Chapter 7 Flashcards by Randi Brabender

DNA

Deoxyribonucleic Acid
Deoxyribose sugar
Bases - Adenine, Thymine, Guanine, Cytosine

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Biosynthesis

processes that synthesize and assemble macromolecule subunits, use ATP energy.

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DNA Structure

Double Helix
Sugar-phosphate chains on outside
Complementary base pairing (A-T, G-C) with hydrogen bonds
Two strands run antiparallel

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Antiparallel strands

One strand of DNA runs one way the other side runs the opposite direction. 5 prime and 3 prime ends

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RNA structure

Ribonucleic acid
ribose sugar
Bases A,G,C,U
Single strand
Three types: mRNA, tRNA, rRNA

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DNA replication

DNA is copied in binary fission to give two exact copies of chromosome to the dividing cell

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What does semiconservative mean in terms of DNA replication

Only one strand is “conserved” from original

- One strand is the template and the other is the copy

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New DNA strand is only made from …

5’ to 3’

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Nucleotides are only added to which end of the DNA strand

3’

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Starting Replication envolves what two areas

Origin of replication

Replication fork

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Origin of replication

Specific DNA sequence that is recognized by enzymes as the starting point
-Unwinding of DNA (unzipping) starts here

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Replication fork

where unwinding occurs

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Two different DNA stands

Leading strand and Lagging strand

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Leading strand

the new DNA strand that is made continuously toward the replication fork 5’ to 3’

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Lagging Strand

the new DNA strand that is made in pieces AWAY from the replication fork

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Leading Strand

process

Helicase unzips DNA
Gyrase relaxes twisting of unwinding strands
Primase adds RNA primer at origin of replication
DNA polymerase adds nucleotides to 3’ end of new DNA through complementary base pairing
goes in direction of unwinding parent DNA

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Lagging Strand

process

Primase starts near the replication fork
DNA polymerase adds neucleotides in 5’ to 3’ direction AWAY from unwinding and replication fork
DNA polymerase detaches and goes back to replication fork and a new primer to make a new Okazaki fragment
RNA Primers are removed by DNA polymerase
Fragments are joined by DNA ligase

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Lagging strand is formed in pieces called…

Okazaki fragments

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Prokaryote DNA replication vs Eukaryote

Prokaryote will only have one point of origin, where eukaryotes can have several replication bubbles to speed up the process

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Protein Synthesis Overview

Transcription - DNA to mRNA

Translation - mRNA to protein using tRNA and ribosomes

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Transcription Steps

protein synthesis

Initiation
Elongation
Termination

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Initiation

Transcription-Protein

Sigma factor on RNA polymerase recognizes promoter on DNA
RNA polymerase binds to promoter
RNA polymerase unwinds DNA

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Elongation

transcription - protein

RNA nucleotides matched to DNA nucleotides

A to U, T to A, G to C, C to G

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Termination

transcription - protein

Terminator on DNA tells RNA polymerase to detach

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Translation | protein synthesis

mRNA to protein using tRNA and ribosomes

Codon

three mRNA nucleotides "translate to one amino acid"

Start codon

AUG - Methionine | protein synthesis will always start with this

Stop codon

UAA, UAG, UGA | will stop synthesis

tRNA

1. Single strand of folded RNA 2. Amino acid attached to one end 3. Anticodon is on other end

Anticodon

match up to amino acid on the other side (will be the opposite "code" of the amino acid)

Location of Anticodon and codon

Anticodon is on tRNA | Codon is on mRNA

Ribosomes are composed of

proteins and rRNA

Prokaryote ribosomes

30S + 50S = 70S

Eukaryote ribosomes

40S + 60S = 80S

Small unit of ribosomes has ____ binding site(s) for ____

one binding site for mRNA

large subunit for ribosomes has ____binding site(s) for ____

three binding sites for tRNA

How does Erythromycin work

binds to the 50S subunit and inhibits protein synthesis

Large subunit binding sites

A site = Amino Acid P site = polypeptide E site = exit Sites are arranged in EPA

Translation : 3 steps

Initiation Elongation Termination

Initiation | Translation

1. ribosome binds to mRNA at ribosome binding site 2. tRNA will bind to starter codon at P site 3. another tRNA will bond to the next codon at the A site and a polypeptide bond will connect the two amino acids

Elongation | Translation

1. Ribosome moves to next codon 2. Ribosome keeps moving along mRNA in 5' to 3' direction and amino acids added one at a time to make a long polypeptide chain

Termination | translation

1. Stop codon on mRNA that is not recognized by any tRNA | 2. components come apart and polypeptide chain is released

Which type of cell can transcription and translation happen simultaniously

Prokaryotes

Comparing Protein Synthesis

``` Eukaryote 1. mRNA has introns and special endings 2. Monocisronic 3. mRNA must be transcribed and moved from nucleus to cytoplasm before translation can start PROKARYOTE 1. mRNA is not processed 2. Polycistronic 3. Transcription can work before translation is finished ```

Monocistronic

information for only one gene is found on the mRNA | Eukarote

Polycistronic

mRNA can carry information for more than one gene | Prokaryote

Post-translation modification of proteins

- polypeptide chain folded into inal functional structure with CHAPERONE proteins - SIGNAL SEQUENCES are added to polypeptides that will be transported to another area of the cell

Bacteria gene regulation

- Bacteria will take nurients from environment | - Bacteria can synthesize many nutrients

Bacteria will take nutrients from environment....

- turn off genes not needed - to save energy of biosynthesis - use energy for cell division

Bacteria can synthesize many nutrients...

- turn on genes needed | - slow down cell division

Alternative sigma factors

- alternative versions of sigma factors can be made to recognize different promoters - anti-sigma factors can be made by cell to inhibit sigma factors

sigma factor

part of RNA polymerase that recognizes specific promoters

Operon

a set of regularoty genes on DNA

Operon's function

1. Genes for protein(s) 2. Promoter 3. Operator 4. Activator- binging site

Promoter | Operon

where RNA polymerase starts

Operator | operon

sequence after promoter

Activator- binding site | operon

sequence before promoter

Repressors - Induction

Repressor protein released from the operator when inducer binds to repressor and transcription can start

Stop = | repressors

Repressor + operator

Go = | repressors

Repressor + inducer

Repressors - Repression

Repressor protein must combine with corepressor to bind to operator and stop transcription

Activators

Activator protein can bind to activator-binding site only when combined with an inducer -then allows RNA polymerase to bind

Stop | activators

Activator protein alone

Go | activators

Activator protein + inducer

Example

lac operon - codes for proeins involved in lactose degredation and transport in E.coli

Chapter 7 Flashcards

(65 cards)