Talaro's Foundations in Microbiology - Chapter 9 - 11th Edition

Genetics is?

The scientific study of heredity and can be studied at the level of organism, genome, chromosome, gene, and DNA

DNA is?

a long molecule in the form of a double helix. each helix consists of a string of nucleotides

A nucleotide consists of?

deoxyribose sugar, nitrogen base, and a phosphate

Adenine base-pairs with _______, while guanine base-pairs with _______

thymine, cytosine

Replication?

requires unwinding the double helix and exposing the nucleotides to serve as templates for synthesis of 2 identical molecules by DNA polymerase

Replication is also?

semiconservative

DNA is used to produce?

RNA and RNA is used to produce protein

RNA unlike DNA is single stranded and contains _______ instead of thymine and ribose instead of deoxyribose

uracil

Codons in the mRNA pair with anticodons on the tRNA to specify which amino acids to assemble on the ______ during translation

ribosome

transcription occurs when _______ copies the template strand of a segment of DNA

RNA polymerase

RNA is always made in the ______ direction

5' to 3'

eukaryotic genes are composed of _____ (expressed sequences) and ______ (intragenic regions)

exons, introns

protein synthesis is regulated through gene induction or repression, as controlled by an ______

operon

Operons consist of several structural _____ controlled by a common regulatory element

genes

inducible operon

An operon under positive control. It is usually "off" but can be turned "on".

repressible operon

An operon under negative control. It is usually "on" but can be turned "off".

________ can also control RNA functions related to transcription and translation in bacteria

riboswitches

changes in the genetic code

occur primarily through mutation and recombination

inheritable changes in the genome of a microorganism are known as?

mutations

Mutations may be?

spontaneous or induced

Point mutations entail a change in one or a few bases and are characterized as ________ baaed on the effect of change in nucleotides

missense, nonsense, silent, and back-mutations

A frame shift is caused by ______ mutations.

deletion and insertion

The ________ measures the mutagenicity of chemicals by their ability to induce mutations in bacteria

Ames test

_________ involves the acquisition of new genetic material from an outside source

recombination

major types of recombination include

conjugation, transformation, transduction

transposons are

DNA sequences that regularly move to different places within the genome of a cell, generating mutations and variations in chromosome structure

DNA viruses tend to replicate in the nucleus while RNA viruses replicate in the?

cytoplasm

Chromosomes are

Coiled up lengths of DNA molecules

genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

Topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Nucleosomes are

complexes of DNA wrapped around histone proteins

James Watson and Francis Crick (1953)

Deduced the structure of DNA using evidence from Chargaff, Franklin, and others
Did not perform a single experiment themselves related to DNA
Proposed a double helix structure

semiconservative replication

Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental DNA strand and one new DNA strand

DNA polymerase III

adding bases to the new DNA chain; proofreading the chain for mistakes

Helicases

enzymes that untwist the double helix at the replication forks

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

ligase

An enzyme that connects two fragments of DNA to make a single fragment

Transcription

synthesis of an RNA molecule from a DNA template

translation

Process by which mRNA is decoded and a protein is produced

Triplets/Codons

carry the message for which amino acid to add when making a protein

Uracil structure

-Pyrimidine w/ 2 N and 2 O.
-1 double bond.

transcription proceeds in 3 stages?

initiation, elongation, termination

introns

sequence of DNA that is not involved in coding for a protein

Exons

Coding segments of eukaryotic DNA.

inducer

A specific small molecule that inactivates the repressor in an operon.

wild type

The phenotype most commonly observed in natural populations; also refers to the individual with that phenotype.

Spontaneous mutations are

the result of errors in the base pairing of nucleotides during replication

induced mutations

refers to those mutations in the DNA resulting from exposure to toxic chemicals or to radiation

missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

back mutation

when a mutated gene reverses to its original base composition

inversion mutation

Mutation in which a chromosome piece reattaches to original chromosome but in reverse orientation

Ames test

Test in which special strains of bacteria are used to evaluate the potential of chemicals to cause cancer.

F factor (fertility factor)

A plasmid found in the donor cell during conjugation and transfers from F+ to F-

Frederick Griffith

Discovered transformation during an experiment that involved injecting mice with smooth S cells, rough R cells, heat-killed S cells, and heat-killed S cells with living R cells.

Transduction in bacteria

DNA is transferred from a donor cell to a recipient via a bacteriophage

generalized transduction

random fragments of disintegrating host DNA are picked up by the phage during assembly; any gene can be transmitted this way

specialized transduction

specific bacterial genes are packaged inside a phage and transferred to a recipient cell

insertion elements

the smallest transposable elements, consisting only of tandem repeats that are capable of inserting themselves into DNA but do not carry any genes

Retrotransposons

Transposable elements that move within a genome by means of an RNA intermediate, a transcript of the retrotransposon DNA.

what is the smallest unit of heredity (genotype)?

gene

A nucleotide contains which of the following?

5 carbon sugar, nitrogen base, phosphate

The nitrogen bases in DNA are bonded to the?

deoxyribose

DNA replication is considered semiconservative because the _______ strand will remain was half of the _______ molecule

template, final DNA

In DNA, adenine is the complimentary base for ______, and cytosine is the complement for ______

thymine, guanine

The base pairs are held together primarily by

hydrogen bonds

Why must the lagging strand of DNA be replicated in short pieces?

the DNA polymerase can synthesize in only one direction

Messenger RNA is formed by _____ of a gene on the DNA template strand

transcription

Transfer RNA is the molecule that

adapts the genetic code to protein structure

As a general rule, the first codon on the DNA template strand that signals the start for a protein is

TAC

What components are involved in transcription?

Sigma factor, RNA polymerase, and promotor

The lac operon is usually in the ____ position and is activated by a/an ____ molecule

off, inducer

For mutations to have an effect on populations of microbes, they must be

inheritable, permanent

Which of the following characteristics is not true of a plasmid?

it is required for normal cell function

Which genetic material could be transmitted naturally by all three methods of intermicrobial transfer?

drug resistance genes

Which of these features is found in eukaryotes but not bacteria?

introns

Which of the following is present in prokaryotes but not eukaryotes?

simultaneous transcription and translation

site of protein synthesis

ribosomes

carries the codon

mRNA

carries the anticodon

tRNA

a process synonymous with mRNA synthesis

transcription

bacteriophages participate in this transfer

transduction

duplication of the DNA molecule

replication

process in which transcribed DNA code is deciphered into a polypeptide

translation

involves plasmids

conjugation, transduction, transformation

Which base will pair with uracil in RNA?

Adenine

What cell structure is responsible for protein synthesis?

ribosome

genome

sum total of genetic material (DNA) of an organism

Most microbial genomes exist as

chromosomes

Genome of viruses -

DNA or RNA

Chrmosomes

discrete cellular structure composed of a neatly packaged DNA molecule
- eukaryotic chrokosoke are located in the nucleus and are multiple and linear
- bacterial chromosomes are a singular circular loop

A chromosome is divided into

genes, the fundamental unit of heredity responsible for a given trait
- site on the chromosome that provides information for a certain cell function
- segment of DNA that contains the necessary code to make a protein or RNA molecule

Three basic categories of genes

Genes that code for proteins - structural genes
Genes that code for RNA
Genes that control gene expression - regulatory genes

all types of genes constitute the genetic makeup

genotype

The expression of the genotype creates observable traits -

phenotype

Smallest virus

4-5 genes

E.coli

single chromosome containing 4,288 genes; 1 mm; 1,000x longer than cell

Human cell

46 chromosomes containing 31,000 genes; 6 feet; 180,000X longer than cell