Gene Editing and CRISPR Developments

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Questions and Answers

What percentage of transcription in a typical human cell is associated with making non-coding RNAs?

80% (correct)

20%

50%

10%

Which of the following is NOT a function of non-coding RNAs?

Act as a scaffold

Serve as a template for protein synthesis (correct)

Block other RNA interactions

Guide molecules to a location

How do non-coding RNAs bind to other molecules?

Through electrostatic interactions

By covalent bonding

Via complementary base pairing (correct)

Using hydrogen bonds

Which role describes a non-coding RNA that binds to another RNA to prevent its function?

Decoy Signup and view all the answers

In addition to guiding, what other roles can non-coding RNAs perform?

Changing the structure of proteins Signup and view all the answers

Which of the following is a possible example of an interaction that non-coding RNAs can facilitate?

Guiding DNA-cutting proteins to specific sequences Signup and view all the answers

Which statement about the functions of non-coding RNAs is accurate?

They can act both as guides and blockers Signup and view all the answers

Which of these molecules can non-coding RNAs bind to?

Small molecules and DNA Signup and view all the answers

What is the primary role of microRNAs (miRNAs) in RNA interference?

Regulating gene expression by targeting mRNAs Signup and view all the answers

How do small-interfering RNAs (siRNAs) primarily interact with their target mRNA?

They are perfectly complementary to their target mRNA. Signup and view all the answers

What is the primary function of telomeres in eukaryotic chromosomes?

To protect chromosome ends from damage. Signup and view all the answers

What are the two sources of non-coding RNA (ncRNA) that can mediate RNA interference?

Endogenous miRNAs and exogenous siRNAs Signup and view all the answers

What complex is responsible for mediating RNA interference in eukaryotic species?

RNA-Induced Silencing Complex (RISC) Signup and view all the answers

What happens to telomeres as cells continue to divide?

They become shorter. Signup and view all the answers

What is a key feature of the signal recognition particle (SRP)?

It chaperones ribosomes to the ER. Signup and view all the answers

What role does telomerase play in cell division?

It adds repeat sequences to the telomeres. Signup and view all the answers

Why can't DNA polymerase fully replicate the ends of chromosomes?

It needs a primer to begin replication. Signup and view all the answers

What happens when the SRP binds to an SRP receptor?

The ribosome is directed to the ER membrane. Signup and view all the answers

How is RNA interference different from traditional gene regulation mechanisms?

It utilizes ncRNAs to specifically target mRNAs. Signup and view all the answers

What consequence occurs when telomeres become critically short?

Cells enter a program of programmed cell death. Signup and view all the answers

What percentage of human protein-coding genes are estimated to be regulated by miRNAs?

60% Signup and view all the answers

Which of the following sequences is the repeat found in human telomeres?

5ʹ–GGGTTA–3ʹ Signup and view all the answers

What is the effect of rapidly dividing cells producing telomerase?

Telomeres can be maintained or elongated. Signup and view all the answers

What occurs to the daughter strand during DNA replication when a primer is removed?

It is left shorter than the complementary strand. Signup and view all the answers

What is one primary function of non-coding RNAs (ncRNAs) in the cell?

They bind to multiple components acting as a scaffold for complex formation. Signup and view all the answers

How do ncRNAs guide one molecule to a specific location in the cell?

Through binding to DNA or another RNA via complimentary base pairing. Signup and view all the answers

In what way can an ncRNA act as a blocker?

By physically preventing a cellular process from occurring. Signup and view all the answers

What is a key difference between a decoy and a blocker ncRNA?

A decoy binds an RNA molecule, while a blocker binds a non-RNA molecule. Signup and view all the answers

Which function describes an ncRNA that has catalytic activity?

Ribozyme Signup and view all the answers

What effect does binding of an ncRNA have on proteins?

It can alter their function or stability. Signup and view all the answers

Which of the following statements accurately describes scaffolding by ncRNAs?

It facilitates the assembly of multiple proteins into a single complex. Signup and view all the answers

Which function of ncRNAs involves preventing their target from performing its intended role?

Blocker Signup and view all the answers

What is the first step in the process of telomere lengthening?

TERC acts as a guide, bringing telomerase to the end of the chromosome. Signup and view all the answers

How does HOTAIR influence gene expression?

By forming a scaffold that binds two protein complexes. Signup and view all the answers

Which of the following accurately describes the role of TERC during telomere lengthening?

It acts as a template for telomerase to extend DNA. Signup and view all the answers

Which of the following statements is true regarding the modifications made by protein complexes guided by HOTAIR?

They silence the target genes through histone modification. Signup and view all the answers

What effect does double-stranded RNA have compared to antisense RNA?

It is more potent at inhibiting mRNA. Signup and view all the answers

What is the main function of siRNAs in relation to mRNA?

To promote mRNA degradation. Signup and view all the answers

Which component is involved in the telomere lengthening process?

Telomerase Signup and view all the answers

Which of the following statements best distinguishes miRNAs from siRNAs?

miRNAs regulate gene expression post-transcriptionally while siRNAs primarily induce degradation. Signup and view all the answers

What triggers the pause in translation when a polypeptide is being synthesized?

Binding of SRP to an ER signal sequence Signup and view all the answers

Which component is critical for the adaptability of the type II CRISPR-Cas system?

Cas proteins that recognize bacteriophage DNA Signup and view all the answers

During the expression phase of the CRISPR-Cas system, which of the following gets transcribed?

The tracrRNA and Cas9 genes Signup and view all the answers

What is the primary role of the tracrRNA in the CRISPR-Cas system?

To guide the Cas9 protein to the target sequence Signup and view all the answers

Which phase follows adaptation in the CRISPR-Cas defense mechanism?

Expression phase Signup and view all the answers

What event characterizes the interference phase of the CRISPR-Cas system?

Cleavage of bacteriophage DNA Signup and view all the answers

Which short sequences are interspersed in the Crispr gene?

Unique spacers Signup and view all the answers

What happens to the GTP-binding proteins during the binding of SRP and the SRP receptor?

They hydrolyze GTP, leading to SRP release Signup and view all the answers

What is the final outcome of the tracrRNA-crRNA complex forming with Cas9?

The bacterial cell is prepared to destroy bacteriophage DNA Signup and view all the answers

What is the result of the bacterial cell's adaptation to a bacteriophage?

It becomes resistant to further infections Signup and view all the answers

Study Notes

Chinese Scientist Claims to Use CRISPR to Make Genetically Edited Babies

A Chinese scientist, He Jiankui, claimed to have used CRISPR to edit the genes of human embryos
He offered no supporting data or evidence for his assertions
The claim sparked concern about the possibility of "designer babies"

Disgraced CRISPR-Baby Scientist Sentenced

He Jiankui, the scientist who claimed to have produced genetically edited babies, was found guilty of conducting illegal medical practices
He and two collaborators forged ethical review documents and misled doctors
The court sentenced him to three years in prison

Nobel Prize in Chemistry 2020

Jennifer Doudna and Emmanuelle Charpentier were awarded the Nobel Prize in Chemistry 2020
Awarded "for the development of a method for genome editing"
Shared the prize equally

Gene Expression- Non-Coding RNAs

In a typical human cell, only about 20% of transcription involves the production of mRNAs, whereas 80% is associated with making non-coding RNAs (ncRNAs)
ncRNAs perform a diverse set of functions
They can bind to small molecules, DNA, or RNA, or to proteins

ncRNA Functions

Scaffold: Bind to components like proteins, acting as a scaffold for complex formation
Guide: Guide one molecule to a specific location in the cell (like guiding a protein to a specific location on DNA)
Alteration of protein function or stability: ncRNA binding affects the protein's ability to be a catalyst or bind to other molecules.
Ribozyme: RNA molecule with catalytic function (like peptidyltransferase activity of ribosomes)
Blocker: ncRNA physically prevents or blocks a cellular process (e.g., blocks the binding of a ribosome to mRNA, inhibiting translation)
Decoy: Recognizes other ncRNAs and sequesters them to prevent them from working

Overview of Non-Coding RNAs

ncRNAs can bind to DNA or RNA molecules through complementary base pairing
ncRNAs can bind to proteins or small molecules
Stem-loop structures may bind or scaffold proteins, or form binding sites for small molecules

Role of ncRNAs in Eukaryotic DNA Replication

Telomeres are composed of repeat sequences that protect the ends of linear eukaryotic chromosomes from becoming tangled or broken
Telomeres shorten with each cell division, eventually leading to cell death
Some cells, like stem cells, express telomerase, which adds telomere sequences, preventing shortening of telomeres

Effects of ncRNAs on Chromatin Structure and Transcription

HOTAIR (Hox transcript antisense intergenic RNA) is an ncRNA that regulates transcription by acting as a scaffold
It binds to two proteins complexes and guides them to particular genes, covalently modifying histones and silencing these modifications

Effects of ncRNAs on Translation and mRNA Degradation

Double-stranded RNA (dsRNA) is more potent at inhibiting mRNA than antisense RNA
This phenomenon is called RNA interference
MicroRNAs (miRNAs) and small-interfering RNAs (siRNAs) are involved in RNA interference, regulating gene expression
miRNAs are partially complementary to mRNA targets, and siRNAs are usually perfectly complementary.

Non-Coding RNAs and Protein Sorting

Signal recognition particle (SRP) is a complex of protein and ncRNA that chaperones ribosomes to the ER
SRP binds to an ER signal sequence and pauses translation
SRP binds to an SRP receptor in the ER membrane, allowing the polypeptide to be threaded through a channel into the ER lumen.

Non-Coding RNAs and Genome Defense

Some bacteria and archaea use the CRISPR-Cas system for defense against bacteriophages and transposons
The type II CRISPR-Cas system contains genes for crRNAs, tracrRNA, and Cas proteins
These phases (adaptation, expression, and interference) allow the bacteria to recognize foreign DNA, cleave it, and prevent infection

Role of ncRNAs in Human Disease and Plant Health

Abnormal expression levels of miRNAs are found in almost all forms of human cancer. Some miRNAs are tumor suppressors, and others are oncogenes.
HOTAIR is highly expressed in several cancers and behaves as an oncogene when overexpressed.
Various ncRNAs are associated with neurological disorders.
ncRNAs play essential roles in plant health, including seed development, growth, and stress responses. This research is useful for agriculture.

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Description

Explore the groundbreaking advancements and controversies surrounding gene editing, particularly the claims made by Chinese scientist He Jiankui regarding genetically edited babies. Additionally, learn about the 2020 Nobel Prize winners in Chemistry and the crucial role of non-coding RNAs in gene expression.