Buhller genetics Flashcards
Pro- vs Eukaryotes
Prokaryote:
- Contains DNA in CIRCULAR strand
- Have FEW RIBOSOMES
- Does NOT contain a NUCLEUS
- NO NUCLEAR MEMBRANE
- Has CELL WALL
- Uni-cellular organisms
Eukaryotes:
- Contains DNA in LINEAR strands
- Have ,MANY RIBOSOMES
- Contains a NUCLEUS
- Has nuclear membrane
- Does NOT have CELL WALL
- Multi-cellular organisms
T/F: Eukaryotic DNA is in direct contact with the cytoplasm
FALSE. THis is true for prokaryotes
Why are eukarotic cells more susceptible to damage compared to prokaryotes?
Because they lack a cell wall
Exaplin what happens when you inject mice with smooth (S) or rough (R) colonies of streptococcus pneumoniae
- if injected with S type, they die. But not if injected with R type. They also do not die if S type is boiled prior to injection
- If mice are injected with boiled S type plus live R type, mice die.
This suggests that DNA from S type passed the info to R type to make them virulent.
It was the PROTEIN that caused death. The code on the S type was still viable, therefore PROTEINS ARE THE FUNCTIONAL MOLECULES OF ORGANISMS
What is the need for a nucleus
to protect DNA from the components of the cytoskeleton and other cellular objects during cell movement
Define isoforms
Isoforms are proteins with similar functions and similar (but not identical) amino acid sequences
Human cell contains __ chromosomes
46
22 pairs of chromosomes are called ___. The other two are ___ chromosomes
22 pairs of chromosomes are called AUTOSOMES. The other two are SEX chromosomes
chromosomes are classified on the basis of what?
the location of centromere
Functions of chromosomes
- contain genetic material
- replicate
- segregate two copies of DNA during mitosis
- Maintain themselves between cell generations
What is the DNA replication sequence?
The region where DNA double helix separates for duplication
What is the centromere sequence?
region required for attachment of DNA molecules to mitotic spindle and to kinetochore proteins
What happens are telomeres shrink?
the ability to duplicate decreases
replication forks originate at a ___ __ in both mammalian and bacterial cells
REPLICATION BUBBLE.
This is a region where two DNA strands have separated.
Usually formed at replication origin sequences.
DNA + protein =
chromatin
2 types of chromatin
- Euchromatin: not condensed and not ready for reading
- Heterochromatin: appears as mass and is along the inner nuclear membrane
Heterochromatin is divided further into two categories
- facultative: may uncoil and be read
2. constitutive: never uncoils and is not read
Major protein associated with DNA?
histones
5 types of histones:
H1, H2A, H2B, H3, HA
histones contain large numbers of what two amino acids? why is this significant?
Histones contain Lys and Arg. These are positively charged, which bind to negatively charged phosphate groups on DNA
Nucleosome histones
- H2A, H2B, H3, and H4
- amino acids
- responsible for coiling DNA into nuclesomes
- 2 copies of each nucleosome
Neuron nd lymphocyte contain the same complement DNA. What does this confirm
This confirms that different cell types in an organism contain the same complement of DNA, but each cell only “reads” the sequence which pertains to its function
a fully differentiated skin cell was taken from a frog. What happened?
The nucleus of the skin cell was taken and implanted into an egg. The egg developed into a tadpole, which did not survive to adulthood.
This study proved that all cells except B cells in the body contain identical DNA which has the capacity to give rise to new offspring.
However, there are other factors involved that result in development of the mature functional organism
a typical cell contains __ different classes of mRNA that code for proteins:
THREE different classes of mRNA that code for proteins:
- abundant class
- intermediate class
- scarce class
Which mRNA class is likely responsible for generating cell diversity?
mRNAs in the scarce class
define gene
a region of DNA that produces a functional RNA molecule (mRNA)
T/F: 100% of genes are unique in prokaryotes (ie. only one copy in the genome)
True. In eukaryotes only 64% are unique
Genes in eukaryotic organisms have been divided into two broad categories:
- Housekeeping genes: encode for proteins essential for cell viability (expressed in most cells)
- Tissue-specific genes: encode proteins required for selected cells (eg. hemoglobin in RBCs, immunoglobulins in B cells)
Explain the lac operon in E. coli as an example of the effect of nutrient availability on gene expression
E. coli grown in glucose + lactose uses glucose first. To use lactose, it must degrade glucose+galactose by B-galactosidase, which is not normally produced in E. coli.
BACTERIAL GROWTH STOPS TO PRODUCE B-GALACTOSIDASE.
-a repressor protein is bound to the promoter region ustream of lac operon inhibiting expression of the B-galactosidase gene
-lactose is converted to allolactose
-allolactose binds to the repressor protein and removes it from the promoter region
-B-galactosidase is now synthesized.
define epigenetics
A stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence
Describe DNA methylation
- Part of epigenetics
- mammalian genomes have CpG islands
- methyl grouops resulting from methylation of cytosine stick out into the major groove of DNA and block binding of transcription factors to DNA and INHIBITING GENE EXPRESSION
DNA methylation patterns can be altered by persisten ____
Inflammation
Describe histone modification
Part of epigenetics
- ACETYLATION promotes a more relaxed chromatin structure ALLOWING TRANSCRIPTION to occur
- DEACETYLATION converts the chromatin into condensed form and REPRESSES TRANSCRIPTION
What can be observed in chronic periodontitis with relation to epigenetics?
changes of DNA methylation patters and cytokine gene expression
What has been reported concerning histone modification in dental pulp cells?
Histone modifications may induce differentiation and mineralization in dental pulp cells and these modifications play a crusial role in gene expression regulation and may promote pup repair and regeneration
What can non-coding RNAs do?
they can bind to an mRNA molecule and cause its degradation or cause translational repression of the target mRNA.
NON CODING RNAs PLAY AN ESSENTIAL ROLE IN ODONTOBLAST DIFFERENTIATION
What percentage of the human genome is made up of transposable elements? what are transposons?
40%.
Transposons are DNA sequenecs which can change positions within a genome. They can move in and out of chromosomes and cause a variety of short additions/deletions of nucleotide sequences.
This results in the alteration of expression of nearby genes and effects various aspects of animal development and/or GENE EXPRESSION
