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Micro Chapter 7

Terms in this set (56)

Chromosomes in typical Prokaryotic Cell
Most have a single circular chromosome some have two or three

When stretched out, this single DNA molecule is about 1mm long (1000x longer than the cell itself)

Fits compactly into the cell nucleoid by twisting around itself (supercoiling)

Contains DNA w/ genetic information that is essential for the continuous survival of the organism
Plasmid
Contains only DNA w genetic information that could be helpful to organisms but is not essential for survival
Bacterial Cells divide by
Binary Fission
Gene
a segment of DNA on a chromosome or a plasmid that codes for a particular trait or information
Locus
A gene's location on a chromosome
Mutations
A permanent change in teh DNA base sequence of a cell that can be passed on to the next generation.

May result in characteristics of progeny
DNA Replication
making duplicate copies of DNA to prepare for cell division
RNA Transcription
making RNA from DNA template
Translation
making proteins from information in messenger RNA
Alleles
Genes with different information at the same locus
False, cytoplasm
T or F in prokaryotic cells, both transcription and translation take place in the nucleus
adenine , cytosine
in DNA replication thymine always paris with _______ guanine paris with _________
Thymine
in RNA transcription, adenine pairs up with ______ a base not normally found in DNA
DNA
Template in RNA transcription
Retrovirus
Have RNA as their genetic material
Reverse Transcription in Retroviruses
RNA can make new DNA by reverse transcription

This new DNA then makes more RNA

Produces more errors resulting in mutations (example- HIV)
Okazaki Fragments and where are they found
DNA polymerase enzyme adds new DNA nucleotides only to the 3' end of each strand.

This means only the new strand can be made continuously (the leading strand)

The second strand is made in small segments called Okazaki Fragments (the lagging strand) these fragments are joined together by DNA ligase enzyme
interons, exons
Regions of genes along the DNA that do not code for a protein are called ____ whereas the coding sequences are called _____
Ribosomal RNA- Structure and Appearance
Tightly binds to specific proteins to produce two ribosomal subunits which combine together to form a ribosome
Ribosomal RNA Function
Combines with specific proteins to form ribosomes

Serves as a site for protein synthesis

Associated enzymes function in controlling protein synthesis
Messenger RNA Structure and Appearance
Has base triples called codons that constitute the genetic code
Messenger RNA Function
Carries information from DNA for synthesis of a protein

Attaches to one or more ribosomes

Molecules correspond in length to one or more genes in DNA
Transfer RNA Structure and Appearance
Molecules have clover leaf shape with an attachment site for a specific amino acid

Each has a single triplet of bases called an anticodon which pairs completely ?? the corresponding codon in mRNA
Transfer RNA Function
Found in cytoplasm where they pick up amino acids and transfer them to mRNA
codon, anticodon
Every 3 mRNA bases make up a ______ whereas every 3 transfer RNA bases make up a _________
False- transcription- nucleus translation- cytoplasm
T or F in eukaryotes, transcription takes place in the cytoplasm whereas translation takes place in the nucleus
Bacteria so ideal for the study of genetic regulatory mechanisms?
The survival of bacteria depends on their ability to grow even when conditions are less than ideal for example when nutrients are in short supply.

Ideal for these studies because:
1. they can be grown in large numbers relatively inexpensively under a variety controlled environmental conditions

2. Produce many new generations quickly

3. THey reproduce so rapidly a variety of mutations can be observed in a relatively short time
Feedback (end-product) inhibition
The regulation of a metabolic pathway by the concentration of one of its intermediates or typically its end product which inhibits an enzyme in the pathway

Regulates the synthesis of various substances other than amino acids.

Occurs in many organisms other than bacteria

Allows cells to conserve energy in two ways because it acts quickly and directly on a metabolic process
Operon
Sequence of closely associated genes that regulate enzyme production.

Includes one or more structural genes which carry information for the synthesis of specific proteins such as enzyme molecules and regulatory sites which control the expression of the structural genes
Inducible Enzyme
Enzymes that are synthesized by genes that are sometimes active and sometimes inactive depending on the presence or absence of substrate
Lac operon
Contains regulatory sites (promoter and operator) and 3 structural genes z y and a which control the synthesis of specific enzymes

an RNA polymerase enzyme molecule must bind to the promoter before transcription can start
Regulator, promoter, operator, and represser when no lactose is present
The repressor protein binds to the operator preventing transcription
Regulator, promoter, operator, and repressor when lactose is present
When lactose is present it binds to the repressor and inactivates it allowing the enzymes to be made
Double Helix
made up of nucleotide pairs joined by hydrogen bonds
Polyribosomes
The presence of many ribosomes all "riding" simultaneously along one piece of mRNA
Repressible Enzymes
enzymes whose synthesis is inhibited in the presence of a signal molecule (repressor)
Constitutive Enzymes
Unregulated enzymes that are always produced at a constant rate because they are always needed
Enzyme Repression
Control processes in which substances needed for growth are synthesized (anabolism)
Trp Operon
Controls synthesis fo the amino acid tryptophan

Has more than one type of regulation
Tryptophan
by the presence of this, the first enzyme in the pathway is subject to feedback inhibition

when it is available to a bacterial cell it binds to an inactive repressor and activates it

the activated repressor binds to the promoter, which represses the synthesis of enzymes required to produce more tryptophan
Catabolite Repression
regulates expression of many genes and operons in response to the availability of carbon sources for growth

Prevents expression of genes encoding catabolism of carbon sources when a better carbon source is available

Saves the cell from expressing the lac operon if a more suitable carbon source is available
Polymerase Chain Reaction (PCR)
Powerful technique which involves taking a small DNA sample from a source containing body fluid or tissue, ancient fossil remains etc. and amplifying billions of copies of DNA all without a living cell
PCR 1
Take a piece of DNA with known short sequences of bases at the ends
PCR 2
Make billions of copies of this sequence in just hours by automated equipment
PCR 3
These sequences act as a primer by binding to target DNA and providing a starting point for DNA replication
PCR 4
Enzymes can cut large DNA pieces into smaller pieces to amplify separately
Phenotype
The specific characteristics displayed by the organism.

Mutations always change the phenotype

Such a change may or may not be expressed in a phenotype depending on the nature of the mutation
Genotype
Refers to the genetic information contained in the DNA of the organism
Point Mutation
Base substitution or nucleotide replacement in which one base is substituted for another at a specific location in a gene

The mutation changes an amino acid sequencing protein

Ex: three sequence of DNA is changed from AAA to AAT during transcription the mRNA codon will change from UUU to UUA
Frameshift Mutation
There is a detection or insertion of one or more bases

Such mutations alter the three-base sequences beyond the deletion or insertion

Usually prevent synthesis of particular protein and they usually change the genotype and the phenotype
Thymine Dimers How are they formed
When ultra violet rays strike DNA they cause adjacent pyrimidine bases to bond to each other there by creating a pyrimidine dimer.

A dimer consists of two adjacent pyrimidines (two thymines, two cytosines, or thymine and cytosine) bonded together in a DNA strand
Thymine Dimers Repaired
Many bacteria and organisms have enzymes capable of repairing certain kinds of damage to DNA

Light Repair and Dark Repair
Light Repair
Photoreactivation. In the presence of visible light, dimers are removed in bacteria that were previously exposed are removed in bacteria that were previously exposed to UV light
Dark Repair
Can take place in the presence or absence of visible light, but requires several enzyme mediated reactions, the defective segment of DNA is removed and replaced
64 codons
how many codons are found in the genetic code?
61 bc there are three "stop" codons
How many mRNA codons actually code for an amino acid?
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