrogen base sequence AUG. The codons that cause translation to cease. There are three.


Question 42

That all organisms are related.

Question 43

The process of assembling proteins from information encoded in mRNA. It begins when a mRNA molecule leaves the nucleus and migrates to a ribosome.

Question 44

The ribosome.

Question 45

tRNA molecules.

Question 46

A sequence of three nitrogen bases on the tRNA molecule that are complementary to a codon on a mRNA molecule. It actually pairs with the codon on mRNA.

Question 47

The complementary base pairing between codons on mRNA and anticodons on tRNA



Question 48

Composed of rRNA and proteins. Make up 2 subunits. Found free in the cytosol and attached to the endoplasmic reticulum.

Question 49

Ribosomes found free in the cytosol produces proteins used inside the cell. Those attached to the E.R. produce proteins used in the cell membrane or outside of the cell.

mRNA holding site

Question 50

One site holds a mRNA transcript so its codons can be read by tRNA. The other two sites (P and A sites) hold tRNA molecules so that their attached amino acids can be bonded to the growing chain.

mRNA binding site

Start codon

Question 51

Methionine. Only initially. It may be removed later.

Question 52

A stop codon.

View Translation

Question 53

Yes. Many can. They may form a chain known as a polysome.


Review of Protein Synthesis: Transcription and Translation

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