AP Bio Unit 6: Gene Expression & Regulation

AP Bio Unit 6 flashcards about gene expression and regulation.

What are plasmids?

Small extrachromosomal, double-stranded, circular DNA molecules.

How is genetic information stored?

As the sequence of bases in DNA which is transmitted from one generation to the next.

What do many viruses use to encode genetic information?

RNA molecules.

Name four similarities between DNA and RNA

Both are macromolecules, have similar structures, are made up of similar elements, and follow rules of base pairing.

What three primary components make up nucleotides?

5 carbon sugar (deoxyribose vs ribose), Phosphate group, Nitrogenous base (ATCG vs AUCG)

What elements make up DNA and RNA?

C, H, O, N, P

Why is the 3’OH group important?

Required for dehydration synthesis of nucleotides during replication and transcription

Why is RNA less stable and less reliable for long term storage of hereditary material?

Accidental use of 2’OH for dehydration synthesis.

What is the difference between purines and pyrimidines?

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

Name the purines.

Adenine and Guanine

Name the pyrimidines.

Cytosine, Thymine, and Uracil

What does it mean for double stranded DNA to be antiparallel?

It runs in the 5’ to 3’ end and 3’ to 5’ end directions

What is found at the 3’ end of a DNA strand?

No phosphate group

What is found at the 5’ end of a DNA strand?

Phosphate group

What kind of bond connects a phosphate and a sugar in DNA?

Phosphodiester bond

How many hydrogen bonds are between A and T?

2

How many hydrogen bonds are between C and G?

3

Name the three types of RNA

messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Describe the structure of tRNA.

T-shaped structure made of RNA nucleotides with amino acids attached on the top and the anticodon on the bottom loop.

What is the function of tRNA?

Responsible for carrying amino acids to the ribosome during translation and transferring them on to the growing polypeptide chain.

Describe the structure of mRNA

Single stranded sequence of RNA nucleotides.

What is the function of mRNA?

An RNA copy of a gene that carries the instructions for producing a specific protein from the nucleus to the ribosome.

Describe the structure of rRNA.

Sequence of RNA nucleotides that bind to ribosomal proteins in order to form the whole ribosome.

What is the function of rRNA?

A structural component of ribosomes that assists with translation of messenger RNA.

Describe the structure of prokaryotic genomes

Circular double helix DNA

Describe the structure of eukaryotic genomes

Linear double helix strands that are tightly coiled around proteins called histones, forming compact structures called chromosomes

How many chromosomes do humans have?

23 pair

Where are prokaryotic genomes located?

In cell in region call nucleoid (NOT enclosed by a nuclear membrane.)

Where are eukaryotic genomes located?

Inside nucleus

Where can plasmids be found?

In some prokaryotes and in mitochondria and chloroplasts of eukaryotes.

What is the function of helicase?

Unwinds the DNA strands.

What is the function of topoisomerase?

Relaxes supercoiling in front of the replication fork.

What is the function of RNA polymerase (primase)

Synthesizes primer

What is the function of DNA polymerase?

Synthesizes new strands of DNA continuously on the leading strand and discontinuously on the lagging strand (requires RNA primers to initiate DNA synthesis)

What is the function of ligase?

Joins the fragments on the lagging strand.

When does DNA replication happen?

S phase of interphase

What does it mean that DNA replication is semiconservative?

Each new DNA molecule consists of one original strand and one new strand.

In what direction can nucleotides only be added?

5' to 3' direction

What direction is the leading strand synthesized in?

5’ to 3’ direction, toward the replication fork.

What direction is the lagging strand synthesized in?

Synthesized discontinuously in the 5’ to 3’ direction, away from the replication fork.

How many RNA primers are required for the leading strand?

Only one RNA primer for initiation

How many RNA primers are required for the lagging strand?

Requires multiple RNA primers, one for each Okazaki fragment.

What is telomeres

The non-coding repeating sequences of chromosome in eukaryotes. This serve as protective caps

What is telomerase?

can add DNA bases at 5’ end; high activity in stem cells and cancers but not in most somatic cells

What happens to Eukaryotic Chromosomes with each replication?

Eukaryotic Chromosomes get shorter with each replication (limits # of cell divisions) → aging process

Why don't prokaryotes have shortening with division?

since their chromosomes are circular so no shortening with division

Where does replication begin in prokaryotes?

origin of replication

Where does replication begin in eukaryotes?

multiple origins of replication.

What three steps describe cell signaling?

Reception, Transduction, Response

What happens during the reception phase of cell signaling?

Ligand binds to its specific receptor on the cell membrane and transmits the signal into the cell.

What happens during the transduction phase of cell signaling?

Kinase phosphorylate and activate, amplifies the signal

What is the final molecule called in transduction?

a transcription factor.

What happens during the response phase of cell signaling?

Cell initiates gene transcription for the target gene and ends with protein synthesis (gene expression)

What is the central dogma of biology?

DNA → RNA → Protein

What is transcription?

DNA to RNA

What is translation?

RNA to protein

What is the non-coding strand?

DNA strand that act as template strand during transcription

What are the three steps of transcription?

Initiation, Elongation, Termination

What happens during transcription initiation?

Transcription Factors and activators recruit RNA Polymerase II to the promoter.

What happens during transcription elongation?

RNA Polymerase synthesizes mRNA in the 5’ to 3’ direction by adding complementary nucleotides across from the DNA strand

What happens during transcription termination?

Transcription of a terminator sequence prevents further transcription of DNA by RNA Polymerase

Where does prokaryotic transcription occur?

in the cytosol

Is prokaryotic mRNA immediately available for translation?

Yes

Where does eukaryotic transcription occur?

in the nucleus

Does eukaryotic mRNA need to be processed before it can leave the nucleus to be translated?

Yes

What are three steps of Eukaryotic post transcriptional processing

Removing of non-coding regions of pre-mRNA, modification for mRNA to go through nuclear pore, and protection against nucleases

What are introns?

non-coding regions of the pre-mRNA transcript left inside nucleus

What are extrons?

coding regions of pre-mRNA are put together and exit the nucleus

What is alternative splicing?

different protein result from combining different exons, it is a feature that Eukaryotes use to produce more than one protein from one gene.

What is the function of the Poly A tail?

aids in nuclear export, protects the mRNA from degradation in the cytoplasm, and helps the ribosome to bind at the the mRNA start codon to initiate translation.

What is the function of the 5’ Cap?

protects the mRNA from degradation in the cytoplasm and helps the ribosome to bind at the the mRNA start codon to initiate translation.

What is translation?

mRNA to protein

Describe the process of translation

Process in which ribosomes and tRNA synthesizes the amino acid sequence coded for in the mRNA

Describe what happens during translation initiation

Large and small subunit of the ribosome bind to the start codon. The small ribosomal subunit binds to the mRNA (aided by interaction with rRNA). The tRNA that matches the start codon (AUG) base pairs, followed by the large ribosomal subunit binding. Sequence of nucleotides on mRNA is Read in triplets called codons.

Describe what happens during translation elongation

Ribosome translocates from to codon. At each codon the tRNA bring correct amino acid to the correct place specified by codon on mRNA

Describe what happens during translation termination

Ribosome continues translating until it reaches the stop codon (UAA, UGA or UAG). Translation of the stop codon results in a release factor protein binding to the ribosome, causing it to release both the mRNA and the newly synthesized polypeptide

Where does prokaryotic translation happen?

in cytosol

Is prokaryotic mRNA translated as it is transcribed?

Yes

Where does eukaryotic translation occur?

occurs on ribosomes attached to the rough endoplasmic reticulum or those found free-floating in the cytoplasm.

What is the reading frame?

mRNA is read from 5’ to 3’ in sets of 3 nucleotides called codons. The ribosome starts at the start codon (AUG) and ends at a stop codon.

What does it mean that the genetic code is universal?

Codons each code for a specific amino acid, no matter what organism the mRNA was produced in.

What is retrovirus translation?

Retroviruses introduce viral RNA, not DNA, into host cells. Reverse transcriptase is an enzyme that copies the viral RNA into viral DNA.

What happens to the viral DNA after the enzyme converts the viral RNA into viral DNA?

the DNA is integrated into the host genome and will be transcribed and translated resulting in assembly of new viral progeny

What causes cells to have the same DNA but they have different structure and function?

due to different gene expression. Present of specific protein within the cell give cell different function

What is gene regulation?

processes in which organisms control which genes are being expressed. It allows for differential gene expression in eukaryotic and prokaryotic cells.

Why is gene regulation important?

Gene regulation allow prokaryotic AND eukaryotic cells to fine-tune how much of a protein is being made at any given time in response to changes in the cell environment (maintaining homeostasis). Allows for cell differentiation

What is cell differentiation?

cells turn on the parts of DNA they need and off those they don’t is the reason why cells with the same DNA but have different look/ function

How does Induction of transcription factors during development results in sequential gene expression?

one group of cells signals neighboring cells to change their gene expression, which often activates or suppresses transcription factors, which in turn regulate specific genes in a sequential manner, creating a cascade effect.

Name three Methods of regulating gene expression

Regulate chromatin structure, regulate transcription initiation, and post-transcriptional regulation

What are epigenetic changes?

involve reversible modification of DNA or histones that affect gene expression.

What are histones?

proteins used to condense DNA.

What is closed chromatin (heterochromatin)?

densely packed, and transcription cannot occur.

What is open chromatin (euchromatin)?

loosely packed, and transcription can occur.

What is methylation?

–CH3 methyl group can be added to either histone or DNA

What does Methylation of histone proteins do?

turns gene expression off in that area of the DNA.

What does Direct methylation of DNA bases do?

permanently silences gene expression of that gene.

What is Acetylation of histone?

The addition of an acetyl (-CH2CH3) group to the histone proteins.

What does Acetylation of histone do?

prevents histone from binding the DNA as tightly, making room for proteins to bind for transcription

What do activators do?

promote transcription

What do repressors do?

prevent transcription