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jmali921
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The haploid human genome consists of ~______ nucleotide pairs.
3.2 billion
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Define: chromatin
- unpackaged DNA material (unwound chromosome)
- Chromatin condenses in Mitosis
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Define gene;
a gene is a sequence of DNA that codes for one polypeptide or one set of closely related polypeptides (via alternative splicing), or a structural RNA, or a regulatory RNA.
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Human cells have ~ _____ genes
~25,000 genes
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only ~___% of DNA codes for proteins.
~1.5%
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all noncoding DNA is termed _____ ___
"junk DNA"
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a Simple sequence repeat is a _____
short nucleotide sequences (>14 NP's) that are repeated again and again for long stretches.
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Mitosis is ~____hr in many mammalian cells
1hr
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2 groups of protein that package DNA;
- 1) Histones
- 2) nonhistones
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Histones package DNA into ________
nucleosomes
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A nucleosome consists of;
- 1) a nucleosome core particle
- 2) Linker DNA - few np's to 80 np's long to the neighbouring nucleosome
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The are _ core histones.
8. A pair of H2A, H2B, H3, and H4 histones.
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Each core histone has a structural motif (region) called a ____ ____
Histone fold.
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Describe the joining process of the core histone octamer.
- H3 and H4 form a dimer and then join a similar dimer, forming a tetramer.
- H2A and H2B form a dimer as well, join a similar dimer, and form a tetramer as well.
- The 2 differnt tetramers join to form the octamer.
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What will you find on each end of a histone fold?
- One N-terminal tail end - amino end
- other end: carbonyl end
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What is nucleosome sliding and how is it accomplished?
- Nucleosome sliding is the act of pushing the DNA wrapped around the histone core. It is catalyzed through ATP-dependant chromatin remodeling complexes. (uses the energy of ATP hydrolysis).
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True/False: H1 is a core histone.
- False. H1 is not apart of the nucleosome core particle.
- one histone H! binds to each nucleosome
- H1 is also a linker histone
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2 major types of chromatin include;
Heterochromatin and euchromatin.
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Describe heterochromatin.
- Condensed
- transcriptionally inactive
- contains few genes
- genes present are to dense to read
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Describe euchromatin;
transcriptionally active.
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_______ causes modifications to core histone tails.
- Histone-modifying enzymes.
- Methylation, phosphorylation, acetylation and ubiquitylation
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Where can heterochromatin be found?
telomeres, and in/around the centeromere.
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______ describes heterochromatin around the centromere.
pericentric heterochromatin.
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______ _______ describes heterochromatin within the centromere.
centric heterochromatin.
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______ molecules link sister chromatids.
Cohesion molecules.
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Centromere Nucleosomes: special proteins called _____ _____ bind to the centromere DNA and form _____ _______.
centromere-specific proteins; centromere-specific nucleosomes.
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Chromosomes are folded into large loops of chromatin are known as _______ chromosomes; found in growing amphibian oocytes.
Lampbrush chromosomes. (largest chromosome known)
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A chromomere is ____
the region on the lampbrush chromosome (end of loop) on the axis of DNA; highly condensed regoin of DNA where genes are generally not expressed.
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protein responsible for forming the mitotic "X" chromosome.
Condensin.
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Condensins bind to chromatin to ___ into the _____ chromosome.
coil; mitotic
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This enzyme can be used to digest linker DNA
Nuclease. Cannot digest DNA wrapped around core histones
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linker DNA is about _____ np's long
200. Wrapped around the histone core ~ 1.7 times.
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What is the function of the N-terminal tail in the histone core?
plas a role to package the nucleosome into thicker fibers
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True/false: There is a single ATP-dependant chromatin remodeling complex?
False. There are many different chromatin remodeling complexes
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Histone-modifying enzymes modify which region of the histone?
N-terminal tail
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Histones may be methylated and acetylated only.
False, histone N-terminal tails made undergoe methylation, acetylation, phosphorylation as well as ubiquitylation (single ubiquiton)
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A histone code is thought to exist because ...
modifications may cause gene silencing, heterochromatin formation, gene expression, silencing of Hox genes
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Nucleosomes pack into the ______ model.
zig-zag model into 30 nm chromatin
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