Microbiology Chapter 8 Microbial Genetics

Describe DNA replication, including the functions of DNA gyrase, DNA ligase, and DNA polymerase

1. Helicase unwinds double helix 2. proteins stabilize unwound parental DNA 3. DNA polymerase makes leading strand 4. lagging strand is also made, Primase makes a short RNA primer which is extended by DNA polymerase 5. DNA polymerase digests RNA primer and replaces it with DNA 6. DNA ligase joins discontinuous fragments of lagging strand

during translation, mRNA is read in the ___________ direction

5' to 3'

Intron

A region in a eukaryotic gene that does not code for a protein or mRNA

Exon

A region of a eukaryotic chromosome that encodes a protein

Why is one strand of DNA synthesized discontinuously

DNA polymerase synthesizes in one direction; consequently the lagging strand is read from the replication fork. Okazaki fragments are made every time the replication form moves down

What is central dogma?

DNA to RNA to protein

What is the advantage of semiconservative replication?

Each offspring cell gets one strand of DNA from the parent cell, which survived to reproduce

Why can't the RNA transcript be used for translation?

Exons must be removed from the RNA transcript before translation

Classify mutations by type

Frameshift mutation- when you add or take a nucleotide pair out Missense mutation- when base substitution causes an amino acid substitution in the synthesized protein Nonsense mutation- stop codon in middle of mRNA molecule, causes only a portion of protein to be synthesized

Describe how DNA serves as genetic info

Genetic information is encoded by the sequence of bases along DNA strand .

Differentiate horizontal and vertical gene transfer

Horizontal transfer is when bacterial cells can give there DNA to not only there offspring but there generation; Vertical transfer is passage of DNA from parents to offspring

Why can translation begin before transcription is complete in prokaryotes but not in eukaryotes?

In prokaryotes, mRNA is produced by transcription and is in the cytoplasm where it is available to ribosomes. In eukaryotes, exons must be removed from the RNA transcript before translation. (Transcription is in the nucleus and translation in the cytoplasm in eukaryotes.)

what is the advantage of degeneracy of the genetic code?

It lessens the chance of deleterious mutations

What does degenerate mean?

It means that an amino acid may be specified for more than one codon

Do all mutagens cause cancer?

NO

Does tRNA contain a codon?

NO....it contains an anticodon

Does a base substitution always result in a different amino acid?

No, because of the degeneracy of the genetic code

describe 2 ways mutations can be repaired

Photolyases- light repair enzymes- uses visible light to bring dimer back to original 2 thymines Nucleotide excision repair- The repair of DNA involving removal of defective nucleotides and replacement with functional ones

primase

RNA polymerase that makes RNA primers from a DNA template

What causes transcription of a repressible enzyme?

Repressible enzymes are transcribed unless the repressor is activated

What causes transcription of an inducible enzyme?

The presence of an inducer, such as the substrate for the enzyme

Transcription

The synthesis of a complementary strand of RNA from a DNA template

Translation

The use of mRNA as a template in the synthesis of protein

Why are transposons sometimes referred to as "jumping genes"?

They insert and excise from DNA randomly

Describe protein synthesis, including transcription, RNA processing, and translation

Transcription-DNA is copied complementary base RNA is formed and used to synthesize specific proteins through translation. Ribosomal RNA (rRNA) forms an integral part of ribosomes. Transfer RNA is also involved in protein synthesis. Messenger RNA (mRNA) carries the coded information for making specific proteins from DNA to ribosomes, where proteins are synthesized. A strand of mRNA is synthesized using specific portion of the cell's DNA as a template

Compare the mechanisms of genetic recombination in bacteria

Transduction involves DNA transfer from a donor cell to a recipient cell inside a virus that infects bacteria Transformation-genes are transferred from 1 bacterium to another Conjugation-plasmid replicates without cell's chromosome

Describe the functions of plasmids and transposons

Transposons are small DNA segments that can move from 1 region of a DNA molecule to another Plasmids are a self replicating gene containing circular pieces of DNA

When does transcription stop?

When the terminator sequence is transcribed

What is the origin of replication?

Where DNA polymerase binds and starts synthesizing new strands

Genome

all the genetic information in a cell

What is a mutagen?

an agent in the environment that brings about mutation

what direction in bacterial DNA replication

bidirectional meaning it goes both ways and then separates into 2 DNA

How can a mutation be beneficial?

can provide new or enhanced activity that enhances the cell

Define operon

control region and structural genes: control region consists of operator and a promoter

RNA polymerase

copies RNA from a DNA template

what does positive (direct) selection do?

detects mutant cells because they grow or appear different

what does negative (indirect) selection do?

detects mutant cells that cannot grow or perform a certain function

what does genetic recombination do?

exchange of genes between 2 DNA molecules, creates genetic diversity

Why is the base pairing in DNA important?

genetic information is coded in base pairs and allows for precise DNA duplication during cell division

What is an open-reading frame?

it is part of the reading frame that has the potential to be translated, it does not contain a stop codon

How does mRNA production in eukaryotes differ from the process in prokaryotes?

mRNA for eukaryotes are produced in nucleus and for prokaryotes in cytoplasm

ligase

makes covalent bonds to join DNA, Okazaki fragments

what turns off genes?

methylating nucleotides (CH3 is added to cytosine)

What is the role of the promoter, terminator, and mRNA in transcription?

promoter is where transcription begins terminator is where transcription ends mRNA molecules carry the coding sequences for protein synthesis and are called transcripts

Gyrase

relaxes supercoiling ahead of replication fork

topoisomerase

relaxes supercoiling ahead of replication fork, separates DNA circles at the end of DNA replication

Genes

segments of DNA that encode functional products, usually proteins

photolyase

separates thymine dimers

genomics

sequencing and molecular characterization of genomes

what is a base substitution mutation example

sickle cell

Chromosomes

structures containing DNA that physically carry hereditary information; the chromosome carries the gene

polymerases

synthesizes DNA, proofreads and repairs DNA

What is a gene?

the basic physical and functional unit of heredity, are made up of DNA, act as instructions to make molecules called proteins

Phenotype

the expression of the gene such as blue eyes or brown hair

Genotype

the genetic makeup of an organism

Genetics

the study of genes, how they carry information, how that information is expressed and how genes are replicated

Helicase

unwinds double stranded DNA

Give a clinical application of genomics

use of genomics to track West Nile Virus by checking blood donations and finding out that it had formed mutations