AP Bio Unit 6 Review Questions

A section of the template strand of DNA reads: 5' -CAACACTAA- 3'. Determine the mRNA sequence and translate it.

3' -GUUGUGAUU -5', Val Val Ile

Referring to question 3, what is the codon that the tRNA binds to?

AUG

Describe transformation. Are all bacteria competent?

Bacteria absorb DNA from their surroundings and incorporates it into their genome.

Describe the process of conjugation.

DNA transfer from one bacterium to another

Why is redundancy in the genetic code important?

It minimizes the harmful effects that incorrectly placed nucleotides can have on protein synthesis.

When does translation stop?

When a stop codon is reached

How can mutations lead to natural selection?

When mutations occur in germ cells, they can be passed on to their offsprings. If the environment changes rapidly, some species may not be able to adapt fast enough through natural selection.

Can a transformed organism pass on its new traits to its offspring?

Yes

The DNA from a certain plant species is analyzed. The DNA contains 22 % thymine. Determine the percent of the other bases.

adenine: 22%, guanine: 28%, cytosine: 28%

Fill in the blanks: tRNA has an _____ region which is complementary and antiparallel to _____.

anticodon, codon

Fill in the blank: the mRNA nucleotide triplets are called _____. These code for ___ _____.

codons, amino acids

If the tRNA anticodon reads 3' -CUU - 5' then what does the mRNA codon read that it can bind to? Knowing this, what amino acid will the tRNA be carrying?

5' - GAA - 3', Glu

If one DNA strand reads: 3' - ACTAG - 5' what would the complementary DNA strand read?

5' - TGATC - 3'

What does it mean if a gene/trait is "evolutionarily conserved?"

A gene that has remained essentially unchanged throughout evolution.

After fertilization a zygote forms. The cells then go through mitosis. Explain how this bundle of cells eventually forms a human with specialized cells.

After mitosis, each cell doubles, and when two haploid cell join, they form a single diploid cell that contains all necessary chromosomes.

An mRNA sequence reads: 5' - CGAUGCAGA- 3', Translate this sequence (Assume you are downstream of the start codon.)

Arg Cys Arg

Describe how it is possible for only one identical twin to express an inherited disease.

Because genes can be affected by the environmental factors.

Is DNA positively or negatively charged? How could you tell just by looking at a strand of DNA?

DNA is negatively charged.

True or false: the genetic code is read in groups of two nucleotides at a time called the doublet code.

False

What is the center of DNA composed of?

Nucleotides

In eukaryotic cells where does transcription occur?

Nucleus

Where does translation occur?

Ribosomes in the cytoplasm

What functional group defines the 3' end of DNA?

hydroxyl group

Circle the correct item: The lac operon is repressible/inducible.

inducible

Fill in the blank: A change in an organism's genotype can cause a change in the organism's ________.

phenotype

What functional group defines the 5' end of DNA?

phosphate group

Circle the correct item: The trp operon is repressible/inducible.

repressible

Fill in the blanks: The process of _____ converts DNA to RNA. The process of ______ turns RNA into proteins.

transcription, translation

What is a promoter region? Are promoter regions upstream or downstream of the gene?

A promoter region is where the transcription is initiated. It's upstream of the gene.

What are restriction enzymes? Where do they come from?

A restriction enzyme is an enzyme isolated from bacteria that cuts DNA molecules at specific sequences. They are found in prokaryotes.

Why does DNA move during gel electrophoresis?

DNA is negatively charged. As a result, the positive electrode when turned on pulls on the DNA, so the DNA moves through the gel towards the positive electrode.

What are the three parts of an operon?

Promoter, operator, structural genes

If a bacterial cell uses up its tryptophan and it builds up inside of the cell, what would happen to the trp operon?

Then the trp operon does not bind to the operator and the genes are transcribed.

If a bacterial cell does not need tryptophan and it builds up inside of the cell, what would happen to the trp operon?

Then the trp operon will bind to the operator and the transcription will be stopped.

What role do cytoplasmic determinants play in early embryonic development?

They are responsible for the regulation of gene expression.

What if you were performing gel electrophoresis and the molecule you were examining moved towards the negative electrode? What does this mean about the charge of the molecule you are analyzing?

This means the molecules are positively charged.

When some people hear of apoptosis, they think that this is a bad thing that cells go through. Provide one example that illustrates the importance of apoptosis(in reference to embryonic development).

Through the apoptosis, it can eliminate pre-cancerous and virus infected cells.

How can PCR be used to produce copies of a gene?

Throughout the PCR process, DNA is subjected to repeated heating and cooling cycles during which important chemical reactions occur. During these thermal cycles, DNA primers bind to the target DNA sequence, enabling DNA polymerases to assemble copies of the target sequence in large quantities.

How does transcription and translation differ between prokaryotes and eukaryotes?

Transcription and translation occurs simultaneously in prokaryotes and in eukaryotes the RNA is first transcribed in the nucleus and then translated in the cytoplasm.

Describe the process of transduction.

Transduction is the process by which a virus transfers genetic material from one bacterium to another.

Errors in DNA replication can lead to natural selection. Why? Would natural selection still occur if all errors were corrected? Why or why not?

Although there's a mistake throughout the DNA replication, it can still lead to a natural selection if that modified trait fits for the survival.

Differentiate between histone acetylation and DNA methylation.

DNA methylation results in methylated DNA bases that lead to gene inactivation, while histone acetylation is a modification of the histone proteins associated with the nucleosome structure.

If an error occurs in DNA replication, how is it fixed?

DNA polymerase repairs, which is called mismatch repair

List 3 differences between DNA and RNA.

DNA- deoxyribose sugar, thymine, double stranded RNA-ribose sugar, uracil, single stranded

Describe the mutation that causes cystic fibrosis.

Deletion of phenylalanine on amino acid 508.

Differentiate between a repressible and inducible operon.

Inducible operons are turned off under normal conditions while the repressible operons are turned on under normal conditions.

If one bacterial cell has a gene that is promoting its survival, explain how other bacterial cells can benefit from it.

It can transfer the gene that promotes its survival to another bacteria.

Referring to question 10: imagine if the coding strand were transcribed and translated instead. Determine the mRNA sequence and translate it. How would this error affect the polypeptide produced?

It would change the whole thing of amino acid sequence.

What are the two reproductive cycles of bacteriophages? Describe each.

Lytic and lysogenic cycle

Referring to question 3, which amino acid does this tRNA carry?

Methionine

Differentiate between silent, missense, and nonsense mutations. Predict which would be most detrimental and why?

Missense: changes an amino acid to another amino acid Nonsense: changes an amino acid to stop codon Missense mutations are more detrimental because it can cause the entire change in the sequence of the amino acid or polypeptide chain.

In which direction does DNA move during gel electrophoresis?

Moves towards the positive charge

Why do introns exist if they are just spliced out of the mRNA during the pre-mRNA modifications?

Not only do the introns not carry information to build a protein, they actually have to be removed in order for the mRNA to encode a protein with the right sequence.

Mutations can be detrimental, beneficial, or neutral. Give an example of a mutation that is detrimental and an example where it is beneficial.

One example would be a cystic fibrosis.

What does it mean that DNA strands are antiparallel?

One strand moves in the direction of 3' to 5', and the other strand moves in the direction of 5' to 3'.

The very first tRNA will enter at which site on the ribosome (A, P, or E)?

P site

Think back to Unit 1. Identify the major classes of macromolecules and then identify their monomers and polymers.

Proteins: amino acids Carbohydrates: monosaccharide, polysaccharide Lipids: fatty acids, phospholipids Nucleic Acids: nucleotide

Differentiate between purines and pyrimidines

Purines: Adenine and Guanine Pyrimidines: Cytosine and Thymine

Describe step-by-step how DNA is replicated.

Replication occurs in three major steps: the opening of the double helix and separation of the DNA strands, the priming of the template strand, and the assembly of the new DNA segment. During separation, the two strands of the DNA double helix uncoil at a specific location called the origin. Several enzymes and proteins then work together to prepare, or prime, the strands for duplication. Finally, a special enzyme called DNA polymerase organizes the assembly of the new DNA strands.

Trace the path of a newly produced polypeptide that will leave the cell?

Rough ER, Golgi, secretory vesicles, cell exterior

In which stage of the cell cycle does DNA replicate?

S phase

During gel electrophoresis, which size of DNA will move the furthest? Why?

Short fragments will move the farthest because all DNA segments have the same charge per mass and the short fragments have less mass.

Circle the correct option: substitutions are small/large scale mutations.

Small

If reference to question 8, what would happen if you then add lactose to the medium?

Still remains off

What is the backbone of DNA composed of?

Sugar and phosphate

How does gel electrophoresis separate DNA fragments?

The electric current separates the DNA fragments.

What would be the immediate effect to transcription if a cell was exposed to a drug that mutated the promoter region?

The initiation will be inhibited.

If a bacterial cell is grown in a nutrient rich, lactose free medium, what would you expect to see at the lac operon?

The lac operon will remain off

Describe the consequences of a chemical that prevents the 5' cap and poly-A tail from forming on eukaryotic mRNA?

The mRNA molecule would not be able to start the translation and it will also be degraded.

Describe the Meselson and Stahl experiment that supported the semi-conservative model of DNA replication.

The presence of one parental subunit for each daughter DNA double helix supported semi-conservative replication.

Summarize the purpose of translation in 1-2 sentences.

The process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis.

If a bacterial cell has a mutation to the trp repressor that changes the shape of the active site, how would this affect the production of tryptophan?

Then the repressor protein would not be able to bind to the active site, and it cannot inhibit the transcription.

List and describe the steps of transcription.

Transcription takes place in the nucleus of the cell. During transcription messenger RNA (mRNA) reads and copies DNA's nucleotide sequence in the form of a complimentary RNA strand. Then the mRNA carries the DNA's information in the form of codons to the ribosome. Codons are a 3 nucleotide sequence in an mRNA strand.

Circle the correct option: microRNAs and siRNAs block transcription/translation.

Translation

True or false: morphogenesis is the process that gives an organism its shape.

True

True or false: only the template strand of DNA is transcribed during transcription.

True

True or false: plasmids replicate separately from chromosomal DNA.

True

What does it mean that DNA strands are antiparallel and complementary?

Two biopolymers are antiparallel if they run parallel to each other but with opposite directionality. An example is the two complementary strands of a DNA double helix, which run in opposite directions alongside each other.

Using a codon chart determine what UAU codes for?

Tyr

Fill in the blanks: protein synthesis occurs in two stages ______ and ______.

transcription, translation