L3. DNA & chromosomes Flashcards
explain the bond between C and G
- triple hydrogen bond
- tight
- harder to dissociate
explain the bond between A and T
- double hydrogen bond
- loose
- easier to dissaociate
what is coding DNA
DNA that codes for proteins
what is non-coding DNA (“junk DNA”)
- DNA that does not encode for proteins
- they instead encode for functional RNA
what is a genome
- total genetic information carried by all chromosomes
- includes coding and non-coding DNA
explain genomic size
- the size is the number of nucleotides or base pairs
- the size does not correspond to the number of genes or the complexity of the organism
explain eukaryotic chromosomes in a diving cell vs a nondividing cell
- dividing cell: chromosomes become condensed as the sister chromatids become apart and then they become visible
- nondividing cell: when dyed, DNA is seen all throughout the nucleus
explain the chromosomes during interphase
the cell grows and the chromosomes duplicate
explain the chromosomes during mitosis
the cell divides and each cell has a set of chromosomes
explain how the DNA looks during interphase
as it is being replicated, DNA is pulled apart for easier access for replication
define chromatid
one of the two identical halves of a chromosome that has been replicated in preparation for cell division
what is euchromatin
a chromosomal region that is spread out an is easily accessible for proteins
what is heterochromatin
a chromosomal region that is condensed and is not easily accessible for proteins
how does Polymerase Chain Reaction work
- Heat up DNA and design primers that will bind to the DNA
- Add an enzyme that normally copies DNA itself and it will instead copy the DNA in the reaction
- Overtime it will give you a DNA product of the sample you are interested in
- Sequence the copied DNA to see the actual piece of DNA with its nucleotides
what must you know for Polymerase Chain Reaction work
a particular region of DNA and how many of each nucleotide is within the DNA region
what are restriction enzymes
they are enzymes that cleave off different parts of DNA
explain the process of agarose gel electrophoresis
- Apply a current to agarose gel, DNA will naturally sink through DNA
- Shorter DNA: goes through the gel quickly and will be at the bottom
- longer DNA: slower to get through the gel and we at the top
explain fluorescent in situ hybridization
- Take RNA or DNA and hybridize it. Then you can label it with a fluorescence tag
- Take a whole tissue and treat it under certain conditions so that it opens RNA or DNA
- Add a probe to the tissue and you will be able to see where the contemporary region is
what is a karyotype
an individual’s complete set of chromosomes
how can karyotypes be seen in fluorescence in situ hybridization
- you can label each gene or chromosome with a fluorescent tag and see where they are
- can then see alterations in chromosomes such as deletion or addition which are associated with certain disorders or conditions
what are nucleosomes
- they are basic structural unit of DNA packaging in eukaryotes
- they exist to tighten and condense the packaged DNA
explain the structure of the nucleosome
- it is composed of DNA wrapped around a set of eight proteins called histones
- they have tails sticking out from histones
what it the difference between chromatin and a nucleosome
- chromatin are thread-like stained bodies with repeating units of nucleosomes
- looks like a bead on a string under the microscope
nucleosome - what are linker histones
- they are histones that help pull nucleosomes together
- H1 and H5
nucleosome - explain the tails
- enzymes will come and modify the tails
- these modifications dictates how tight or loose the DNA is wound
nucleosome - what are chromatin remodeling complexes
they are multiprotein complexes that use the energy of ATP hydrolysis to mobilize and restructure nucleosomes
nucleosomes - what are the core histones
histone H2A, H2B, H3, and H4
nucleosomes - explain how modifications can affect how tightly DNA is wound
- if methionine is on the histone tails: DNA is more tightly wound and the gene is silenced
- if acetylation is on the histone tail: DNA is more loosely wound and the gene will be expressed
