AP Bio Unit 6

In what direction is DNA synthesized?

5' to 3'

Which nitrogenous bases are purines?

Adenine and Guanine

How do mutations affect genes?

Alter the gene expression by changing the proteins that are coded for

How do negative regulatory molecule inhibit gene expression?

Blocks RNA polymerase and minimizes gene expression

How is eukaryotic DNA shaped?

Double stranded in chromosomes, in a membrane-bound nucleus

What is the function of RNA polymerase?

Enzyme that makes mRNA from DNA during transcription.

How does the location of translation differ between a prokaryote and a eukaryote?

Eukaryotes: in the nucleus Prokaryotes: in the cytoplasm

Identify two examples of retroviruses

HIV, SIV

What is miRNA?

RNA Interference molecule that targets specific mRNAs

Why does a purine always pair with a pyrimidine?

So they can form hydrogen bonds and has consistent ratios

What is the enhancer region?

Stretch of DNA that alters gene expression by binding transcription factors.

How does the DNA sequence determine the RNA sequence?

The DNA is the template

What happens in the initiation step of translation?

The DNA molecule unwinds and separates to form a small open complex

Describe the process that takes place during transcription

The major steps of transcription are initiation, promoter clearance, elongation, and termination

What is cell differentiation?

The process in which cells become specialized.

How is DNA modified to initiate transcription?

The promoter region of DNA opens up so that the RNA polymerase can begin

How does the repressor interact with the promoter?

The repressor protein works by binding to the gene's promoterregion, preventing the production of mRNA

What is a plasmid?

a small, often circular DNA molecule found in bacteria and other cells—separate from chromosomal DNA

What is a codon?

a three-nucleotide sequence that codes for an amino acid

How does a retrovirus violate the central dogma?

by synthesizing DNA from their RNA genomes, and also by replicating their RNA genomes.

True or false: One codon can code for more than one amino acid

false

What is the function of rRNA?

help hold ribosomal proteins in place and help locate the beginning and end of the mRNA message. They may also carry out the chemical reaction that joins amino acids together.

What is the function of the poly-A tail?

increases mRNA stability in eukaryotes

Is the lac operon repressible or inducible?

inducible

What is the function of the promoter?

initiate transcription

What are the three steps of translation?

initiation, elongation, termination

What is the central dogma?

it is a statement that summarizes how information flows in one direction from DNA to RNA to proteins

Where does translation take place?

ribosomes in the cytoplasm

How is prokaryotic DNA shaped?

single chromosome without a nuclear membrane

Where does translation start?

start codon

What is the function of the GTP cap?

the cap plays a role in the ribosomal recognition of messenger RNA during translation into a protein

What is differential gene expression?

the expression of different genes by cells with the same genome

What is the central dogma?

the process by which the instructions in DNA are converted into a functional product

What happens when tryptophan is absent?

the repressor protein does not bind to the operator and the genes are transcribed

Which nitrogenous bases are pyrimidines?

thymine and cytosine

What is the function of DNA polymerase?

to add nucleotides to the end of a growing DNA strand

Identify two functions of plasmids.

to enhance the survival of an organism by defending the host cell and facilitating replication

What is the function of RNA splicing?

to remove introns and connect the exons

What is the function of helicase?

to separate DNA strands

What is the structure of a purine?

two rings

What is the function of reverse transcriptase?

catalyzing the formation of DNA from a RNA template

What is the function of DNA ligase?

connects okazaki fragments

What is transcription?

synthesis of an RNA molecule from a DNA template

What is the function of tRNA?

transfers each amino acid to the ribosome as it is specified by the coded messages in the mRNA.

What are the nucleotide base pairing rules?

A with T and C with G

What is the function of mRNA?

To bring the instructions to make a protein from the nucleus to the ribosome.

What is the function of RNA primers and primase?

To serve as a starting for DNA synthesis

How is DNA modified to inhibit transcription?

Repressors respond to external stimuli to prevent the binding of activating transcription factors.

What is a promoter?

A sequence of nucleotides on the DNA that designates a start point

What is the TATA box?

A sequence on DNA that signals the beginning of a gene

What are the three sites found on a ribosome and what is their function?

A site: accepts the incoming tRNA P site: holds the tRNA E site: binds a free tRNA

What happens in the termination step of translation?

A stop codon enters the A site

Which direction is the template strand read?

3' to 5' direction

If there is 20% thymine in a DNA strand, how much cytosine is there?

30%

What direction does the DNA polymerase READ the DNA template?

5' to 3'

Which direction does transcription take place (which direction is the RNA synthesized)?

5' to 3'

What are epigenetic changes?

Changes that don't affect DNA sequence, but can effect gene regulation.

What is the primary source of heritable information?

DNA and sometimes RNA

Why is DNA a better hereditary material than RNA?

DNA is more stable

How is genetic information transmitted from one generation to the next?

DNA is organized in chromosomes which are separated and passed down from the parents through meiosis

Why are RNA primers required for DNA replication?

DNA polymerase can only extend a nucleotide chain, not start one

How does the leading and the lagging strand differ?

Leading: 5' to 3' and continuous Lagging: 3' to 5' and in fragments

How do transcription factors affect the binding at the promoter?

Makes it either easier or harder for RNA polymerase to bind to the promoter

What is DNA?

Molecule that encodes the genetic instructions used in all known living organisms

What happens when tryptophan is present for the trp operon?

RNA polymerase is blocked

What happens in the elongation step of translation?

RNA polymerase moves along the template strand, synthesising an mRNA molecule

What are regulatory sequences?

Regions that impact how genes are used (gene switches, promoters, leader/trailer, etc.)

How does the genetic code demonstrate common ancestry?

Similarities can be tracked back

What is siRNA?

Small interfering RNA. They block expression of a gene with the same sequence as the RNA

Describe the process of DNA replication using the enzymes described above (helicase, topoisomerase, DNA polymerase, primase, RNA primers, and DNA ligase)

The strands of DNA are separated using the helicase, the topoisomerase gets rid of the knots at the replication fork so that the strands can separate, then primers and primase act as a starting point so that the polymerase can add on nucleotides, then the ligase connects the okazaki fragments

How do siRNA and miRNA affect gene expression?

They inhibit gene expression

How is DNA stored?

Tightly packed as chromosomes in the nucleus

True of False: All somatic cells have the same DNA

True

What is a repressor?

a protein that binds to the operator and prevents transcription

What is the promoter region?

a region of DNA that initiates transcription of a particular gene

What is an operon?

a unit made up of linked genes that is thought to regulate other genes responsible for protein synthesis.

How do new phenotypes arise?

environment

How can multiple proteins be synthesized from the same mRNA transcription?

multiple codons can code for the same amino acid

What are other names of the template strand?

noncoding strand

How does the mRNA, tRNA, and rRNA all interact?

rRNA forms ribosomes which physically move along an mRNA molecule to catalyze the assembly of amino acids into protein chains. They also bind tRNAs and various accessory molecules necessary for protein synthesis.

What is the function of transcription factors?

recognition of sequences within the enhancer and promoter and activation of transcription, and control expression

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

Is the trp operon inducible or repressible?

repressible

What are the three types of substitution point mutations?

silent, missense, and nonsense mutations

What is the structure of a pyrimidine?

single ring

Which strand is the template strand?

template strand

How does a virus incorporate its viral genome into a host genome?

the RNA of the retrovirus is reverse-transcribed into DNA by reverse transcriptase, then inserted into the host genome by an integrase

Identify three post-transcriptional modifications that alter the pre-mRNA prior to its release from the nucleus

the addition of a 5' cap, the addition of a 3' polyadenylated tail, and RNA splicing

What happens when lactose is absent for the lac operon?

the lac repressor binds tightly to the operator, preventing transcription by RNA polymerase

What happens when lactose is present for the lac operon?

the lac repressor loses its ability to bind DNA