BIO 245- exam 3

Sum total of genetic material of a cell (chromosomes + mitochondria/chloroplasts and/or plasmids

Genome

Genome of cells

DNA

Genome of viruses

DNA or RNA

DNA complexed with protein constitutes the genetic material as ______

Chromosomes

Describe bacterial chromosomes

Single circular loop

Describe eukaryotic chromosomes

multiple and linear

What is a chromosome subdivided into

Genes

The fundamental unit of heredity responsible for a given trait

gene

site on the chromosome that provides information for a certain cell function

Gene

Segment of DNA that contains the necessary code to make a protein or RNA molecule

gene

Three basic categories of genes

Genes that code for proteins
Genes that code for RNA
Genes that control gene expression

Genes that code for proteins

Structural genes

What are most genes considered

Structural genes

Genes that control gene expression

Regulatory genes

True or false: genomes vary in size

True

Smallest virus contains how many genes

4-5 genes

Describe E.coli genome

Single chromosome containing 4,288 genes; 1mm; 1,000X longer than cell

Describe human genome

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

How many origins of replication do bacteria have?

one

Nucleotides of Ribonucleic Acid (RNA)

- Sugar: ribose
- phosphate
- base

Nucleotides of Deoxyribonucleic Acid (DNA)

- sugar: deoxyribose
- phosphate
- base

How to spot the difference between DNA and RNA

-different sugars
- 2' OH in ribose
- 2' H in deoxyribose

Where is the only place DNA polymerase can attach nucleotides

Growing point at 3' OH

Polymerization

Growth ( joining of monomers to form a polymer)

How are the two strands of DNA arranged

Antiparallel

Purines and pyrimidines are

The "base" component of a nucleotide

Purines

Adenine and Guanine

Which bases have a double ring

Purine

Which bases have a single ring

Pyrimidine

What end of a DNA or RNA molecule is the growing end?

3' end

The amount of _____= the amount of ______

Adenine= thymine
Cytosine= guanine

How many bonds between C and G

Three

How many bonds between A and T

Two

DNA secondary structure consists of

Double helix

True or false: DNA supercooling occurs in only bacterial DNA

False: all DNA

The "central dogma"

Replication of DNA
Transcription into RNA
Translated into protein

The genes that contribute to a particular phenotype

Genotype

The observable traits or characteristics that result from genes

Phenotype

What are the three processes involved in information transfer in the cell

Replication, Transcription, and translation

Describe DNA replication

Semiconservative- one old strand and one new strand

Replication of the bacterial chromosome

- one origin of replication
- bidirectional
- dual replication forks
- leading and lagging strand synthesis

DNA replication steps

- synthesis takes place simultaneously but in opposite directions on the two DNA template strands
- DNA replication at a single replication fork begins when a double-stranded DNA molecule unwinds to provide two single-strand templates

Short fragments of DNA produced by discontinuous synthesis

Okazaki fragments

Which strand produces Okazaki fragments

lagging strand

The DNA "replisome"

1. Chromosome unwound by helicase forming replication fork
2. DNA Poly III adds nucleotides adds to leading and lagging strands
3. Lagging strand synthesis must have RNA primer laid down before replicating
4. DNA poly I removes RNA primers and fills in gap
5. Ligase connects unjointed ends of nucleotides (a nick)

Leading strand synthesis

Towards the replication fork

Template for leading strand

3' to 5'

template for lagging strand

5'-3'

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

DNA polymerase III can only synthesize in one direction

Which strand of DNA grows continuously towards the fork

Leading strand

What happens if a mismatch in base pairing during replication occurs

DNA Poly III has proofreading ability to cut out mismatches nucleotide and insert the correct base

Where does RNA polymerase bind to initiate transcription

Promoter region

One gene forms

One protein

Transcription

RNA polymerase moves along DNA template, synthesizing mRNA in the 5' to 3' direction and unwinds and rewinds DNA

Is information processing more complex in prokaryotes or eukaryotes

Eukaryotes

_____ are excised during processing

Introns

Where does replication and transcription occur in eukaryotes

Nucleus

Where does translation occur in eukaryotes

cytoplasm

Where does replication occur in prokaryotes

cytoplasm

Where does transcription occur in prokaryotes

cytoplasm

Where does translation occur in prokaryotes

cytoplasm

The master genetic code

Represented by the mRNA codons and the amino acids they specify
Code is universal among organisms
Code is redundant

What does it mean to say the genetic code is redundant

More than one codon can specify the addition of the same amino acid. (Protects from mutations)

What does every protein start with

AUG (Met)

What does every protein end with

Stop codon

What structure contains the anticodon during translation

TRNA

Where does translation occur

ribosome

______ and _______ occur simultaneously in prokaryotes

Transcription and translation

What happens during elongation during translation

Ribosome attaches at 5' end of transcript

Which strand is transcribed

Template

Which strand during replication has the 5' end towards the replication fork

Lagging strand

Which strand has 3' end and can grow continuously towards the replication fork

Leading strand

A theta structure is formed during which process

Replication

Three levels at which enzymes can be refulated

At transcription, at translation, or _____

In prokaryotes, expression is generally regulated at the level of ______

Transcription

In bacteria and archaea, genes are usually organized into what

Operons

A cluster of genes whose expression is controlled by a single operator

Operon

a specific region of the DNA at the initial end of a gene or operon, where a repressor protein binds and blocks mRNA synthesis

operator

A regulatory protein that binds to specific sites on DNA and blocks transcription

repressor protein

When a drug is used to control an infection, the practice is termed

Antimicrobial chemotherapy

A class of compounds which inhibit or kill microorganisms

Antimicrobial drugs

Natural antimicrobial drugs

Antibiotics

Man-made microbials

Synthetics

Antibiotics which have been chemically modified

semisynthetics

Target a wide variety of pathogenic bacteria

Broad spectrum agents

Target only a narrow subset of pathogens

Narrow spectrum agents

Who discovered penicillin

Alexander Fleming

Main sources of useful antibiotics

Streptomyces and Bacillus (bacteria), Penicillium and Cephalosporium (fungi)

True or false: thousands of antimicrobials have been discovered but relatively few of these are useful

True

Why cant penicillin be toxic to human cells

We dont have peptidoglycan and bacteria do

The main trick if one were to design an antibiotic

find something the target pathogen has or does (e.g. a structure or pathway) which the host cell doesn't

True or false: most bacteria have peptidoglycan while eukaryotes dont so a compound which destroys or inhibits its production (like penicillin) shouldn't affect eukaryotes

True

True or false: toxicity to the host is a major concern of antimicrobials

True

What is therapeutic index

ratio of a drug's toxic dose to its minimum therapeutic dose

5 main approaches of antimicrobials

Inhibition of cell wall formation
Inhibition of cell membrane function (less common)
Inhibition of DNA synthesis
Inhibition of ribosomes/protein synthesis
Inhibition of metabolic pathways

Which antimicrobial inhibit cell wall formation

Penicillins and cephalosporins (beta lactam antibiotics)

What antimicrobial inhibits cell membrane function

Polymixin

Which antimicrobial inhibits DNA synthesis

Ciprofloxacin

Which antimicrobials inhibit ribosomes/protein synthesis

Tetracyclines and erythromycin

Which antimicrobials inhibit metabolic pathways

Sulfa drugs