Concept Map 3

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Semiconservative replication

Two strands of the parental molecule separate and function as a template for synthesis of a new, complementary strand

Parental molecule has two complementary strands of DNA

Each base is paired by hydrogen bonding with its specific partner

Two DNA strands are separated

Each parental strand serves as a template for a new complementary strand.

Nucleotides complementary to the parental strand are connected

Form the sugar-phosphate backbones of the new daughter strands

Histones

H4

H3

H2B

H2A

Histone Core (Octamer)

H1

links histones together to form the nucleosome

Structural genes

Lac Y: Permease

Lac A: Trans-acetylase

Lac Z: B-galactoisdase

lac Operon

Operon Off

Nothing Present

Glucose and lactose present

Glucose present

Operon On

Lactose Present, no glucose

Lactose present

Lac L: Regulatory Gene

Operator

Positive Regulation

No Activator

Activator bound

Transcription

Negative Regulation

No repressor

Repressor bound

No transcription

Concept Map 3

DNA Replication

Process by which a cell copies its DNA to produce two identical copies

Models of DNA Replication

Alternate Models of DNA Replication

Conservative Replication

Two parental strands reassociate after functioning as templates for new strands

Restore the parental double helix

Dispersive Replication

Each strand of both daughter molecules contains a mixture of old and newly synthesized DNA

Initiation of DNA Replication

Enzymes separate the two strands

Helicase unwinds and separates parental DNA strands

Next, there is a formation of a daughter strand or a new polymer of DNA

Many Okazaki fragments are made at the lagging strand

DNA pol I removes the RNA primer and replaces it with DNA nucleotides

DNA ligase seals gaps

Synthesis of Leading Strand

After RNA primer is made, DNA pol III starts to synthesize the leading strand

Leading strand is elongated continuously as the fork progresses

DNA Polymerases

Two DNA polymerases needed in bacterial replication

DNA Polymerase III

DNA Polymerase I

Need sliding clamp

Converts DNA pol III from being distributive to processive

Need RNA primer to add nucleotides to

Nucleotides added to 3' end of primer

Polymerization occurs in 5' to 3' direction

Add complementary base to daughter strand

Primase synthesizes RNA primers and uses parental DNA as a template

Single-strand binding proteins stabilize unwound parental strands

Topoisomerase breaks, swivels and rejoins parental DNA ahead of replication fork

Relieves the strain caused by unwinding

DNA Expression

mRNA Processing

Splicing

Poly A tail

5' cap

Transcription (DNA --> RNA)

RNA Splicing

Introns (Removed)

Exons (Expressed)

Termination

Elongation

Transcription factors

RNA Polymerase

Chromatin Modifications

Remodeling

Histone Acetylation

Gene Activation

Regulatory Elements

Silencers

Promoter

DNA Regulation

Operon

Eukaryotes

Control Elements

Distal

Bind to specific transcription factors (activators/repressors)

Enhancers

Proximal

Bind to general transcription factors

10nm fiber

Nucleosomes

30nm fiber

300nm fiber

Metaphase Chromosome

Transcription Factors

Specific

Repressors

If there is a high level of transcription, reduces levels

Activators

Increases levels of transcription

General

(Basal/background) low levels of transcription

DNA Structure

Enables a cell molecule to copy itself during cell division

Double Helix

Discovered by James Watson and Francis Crick

The strands run antiparallel

3' -> 5'

5' -> 3'

Made up of Phosphate groups

Made up of Deoxyribose

Attached to the sugars are the four Nitrogenous bases:

Thymine (T)

Guanine (G)

Cytosine (C)

Adenine (A)

Connected by chemical bonds