An organism is described as 2n = 14. Fill in the blanks to indicatethe number of

Question

An organism is described as 2n = 14. Fill in the blanks to indicatethe number of chromosomes in one cell of that stage and the numberof chromatids per chromosome in that stage.
The number of chromosomes in one cell that is in the meioticanaphase I stage in this organism is.
The number of chromatids per chromosome in a meiotic anaphse I cellof this organism is.
The number of chromosomes in one cell that is in the mitoticanaphase stage in this organism is.
The number of chromatids per chromosome in a mitotic anaphase cellof this organism is .
The number of chromosomes in one cell that is in the G2 stage inthis organism is .
The number of chromatids per chromosome in a G2 cell of thisorganism is .

Explanation / Answer

Hi Unique7. 2n=14, which means that this organism has 7 pairs of chromosomes(7*2=14). We can also write that as n=7. Remember that mitosis is cell division with maintaining ofthe 2n, while meiosis is cell division with reduction ofthe chromosomes to just n. This way, if you cut yourself and yourbody undergoes mitosis to create new cells to heal, each of thosenew cells will also have 46 chromosomes. However, when your bodyundergoes meiosis to create sperm or ova, it needs to reduce thenumber of chromosomes to 23 (upon fertilization, the new cell willhave 23 chromosomes from mom and 23 from dad, for a complete set of46). This question is asking about both mitosis and meiosis, sosometimes you will have reduction of chromosomes and sometimes youwill have maintenance. Additionally, you have to remember that during these parts of thecell cycle, the DNA in the cell has condensed intochromosomes and it has also replicated itself intothat familiar X shape. In the replicatedstate, each of the "sides" of the X is identical to the other side,and they are joined together at the centromere.Each of these pieces is a chromatid and togetherthey are called sister chromatids. Think of thereplicated chromosome as conjoined twins connected at the hip. Theyare identical to each other, they are sisters, but they areconnected together in the middle and so come as a set until theyare separated from each other. The second part of understanding this question is understanding thecell cycle. This question deals with two parts of the cycle:anaphase and G2. It's easy to remember what happens in anaphase because inAnaphase, the chromosomesmove Apart. The important thing about the G2 phase is that it occursafter the DNA has replicated itself in S phase. So in G2,each chromosome consists of two sister chromatids. 1 chromosome = 2chromatids In Meiosis I, the chromosomes pair up inhomologues, that is, chromosome 1 finds the otherchromosome 1, chromosome 2 finds the other chromosome 2, etc. Thinkof a shoe closet - you could have 14 shoes in the closet, but whenyou pair them with their match, you have 7 sets. So in yourorganism, if there 14 chromosomes (2n=14) then you will have 7homologous sets. So let's consider. Your cell is in meiotic anaphase I, in which the homologouschromosomes will move apart. For meiosis, the chromatids do notseparate from each other until anaphase II.           How manyhomologous sets are present in the cell? We already establishedthat there are 7.           If eachhomologous set consists of 2 chromosomes, how many chromosomes arein the cell? Again, we already know the answer is 14.           Finally, howmany chromatids does each of these chromosomes have? Thinkconjoined twins... In mitosis, the chromosomes don't line up in homologues. Instead,they all line up single file and the chromatids themselves separatein anaphase (separation surgery for our "twins").           How manychromosomes are in the cell i.e. what is the 2n number? From thegiven information, we know that 2n=14           How manychromatids does each of these chromosomes have? Again, thinkconjoined twins. In G2, replication of the chromosomes has already happened. Wealready have our twins. If there are 14 total chromosomes in thecell, we will still have 14 chromosomes after replication. The onlydifference is that they will each now consist oftwo chromatids. So we have 14 chromosomes, eachwith two chromatids. You can do that math. Hope this helps you! If you are a visual learner, there are somegreat animations online - just do a google search for mitosisanimation and/or meiosis animation. Good luck!

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