CH 10.2 Eukaryotic Chromosomes

Question 1

What is Mitosis?

Answer 1

-It is the process in Eukaryotic cells replicated chromosomes are separated into 2 nuclei= daughter cells

Question 2

What is the range of Chromosomes that most Eukaryotes have?

Answer 2

10 to 50 chromosomes

Question 3

What is Monosomy?

Answer 3

-It is the condition where human embryos are missing 1 chromosome= fatal

Question 4

What is Trisomy?

Answer 4

-It is the condition where human embryos have an extra copy of anyone chromosome= usually fatal unless its a smaller chromosome

Question 5

What is a Karyotype?

Answer 5

-It is the organized view of all 23 human chromosomes under a light microscope

Question 6

What does Haploid mean?

Answer 6

• One complete set of chromosomes necessary to define an organism
• Represented as (n)
• So for humans it n=23

Question 7

What is does Diploid mean?

Answer 7

• It is the total number of chromosomes in a cell
• Represented as (2n) bc its twice the haploid number
• SO for humans 2n=46

Question 8

What are Chromosomes made up of?

Answer 8

• Chromatin

- Also has hella RNA

Question 9

What is Chromatin?

Answer 9

-It is a complex of 40% DNA & 60% Protein

Question 10

Why is RNA present in Chromosomes?

Answer 10

-Bc Chromosomes are the sites for RNA synthesis

Question 11

What do Chromosomes contain?

Answer 11

-a single uninterrupted DNA molecule

Question 12

How many Nucleotides does a human Chromosome have?

Answer 12

140 million

Question 13

What is the average length of a stretched out DNA strand in a human chromosome?

Answer 13

4.3 cm

Question 14

What is Heterochromatin?

Answer 14

• It is the part of a eukaryotic chromosome that IS NOT transcribed into RNA= not active
• Remains condensed in Interphase & stains in histological preps

Question 15

What is Euchromatin?

Answer 15

• It is the part of the eukaryotic chromosome that IS transcribed into mRNA=active
• It contains active genes that not tightly condensed during interphase

Question 16

What is Nucleosome?

Answer 16

-It is a complex of DNA wrapped around 8 Histone proteins

Question 17

What are Histone Proteins?

Answer 17

-They are positively charged= attracted to the negative charge of DNA= DNA coils around them forming Nucleosome

Question 18

What are the 6 levels of Eukaryotic Chromosomal Organization?

Answer 18

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

Question 19

What are the 4 primary Histones that Nucleosomes contain?

Answer 19

H2A
H2B
H3
H4

Question 20

What is a Histome Octamer?

Answer 20

-It acts like a spool that DNA is wound around

Question 21

What makes up the Histome Octamer?

Answer 21

-The 4 primary histones associate together to a form a large complex

Question 22

How do we get the “beads on a string” look?

Answer 22

• 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

Question 23

What are Chromosomes doing during Cell division?

Answer 23

-They are being condensed and decondensed

Question 24

When do Chromosomes oscillate between being condensed & decondensed?

Answer 24

• Chromosomes condense to allow separation of chromosomes during cell division
• And they decondense after separation

Question 25

What protein is involved in the Condensation/ Decondensation of chromosomes?

Answer 25

-Condensin

Question 26

What does protein Condensin include?

Answer 26

-2 SMC proteins that are related to the SMC proteins in bacterial nucleoid compaction

Question 27

How does Condensin condense the chromosomes?

Answer 27

-It does this by using energy from ATP hydrolysis to cause the DNA looping & constrain them into the x shape

Question 28

What is Cohesin?

Answer 28

• 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

Question 29

What is a Sister Chromatid?

Answer 29

-It is 2 identical copies of a single chromosome & are held together at their centromeres by the cohesin protein after DNA replication

Question 30

What Are Homologous Chromosomes?

Answer 30

-They are maternal & paternal copies of the same chromosome (Ex chromosome 22)

Question 31

What is Kinetochore?

Answer 31

-It is composed of proteins that are found at the centromere that attaches to microtubules during mitosis

Question 32

What problem does the cell face in terms of its chromosomes & how does it solve it?

Answer 32

• 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

Question 33

What is the higher-order structure of a Chromatin?

Answer 33

-An organized crystal or disorganized liquid