What is centromeric and telomeric?
Definition. Centromere is a structure present in the chromosomes that binds the two sister chromatids together. Telomeres are repetitive sequences of nucleotides present at the end of chromosomes. Sequence. Centromeres are made up of repeated satellite DNA where the sequence in each repeat is similar but not identical.
What are centromeric sequences?
The centromere is a specific chromosomal region where the kinetochore assembles to ensure the faithful segregation of sister chromatids during mitosis and meiosis. Centromeres are defined by a local enrichment of the specific histone variant CenH3 mostly at repetitive satellite sequences.
What is centromeric DNA?
The centromere appears as a constricted region of a chromosome and plays a key role in helping the cell divide up its DNA during division (mitosis and meiosis). Specifically, it is the region where the cell’s spindle fibers attach.
What is a primary function of the centromeric DNA region found on chromosomes?
The primary function of the centromere is to provide the foundation for assembly of the kinetochore, which is a protein complex essential to proper chromosomal segregation during mitosis.
What causes Dicentric chromosomes?
Dicentric chromosomes are formed by the fusion of two chromosome ends, which then initiates an ongoing chromosomal instability via breakage-fusion-bridge cycles (BFB).
What is heterochromatin and euchromatin?
Heterochromatin is defined as the area of the chromosome which is darkly stained with a DNA specific stain and is in comparatively condensed form. Euchromatin is defined as the area of the chromosome which is rich in gene concentration and actively participates in the transcription process.
What are centromeric repeats?
While found as solo repetitive units scattered among other satellites in the pericentromeric regions of human chromosomes without higher organization, α satellites within human centromeres are tandemly repeated to form a block of satellites, called a higher order repeat (HOR).
What DNA sequences are commonly found at centromeric regions of human chromosomes?
Two classes of highly abundant repetitive sequences, satellite DNAs (satDNAs) and transposable elements (TEs), represent major DNA components of many centromeric regions.
What is P arm and Q arm?
Each chromosome is divided into two sections (arms) based on the location of a narrowing (constriction) called the centromere. By convention, the shorter arm is called p, and the longer arm is called q. The chromosome arm is the second part of the gene’s address.
What is Acentric and dicentric?
A dicentric chromosome is an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments.
Why are dicentric chromosome unstable?
Dicentric chromosomes are genetically unstable during cell division because microtubules pull in opposite directions on the two centromeres of the same chromatid. This normally leads to the formation of chromosome bridges during anaphase, causing DNA breakage (see below).
Is DNA euchromatin or heterochromatin?
Euchromatin is a lightly packed form of chromatin (DNA, RNA, and protein) that is enriched in genes, and is often (but not always) under active transcription. Euchromatin stands in contrast to heterochromatin, which is tightly packed and less accessible for transcription. 92% of the human genome is euchromatic.
What is the main difference between heterochromatin and euchromatin?
Why are tandem repeats important?
Tandem Repeat Tandem repeats are generally present in non-coding DNA. In some cases, tandem repeats can serve as genetic markers to track inheritance in families. They can also be useful for DNA fingerprinting in forensic studies.
Which alternate form of histone is seen in centromeric histone of humans?
12. Which alternate form of histone is seen in centromeric histones of humans? Explanation: It has been observed that the human chromatin near the centromere has a unique structure. In particular, histone H3 is replaced by its variant CENP-A.
Why is the p arm called the p arm?
The shortest ‘arm’ of a chromosome, based on the distance from the centromere. The ‘p’ comes from the word ‘petit’, the French translation of ‘small’.
Which chromosome p and q arms Cannot distinguish?
metacentric chromosome – has centromere in the center with arms of identical length on either sides (p=q) telocentric chromosome: has centromere at terminal end, one single arm, not distinguished as p and q sub metacentric chromosome: centromere slightly away from the centre, forming two unequal arms – p -shorter and q …
What is meant by the term dicentric?
Definition of dicentric : having two centromeres a dicentric chromosome.
What is meaning of acentric?
: lacking a centromere acentric chromosomes.
Is centromeric transcription dependent on RNA polymerase II?
Although active centromeric transcription has been documented for over a decade, the role of centromeric transcription or transcripts has been elusive. Here, we report that centromeric α-satellite transcription is dependent on RNA Polymerase II and occurs at late mitosis into early G1, concurrent with the timing of new CENP-A assembly.
What is centromere RNA?
Centromere RNA is a key component for the assembly of nucleoproteins at the nucleolus and centromere NCBI Skip to main content Skip to navigation Resources How To About NCBI Accesskeys My NCBISign in to NCBISign Out PMC US National Library of Medicine National Institutes of Health
Does centromeric α-satellite RNA affect the nucleolar localization of CENPC1 and INCENP?
We have shown that the presence of centromeric α-satellite RNA is closely associated with the nucleolar localization of CENPC1 and INCENP, since RNase treatment induces a complete disruption of this localization.
What is RNA polymerase?
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol, and officially DNA-directed RNA polymerase ), is an enzyme that synthesizes RNA from a DNA template.