CH 10.2 Eukaryotic Chromosomes Flashcards
What is Mitosis?
-It is the process in Eukaryotic cells replicated chromosomes are separated into 2 nuclei= daughter cells
What is the range of Chromosomes that most Eukaryotes have?
10 to 50 chromosomes
What is Monosomy?
-It is the condition where human embryos are missing 1 chromosome= fatal
What is Trisomy?
-It is the condition where human embryos have an extra copy of anyone chromosome= usually fatal unless its a smaller chromosome
What is a Karyotype?
-It is the organized view of all 23 human chromosomes under a light microscope
What does Haploid mean?
- One complete set of chromosomes necessary to define an organism
- Represented as (n)
- So for humans it n=23
What is does Diploid mean?
- It is the total number of chromosomes in a cell
- Represented as (2n) bc its twice the haploid number
- SO for humans 2n=46
What are Chromosomes made up of?
- Chromatin
- Also has hella RNA
What is Chromatin?
-It is a complex of 40% DNA & 60% Protein
Why is RNA present in Chromosomes?
-Bc Chromosomes are the sites for RNA synthesis
What do Chromosomes contain?
-a single uninterrupted DNA molecule
How many Nucleotides does a human Chromosome have?
140 million
What is the average length of a stretched out DNA strand in a human chromosome?
4.3 cm
What is Heterochromatin?
- It is the part of a eukaryotic chromosome that IS NOT transcribed into RNA= not active
- Remains condensed in Interphase & stains in histological preps
What is Euchromatin?
- It is the part of the eukaryotic chromosome that IS transcribed into mRNA=active
- It contains active genes that not tightly condensed during interphase
What is Nucleosome?
-It is a complex of DNA wrapped around 8 Histone proteins
What are Histone Proteins?
-They are positively charged= attracted to the negative charge of DNA= DNA coils around them forming Nucleosome
What are the 6 levels of Eukaryotic Chromosomal Organization?
1) Mitotic chromosome
2) Rosettes of chromatin loops= have scaffold proteins at loops
3) Chromatin loop= scaffold proteins at tips
4) Solenoid
5) Nucleosome= DNA wrapped around Histone core
6) DNA double helix= Duplex
What are the 4 primary Histones that Nucleosomes contain?
H2A
H2B
H3
H4
What is a Histome Octamer?
-It acts like a spool that DNA is wound around
What makes up the Histome Octamer?
-The 4 primary histones associate together to a form a large complex
How do we get the “beads on a string” look?
- By wrapping 147bp in 1.7 left handed turns around the Histome Ocatmer to form nucleosome core
- THEN it is separated by variable length of DNA od 20-80bp= Linker DNA
What are Chromosomes doing during Cell division?
-They are being condensed and decondensed
When do Chromosomes oscillate between being condensed & decondensed?
- Chromosomes condense to allow separation of chromosomes during cell division
- And they decondense after separation
What protein is involved in the Condensation/ Decondensation of chromosomes?
-Condensin
What does protein Condensin include?
-2 SMC proteins that are related to the SMC proteins in bacterial nucleoid compaction
How does Condensin condense the chromosomes?
-It does this by using energy from ATP hydrolysis to cause the DNA looping & constrain them into the x shape
What is Cohesin?
- It is the protein that holds the sister chromatids together during cell division
- It also breaks down during the process of mitosis to allow for the sister chromatids to separate fully
What is a Sister Chromatid?
-It is 2 identical copies of a single chromosome & are held together at their centromeres by the cohesin protein after DNA replication
What Are Homologous Chromosomes?
-They are maternal & paternal copies of the same chromosome (Ex chromosome 22)
What is Kinetochore?
-It is composed of proteins that are found at the centromere that attaches to microtubules during mitosis
What problem does the cell face in terms of its chromosomes & how does it solve it?
- The cell has to make sure that each new cell receives a complete set of chromosomes
- It glues replication products in the centromere & mitosis separates them
What is the higher-order structure of a Chromatin?
-An organized crystal or disorganized liquid
