DNA Packaging In Chromosomes

Question 1

____ structure changes throughout the cell cycle

Answer 1

DNA

Question 2

______ has beads on a string appearance. A ____ is a structural chromatin unit. This occurs when genes are under active transcription.

Answer 2

Chromatin
Nucleosome

Question 3

A nucleosome consists of DNA wrapped twice around a core of ___ ____. Two each of H2A, H2B, H3 and H4. ____ is the linker histone

Answer 3

Eight histones
H1

Question 4

_____ ____ is a 30 nm fiber, that consists of ____, which are four nucleosomes stacked together. This occurs in less active genes

Answer 4

Chromatin fiber
Tetranucleosomes

Question 5

Chromatin fibers are arranged in _____ that are attached to chromatin scaffold. This is called ____ ____. A stretch of loop chromatin known as _____ fiber, is thicker than the chromatin fiber.

Answer 5

Loops
Loop chromatin
Chromonema

Question 6

Loop chromatin or chromonema occurs during _____ and _____.

Answer 6

Interphase and prophase

Question 7

When Chromonema coils onto itself, it is called _____ _____ ____. This occurs during cell division also known as the metaphase chromosome. It has the signature X look.

Answer 7

Coiled Chromonema fiber

Question 8

Only during _____, chromosomes have higher order of packaging.

Answer 8

Mitosis

Question 9

During interphase, including G1, S, and G2, chromosomes are ____ condensed. ____ phase is when each of the 46 chromosomes are duplicated by the cell.

Answer 9

Less
S

Question 10

Mitosis stages include

Answer 10

Prophase, metaphase, anaphase and telophase

Question 11

The ____ is the region of DNA were sister chromatids are joined together. Contain specific DNA sequences typically _____ ____.

Answer 11

Centromere
Tandem repeats (satellite DNA)

Question 12

When the centromere is in the center of DNA it is called _____. When it is slightly off-center, it is called _____. When it is very close to the end, it is called _____. And when it is at the end, it is called _____.

Answer 12

Metacentric
Sub metacentric
Acrocentric
Telocentric

Question 13

The centromere contains a specific histone, each three variant that helps to assemble the ____, which attaches to _____ during mitosis to pull sister chromatids apart

Answer 13

Kinetochore
Microtubules

Question 14

structures at the end of chromosomes are called ____, that protect chromosome ends from fraying.

Answer 14

Telomeres

Question 15

Proteins, such as the ____ ____ find to these telomeric repeats to cap and protect chromosome from degradation

Answer 15

Shelterin complex

Question 16

The sequence TTAGGG is added by the enzyme ____ , which maintains telomere length.

Answer 16

Telomerase

Question 17

Most human somatic cells actually have _____ telomerase activity, therefore telomeres shorten with age

Answer 17

Low

Question 18

Embryonic stem cells have ____ Telomeric activity

Answer 18

High

Question 19

What do you predict of a cell with highly shortened telomeres?

Answer 19

This will result in senescence and likely result in DNA damage and cell death

Question 20

What would happen if telomerase levels were abnormally elevated in adult cells?

Answer 20

This is often reactivated in cancer cells, because there is no signal for the cell to die. The cells can then continually divide.

Question 21

What happens when your cells are unable to protect its telomeres?

Answer 21

Dyskeratosis congenita is the prototype of telomere biology disorder. Symptoms include abnormalities in tissue with high turnover rate bone marrow failure at 40 years old and mutations in gene encoding telomerase complex.

Question 22

____ ____ are these sites at which DNA replication is initiated

Answer 22

Replication origins

Question 23

Because DNA replication has to occur within a short time in the cell, There are multiple ____ _ ____ on a chromosome

Answer 23

Origins of replication

Question 24

True or false
Chromatin equals DNA double helix plus histones

Answer 24

True

Question 25

True or false
Chromosomes are always organized into higher ordered Chromonema fibers to be able to fit in the nucleus

Answer 25

False, chromosomal organization is dynamic throughout the cell cycle, staying more relaxed until the mitotic phase during which DNA starts to be more highly packaged.

Question 26

True or false
Centromere’s are rich in tandem repeats, and the site where are sister chromatids are associated

Answer 26

True

Question 27

True or false
Telomeres which function to maintain chromosomal integrity are often prematurely, shortened in cancer cells

Answer 27

False
Telomeres shorten as cells divide. Telomere length is maintained in cancer cells, allowing them to continually divide.

Question 28

True or false
Each chromosome has one origins of replication that is used during DNA replication

Answer 28

False