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The structure of chromosomes

Billions of cells in the human body divide every day. During the synthesis phase (S, for DNA synthesis) of interphase, the amount of DNA within the cell precisely doubles. Therefore, after DNA replication but before cell division, each cell actually contains two copies of each chromosome. Each copy of the chromosome is referred to as a sister chromatid    and is physically bound to the other copy. The centromere    is the structure that attaches one sister chromatid to another. Because a human cell has 46 chromosomes, during this phase, there are 92 chromatids (46 × 2) in the cell. Make sure not to confuse the concept of a pair of chromatids (one chromosome and its exact copy attached during mitosis) and a homologous pair of chromosomes (two paired chromosomes which were inherited separately, one from each parent) ( [link] ).

A homologous pair of chromosomes with their attached sister chromatids

This image shows a pair of chromosomes. The major parts such as the homologous chromosomes, kinetochore and the sister chromatids are labeled.
The red and blue colors correspond to a homologous pair of chromosomes. Each member of the pair was separately inherited from one parent. Each chromosome in the homologous pair is also bound to an identical sister chromatid, which is produced by DNA replication, and results in the familiar “X” shape.

Mitosis and cytokinesis

The mitotic phase    of the cell typically takes between 1 and 2 hours. During this phase, a cell undergoes two major processes. First, it completes mitosis, during which the contents of the nucleus are equitably pulled apart and distributed between its two halves. Cytokinesis then occurs, dividing the cytoplasm and cell body into two new cells. Mitosis is divided into four major stages that take place after interphase ( [link] ) and in the following order: prophase, metaphase, anaphase, and telophase. The process is then followed by cytokinesis.

Cell division: mitosis followed by cytokinesis

This tabular image shows the different stages of mitosis and cytokinesis using both drawings and text. The top panel is a series of schematics for each step, followed by text listing the important aspects of that step. The bottom panel shows fluorescent micrographs for the corresponding stage.
The stages of cell division oversee the separation of identical genetic material into two new nuclei, followed by the division of the cytoplasm.

Prophase is the first phase of mitosis, during which the loosely packed chromatin coils and condenses into visible chromosomes. During prophase, each chromosome becomes visible with its identical partner attached, forming the familiar X-shape of sister chromatids. The nucleolus disappears early during this phase, and the nuclear envelope also disintegrates.

A major occurrence during prophase concerns a very important structure that contains the origin site for microtubule growth. Recall the cellular structures called centrioles that serve as origin points from which microtubules extend. These tiny structures also play a very important role during mitosis. A centrosome    is a pair of centrioles together. The cell contains two centrosomes side-by-side, which begin to move apart during prophase. As the centrosomes migrate to two different sides of the cell, microtubules begin to extend from each like long fingers from two hands extending toward each other. The mitotic spindle    is the structure composed of the centrosomes and their emerging microtubules.

Questions & Answers

What is the differences between anabolism and catabolism?
Ikenze Reply
what are steroid hormones
Mwesige
it doesn't have nothing to do with are sex hormones
isaiah
it's something with food we eat,the air we breathe into the energy we need to function
isaiah
whats the difference between regional anatomy and systematic anatomy?
mitchxidyllic Reply
Regional anatomy is the scientific study of the structure of a particular region of the body, e.g the heart. systematic anatomy is the scientific study of the structure of a particular body system. e.g The reproductive system.
Ikenze
how many litres of blood does a human body have
George Reply
hi
Sweetlin
hliii
Mohd
there are around 10.5p.(5literes) adult body
Shubu
what is homeostasis
Antwi Reply
it is self regulating ability of the body to adjust to the surroundings
Angela
it is like maintaining an equilibrium type of environment between the inside and outside of the body, so that our body can adjust to the external environmental changes
Angela
this is the negative feedback loop of the body,.... that naturally helps to keep the body in a stable or constant internal environment.
Matthew
this is the activities in the body that keeps the internal environment of the body in equilibrium or to keep it constant.
Ikenze
list four long bones
Mary Reply
the four long bones are: tibia, fibula, femur, and humerus.
Isaac
from Zambia
Mary
femur, radius , ulnar, humerus
Om
humerus, femur, tibia and fibula
Sheryl
Humerus,redius,ulnar,in hand. Femur,tibia,fibula in leg. it is long bone.
Sneha
there is contradiction between radius ulna & tibia fibula because of the variation in the upper and lower limb of the according to growth and development of human body so humerus & femur are longer bones ( ex you can see Michael phaleps upper limb is longer than the lower limb)
Prashant
if anyone having dout so he she can please explain it to me
Prashant
which one want explain something
Dr
sir post which I have send look at it & tell is it correct or not
Prashant
about four long bones is the topic
Prashant
femur, humerus, tibia and fibula
Ikenze
how are you doing
Rekah Reply
hi everyone.
AR
Im new here, I came from the philippines. I study nursing. Im a first year student.
AR
really
Isaac
so what help do you want
Isaac
yeah I came from the philippines..and I have struggle about this subject the anatomy and physiology because I dont any books that I barrowed with. I cant afford buy books.
AR
hii
Meher
I'm from India
Jamy
I struggle with this subject
Jamy
can I ask here a question I hope you can help me because I dont have any references/books that I should see or read it.
AR
AR
Meher
you are from india nice to talk to you jamy.
AR
Alright Always drop your concerns here and they will be addressed. Thanks sister.
Isaac
nice meeting with you
Jamy
I am also from India
shiv
thank you Isaac.
AR
yes Meher?
AR
you are all india
AR
By the way I have question
AR
describe a person in anatomical position?
AR
i come from Ghana
Isaac
are you all nursing students?
AR
no I'm pharmacy student
Jamy
oh nice.
AR
yes
shiv
jamy me too
Meher
yes
shiv
yes
shiv
my name is sweety
Jamy
you have any chat group that we can talk there.
AR
Anatomical position is the description of any region or part of the body in a specific stance. In the anatomical position, the body is upright, directly facing the observer, feet flat and directed forward. The upper limbs are at the body's sides with the palms facing forward. The standard anatomic
Isaac
yes
shiv
jamy is my nick name
Jamy
I am a nursing student
Isaac
thank you Isaac
AR
Final year, level 400
Isaac
ohh what year are you now?
AR
Nice
AR
welcome madam
Isaac
do you have any chat group here
AR
describe the six levels of organization of the body and describe the major characteristics of each level?
AR
ahh its okay jammy
AR
jammy i am from kashmir nd u
Meher
It is convenient to consider the structures of the body in terms of fundamental levels of organization that increase in complexity, such as (from smallest to largest): chemicals, cells, tissues, organs, organ systems, and an organism.
Isaac
hi
Yaminah
am from somalia
Yaminah
5th year in medical student nice to meet ya all
Yaminah
thxs yaminah
Meher
y not.. jamy for what purpose...?
Meher
inbox me i will guide u ...?
Meher
i also dont know...?
Meher
open this app - click 'start learning' - click 'preface' - select the chat that you wanna join into I guess that is it !
Angela
Hello am from Sierra Leone
junisa
I am from Kerala
Angela
I am from india
Om
tell the easyst way to learn anatomy
Khaliif Reply
try to draw 👌
Rahil
what
shiv
learn subject with drawing anatomy diagrams some with flow chart i dont say it is easiest way bt yes u can rember for longer period
Shakerah
ooh
shiv
Can u say me parturation
Sweetlin
parturition is one of the 7 stages of human reproduction. parturition is actually that last or the 7th stage, that is giving birth to the baby or the delivery of the baby.
Angela
Mr. khaliff.. never ever use a short cut or easiest way to Acquire knowledge.. the knowledge what we got from an easiest way , cuz it will be become temporary, not permanent.. especially in the anatomy.. cuz it's a complex subject.. you can shortlist as per your syllabus, not yourself..
Sanjith
I think shakeerah's ideology of learning anatomy is one of a best method to easy learning.. and try to share with your friends or here, what you've acknowledged each day.. thankyu
Sanjith
I am agree with that point
shiv
if u get time aftr learning this 2_3 ppl join , make group make questions if urself even if its silly make it as flash card sometimes u fail , its okay. dont be less heart. u vl do it anyway if u concentrate. bt choosing ppl or the selection of ppl during studying it really matters.
Shakerah
if u get time aftr learning this 2_3 ppl join , make group make questions if urself even if its silly make it as flash card sometimes u fail , its okay. u vl do it anyway if u concentrate. bt choosing ppl or the selection of ppl during studying it really matters.
Shakerah
😊
Sanjith
what Tk
shiv
good night all... stay safe.. bye
Sanjith
hello im new here, im a nursing student
SHUGA Reply
ooh
shiv
welcome
shiv
wlcm
Rahil
dub
Ndowmi
maleria
Ndowmi
Anopheles
shiv
welcome shuga
Om
please am new here. Am a nurse awaiting to be posted .
Ntiamoah
hi I'm new here too
faleke
FAKE DrLUPO thank you
faleke
hello guys
Chuks
hello guys 🤗
Sneha
hello
Chuks
whose in Nigeria
Chuks
🙋🙋
faleke
what is inner breeding
Vijay Reply
you don't have any answer
Vijay
please don't waste my time
Vijay
wait
shiv
inbreeding is mating or breeding with organism that are genetically related
shiv
s
Pankaj
who this SRY
Pankaj
inner breeding is breeding among the same species of organisms
Anna
*inbreeding
Anna
yes same speciesor same genetic organism
shiv
description of the menstruation cycle
Namyalo Reply
explain the menstruation cycle
Namyalo
explain the menstrual cycle
Ugo
menstrual cycle is came due to FSH and LH
shiv
fsh
Ndowmi
This is the periodic release of waste(blood) from the reproductive organ of the females (human) for a period of some days, after which or during then, ovulation takes place, which is the release of eggs from the ovaries for fertilization by the spermatozoa.
Ikenze
Description of menestraul cycle
Amos Reply
i want to improve my study i like this app i interest physiology and anatomy
Su Reply
I also like this app am really interested in learning anatomy and physiology.
Johny
I have this book with my anatomy class it's awesome! also if look at crashcourse anatomy on you tube!
AMY
what the name
isaiah
umesh. rede
Rede
what is heart and long type answer
Lalita Reply
its a organ in the body
ay
describe about hear chambers.. valves.. arteries.. veins.. circulation.. inferior/superior venacava, aorta., tricuspid valve, mitral valve. pulmonary artery/vein, how oxigenation occur,systolic presure diastolic pressure.. stroke volume,cardiac output, ets.. heart located in which place, describe it
Sanjith
if you describe what I cited up, thogh you can write a long type answer about heart
Sanjith
hi
Riyaz
autonomic functions took over
Vanarith Reply
What did they take over?
Eric
what is the average volume of blood in men and why does it varrie from women?
Esther Reply
what is the average volume of blood in men
Esther
5to6liter
Sarita
5to6liter dt
Sarita
umesh. rede
Rede
estimated at 5.5litres
Ikenze

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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