Chapter 8 Flashcards
(45 cards)
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)
What types of RNA are ——— used in translation: protein synthesis?
Messenger RNA -> Cary genetic information from the chromosome to ribosomes
Ribosomal RNA -> combine with ribosomal polypeptides to form ribosomes
Transfer RNA -> deliver correct sequences of amino acids to ribosomes based on the sequence of nucleotides in mRNA
Original DNA -> first replication -> second replication
Original DNA is the original form it comes in
- first replication is when the original strand is combined with a new strand
- second replication is when the first replication pair is joined by another separate pair of DNA
What does the DNA polymerase 111 do in DNA replication? What do stabilizing proteins do?
The DNA polymerase 111 does the work in the end for the DNA replication
The stabilizing proteins keep the replication pieces separate but keep them together to continue with the replication process
what repairs the junctions in DNA replication
Ligase (German for glue)
What does the RNA primer, the Okazaki fragments, DNA polymerase 1 and DNA polymerase 3 do in DNA replication
- RNA primer -> helps us to know where to start replication
- Okazaki help us associate with leading or lagging lines (specifically lagging)
- DNA polymerase 1 - helps repair by removing the RNA primer
DNA Polymerase 3 - makes the long chains or lines
What is essentially the outcome from DNA to protein?
mRNA