The flashcards below were created by user
on FreezingBlue Flashcards.
In prokaryotes, the genome is usually contained in a single, circular DNA molecule, localized within the __
- nucleoid (no real nucleus)
Chromosomes of most prokaryotes are __
circular and single (chromosome is haploid)
- small, circular, DNA molecules that are found inside some prokaryotic cells in multiple copies
- considered as independent entities from bacterial genome and are not part of bacterial genome
Plasmids are important for __
antibiotic resistance or virulence genes
Bacterial genomes have __ genetic organizations & only __ of E. coli genome is noncoding DNA. A very small part of E. coli genome is the __
- compact (very little space between genes);
- origin of replication (the start point of DNA polymerization)
Chromosomes of eukaryotes are __
- linear and multiple (variable numbers from organism to organism)
- usually diploid, but at some stages of life can be haploid (gametes), sometimes polyploid
The genome of eukaryotes is enclosed in __
DNA is packaged with __ into a structure known as a chromosome
importance of chromosomes
- Packaging of DNA is very important as it is a very long and narrow molecule. (DNA is compacted and packaged into the chromosome).
- DNA is more protected and stable in the chromosome.
- Only packaged DNA can be reliably transmitted to the daughter cells during cell division.
- DNA is organized in the chromosome and its accessibility and expression of its info is regulated within the chromosome.
In the nucleus of eukaryotic cells that are not dividing, __ is the DNA with its associated proteins.
The most abundant proteins associated with DNA are __ that are small basic proteins.
DNA is wrapped around histone octamers.
__ proteins (less common) include DNA interacting proteins involved in DNA repair, replication, recombination, transcription, etc.
In eukaryotes, the __ is more correlated with the complexity of the organism, not the __
- number of genes;
- size of the genome
- The size of genome is very variable between different organisms.
Genes are more __ in prokaryotes than eukaryotes. Roughly, there is a __ between the density of genes and the complexity of the organism.
dense; reverse correlation
Viruses have the highest gene density, followed by bacteria. In eukaryotes, large sequences of DNA allocated for the regulation of gene expression.
Proteins coded by eukaryotes on average have __ sizes to prokaryote proteins
The reasons for increase in the size of eukaryotic genomes are:
- increase in the size of intergenic sequences
- interrupting sequences within the gene (introns)
In humans, 95% of the size of the gene is from __ and 5% is from __
introns; coding sequences
(More complex organisms have more and longer introns.)
Humans have a __ % of repetitive DNA and has __ gene density. Fungi has a __ % of repetitive DNA but has __ gene density.
- large; low
- small; large
- does not code for structural or functional proteins or functional RNAs
- make up 60% of the genome of humans (The other 40% are genes and gene related sequences.)
- 2 types: unique and repeated
- the areas of the genome that contribute in regulating expression of genes
- also part of non-coding regions of DNA
It has been discovered that intergenic sequences also contain __
- the genes for regulatory RNA molecules such as long intervening non-coding RNA (lincRNA)
Sequences that are associated with the gene, such as introns and untranslated regions are __ than the coding areas.
- much larger
Approximately 62% of the human genome comprises of __, which have no known function. These sequences used to be called junk DNA (but in fact they may have important functions)
intergenic regions (between genes)
The bulk of intergenic DNA is made up of __ (half of human genome)
individual repeat units distributed around the genome
- interspersed repeats (genome wide repeats)
- 45% of genome
- (longer than tandem repeats)
repeat units that are placed next to each other in an array
tandemly repeated DNA
- (Some of these tandem repeats are in the centromere and telomere - may have structural function - and also in other parts of the genome.)
repeats of 6-10 nucleotides. e.g. telomeric DNA, which in humans comprises hundreds of copies of the motif 5'-TTAGGG-3'
the repeat unit is short - from 1 to 5 bp in length - The most common type is dinucleotide repeats and single nucleotide repeats (e.g. AAAAA)
nonfunctional gene copies
- (accumulate more and more mutations during evolution)
a gene that has been inactivated because its nucleotide was changed by mutation
- looks like a CDNA copy of an mRNA which reinserted into the genome
- doesn't contain any introns and lacks 5'
Chromosomes need a __ to be maintained during cell divisions
- centromere, telomere, and origin of replication
- (These are neither genes nor regulatory sequences.)
origin of replication
- the site at which DNA replication machinery assembles and replication is started
- One in very 30 - 40kb in eukaryotic chromosome, in the non-coding region of the chromosome
- There is one origin of replication in prokaryotes in their single chromosome.
metaphase chromosomes: For the purpose of cell division, the DNA adopts a more __ form of packaging.
(resulting in the highly condensed form that can be seen with the light microscope)
The metaphase chromosomes form after __ has taken place, and so each contains __ copies held together at the __
- DNA replication;
The arms of the chromosomes are called __ and have terminal structures called __
- chromatids (2 sister chromatids); telomeres
In the majority of eukaryotes, the centromere is __ and is made up of __
large; repetitive sequences
The structure (contains > 20 proteins) binds to the centromere and acts as the attachment point for the microtubules (spindles) which pull the divided chromosomes into the daughter nuclei