Bio 178 destroyer

[Sublimation]

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Ok so the Q is this.

An Egg cell will contain?

A. 23 Chromosomes, 46 chromatids
B. 23 , 23
C. 46 , 46
D. 46 , 23

Now when it said egg and i saw the 23 i assumed it was a human egg. And i know that a human egg (2*oocytes are halted at metaphase II till they are fertilized) therefore the answer should be 23 chromosomes and 46 chromatids. The sister chromatids have not been seperated....could this be a mistake or am i not catching something here?

 

[joonkimdds]

Mitosis = 2n --> 2n
meiosis = 2n --> 1 n --> 1n
if I picture the meiosis
XX --> x and x --> / and / and / and /

thus after the 1st meiosis, we got 1 x per cell
and after the 2nd meiosis, we got / per cell.
when we talk about n or 2n, think of n as centreomere although most people define it as chromosome or chromatids.
so basically, we saw 2 centromere, which became 1 centromere and it stays 1 centromere.
x is 1 chromosome with 2 chromatids.
/ is 1 chromosome with 1 chromatids.

thus if we started with 46, it becomes 23 chromosome with 23 chromatids.

if u are wondering how can / be both 1 chromosome and 1 chromatids when people say 1 chromosome has 2 sister chromatids, that's only when / becomes x during interphase. When it's in / form, it is 1 chromosome = 1 chromatid.

 

[Nasem]

I think your overthinking this questions... the whole point is to recognize that this is an egg is a diploid cell, so 46 becomes 23...

I believe that if DAT wanted to ask you a question about this, they would specifically tell you if the sperm has entered the cell or not (cause your right, it does make a HUGE difference in the answer)

 

[suhshi]

so is it 23 chromosomes and 23 chromatids?

 

[UCB05]

Sperm and egg cells are haploid gametes containing single chromosomes/chromatids. The answer should be 23/23. In humans, meiosis is suspended, yes, and the oocytes are 46/92 and 23/46 depending on stage, but primary and secondary oocytes are not true egg cells because they are in a suspended transition state.

I'm sure if a question wants to know the DNA complement of a primary or secondary oocyte/spermatocyte stage, they'll specify. If they refer just to a gamete cell, take it as meiosis complete.

 

[imju85]

(from Wikipedia): hope this helps you understand little better... (it did for me 😛)

4N
In a cell with 4N chromatids, there are 23 chromosome pairs (46 chromosomes), and each chromosome has 2 chromatids. Thus, there are 92 chromatids in each cell (4N). It occurs after the S phase of interphase. (See cell cycle).


2N
Immediately after a mitosis, where a cell has divided in two, but not yet duplicated its DNA in S phase, there are still 23 chromosome pairs (46 chromosomes). However, each chromosome only has one chromatid. Thus there are 46 chromatids (2xN)

Alternatively, a haploid cell with two chromatids per chromosome also has 46 chromatids. However, this doesn't occur naturally in human somatic cells.


1N
Immediately after meiosis, each cell, called a gamete, only has half the number of chromosomes (23 chromosomes). Furthermore, each chromosome only has one chromatid. Thus, there are 23 chromatids (1xN)

 

[Sublimation]

Ok cool. I kno gametes are 23/23 but when they said eggs lol i felt likeit was a trap cuz like u said the oocytes are diff. but thanks for clarifying guys.