DNA Packaging In Chromosomes Flashcards
____ structure changes throughout the cell cycle
DNA
______ has beads on a string appearance. A ____ is a structural chromatin unit. This occurs when genes are under active transcription.
Chromatin
Nucleosome
A nucleosome consists of DNA wrapped twice around a core of ___ ____. Two each of H2A, H2B, H3 and H4. ____ is the linker histone
Eight histones
H1
_____ ____ is a 30 nm fiber, that consists of ____, which are four nucleosomes stacked together. This occurs in less active genes
Chromatin fiber
Tetranucleosomes
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.
Loops
Loop chromatin
Chromonema
Loop chromatin or chromonema occurs during _____ and _____.
Interphase and prophase
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.
Coiled Chromonema fiber
Only during _____, chromosomes have higher order of packaging.
Mitosis
During interphase, including G1, S, and G2, chromosomes are ____ condensed. ____ phase is when each of the 46 chromosomes are duplicated by the cell.
Less
S
Mitosis stages include
Prophase, metaphase, anaphase and telophase
The ____ is the region of DNA were sister chromatids are joined together. Contain specific DNA sequences typically _____ ____.
Centromere
Tandem repeats (satellite DNA)
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 _____.
Metacentric
Sub metacentric
Acrocentric
Telocentric
The centromere contains a specific histone, each three variant that helps to assemble the ____, which attaches to _____ during mitosis to pull sister chromatids apart
Kinetochore
Microtubules
structures at the end of chromosomes are called ____, that protect chromosome ends from fraying.
Telomeres
Proteins, such as the ____ ____ find to these telomeric repeats to cap and protect chromosome from degradation
Shelterin complex
The sequence TTAGGG is added by the enzyme ____ , which maintains telomere length.
Telomerase
Most human somatic cells actually have _____ telomerase activity, therefore telomeres shorten with age
Low
Embryonic stem cells have ____ Telomeric activity
High
What do you predict of a cell with highly shortened telomeres?
This will result in senescence and likely result in DNA damage and cell death
What would happen if telomerase levels were abnormally elevated in adult cells?
This is often reactivated in cancer cells, because there is no signal for the cell to die. The cells can then continually divide.
What happens when your cells are unable to protect its telomeres?
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.
____ ____ are these sites at which DNA replication is initiated
Replication origins
Because DNA replication has to occur within a short time in the cell, There are multiple ____ _ ____ on a chromosome
Origins of replication
True or false
Chromatin equals DNA double helix plus histones
True
True or false
Chromosomes are always organized into higher ordered Chromonema fibers to be able to fit in the nucleus
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.
True or false
Centromere’s are rich in tandem repeats, and the site where are sister chromatids are associated
True
True or false
Telomeres which function to maintain chromosomal integrity are often prematurely, shortened in cancer cells
False
Telomeres shorten as cells divide. Telomere length is maintained in cancer cells, allowing them to continually divide.
True or false
Each chromosome has one origins of replication that is used during DNA replication
False
