Genes and Genome Flashcards
Genome
all hereditary material in a virus, cell, or organism, including but not confined to genes
Does genome only refer to DNA?
no
a viruses genome can be made out of RNA
Does genome only include the coding regions?
no
includes coding and non-coding regions
Size of eukaryotic and prokaryotic genomes
eukaryotes have more DNA than prokaryotes
Structural differences between eukaryotic and prokaryotic genomes
eukaryotes have multiple linear chromosomes
prokaryotes have a single circular chromosome
plasmids
circular components of prokaryotes genome that can be transferred between cells
contain a subset of genetic information that may be needed to pass on to another cell
packaging of eukaryotic vs prokaryotic DNA and effects
eukaryotes DNA is more tightly packed around histones
leads to eukaryotes having more chemical modifications of genome because methyl groups are added to histones to control packaging
genetic makeup of eukaryotic vs prokaryotic genomes
eukaryotes have many more regions of non-coding DNA
most of prokaryotic DNA codes for proteins
why do prokaryotes express mutant phenotypes more often?
they are haploid
if one copy of the gene is mutated, the phenotype is mutated
no extra copy to use in the event of a mutation
do prokaryotes have introns and exons?
no
operons
a feature of the prokaryotic genome
multiple genes that are transcribed together onto single mRNA but translated independently
can turn and turn off all the genes in an operon at the sametime
advantage and disadvantage of operons
advantage: efficient
disadvantage: cannot fine tune specific genes
similarity between prokaryotic and eukaryotic genome
both contain double stranded DNA
exons
genes that are expressed
introns
interventions that contain regulatory sequences
allow eukaryotes to turn on specific genes at specific times
what do introns promote?
cell specialization because certain genes can be turned on at certain moments in certain cell-types
What does looking at the bacteria genome show us?
- there are very little non-coding regions. mostly genes.
- regulatory sequences are physically close to the promoter they affect
- genes within an operon are related to eachother
regulatory sequences
sites where regulatory proteins like activators and inhibitors bind
what does an arrow indicate in a genome?
promoter
What does looking at the eukaryotic genome show us?
- one gene can encode for multiple products by splicing together different combinations of exons
- regulatory elements are found throughout the genome
- repetitive sequences
- there is lots of space for noncoding regions
alternative splicing
putting together different combinations of exons to allows one gene to encode for multiple products
do genes go in both directions?
yes
they can be on the top or bottom DNA strand of the double helix
this is true for both prokaryotes and eukaryotes
what is half of repeated DNA in eukaryotes?
transposable elements / transposons
transposons
can be copied and inserted elsewhere in the genome, which is why they account for a large percentage of the repeated DNA
what can cause repeated DNA?
slippage during DNA replication by DNA polymerase
who discovered transposons?
Barbara McClintock
she used corn to discover that DNA can jump which produces different looking phenotypes
what are transposons composed of?
- long interspersed nuclear element (LINE)
2. gene for integrase which allows it move
Lateral gene transfer
often observed in prokaryotes
genes can be transferred from one species to another
responsible for chloroplasts, mitochondria, and the spread of antibiotic resistance
gene duplication
mistakes during crossing over can result in genes being replicated
what does gene duplication often result in?
gene “families”
genes with similar functions
example of a gene family?
hemoglobin groups
have different genes for oxygen carrying during different points in development
B-globin
How do transposons work?
- RNA polymerase makes mRNA of whole transposon
- LINE mRNA leaves the nucleus to be translated
- mRNA returns to nucleus
- Reverse transcriptase converts mRNA to LINE cDNA
- Integrase cuts the chromosomal DNA and inserts the LINE cDNA
What does integrase do?
cuts the chromosomal DNA in order for the LINE cDNA to be inserted
Where does LINE DNA originate?
it is part of chromosomal DNA sequence
