AP Bio - Unit 6

What are the purines?

• double-ring

• A and G

What are the pyrimidines?

• single ring

• C, T, and U

What are nucleotides composed of?

• pentose sugar

• Phosphate group

• nitrogenous base

What is the flow of genetic information?

DNA to RNA to Protein

Gene expression

The process by which a gene produces a protein

Gene regulation

The control of gene expression

Chromosomes: prokaryotes vs eukaryotes

Prokaryotes: Single, circular

Eukaryotes: Multiple, linear strands

How do the structures of DNA and RNA ensure the storage and transmission of genetic info?

Where does transcription and translation occur in prokaryotes? Why do they occur at the same time?

• Cytoplasm

• No nucleus → no nuclear membrane to separate processes

What are plasmids and what do they do?

• small circles of extra DNA

  • Replicate independently

• can help survival or reproduction under certain environmental conditions

Where are the chromosomes located in the prokaryote and eukaryote.

P: Nucleoid

E: Nucleus

How many bonds are between each base pairing?

A - T →2

C - G →3

How does the mechanism of DNA ensure the accurate transmission of genetic information?

Which way is DNA READ?

3’→5’

Which way is DNA SYNTHESIZED?

5’ to 3’

What is on the 5’ end?

What is on the 3’ end?

5’: Phosphate group

3’: Hydroxyl group

What provides the energy for the bond formation of nucleotides.

The release of 2 phosphate groups from the nucleotide.

Topoisomerase

Unwinds the DNA supercoil

SSBP

Coat the DNA strands to prevent them from recoiling

Helicase

Unzip the DNA strands

RNA primer

• made by primase

• Signals were DNA polymerase should add nucelotides

DNA polymerase

• can only add onto the 3’ end (follows) helicase

• Extends 5’ →3’

Leading strand

• 5’ →3’ following helicase

• Synthesized continuously

Lagging strand

• 5’→3’ away from helicase

• Synthesized discontinuously

Okazaki fragments

• On the lagging strand

• Created by gaps in the DNA strand

Ligase

Fills in gaps between okazaki fragments

Transcription

The process of creating mRNA from a section of DNA (gene)

Initiation

• RNA polymerase binds to a promoter

• Once bound RNA polymerase separates the DNA strands

Elongation

• RNA polymerase reads the template strand and synthesizes an mRNA strand

Termination

• RNA Polymerase reaches a DNA sequence called a terminator

  • mRNA can form a hairpin that inhibits the ability of the polymerase

  • the polymerase can also recognize a sequence that causes a conformational change and cause it to let go

How is DNA read?

3’ →5’

How is RNA synthesized?

5’→3’

What is the template strand? What are other names for it?

The strand the RNA polymerase reads.

• antisense, minus, noncoding

What is the coding strand? What are other names for it?

The strand that the new mRNA is identical to (with thymine swapped for uracil)

• sense, plus

Where is the GTP cap added and what does it do?

• added to the 5’ end

• keeps the mRNA from being degraded

• helps the ribosome to attach

Where is the poly-A tail added and what does it do?

• added to the 3’ end

• increases instability

• helps with exportation from the nucleus

What are introns and exons?

Introns: nonsense groups of nucleotides

Exons: the coding sections that are kept

Alternative splicing

The ability of a pre-mRNA strand to be spliced in many different ways.

Translation

The process of a protein being synthesized from an mRNA strand

AUG

• Codes for met

• Start codon

Stop codons

• UAA

• UAG

• UGA

What is the difference between prokaryotic and eukaryotic ribosomes?

prokaryotes only have cytosolic ribosomes.

Eukaryotes have both cytosolic and membrane bound ribosomes.

N-terminus and C-terminus

The N-terminus is the start of the protein; the C-terminus is the end.

Initiation

Ribosome subunits assemble around the mRNA, forming an initiation complex.

Elongation

• mRNA is read one codon at a time

• After the amino acid for one codon is brought, the mRNA is shifted by one codon

Termination

the chain is released once a stop codon is reached

Retroviruses

Introduce RNA into host cells

• Reverse transcriptase copies RNA into DNA

• The viral DNA gets incorporated into the hosts genome and is transcribed and translated

What are 3 types of non coding RNA?

tRNA, rRNA, and small RNA

What is the difference between tRNA and rRNA in translation?

tRNA reads the mRNA codons and brings down the amino acids, rRNA actually catalyzes the reaction that releases the amino acid and binds them together.

What is the difference between an activator and an inducer?

• Activators bind to the promoter to allow RNA polymerase to bind

• Inducers increase transcription by inactivating repressors or activating activator proteins

Operator

An operator is where the repressor molecule would bind.

Chromatin remodeling

When the nucleosomes are repositioned to expose different sequences of DNA.

How does DNA methylation affect gene expression?

Causes it to coil tighter an prevents certain genes from being exposed.

How does acetylation affect gene expression?

Causes the chromosome to unwind and expose genes for transcription.

What sorts of changes does epigenetic refer to.

Changes in the manner in which DNA is packaged.

Development

The process of a fertilized egg going through many rounds of division to become an embryo with specialized tissues and organs.

What is differentiation and how does it relate to gene regulation

• The process by which cells become progressively more specialized

• Gene regulation allows for certain genes to be turned on and off, giving the cells certain functions

How does cell development affect its developmental potential?

As cells go through development they become increasingly more limited in the types of cells they can become. This is because as they become more specialized, genes that are no longer needed are turned off, repressed or more difficult to turn on again.

Totipotent

Cells can create an entire organism on their own

EX: fertilized egg

Pluripotent

Cells can give rise to any cell of the body

Multipotent

Cells can become a limited range of cells

EX: stem cells

Why can transcription factors for mice cause eye development in a fruit fly?

The transcription factors are similar enough that they can activate the same gene in both mice and fruit flies.

How can transcription factors affect the expression of genes other than the target?

Their target gene can code for proteins that contiuously activate other genes.

Combinational control

Regulation of transcription according to the combination of transcription factors.