Bio exam 2 unit 5

unit 5

What is a gene?

A segment of DNA that contains the instructions for synthesizing a specific protein or RNA molecule.

What is RNA polymerase?

An enzyme that catalyzes the transcription of DNA into RNA by assembling nucleotides in a sequence complementary to the DNA template(binding)

What is a promoter?

A specific DNA sequence that signals the start of transcription for a gene by providing a binding site for RNA polymerase.

What is a transcription factor/sigma factor?

Proteins that regulate gene expression by binding to specific DNA sequences, assisting RNA polymerase in initiating transcription.

What is a transcription bubble?

A transient structure that forms during transcription where the DNA strands unwind, allowing RNA polymerase to access the template strand for RNA synthesis.

What is an exon/intron?

Exons are the coding regions of a gene that are retained in the final mRNA transcript, while introns are the non-coding regions that are removed during RNA splicing.

What would a diagram of the central dogma of molecular biology look like and include?

how is genetic code unambiguous?

A codon never codes for more than one amino acid

How is genetic code redundant?

Most amino acids are coded or specified by more than one codon

how is genetic code nearly universal?

All specify the same amino acids in nearly all organisms

How do you transcribe between mRNA?

RNA polymerase(enzyme) transcribes using A—→U, T—→A, C—→G.

What is DNA splicing?

Introns removed, only leaving exons for coding

What is capping and tailing?

5’ cap and poly A tail added to protect the mRNA molecule

Do we read from 5’-3’ or 3’-5’?

5’ to 3’

What are the three modifications that are needed to turn a pre-mRNA to a mature mRNA?

RNA splicing, 5’ capping, 3’ poly

How can alternative splicing allow for the same gene code for multiple proteins?

By selectively including or excluding different coding segments

What is aminoacyl tRNA-synthesis?

Making charged tNA from tRNA

What is translocation(of the ribosome)?

When the ribosome slides along the mRNA by one codon

What is point mutation?

Changing the DNA base sequence

What is a chromosomal mutation?

Large scale mutations in chromosomes

What is the function and structure of the ribosome?

Function: site of protein synthesis

Structure: nearly spherical, non membranous structures

What is a detailed structure of a ribosome contain?

What are the three steps of translation?

Initaiation, elongation, and termination

What happens during initiation?(translation)

the assembly process, where the small and large ribosomal subunits, messenger mRNA, and an initiator transfer tRNA come together at the start codon (AUG) to begin protein synthesis

What happens during elongation?(translation)

1. condon in A site recognized

2. Amino acids in A and P bond

3. Ribosome slides along mRNA by one codon

What happens during termination?(translation)

When a stop codon is encountered

What are the types of point mutations?

Missense, nonesense, silent, frameshift mutations

What happens during a missense mutation? How does this affect the protein?

A single DNA nucleotide change alters a codon, resulting in a different amino acid being added to the chain.

What happens during a nonsense mutation? How does this affect the protein?

A single DNA nucleotide is changed, resulting in the protein translation ending much sooner than expected.

What happens during a silent mutation? How does this affect the protein?

No alteration to the protein

What happens during a frameshift mutation? How does this affect the protein?

Nucleotides are added or deleted in a DNA sequence by a number that is not a multiple of 3

What are the chromosomal mutations?

Deletion, duplication, inversion, translocation

What does deletion do?

Removes a chromosonal segment

What does a duplication do?

Repeats a segment

What does an inversion do?

Reverses a segment withen a chromosome

What is translocation(of a chromosone segment)

moves a semgment from one chromosone to another

What is gene expression?

the proccess of “turning on” a gene to produce mRNA and proteins

What is an operon?

A group of structural and regulatory genes that function as a single unit, encoding proteins

What do cells need to control gene expression?

They need to regulate their patterns of gene expression in response to changes in the external and internal environment

How do repressor operons function in prokaryotes?

They repress the function of normally functioning operons(such as the trp operon), which results in stopping the RNA polymerase(enzyme) from making proteins

How do activators and repressors regulate operons in prokaryotes?

Activator = increases transcription of a gene

Repressor = blocks RNA polymerase, preventing transcription

What is epigenetic control?

not perminate and doesnt alter the nucleotide sequence of DNA

What is transcriptional control?

Controls whether or not an mRNA is transcribed from a gene; it requires an RNA polymerase to bind to a promoter to initiate transcription

What is post-transcriptional control?

Occurs after the mRNA is transcribed but before the translation can begin

What is translational control?

Regulated at the level of binding of the mRNA to the ribosome or by controlling the speed of translation

What is post-translational control?

Modifying the protein after it’s made in a way that affects its activity. ex: inhibiting an enzyme so it cannot bind to its substrate

What does a pre-mRNA look like with at least 4 exons and 3 introns? What possible mRNAs can result from alternative splicing of this RNA? What level of control does alternative splicing?

What does the central dogma of molecular biology look like?

DNA —→ transcription —→ mRNA —→ translation —→ protein

What type of gene regulation is for DNA?

epigenetic control

What type of gene regulation is for transcription?

transcriptional control

What type of gene regulation is for mRNA?

post-transcipritonal control

What type of gene regulation is for translation?

translational control

What type of gene regulation is for proteins?

post-translational control

After the mRNA is made, it is alternatively spliced to make different proteins. What type of gene regulation is this?

post-translational

The mature mRNA is blocked from binding to the ribosome, so that translation cannot occur. Which form of DNA control is this?

Translational control

The DNA of a gene is modified in such a way that it can be passed on to offspring. Which form of gene regulation is this?

Epigenetic control

A repressor protein binds to a gene’s promoter so that RNA polymerase cannot bind and transcribe the gene. Which form of gene regulation is this?

Transcriptional control

After a protein is made, it is folded in such a way that it cannot do its function. Which form of DNA control is this?

Post-translational control

What is the promoter regulated by?

transcriptional regulation

What is a repressor?

A protein that suppresses transcription of a gene

What is an activator?

A protein that increases transcription of a gene

What is a transcription factor?

Any protein that affects transcription of a gene

Where does the trp repressor attach if it binds?

To the operator

Where is the RNA polymerase located?

Attaches to the promoter

Where does the lac repressor attach if it’s preventing the RNA polymerase from making proteins?

to the operator

Where does lactose attach when RNA polymerase is able to function?

to the lac repressor

Where does trp attach when RNA polymerase functioning?

trp is not present, therefore it is not attached to the trp repressor and RNA polymerase can proceed

Where does transcription take place?

in the cytoplasm