Cells and Genomes Flashcards
what is the universal feature of all cells?
- they all start from one cell
- hereditary information in DNA will predetermine the cell function
What is the structure of DNA?
phosphate atom bonded to a sugar (either ribose or deoxyribose) and that is bonded to a nucleotide base
what are the 4 bases in DNA?
Adenine, Guanine, Cytosine, and thymine
What bases are purines?
adenine and guanine
what bases are pyrimadines
cytosine, thymine, and uracil
What sugar is more stabile and less reactive?
deoxyribose
why is RNA hard to work with?
because our skin produces RNAases and you cannot touch it at all or it will destroy it, and it requires colder temperatures
Why does DNA have a negative charge?
because of the phosphate group, and it allows a connection to the next phosphate
which nucleotides have 3 bonds?
cytosine - guanine
what are ambigious bases?
when you only know the bonding structure you can determine if it is strong (S) = C or G, or if it is weak (W) = A or T
What is the bond between two sugars called?
phosphodiester
How do cells replicate their hereditary information?
templated polymerization
In transcription, what is synthesized by DNA sequences?
mRNA
In translation, the RNA molecules synthesize what?
protein
What happens when RNA is left free floating?
it hairpins back and base pairs with itself
what is horizontal gene transfer?
outside cell replication and reproduction commonly between bacteria
what is vertical gene transfer?
sexual reproduction
How can the function of genes be deduced?
by the sequence of the genes and the mutations
What functions are basal to life?
- translation
- amino acid transport and metabolism
What are the three domains of life?
archaea, bacteria and eukarya
what is the difference of prokaryotes and eukaryotes
prokaryotes
- no nucleotides
- no organelles
- much smaller
what domain has the most biochemical diversity?
prokaryotic cells
do all the domains have a common ancestor?
yes
what organism did our understanding of the mechanisms of life initially come from?
E coli
why is E coli a good model organism?
small and compact genome
Why is yeast used as a model organism?
- small genome size
- simple to modify the genetics
- used to study eukaryote process (ie cell division)
why is arabidopsis a good model organism?
- close evolutionary relationship between the flowering plants
- small and can produce thousands of offspring per plant after 8-10 weeks
- 220 million nucleotide pairs
why are armadillos sometimes used as a model species?
they can sometimes have identical DNA of triplets eliminating genetic variability
why is C elgans a model organism?
- most applicable to humans
- survive being frozen indefinitely
- very constant during maturity
why are drosophila used as a model organism?
- animal development from egg to adult
- encodes homologs
what is a homolog?
a gene inherited in two species
what is an ortholog?
homologous genes where a gene diverges after a speciation event, but the gene and its main function are conserved
what is the function of hox genes?
they are the genes encoding for the body plan
what organism were hox genes altered in? and what did that show?
- in fruit flies
- it showed homology in hox genes since the genes in fruit flies are very similar to a mouse
why are zebrafish used as model organisms?
- small and hardy
- transparent embryos
why are mice used for human research?
similar genetic mutations and a lot of homology between us and them
what molecule carries heritable materials?
DNA
how was DNA determined to be heritable?
using R and S strains of Pneumonia where the R strain was transformed into S strain determinining that DNA changes molecules.
Where is genetic mutations most common?
in smaller chromosomes
what is the difference between yeast genomes and human genomes?
yeast have very dense and fully packed genes with small repeated sections, whereas humans have a lot of repeated junk and small gene sections
why are human genomes less dense?
because there is finer more complex control mechanisms in the human genome that change transcription and more complex control over gene expression
what is an intron?
nucleotide sequence that is removed during maturation of the final RNA product
(present in DNA and present in first transcribed DNA but removed in proteins)
what is an exon?
this is a nucleotide sequence that is expressed and is part of the mature RNA molecule
when is DNA visible?
when it is compacted in preparation for cell division
what are the componants of DNA molecules?
centromere, two telomeres, and two replication origin
What is the beads on a string conformation?
this is when chromatin is wrapped around histones
why does chromatin compact everything?
when it is not compact it is not secure and it is not accessible to the machines doing gene expression
(it folds so it cannot be useful or functional and so replication can easily be duplicated)
what are the histone optomers?
H2A, H2B, H3 and H4
what is heterochromatin?
- tightly packed DNA
- tends to be more silent but not always generally not transcribed
- localized to the periphery of the nucleus
what is euchromatin?
- lightly packed DNA
- often under active transcription
- beads on a string
How does heterochromatin spread?
it spreads via signalling proteins that attach and continue on by signals (making it self propogating) this is stopped by barrier proteins
what happens when barriers are in the wrong location?
there is no stopping the heterochromatin and it might overwrite the euchromatin causing genetic issues and silencing certain genes
how are calico cats coloured?
they have X-linked inactivation in heterozygous females, the white patches are due to the expression of autosomal genes
when a calico cat is either all orange or all black what happened?
the opposite colour would have been silenced at random by heterochromatin spread
what are the histone tails?
made of lysine with certain modifications depending on the type:
- lysine
- monomethyl lysine
- trimethyl lysine
- acetyl lysine
what type of bond do core histones have?
covalent bonding
