biology- structure of chromosomes

definitions and cell cycle

what is a chromosome

highly coiled ribbon like structure formed by the condensation of chromatin during cell division, containing DNA and proteins.

what are the rungs of the DNA ladder made of

the four nitrogen bases: adenine, thymine, cytosine, and guanine.

adenine pairs with thymine(, while cytosine pairs with guanine.

what is the function of a centromere

attaches to spindle fibres during cell division and detaches sister chromatids during anaphase

define genes

specific sequences of nucleotides encoding particular proteins which are expressed in the body in the form of particular characteristics

what is cellcycle

series of events that take place in a cell leading to the duplication of dna and simultaneous division the cell into 2 daughter cells

mention the three phases of the interphase along with its characteristics

first growth phase -RNA and proteins are synthesized -volume of the cytoplasm increases -mitochondria and chloroplast divide because they have their own DNA’s

synthesis phase - DNA is synthesised , chromosomes duplicate

second growth phase- more RNA and proteins are synthesized

what are the characteristics of prophase

-chromosome: short and thing are duplicated to form 2 daughter cells

- centromere splits in 2 along with the simultaneous duplication of centrioles which are then surrounded by rays called asters

-nucleosome and nuclear membrane disappears

• spindle fibers begin to form and attach to centromeres

identify the phase and give its characteristics

metaphase:

chromosome arrange themselves on the equatorial plane and attach to the spindle fibers

what are the characteristics of anaphase

-centromere divides

-chromosomes separate and move to opposite poles due to the contraction of spindle fibers