B&G unit 2

Central dogma

DNA → RNA → Protein

RNA Polymerase 2

Unwinds the DNA double helix

synthesizes mRNA

Why is Central Dogma important?

Shows how genetic information flows from DNA → RNA → protein

1st step of transcription

RNA Polymerase 2 binds to promoter

2nd step of transcription

DNA unwinds and RNA is made

3rd step of transcription

Hairpin loop stops transcription

initiation

RNA Polymerase 2 binds to promoter

elongation

mRNA is made

1st step of RNA processing

initiation, RNA polymerase 2 binds to promoter

2nd step of RNA processing

elongation, synthesize MRNA

3rd step of RNA processing

termination, hairpin loop

exon

stays in mRNA and is translated into protein

intron

spliced out before translation

splicesome

removes introns from mRNA

alterative splicing

introns can act as exons or vice versa

what can affect alternative splicing

Environment, developmental state, and tissue type

messenger (mRNA)

nucleic acid that is translated into protein

ribosomal (rRNA)

nucleic acid that forms part of the ribosome

transfer (tRNA)

nucleic acid that links codons in mRNA to amino acids in protein

start codon

signal the beginning of translation

Aminoacyl (A) site

Where a new tRNA enters

Peptidyl (P) site

Where amino acids are linked together

3 stop codons

UAA, UAG, UGA

1st step of translation

Small ribosomal subunit binds to mRNA

2nd step of translation

start codon is found and large ribosomal subunit joins

3rd step of translation

Complementary tRNA enters the aminoacyl region

4th step of translation

Ribosome shifts 3 nucleotides and a new tRNA enters

5th step of translation

Amino acids are transferred/linked

6th step of translation

repeat steps 4-5 until a stop codon enters the aminoacyl region

Promoter

Where RNA Polymerase 2 binds

enhancer

DNA sequence looped back toward the promoter

transcription factor

increases gene expression

repressor protein

decreases gene expression

similarity of transcriptoin factors and repressors

both regulate gene expression

difference of transcription factor and repressor

TF increases; repressor decreases

epigenetics

Changes around DNA that regulate gene expression without changing DNA sequence

High DNA methylation

DNA coils up → gene expression decreases

Unmethylated DNA

DNA loosens → gene expression increases

Increased histone acetylation

Increases gene expression

What can cause epigenetic changes?

Environmental changes

Can the epigenome change over time?

yes

Transgenerational epigenetic inheritance are

Epigenetic changes that are inherited

microRNA

short 20-30 nucleotide RNA sequence

main function of microRNA

Downregulates gene expression by binding to mRNA

Complete complementarity

perfect base pairing

partial completarity

imperfect base pairing

when microRNA is completely complementary to messenger RNA

RISC cleaves the MRNA

When microRNA is partially complementary to the messenger RNA

RISC binds to MRNA and prevents translation by the ribosome

pri-microRNA

DNA sequence that harbors a mircroRNA

1st step of microRNA processing

immature microRNA is transcribed from DNA

2nd step of mircroRNA processing

drosha removes hairpin loop from the rest of the pri-microRNA

3rd step of microRNA processing

dicer removes the loop in the hairpin loop

4th step of microRNA processing

RISC removes the miRNA-star and binds the miRNA

first step of gene editing

guide RNA is designed to compliment the targeted DNA

second step of gene editing

CAS9 binds to guide RNA

third step of gene editing

random nucleotides are inserted at the break sit to ligate DNA

changing DNA sequence

add SSDNA complementary to the target DNA sequence with desired change

what do GMO’s do

insert foreign data

what do gene edits do

change DNA sequence

what does the CAS9-CRISPR system do

protects cells from invading viruses

first step of cloning

isolate donor cells

second step of cloning

remove and discard the nucleus from egg cell

third step of cloning

transfer somatic cell nucleus into enucleated egg cell

fourth step of cloning

stimulate cell division

fifth step of cloning

implant embryo into surrogate mother