Lec 2.1 Specialized chromosome structure/ sequence and DNA packaging Flashcards
What is a telomere?
region of repetitive nucleotide sequences at each end of a chromosome.
What is the human telomere sequence?
TTAGGG
What does a telomere do?
Protects the end of the chromosome
Which telomere is longer? A G-rich strand or C-rich strand?
G-rich
How do euk solve the problem of having nucleases around?
G-rich strand folds over and pairs with a short stretch of DNA to form a t-loop.
Shortened telomeres are associated with what?
Shorter life span and increased incidence of disease
What are two ways that children can have shortened telomeres?
Lead exposure, stressed environments
What happens to your telomeres when you age?
the shorter they get
Do telomeres contribute to that negative impact of aging or are they just a molecular clock?
Conclusion: we dont know
What is a centromere?
Region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.
What is a kinitochore?
group of proteins that attach at the centromere, that are responsible for events of chromosome segregation
What is a centriole?
Small, cylindrical cell organelle, located near the nucleus in the cytoplasm of most euk cells, that divides in perpendicular fashion during mitosis.
What is the chromosomal locus essential for chromosome inheritance and genome stability?
Centromere
What is cohesin?*
Wraps around strands around the chromosomes and keeps them together during mit/meiosis. When signla comes in, it melts
What happens if the kinetochore protein is mutated?*
Miscarriages.
What happens when a chromosome breaks producing a fragment without a centromere?
Loss of a chromosome and a deletion of whatever chromosome was lost, and its genes
What is important to fit the entire genome into such a compact place?
Supercoiling
What are topoisomerases responsible for?
adding and removing turns in the coil
What does the chromatin structure contain?
Euchromatin, heterochromatin, histone proteins
If a chromatin structure is hyperacetylated it is?
Open active
If a chromatin structure is hypoacetylated it is?
closed/ inactive
Why are lysines important for histones?
Keeps DNA highly compacted, less likely for transcription
What keeps histones and DNA together?
the charge between them. DNA is - and histones are +.
What is a nucleosome? *
8 proteins, coming together to form this octomere of proteins that makes a ball that DNA can bind around
What is chromatin?
Nucleosome core, including proteins + DNA that allow wrapping and packaging of DNA
What is a chromatosome?
basically the nucleosome + linker
What are the several levels of organization for DNA packaging?
- DNA. 2. Coiling happens. 3. Coil wraps around the histone octomere to make the nucleosome. 4. Nucleosomes coil around each other. 5. Chromosome
What is the fundamental repeating unit of chromatin?
the nucleosome
Where is euchromatin location?
Chromosome arms
Where is heterchromatin location?
centromeres, telomeres, and other places
What type of sequences does euchromatin have?
unique
What type of sequences does heterochromatin have?
Repeated
when is euchromatin replicated?
throughout S phase
when is heterochromatin replicated?
Late S phase
How often does transcription occur for euchromatin?
Often
How often does transcription occur for heterochromatin?
Infrequent
How common is crossing over for euchromatin?
Common
How common is crossing over for heterochromatin?
Not common
What are polytene chromosomes?
Strands of chromatin that have been replicated multiple times
What does DNase I sensitivity correlate with?
transcription or gene activity
How can epigenetic changes change chromatin structure?
methylation. Can be reversed.
What is epigenetics?
Heritable alteration of phenotype because of altered chromatin structure or the modification of DNA without changing the DNA sequence.
The bigger the genome the more what?
More repetitive sequences
The majority of repetitive sequences show their origin to be?
Retro viral transposons origin
What is Microsatellite DNA?
Tandemly repeated DNA motifs that range in length from 2 to 5 nucleotides, repeated 5-50 times.
What are Microsatellite DNA used for?
Mapping locations within the genome. Each person has a unique fingerprint of microsatellites, useful in forensics.
