AP BIO Unit 6 questions

List three differences between RNA and DNA.

1. RNA can leave the nucleus but DNA canot 2. RNA has the ntrogenous bases A, U, G, C, while DNA has the nitrogenous bases A, T, G, C 3. RNA is single stranded and DNA is double stranded

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

22%Adenine 28%Cytosine 28%Guanine

Describe the process of transduction.

A bacteriophage passes DNA from one bacteria cell to another (transfer of DNA from one cell to another via a viral vector)

If a bacterial cell uses up its tryptophan storage

A repressor would bing to the operator, blocking RNA polymerase and therefor no morer trp would be synthesized.

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

Advantageous genes can help an organism better survive so when a mutation occurs this can lead to a higher likely hood of negative effects occurring in their life. The mutated DNA can still be apart of future generations

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

Apoptosis is programmed cell death. In the care of embryonic development, it is what allows organs to take their forms.

Fill in the blank: the mRNA nucleotide triplets are called ________. These code for ______.

Codons and amino acids

What role do cytoplasmic determinants play in early embryonic development?

Cytoplasmic influence the pattern formation for the organism, or its body plan.

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

DNA is negatively charged because of the presence of phosphate groups in nucleotides. The phosphate backbone of DNA is negatively charged, which is due to the presence of bonds created between the phosphorus and oxygen atoms.

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. The gel acts like a seive.

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

False the genetic code is read in groups of 3 nucleotides at a time called the triplet code.

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

False, the genetic code is read in groups of 3 nucleotides at a time called the triplet code.

What functional group defines the 3' end of DNA?

Free hydroxyle group

What functional group defines the 5' end of DNA?

Free phosphate group

Describe step by step how DNA is replicated.

Helicase opens up the DNA at the replication fork. Single-strand binding proteins (SSBPs) coat the DNA around the replication fork to prevent rewinding of the DNA. Topoisomerase works at the region ahead of the replication fork to prevent supercoiling. Primase synthesizes RNA primers complementary to the DNA strand. DNA polymerase III extends the primers, adding on to the 3' end, to make the bulk of the new DNA. RNA primers are removed and replaced with DNA by DNA polymerase I. The gaps between DNA fragments are sealed by DNA ligase.

Differentiate between histone acetylation and DNA methylation.

Histone acetylation is the process by which acetyl groups are added to histones, which will loosen the tightly wound DNA so it can be accessible for transcription. DNA methylation does the opposite. The process adds methyl groups which causes the chromatin to condense even further, preventing transcription.

How can mutation lead to natural selection?

If a trait is advantageous and helps the individual survive and reproduce the genetic variation is more likely to be passed to the next generation

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

If an error occurs in DNA replication then it is detected when it the DNA is being proof read. Then mismatch repair will take place which is when enzymes fix the incorrect nucleotide paring for the correct nucleotide pairing.

In reference to question 8, what would happen is you then add lactose to the medium?

If lactose was added to the medium, lactose would bind to the lac repressor, meaning it will detach from the DNA. That means the genes can now be transcribed to digest the lactose.

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

If the promoter region was mutated then RNA polymerase would not be able to bind to the DNA and transcription would not be able to take place.

In eukaryotic cells where does transcription occur?

In the nucleus

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

Introns exist so that there will be more genetic variation in the DNA; a single gene can produce many different proteins due to splicing.

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

It is expected that the lac repressor is bound to the operator, making it allosterically active. Transcription is OFF.

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

It is possible for only one identical twin to express an inherited gene because chromatin modifications do not alter the nucleoid sequence of DNA but can be heritable to future generations. These modifications can also be reversed explaining the transfer of the diseases to only one of the twins. This is called epigenetic inheritance.

Describe transformation. Are all bacter competent?

It is the process by which bacteria uptakes DNA from its extracellular environment. Most if not almost all bacteria is competent

What does it mean that DNA strands are antiparallel?

It means that one strand runs in the 5' to 3' direction and the other strand runs in the opposite, upside down direction 3' to 5'.

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

It would read 5'-TGATC-3'

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

Lytic: the virus introduces its genome into a host cell and initiates replication by hijacking the host's cellular machinery to make new copies of the virus lysogenic: The phage infects a bacterium and inserts its DNA into the bacterial chromosome, allowing the phage DNA (now called a prophage) to be copied and passed on along with the cell's own DNA

What is the center of DNA composed of?

Nucleotide paring

What are the three parts of an operon?

Promoter- where RNA polymerase binds Genes- code for related enzymes in a pathway operator- a segment of DNA to which a repressor binds and it acts as the on off switch

DIfferentiate between purines and pyrimidines.

Purines have a double ring structure, while pyrimidines have a single ring structure.

Why is redundancy in the genetic code important?

Redundancy in the genetic code means that more than one codon code for each amino acids. It is important because it minimizes the harmful effects that incorrectly placed nucleotides can have on protein synthesis.

Differentiate between a repressible and inducible operon

Repressible operon is when the operon is typically on but is is now turned off. Inducible operon is when the operon is typically off but now it is turned on.

What is the backbone of DNA composed of?

Sugar-phosphate

In which stage of the cell cycle dose DNA replicate?

The S stage.

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

The mRNA would not be able to leave the nucleus. Without a 5' cap and poly-A tail, the mRNA would not be protected from dehydration and ribosomes would not be able to attach to 5' end as the mRNA would never reach the cytoplasm.

Descsibes the mutation that causes cystic fibrosis.

The mutation that causes c.f. is mutation of the protein with the deletion of the phenylalanine 508 gene

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

The production of tryptophan would be constant. Since the trp repressor has a differentially shaped active site, tryptophan would be unable to it and could not shut off transcription.

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

The promoter region of DNA where the RNA polymerase molecules attach to and they are upstream of the desired gene to be transcribed.

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

The trp operon would be switched off. This means that tryptophan will bind to the repressor and temporarily shut off transcription of that gene.

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

They cultured bacteria with the heavy isotope, 15N. Then they transferred to bacteria to a medium 14N, a light isotope. Then they centurfuged the bacteria and analyed it after serverl generations. They results supported the semi-conservation model of DNA replication.

What does it mean that DNA strands are antiparalled and complementary? Draw a strand of DNA with 6 nucleotides to support your answer.

This means that one DNA strand runs in the 3' to 5' direction, while the other strand of DNA runs in the 5'3 direction. Also, the nucleotide corospod depending on the DNA strand (ex. A=T and C=G)

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

Transcription and translation

True or False: only the template strand of DNA is trandscribed during transcription.

True

True or false: plasmids replicate separately from chrosmosomal DNA.

True

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

Using conjugation the bacteria can use a pilus to transfer a plasmid to the other bacteria

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

Yes as the DNA is already in the organism it will transform along with the parent

What are restriction enzymes? Where do they come from?

a protein that will isolate specific DNA sequence sites producing sticky ends at the open ended sites. they are found in bacteria

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

as the DNA strand is subjugated through heating and cooling processes this lets chemical process to occur allowing for the primer to mass produce the copy

After fertilication a zygote forms. The cells then go though mitosis. Explain how this bundle of cells eventually forms a human with specialized cells (i.e. liver cells

blodd cells, neurons, etc.), The zygote will undergo mitosis and become an embryo. During embryonic development, cell differentiation will occur through cytoplasmic determinants and induction. Substances in the maternal egg can influence cells and so can cell to cell signals can cause changes in gene expression. These processes of differentiation influence the pattern formation for the organism, or its body plan. Programmed cell death, or apoptosis, will allow these organs to take their form.

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

detrimental: cystic fibrosis beneficial: mutations that can help prevent heart disease or having harder bones neutral: silent point mutations

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

inducible

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

it means that the molecule is positively charged

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

it means the gene is essentially the same even through evolution

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

phenotype

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

repressible

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

silent: a change of a single nucleotide that does not affect the amino acid missense: a single nucleotide change causes a new amino acid to form nonsense: the genetic alteration that causes the premature end of a protein The most detrimental would be a nonsense mutation because the protein itself would not exist

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

small

Describe the process of conjugation.

the process by which one bacterium transfers genetic material to another through direct contact

How does gel electrophoresis separate DNA fragments?

the shorter fragments move farther along towards the positive end

In which direction does DNA move during gel electrophoresis?

towards the positive end

Cicle the correct option:microRNA and siRNAs block transcription/translation.

translation

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

true

Using a codon chart determine what UAU codes for?

tyrosine

During gel electrophoresis

which size of DNA (long vs short fragment) will move the furthest? Why?, shorter fragments; it is easier for them to move across when there are less hydrogen bonds bringing you down