DNA & RNA-IB Biology

The diagram below shows the bases on a short section of DNA during replication. Identify the sequence of bases on the new complementary strand labelled I in the diagram. "GATC"

"CTAG"

A certain gene in a bacterium codes for a polypeptide that is 120 amino acids long. How many nucleotides are needed in the mRNA to code for this polypeptide?

360 (120 x 3)

During the process of replication, which bond(s) in the diagram of DNA below is/are broken?

4, 5 The bonds between the bases (4-three lines 5-two lines)

Which of the following are connected by a hydrogen bond?

A base pair of a DNA molecule

Explain briefly how termination of translation occurs

A release factor binds to the stop codon and hydrolyzes the bond between the polypeptide and its tRNA in the P site. This freezes the polypeptide and the translation complex disassembles. The subunits of ribosome separate.

What is an intron?

A section of mRNA removed before translation

Sickle cell anemia. Explain how a single base substitution mutation can have significant consequences for an individual

A single base substitution mutation changes the sequence of DNA. This change alters the mRNA produced in transcription; an amino acid in a polypeptide is changed; affecting the primary structure of a polypeptide completely alters its function; single cell anemia changes codon GAG to GTG, causes a sickle shape of the hemoglobin

What is the composition of the backbone of DNA?

Alternating sugar and phosphate molecules

What is a role of carbohydrates in animal cells?

As energy storage

Explain why the process used during protein synthesis in cells is called translation

Because the mRNA is translated into amino acids, a codon codes for a triplet of bases to the amino acid, and the genetic code is translated

Shape, place, and purpose of DNA Polymerase III

Circular donut shape around the top completed strand of the DNA fork. Synthesizes new strand by adding nucleotides onto the primer

Which of the following reactions occurs when a dipeptide is formed from amino acids?

Condensation

Identify two locations within a eukaryotic cell where translation occurs

Cytoplasm Endoplasmic reticulum

What are the components of a DNA nucleotide?

Deoxyribose, a phosphate and one of the bases: adenine, cytosine, guanine, or thymine

The diagram below represents a DNA nucleotide. What could the part labelled X represent? *Base

Guanine

Which substance is a base that is found in DNA?

Guanine

What type of bond holds the complementary base pairs together in a double helix of DNA?

Hydrogen bonds

What causes water to have a relatively high boiling point?

Hydrogen bonds between water molecules

Describe the structure of parts of ribosome during protein synthesis

I. Small ribosomal subunit, outer bottom left II. Large ribosomal subunit, top outer left III. Transfer RNA dark circle in the middle center IV. Messenger RNA, Strand sticking out of bottom right portion

The drawing below shows a short section of a DNA molecule. What is labelled by I, II, and III? *I top layer, II middle layer shaded, III in between third and fourth layer

I: 5' end II: Purine III: Covalent bond

Which events take place in DNA replication? I. Formation of messenger RNA II. Unwinding of DNA double helix III. Formation of complementary strands by DNA polymerase

II and III only Unwinding of DNA double helix and formation of complementary strands by DNA polymerase

To which parts of the deoxyribose molecule do phosphates bind in DNA?

III and V *At the OH at the bottom left and the OH at the top left

What is a difference between the sense and antisense strands of DNA?

Nucleotides are linked to the antisense strand by hydrogen bonding during transcription, but not to the sense strand

The diagram shows part of a molecule produced by replication of DNA. What is the significance of the shaded and the unshaded regions? *Left side w/ phosphates up shaded, right side unshaded. Double bond, triple bond, double bond down the middle

One of the parts has been newly synthesized and the other was part of a pre-existing DNA molecule

Consider the metabolic pathway shown below If there is end-product inhibition, which product (B to E) would inhibit which enzyme (1 to 4)?

Product: E Enzyme: 1

What enzyme is used in transcription but not in translation?

RNA polymerase

List three of the other molecules, apart from mRNA, required for transcription

RNA polymerase DNA Nucleoside triphosphates

Which are the correct directions of replication transcription and translation?

Replication: 5' to 3' Transcription: 5' to 3' Translation: 5' to 3'

The diagram below represents DNA replication. Some of the bases are indicated. "ACG" *Forks are opening to the right side In which direction is the replication fork moving and which bases would be needed to replicate the section of DNA shown?

Right to left "TGC"

Shape, place, and purpose of Helicase

Right where the fork opens, no real shape. Unwinds the double helix at replication forks

State at which period during the cell cycle DNA replication occurs.

S Interphase

Suggest one reason for the differences in the numbers of exons found in genes of S. cerevisiae and mammals

S. cerevisiae is prokaryotic and mammals are eukaryotic. Mammals have more transcriptional regulation

Explain how the amino acid was attached to the tRNA

The amino acid was attached to the tRNA at the 3' end with a specific enzyme for the specific tRNA molecule. These enzymes are called aminoacecl-tRNA synthetase, and use ATP for energy. There is a specific enzyme for each amino acid

Describe the genetic code

The genetic code is found in DNA; a sequence of three nitrogenous bases forms a codon, which codes for amino acids; genetic code is universal for all life; more than one codon can code for a specific amino acid (an amino acid can have more than one codon); but a specific codon can only code for one amino acid; genetic code is transcribed to mRNA in transcription; carried in genes, which are what determine specific traits of an individual; genetic code in DNA can be copied by DNA replication; the same in genomes of each cell in an individual; can be mutated, which changes codons, thus changing the amino acids formed; alterations of the genetic code due to mutations changes the function of polypeptide produced during translation; there are 64 possible codons in the genetic code, 3 of which are stop codings

Living organisms use DNA as their genetic material. Explain how DNA is replicated within the cells of living organisms

The process of DNA replication within the cells of living organisms begin with the helix being unwound so the two strands are separated. Helicase is responsible for this, separating the strands by breaking the hydrogen bonds between the bases. Following this, new strands are formed, or replicated, on each of the two single strands from nucleotides being added. The new strands have complementary base pairing; adenine is paired with thymine and guanine is paired with cytosine. DNA polymerase forms the newly made complementary strands. Each of the DNA molecules formed has one old and one new strand, making replication semi-conservative. Living organisms use DNA as their genetic material, making replication vital.

The graph below shows the effect of changing the substrate concentration on an enzyme controlled reaction. What is the correct interpretation of these data?

The rate of reaction increases up to a point and then remains constant

What is the maximum number of fatty acids that can be condensed by glycerol?

Three

Where do transcription and translation occur in eukaryotic cells?

Transcription: Nucleus Translation: Cytoplasm

What are pyrimidines in DNA?

Types of base pairs

Determine the strand of mRNA that is transcribed from the DNA strand below A-T-C-C-A-G-G-T-C-A-A-G

U-A-G-G-U-C-C-A-G-U-U-C

How would the following DNA sequence, ACGTTGCATGGCA, be transcribed?

UGCAACGUACCGU

What is responsible for the conservation of the base sequence during DNA replication?

Unpaired bases always attracting their complementary nucleotides.

Which substance is a base found in RNA?

Uracil

State two differences between the structure of DNA and RNA

a. Deoxyribose sugar vs. ribose sugar b. Thymine vs. uracil c. Double helix vs. single strand

The information....during translation. The diagram below represents the process of translation. a. Annotate the diagram to show the direction in which the ribosome moves during translation b. state the name of the next amino acid which will attach to the polypeptide *ends with "UUAAAAA"

a. arrow head pointing to right b. Alanine

Outline the process of translation

mRNA acts as a template, being read in codons (base triplets); Each codon specifies the addition of a particular amino acid to the growing polypeptide; ribosomes bind to the mRNA and move along it, facilitating elongation; tRNA brings amino acids to the mRNA-ribosome complex; tRNA has a complementary an anti-codon that binds to a specific codon; the stop codon releases a polypeptide and causes termination

The structure of the DNA double helix was describe by Watson and Crick in 1953. Explain the structure of the DNA double helix, including its subunits and the way in which they are bonded together.

subunits are nucleotides; one base, one deoxyribose and one phosphate in each nucleotide; diagram showing base linked to deoxyribose C1 and phosphate to C5; four different bases- A, C, G, T; Nucleotides linked up with sugar-phosphate bonds; covalent/phosphodiester bonds; two strands of nucleotides linked together; base to base; A to T and G to C; hydrogen bonds between bases; antiparallel strands; double helix described or drawn

State the name of a structure shown on the diagram that has an anticodon

tRNA

Describe the consequence of a base substitution mutation with regards to sickle cell anaemia

base substitution mutation changes the DNA sequence and changes the mRNA during transcription; the amino acid sequence is changed; One codon is changed; glutamic acid is changed to valine; shape of hemoglobin is changed; less soluble and crystallizes out; don't carry oxygen as well; red blood cells sickle and impair the blood flow; health problems such as anemia and fatigue

In the structure of DNA what binds with cytosine?

Deoxyribose

In an electron micrograph, a DNA molecule appears 1mm wide. The magnification of the micrograph is 500,000. What is the width of the DNA molecule?

2 nm

Outline the structure of DNA

DNA is constructed with subcomponents called nucleotides. Every nucleotide of DNA is composed of a phosphate group, a sugar, known as deoxyribose, and a molecule that is a nitrogenous base. There are four possible nitrogenous bases in the nucleotides of DNA: adenine (A) thymine (T) cytosine (C) and guanine (G). Nucleotides are covalently linked together to form a strand of DNA. DNA molecules have the shape of a double helix; two single strands of DNA interact to form this shape. The nitrogenous bases pair with each other to form hydrogen bond. Also, at the end of each strand there is a phosphate group attached to the carbon atom number 5 of the deoxyribose (5') and at the other end of each strand is a hydroxyl group attached to the number 3 of the deoxyribose (3').

A biochemist isolated and purified molecules needed for DNA replication. When some DNA was added replication occurred, but the DNA molecules formed were defective. Each consisted of a normal DNA strand paired with segments of DNA a few hundred nucleotides long. Which of the following had been left out of the mixture?

DNA ligase

Explain the significance of complementary base pairing during DNA replication

DNA replication is semiconservative; each parental strand acts as a template to form a complimentary strand. Two daughter DNA molecules are formed. Primer is added at the replication fork which is complementary to the DNA strand; DNA polymerase replaces the primer with DNA nucleotides.

Distinguish between the structure of DNA and RNA

DNA: double-stranded molecule; 5-carbon sugar is deoxyribose; has nitrogenous bases (A, G, C, T) RNA: single-stranded molecule; 5-carbon sugar is ribose; has the same bases, except uracil replaces thymine

What effect do enzymes have on the activation energy of exergonic and endergonic reactions?

Decreases both

Explain the process of transcription in eukaryotes

In eukaryotes, transcription occurs in the nucleus in a 5' to 3' direction; antisense strands is copied, sense strand is not; mRNA is produced from a gene found in DNA; RNA polymerase is a key enzyme in this process-it unzips the double helix by breaking H bonds between complementary base pairs in DNA; RNA polymerase, beginning at the promotor (TATA box), adds RNA nucleotides and helps them bond together to from a single strand of RNA; RNA polymerase rewinds the double helix of the DNA after it is transcribed; In eukaryotes, replication ends after the "terminator" (a sequence of bases that signals the end of transcription is reached); Extra nucleotides are removed from the RNA strand before translation occurs; RNA splicing removes introns (non-coding sequences) and keeps exons (coding sequences); specific steps are initiation (RNA polymerase binds to the promoter), elongation (RNA strand being produced), and termination (stop codon is reached, mRNA detaches)

Why are the messenger RNA molecules received by eukaryotic ribosomes shorter than the messenger RNA molecules formed by transcription of DNA?

Introns are removed before the RNA is translated

Draw a diagram of the molecular structure of a portion of DNA

Look at bottom right corner of first question on DNA Structure Worksheet

Explain the process of translation

mRNA is translated into amino acids, which form polypeptides; In prokaryotes, transcription and translation occur at the same time; eukaryotes, translation happens after transcription; mRNA exits out of the nucleus into the cytoplasm (where translation occurs in eukaryotes; in prokaryotes, it occurs in the nucleolus); rRNA, because it makes up ribosomes; translation occurs in specific steps; the first yep is initiation, where the mRNA binds to the binding site in the ribosomes; tRNA with an anticodon complimentary to the mRNA's codon goes to the "A" site of the ribosome, where it forms H bonds with the mRNA. The tRNA has an amino acid attached to its 3' end which is coded for by the codon in the mRNA. The first tRNA moves into the "P" site where the polypeptide chain grows and is carried by the tRNA> This process continues; the amino acids form peptide bonds withe ash other. When tRNA needs to exit the ribosome, it moves to the "E" site; Process of elongation consists of codon identification, where the tRNA anticodon binds with the mRNA codon; peptide bond formation where amino acids bind together; ad translocation, where the polypeptide chain is transferred from one tRNA molecule, to the next. The ribosome moves along the mRNA in a 5' to 3' direction. The final step of translation is termination; when the final codon reaches the "A" site of the ribosome; a termination factor hydrolyzes the peptide bond formation and the polypeptide detaches from the ribosome; the mRNA leaves the mRNA binding site, and the ribosome disassembles (the small subunit and the large subunit separate); structure of tRNA helps it function; the shape of a 3-D clover leaf; has an anticodon on one end and an amino acid attached to CCA on the other end by a covalent bond (3' end). H bonds form b/w some complimentary base sections, these sections may be helical