FluffyCherry
Badges: 18
Rep:
?
#1
Report Thread starter 5 years ago
#1
Okay, I know a chromosome is made up of DNA
but like in different text books when it comes to cell division it's either the chromosomes will replicate or the DNA, so they are both the same, i guess. However, in my textbook it says when a DNA replicate it forms a X-shaped chromosome so does that mean 2 DNA's = a chromosome and in my other textbook it says that the chromosome replicates to produce another chromatid. I'm confused now..
0
reply
interstitial
Badges: 18
Rep:
?
#2
Report 5 years ago
#2
(Original post by Anne james)
Okay, I know a chromosome is made up of DNA
but like in different text books when it comes to cell division it's either the chromosomes will replicate or the DNA, so they are both the same, i guess. However, in my textbook it says when a DNA replicate it forms a X-shaped chromosome so does that mean 2 DNA's = a chromosome and in my other textbook it says that the chromosome replicates to produce another chromatid. I'm confused now..
Well, chromosomes are made up of DNA, which in turn is made up of lots of amino acid chains.

The DNA is in a double helix shape, which kind of unzips and each side serves as a template for the replication of the other. A molecule then 'walks' down the gap and produces the correct bases to pair with each corresponding base so the DNA replicate, and then it seals up into one long strand and rezips again.

Hope this helps.

Posted from TSR Mobile
0
reply
username1149337
Badges: 1
Rep:
?
#3
Report 5 years ago
#3
Chromosomes are basically long strands of DNA so its like a table made of wood (sorry awful example but you get the idea, the DNA is the building material of the chromosome)

On a similar topic but A2 could someone explain the difference between a:

Chromosome
Chromatid
Homologous pair
Bivalent

In meiosis
0
reply
anosmianAcrimony
Badges: 20
Rep:
?
#4
Report 5 years ago
#4
(Original post by majmuh24)
Well, chromosomes are made up of DNA, which in turn is made up of lots of amino acid chains.

The DNA is in a double helix shape, which kind of unzips and each side serves as a template for the replication of the other. A molecule then 'walks' down the gap and produces the correct bases to pair with each corresponding base so the DNA replicate, and then it seals up into one long strand and rezips again.

Hope this helps.

Posted from TSR Mobile
DNA is made up of nucleotides, not amino acids. You're thinking of proteins.
1
reply
interstitial
Badges: 18
Rep:
?
#5
Report 5 years ago
#5
(Original post by RadioheadHermie)
Chromosomes are basically long strands of DNA so its like a table made of wood (sorry awful example but you get the idea, the DNA is the building material of the chromosome)

On a similar topic but A2 could someone explain the difference between a:

Chromosome
Chromatid
Homologous pair
Bivalent

In meiosis
Chromosome is a single strand of coiled DNA

A chromatid is the single half when it divides.

Homologous pairs are the pairs of matching chromosomes from the mother and father

Not too sure, but I think it's two homologous pairs that are held together after the chromosomes replicate.

Posted from TSR Mobile
0
reply
username1149337
Badges: 1
Rep:
?
#6
Report 5 years ago
#6
(Original post by majmuh24)
Chromosome is a single strand of coiled DNA

A chromatid is the single half when it divides.

Homologous pairs are the pairs of matching chromosomes from the mother and father

Not too sure, but I think it's two homologous pairs that are held together after the chromosomes replicate.

Posted from TSR Mobile
So chromosome is just a single one without any division and the chromatid is half the replicated chromosome in the homologous pair
0
reply
SHABANA
Badges: 15
Rep:
?
#7
Report 5 years ago
#7
(Original post by RadioheadHermie)
Chromosomes are basically long strands of DNA so its like a table made of wood (sorry awful example but you get the idea, the DNA is the building material of the chromosome)

On a similar topic but A2 could someone explain the difference between a:

Chromosome
Chromatid
Homologous pair
Bivalent

In meiosis
Chromosome - When it looks like an 'X'
Chromatid - One arm of the 'X'. Usually only called this when it is part of replication during cell division
Homologous pair - A pair of chromosomes e.g. chromosome 1, will be in pairs with one chromosome from mum and one from dad
Bivalent - what you call it when the 'crossing over' of genes is happening in meiosis

I think the main reason there is confusion between chromosome and chromatid is because of the following:
1. When you see the diagram of all 46 chromosomes, in pairs, each chromosome looks like an 'X'
2. During cell the division, each 'X' then looks like a single strand - I - it is still a chromosome. When it duplicates, each strand - II - is called a chromatid

Think of mitosis and the number of chromosomes :
23 pairs i.e. 46 chromosomes they look like an 'X' for each chromosome
Duplication happens - 46 pairs of chromosomes. Each pair looks like an 'X' made up of 2 sister chromatids i.e. the original chromosome and the duplicate one
Then divides - left with 23 pairs in each of the 2 daughter cells
0
reply
Artemis200
Badges: 1
Rep:
?
#8
Report 5 years ago
#8
I'm pretty sure that it's a chromosome when it's a single straight line- l - and also when it's an X shape. So normally you have 46 chromosomes in a cell, l shaped. When your DNA replicates for mitosis or meiosis you get an X shaped chromosome- this is one chromosome with two chromatids, held together by the centromere, which is that dot at the middle of the X. Think of it like two identical pieces of string, each one being a chromatid, which are tied together in the middle. When the cell divides (for mitosis), the two chromatids are separated to from two chromosomes with are l shaped, one single strand. These two chromosomes formed from the two chromatids are totally identical.

Of course in meiosis it gets fancy and divides twice but that's basically it for the whole chromosome vs chromatid thing. My teacher says people always gets confused by that because textbooks talking about mitosis/meiosis always show chromosomes as X because they're in the middle of replicating, but in fact normally they aren't X shaped, just one strand.
0
reply
littleangel9914
Badges: 15
Rep:
?
#9
Report 5 years ago
#9
(Original post by Artemis200)
I'm pretty sure that it's a chromosome when it's a single straight line- l - and also when it's an X shape. So normally you have 46 chromosomes in a cell, l shaped. When your DNA replicates for mitosis or meiosis you get an X shaped chromosome- this is one chromosome with two chromatids, held together by the centromere, which is that dot at the middle of the X. Think of it like two identical pieces of string, each one being a chromatid, which are tied together in the middle. When the cell divides (for mitosis), the two chromatids are separated to from two chromosomes with are l shaped, one single strand. These two chromosomes formed from the two chromatids are totally identical.

Of course in meiosis it gets fancy and divides twice but that's basically it for the whole chromosome vs chromatid thing. My teacher says people always gets confused by that because textbooks talking about mitosis/meiosis always show chromosomes as X because they're in the middle of replicating, but in fact normally they aren't X shaped, just one strand.
X is often referred to as a chromosome but I think technically they're sister chromatids rather than a chromosome which is the diffuse form(singular line).
0
reply
Artemis200
Badges: 1
Rep:
?
#10
Report 5 years ago
#10
(Original post by littleangel9914)
X is often referred to as a chromosome but I think technically they're sister chromatids rather than a chromosome which is the diffuse form(singular line).
Could be yeah, I'm not totally sure on that- I think at GCSE the exam board are fine with you calling X a chromosome though
0
reply
littleangel9914
Badges: 15
Rep:
?
#11
Report 5 years ago
#11
(Original post by Artemis200)
Could be yeah, I'm not totally sure on that- I think at GCSE the exam board are fine with you calling X a chromosome though
Didn't realise the thread was aimed at GCSE students in that case your right X is thought of as a chromosome that has under gone replication.
0
reply
Artemis200
Badges: 1
Rep:
?
#12
Report 5 years ago
#12
(Original post by littleangel9914)
Didn't realise the thread was aimed at GCSE students in that case your right X is thought of as a chromosome that has under gone replication.
I think it's a mix of GCSE people and A2 people..? Honestly I don't know, oh well XD
0
reply
FluffyCherry
Badges: 18
Rep:
?
#13
Report Thread starter 5 years ago
#13
Thanx everyone for the answers, one more thing in Meiosis, in the first division, is there a genetic variation cos I think that the "second division" is the one that causes the variation to occur, am I right?
0
reply
username1149337
Badges: 1
Rep:
?
#14
Report 5 years ago
#14
What I understand is that you have 23 pairs of chromosomes one from each pair from mother and father. I'll represent this with II. Then they replicate to make a chromosome made of sister chromatids joined at the centromere so XX. and that a homologous pair is this XX and the chromosome is just one X. So I think that maybe a chromosome is both an I and an X during replication?
0
reply
username1149337
Badges: 1
Rep:
?
#15
Report 5 years ago
#15
(Original post by Anne james)
Thanx everyone for the answers, one more thing in Meiosis, in the first division, is there a genetic variation cos I think that the "second division" is the one that causes the variation to occur, am I right?
Crossing over happens during the first division which is where the homologous pairs swap genetic infomation. This is where some variation will be from, and then also there will be variation caused during both stages when they randomly line up
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Norwich University of the Arts
    Postgraduate Open Day Postgraduate
    Thu, 23 Jan '20
  • SOAS University of London
    Development Studies, Interdisciplinary Studies, Anthropology and Sociology, Languages, Cultures and Linguistics, Arts, Economics, Law, History, Religions and Philosophies, Politics and International Studies, Finance and Management, East Asian Languages & Cultures Postgraduate
    Sat, 25 Jan '20
  • University of Huddersfield
    Undergraduate Open Day Undergraduate
    Sat, 25 Jan '20

How are your mock exams going?

Love them - Feeling positive (10)
6.17%
They've been reasonable (67)
41.36%
Not feeling great... (44)
27.16%
They are TERRIBLE! (41)
25.31%

Watched Threads

View All
Latest
My Feed