Mitosis is the process where a cell divides to form two identical copies from the original cell. On the other hand, meiosis is a specializes kind of cell division that produces four cells that contain that contain half the original genetic information.
Differences between mitosis and meiosis
Mitosis / Meiosis
Transpires in the somatic cells of the body / Transpires in the germ cells
The process happens in both sexually asexually reproducing organism. / The process happens in sexually reproducing organisms only.
The cell division occurs only once / Cell division occurs twice, meiosis I and meiosis ii
Interphase takes place before each division / Interphase only occurs in meiosis I and does not occur in meiosis ii
For one cell division DNA replication occurs only once / For two the two cell division DNA replication occurs only once.
In the prophase, the duration is short usually a few hours / The prophase is long and may take days
The chromosomes divides only once / The chromosomes divide once despite having two cell divisions.
There is no synapsis / During the prophase synapsis of the homologous chromosomes takes place
There is no exchanging of segments during the prophase by the two chromatids / There is the exchange of segments between the two homologous chromosomes during the cross over.
At the beginning of prophase chromosomes are duplicated / Despite the DNA replication taking place, at the commence of prophase I chromosomes still appear single.
There is the absence of chiasmata / There is the observation of chiasmata between homologous chromosomes of bivalents during prophase I and metaphase i
All the centromeres align in the same plane during the metaphase. / The centromeres are aligned in two planes that are parallel to each other during metaphase I
Division of Centromeres occurs in the anaphase / Division of centromeres occurs during anaphase ii and not anaphase I
In anaphase, the chromosomes are single stranded / In anaphase ii the chromosomes are single stranded but are double stranded in anaphase i
In anaphase, same chromosomes moves towards the opposite poles / In both anaphases, I and ii different chromosomes move towards opposite poles.
In telophase, spindle fibres vanish completely. / In telophase I, the spindle fibres do not vanish completely.
In telophase, the Nucleoli reappears. / In telophase, the nucleoli do not reappear.
In every mitosis, the cytokinesis occurs, and it produces two new cells. / In the first division cytokinesis does not occur, but in the second division, it is simultaneous producing four new cells.
The number of chromosomes at the end of mitosis remains constant. / At the end of meiosis, the number of chromosomes is reduced from diploid to haploid.
It assists in multiplication of cells / It does not involve multiplication of cell
It has a hand in repairing and healing / It has a hand in forming of meispores and maintaining some chromosomes of the race.
Compare the organization and functions of axial and appendicular skeletons, and describe in detail the girdles of the latter.
The skeletal system consists two main divisions the axial and appendicular. The axial helps in the formation of the vertical, central axis of the body which entails the head, neck, and back. It functions in protecting the brain, spinal cord, heart, and lungs. It also, functions in serving as an attachment site for muscles that helps in moving the head, neck, and back and for muscles that transverse the shoulder and hip joint to move their correlating limbs. An adult skeleton consists of 80 bones which include 22 bones of the skull, 32 bones of the vertebral column and 24 ribs of the thoracic cage. Also, in the head, there are additional seven bones that include the hyoid bones and ear ossicles.
The appendicular system consists 126 bones that entail four of the pectoral girdle, clavicle and scapula, 6 of the arm and forearm, humerus, ulna and radius. Also 58 of the hands that entail 16 carpals,10 metacarpals, 28 phalanges and 4 sesamoids. Also 2 bones of the pelvis, 8 leg bones, the femur, tibia, patella and fibula, and 56 feet bones that include the sesamoid, phalanges, metatarsals and tarsals. These bones are composed of the upper limbs that help in grasping and manipulating objects and the lower limbs that permit movement and locomotion. Pectoral and the pelvic girdle are also included since they assist in attaching the upper and lower limbs to the body respectively.
The pectoral girdle
Pectoral girdle consists of two bones namely the scapula and the clavicle. The clavicle has various significant roles, first, fixed above by muscles it acts as a strut extends sideways to give support to the scapula. Hence, it superiorly holds the joint shoulder and sideways from the body, thus it allows maximum freedom of movement from the upper limb. Secondly, it conveys forces that act on the upper limb to the sternum and axial skeletal system. Finally, it acts as a protector of the underlying nerves and blood vessels passing between the upper limb and the body trunk.
There are three regions in the clavicle that is the medial end, the lateral end and the shaft. Also known as the sternal end of the clavicle, the medial end is triangular in shape articulates with the manubriums segment of the sternum. Hence, leading to the formation of the sternoclavicular joint making it the only articulation that has bones between the pectoral girdle of the upper limb and the axial skeleton. The joint allows the shoulder to move in the upward and downward directions and also in anterior and posterior directions. Moreover, the joint is supported by a ligament called costoclavicular that spans the underlying first rib and the sternal end of the clavicle. The lateral also referred to as the acromial end of the clavicle; it articulates with acromion of the scapula.
The scapula also plays a key role in anchoring the upper limb of the body. The location of the scapula is at the posterior side of the shoulder. Also, it is surrounded by muscles on its anterior and posterior sides nut does not articulate with the ribs of the thoracic cage. The scapula ha three margins namely the superior border, the medial and lateral border of the scapula. The scapula also has other landmarks such as the suprascapular that is located at the midpoint of the superior border located between the medial and superior borders are the superior angle of the scapula. Also, between the medial and lateral borders is the inferior angle of the scapula which is the most inferior part of the scapula because it acts as the centre of attachment for various powerful muscles involved in the movement of the shoulder and upper limb. Between the superior and lateral border is the glenoid cavity that articulates with the bone of humerus to form the glenohumeral joint or the shoulder joint.
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