Ch. 8 Microbial Genetics and Genes

Réussis tes devoirs et examens dès maintenant avec Quizwiz!

Genome of all non viral cells are

DNA

Repressible (operon)

(repression) genes in a series are turned OFF by the product synthesized: -anabolic operon

RNA consist of

-5 carbon sugar is ribose -One of 4 nitrogenous bases - adenine, uracil (instead of thymine), guanine, or cytosine -Phosphate

some other traits acquired by conjugating bacteria

-Drug or antibiotic resistance (acquired first by random mutation in the DNA that gives bacteria a selective advantage in its environment) -New enzymes -Toxin production -Metal resistance

Translation

-Each "triplet" of nucleotides on the mRNA, called a codon, specifies a particular amino acid. The information contained in the mRNA molecule is used to produce proteins in a process called translation, which occurs in the ribosome (which is in the cytoplasm).

examples of conjugation

-Gram-negative cells have a fertility factor, which is a plasmid that contains genes that code for the synthesis of a conjugative pilus -Recipient cell is a related species or genus without a fertility factor -Donor replicates its plasmid and then transfers fertility factor to recipient through its pilus; now recipient can synthesize pili, thus acquiring a new ability to initiate "sex" (to conjugate)

Transcription

-Information stored on the DNA molecule is conveyed to "messenger RNA" molecules (mRNA) through the process of transcription (occurs at the chromosome)

DNA Replication

-Making an exact duplicate of the DNA involves 30 different enzymes -Begins at an origin of replication

the master genetic code

-Represented by the mRNA codons and the amino acids they specify -Code is universal -Code is redundant (repetitious)

Application of the DNA code

-The enzyme RNA polymerase binds the DNA at the starting point of the gene to be transcribed, and begins binding together nucleotides that are complementary but in the same sequence as those within the DNA template strand, forming the mRNA segment. -The mRNA segment then moves to a ribosome where the code is translated into a protein. (Note: "AUG" is always the first triplet of nucleotides in the mRNA, and always codes for the first amino acid in a protein, so the first triplet in the template strand is "TAC".)

a gene is

-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 (a specific sequence of nucleotides) that contains the necessary code to make a protein or RNA molecule

a mutation can result IN:

-a variance in morphology -nutritional characteristics -genetic control mechanisms -resistance to chemicals -antibiotics, etc.

DNA polymerase

-adds nucleotides -Both strands are copied (synthesized) -removes the RNA primers and replaces them with DNA -Separation of the daughter molecules is complete

transduction

-bacteriophage serves as a carrier of new genes by acquiring random fragments of the host cell's DNA during assembly of new viruses within the host cell

Transformation

-chromosome fragments from a lysed cell are accepted by a recipient cell that has special DNA-binding proteins on its cell wall; the genetic code of the DNA fragment is acquired by the recipient and inserted into its own chromosome -Donor and recipient cells can be unrelated species

lactose operon is made of what?

3 genes each coding for an enzyme needed to catabolize lactose : -b-galactosidase -permease -b-galactosidase transacetylase

smallest virus has how many genes?

4-5

human cell (gene size)

46 chromosomes containing 31,000 genes; 6 feet long

Each nucleotide consists of 3 parts

A 5 carbon sugar - (deoxyribose) A phosphate group One of 4 nitrogenous bases

Mutations definition

A change in phenotype due to a change in genotype (i.e., a change in the nitrogenous base sequence of DNA)

mutant strain

An organism that has a mutation

nucleotide

Basic unit of DNA structure is a

Genome of viruses are

DNA or RNA

what turns on the Lac Operon?

Lactose: -Binding of lactose to proteins covering and blocking the DNA code turns the genes "on" and genes are transcribed.

DNA definition?

Nitrogenous bases covalently bond to a carbon of each sugar and span the center of the molecule to pair with an appropriate complementary base on the other strand

the "backbone"

Nucleotides covalently bond (share electrons) in an arrangement that forms a sugar-phosphate linkage

what constitutes the DNA code?

Order of bases

repair of mutations

Since mutations can be potentially fatal, the cell has several enzymatic repair mechanisms in place to find and repair damaged DNA (uses DNA polymerase)

what is RNA

Single-stranded molecule made of nucleotides

wild type (wild strain)

The natural, non-mutated characteristic of a mutation

what does a mutation result FROM?

a deleted, added, or substituted nucleotide, which changes the sequence and thus the code

operons

a set of genes, all of which are regulated as a single unit

catabolic operon

a set of structural genes that code for the synthesis of an enzyme needed to metabolize (break down, catabolize) a nutrient; this inducible operon is "induced" when the substrate (nutrient) is present;

anabolic operon

a set of structural genes that code for the synthesis of an enzyme used to synthesize (anabolism) products, such as an amino acid; this repressible operon is "repressed" by the product of which the enzyme catalyzes the production of. (as the product accumulates, it turns off the very gene that produces it, so that too much is not produced.)

bacterial chromosomes are

a single circular loop

what does each DNA strand provide?

a template for the exact copying of a new strand

what is an anticodon?

a triplet of nucleotides that binds to a complementary codon in the mRNA. Hence the amino acids are brought to the ribosomes in the proper order, and then bonded together in the proper sequence.

bacteriophage

a virus that infects bacteria

what does viral genome require?

access to host cell's genetics and metabolic machinery to instruct the host cell to synthesize new viral particles

4 nitrogenous bases (DNA)

adenine, guanine, thymine, or cytosine

4 nitrogenous bases (RNA)

adenine, uracil (instead of thymine), guanine, or cytosine

Methionine

all amino acids start with AUG (a start codon)

There exist a specific tRNA molecule for each kind of

amino acid

each tRNA carries?

an anticodon

bacteriophages produce

an enzyme that breaks up the host cell DNA

mutagens

are physical (primarily radiation) or chemical agents that interact with DNA in a disruptive manner

mRNA characteristics

are relatively short single-stranded segments of nucleotides that code for proteins

example of phenotype

blue eyes

what do tRNA (transfer RNA) do?

bring the proper amino acids to the ribosomes, in the sequence encoded in the mRNA. (during translation)

what does perm ease do?

brings lactose across cell membrane

Upon infecting a new host bacterial cell, what happens to the new genes?

can be inserted into the recipient cell's genome

Organisms with mutations that are beneficial in their environment can

can readily adapt, survive, and reproduce - these mutations are the basis of changes in populations (evolution)

Genomes include

chromosomes w/DNA + the DNA in mitochondria/chloroplasts and/or plasmids

Guanine always binds to

cytosine with 3 hydrogen bonds

Providing variety

differences in the order of bases responsible for variable traits and unique qualities of each organism

induced mutations result from

exposure to known mutagens

Chromosomes are subdivided into

genes

structural genes

genes that code for proteins

regulatory gene

genes that control gene expression

example of genotype

genes that express blue eye color

All types of genes constitute the genetic makeup

genotype

Mutations leading to nonfunctional proteins are

harmful; possible fatal

what does b-galactosidase do?

hydrolyzes lactose

example of catabolic operon

if the substrate lactose (a sugar) is present, bacteria induces the operon that codes for the synthesis of lactase; lactase is the enzyme that catalyzes the breakdown of lactose.

Lactose Operon is which class of operons?

inducible

RNA primer

is synthesized at the origin of replication (short strand of RNA that serves as a starting point for adding nucleotides)

what is semiconservative?

it preserves the exact sequence of genes in the original parent molecule, because each chromosome ends up with one new strand of DNA and one old strand.

Eukaryotic chromosomes are

multiple and linear

Genetic recombination

occurs when an organism acquires and expresses genes that originated in another organism

Lac Operon is normally off or on?

off: -In the absence of lactose, transcription is blocked so that genes encoding the enzymes are not active

Viral genome

one or more pieces of DNA or RNA; generally contains only genes needed for production of new viruses

mRNA is transcribed from

only one strand of DNA, the template strand, which contains the gene

The expression of the genotype creates observable traits

phenotype

DNA polymerase

proofreads nucleotides during DNA replication

DNA complexed with

protein constitutes the genetic material as chromosomes

Spontaneous mutations

random change in the DNA due to errors in replication that occur without known cause

Transformation is a useful tool for what?

recombinant DNA technology (genes from humans and other organisms can be inserted into a plasmid and then introduced into bacteria through transformation; as the bacteria reproduces, it replicates its entire genome, including the new plasmid, before dividing into two new daughter cells. Using this recombination technique, many copies of a gene can be made.)

DNA replication is what?

semiconservative

E. coli (gene size)

single chromosome containing 4,288 genes and is 1 mm in length

what may happen during assembly of new viruses?

some of the viral assemblies may take up one of the host cell's DNA fragments instead of the viral DNA or RNA

Genome

sum total of genetic material, including both DNA and the chromosomal structures that package the DNA within a cell

Substrate

the reactant molecule(s) that an enzyme binds to, causing a reaction and forming products

Genetics

the study of heredity

Adenine binds to

thymine with 2 hydrogen bonds

conjugation

transfer of a plasmid or chromosomal fragment (DNA) from a donor cell to a recipient cell via a direct connection (pilus)

what does b-galactosidase transacetylase do?

uncertain function

what is selection pressure?

when the environment selecting one feature over another in favor of survival and enhanced reproduction

Any change in genes that confers an advantage during selection pressure

will more likely be retained by the population, and passed on to offspring.

Maintenance of code during reproduction

Constancy of base pairing guarantees that the code will be retained

how does regulation of protein synthesis work in prokaryotes?

by operons

Helicase

(enzyme) unwinds and unzips the DNA double helix

Inducible

(induction) operon is turned ON by the presence of the substrate: -catabolic operon -substrate

from DNA to Protein

1. A protein's primary structure determines its shape and function 2. Proteins determine phenotype. Living things are largely what their proteins make them. 3. DNA is mainly a blueprint that tells the cell which kinds of proteins to make and how to make them.

3 means for genetic recombination in bacteria

1. Conjugation 2. Transformation 3. Transduction

2 types of operons

1. inducible 2. Repressible

Significance of DNA Structure

1.Maintenance of code during reproduction 2.Providing variety

The science of genetics explores

1.Transmission of biological traits from parent to offspring 2.Expression and variation of those traits 3.Structure and function of genetic material 4.How this material changes

Three basic categories of genes

1.structural genes 2.Genes that code for RNA 3. regulatory genes

regulation of protein synthesis and metabolism

Genes are regulated to be active only when their products are required (In other words, we only want to transcribe and translate a gene when the protein it codes for is needed.)

nontemplate strand

The other complementary DNA strand (opposite of the template strand).

what is DNA

Two strands twisted into a double helix


Ensembles d'études connexes

Neurosensory and Musculoskeletal ATI

View Set

Crash Course: Due Process of Law

View Set

Vision and Hearing Problems in the Older Adult

View Set

AP Lang - Mark Twain (Corn-Pone Opinions)

View Set

What is the Purpose of Government

View Set

Texas Real Estate Finance - Chapter 6

View Set