Chapter 8 Flashcards
Which statement regarding prokaryotic chromosomes is incorrect?
• There are two copies of the chromosome so that cells are diploid.
• There is a single copy of the chromosome so that cells are haploid.
• Prokaryotic chromosomes are located in the nucleoid.
• Prokaryotic chromosomes are now known to be circular or linear.
There are two copies of the chromosome so that the cells are diploid
Genetics
- the study of genes, how they carry information, how information is expressed, and how genes e replicated
Chromosomes
- structures containing DNA that physically carry hereditary information; the chromosomes contain genes
Genes
- segments of DNA that encode functional products, usually proteins
genome
- all the genetic information in a cell
Genotype
Phenotype
Genotype - a set of genes in the genome
Phenotype - physical features and functional traits of the organism
The structure and replication of genomes
- prokaryotic chromosomes
- main portion of DNA, along with associated proteins and RNA
- prokaryotic cells are haploid (single chromosome copy)
- typical chromosome is a circular molecule of DNA in the nucleaid
The structure and replication of genomes
- the structure of prokaryotic genomes
- plasmids
- small molecules of DNA, among with associated proteins and RNA
- not essential for normal metabolism, growth, or reproduction
- can confer survival advantages
- many types of plasmids:
- fertility factors
- resistance factors
- bacteriocin factors
- virulence plasmids
The structure and replication of genomes
- DNA replication
- key to replication is the complementary structure of the two strands
- replication is semi conservative
- new DNA composed of one final and one daughter strand
- anabolic polymerization processes require monomers and energy
- triphosphate deoxyribonucelotides serve both functions
The structure and replication of genomes
- DNA replication -> initial processes in bacterial NDA replication
- bacterial DNA replication begins at the origin
- DNA polymerase replicated DNA only 5’ to 3’
- because strands are anti parallel, new strands are synthesized differently
- leading strand synthesized continuously
- lagging strand synthesized discontinuously
The structure and replication of genomes
- DNA replication -> other characteristics of bacterial DNA replication
- bidirectional (think of a phone cord and all of the circles it creates/how wound up it would be)
- gyrases and topiocomerases remove supercoils in DNA
- DNA is methylated (telling a gene to be quiet. Ex: giving/surrounding it by a bunch of cups continuing to say you be quiet as you add them. “You be quiet or you have activity”)
- control of genetic expression
- initiation of DNA replication
- protection against viral infection
- repair the DNA
The structure and replication of genomes
- DNA replication -> replication of eukaryotic DNA
- similar to bacterial replication (bacterial have leading and lagging strands, may have more DNA polymerase that is more specialized, and have longer Okazaki fragments)
- some differences:
- uses four DNA polymerases
- thousands of replication origins
- shorter Okazaki fragments
- plant and animal cells methylate only cytosine bases
What determines the genotype of a cell?
It’s proteins
It’s RNA
It’s DNA
It’s ribozymes
- It’s DNA
Four types of RNA
- RNA primer molecules
- used for DNA polymerase during DNA replication
- messenger RNA
- carry genetic information from chromosome to ribosome
- ribosomal RNA
- combine with ribosomal polypeptides to form ribosomes
- transfer RNA
- deliver the correct sequence of amino acids to ribosomes based on the sequence of nucleotides in mRNA
Transcription
Promoter region - DNA sequences located upstream of transcriptional start site
Sigma factor - specificity to promoter region, the region interacts with RNA polymerase
RNA polymerase - workhorse of the transcription-> does all of the work
Transcriptional start site - the position in the gene where transcription starts
Termination - the sequence where transcription stops
Transcription in the eukaryotes
- in eukaryotes, transcription occurs in the nucleus, whereas translation occurs in the cytosol or RER
- exons are regions of DNA that code for proteins
- introns are regions of DNA that do not code for proteins
Prokaryotic vs. eukaryotic transcription
Prokaryotic - located in the cytoplasm, have one polymerase, have pretty simple mRNA, are Rho in/ dependent termination
Eukaryotic - located in the nucleus, have many polymerases, have complex (processing) mRNA, and the termination sequence if polyU
Translation: protein synthesis
- players in translation
Messenger RNA (MRNA, start)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Ribosomes (work horse)
Polypeptides (outcome)