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I am new to genetics , and am stuck with the following question at hand:

If $2$ cells with genotypes $(A/a)$ and $(A/a,B/b)$ undergo mitotic and meotic cell divisions respectively, what will be the genotypes/gene compositions in the resultant diploid and haploid cells with respect to the above mentioned alleles?

Can someone help me how to proceed?

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  • $\begingroup$ can you give a little more information - like what you think the answer might be? Is this a homework question? $\endgroup$ Oct 12, 2016 at 18:43
  • $\begingroup$ @VanceLAlbaugh Not homework in the true sense. It is actually a question in one of the previous year's question paper (so I doubted to give the self study tag ) that I couldn't solve and sadly neither is my professor available , nor are my friends getting anywhere. $\endgroup$
    – Qwerty
    Oct 12, 2016 at 18:51
  • $\begingroup$ Related: biology.stackexchange.com/questions/53110/… $\endgroup$
    – user25568
    Nov 4, 2016 at 17:07

1 Answer 1

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Though broad, here I provide a summary in graphical way.

Mitosis:

Mitosis .


MEIOSIS: 2 successive steps : Meiosis-1 and meiosis-2

Meiosis-1

Meiosis 1


Meiosis-2

meiosis-2


So lets see what happens with cells given at question.

1. Cell with genotype Aa

(monohybrid or one-point cross-experiments; that means we are looking to gene-pair at 1 loci; not looking to any other genes):

1. A. Mitosis:

Possible genotypes of their offsprings: All Aa.

1. B. Meiosis:

gametes will show 2-possibilities ; A, a.


2. Cell with genotype AaBb

(dihybrid or 2-point cross-experiments; that means we are looking on genes of 2 loci; not to any other cells):

2.A. Mitosis:

all offsprings AaBb.

2.B. Meiosis:

If given condition says the loci for A (or a) and B (or b) are on same chromosome (linked genes) and no crossing-over is there;

then We will get only 2 types of gamete AB and ab.

If crossing over(s) take place between the 2 loci; then we'll get 4 types of gamete AB, Ab, aB, ab; but their ocurring frequency will deviate from Mendel's independent assortment.

If the 2 loci are not-linked; i.e. they are located in distinct chromosome; then also we'll get 4 types of gametes AB, Ab, aB, ab; but they will follow Mendel's independent assortment pattern.

Reference:

  1. Concepts of Genetics, 8th Edition (EBook) By William Klug, Michael Cummings, Charlotte Spencer / Pearson; chapter 2 (mitosis and meiosis)

  2. The science of Genetics, 6th edition, by George Burns and Paul Bottino, Macmillan.

  3. Genetics/ P.K. Gupta/ Rastogi Publication Meerut

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  • $\begingroup$ That was a wonderful explaination. Can you please (if possible) give me the source where genetics is so wonderfully expalined in detail? $\endgroup$
    – Qwerty
    Oct 12, 2016 at 19:15
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    $\begingroup$ @Qwerty I did it completely from memory and it is based on many days of classes and many books. Ok I'll look back to my books and will add some relevant reference. $\endgroup$
    – user25568
    Oct 13, 2016 at 3:43
  • $\begingroup$ @Qwerty I've added them $\endgroup$
    – user25568
    Oct 13, 2016 at 4:25
  • $\begingroup$ For your purpose you could also visit a book by Robert Tamarin, and for chromosome aberrations, there is an excellent genetics book by Monroe Strickberger (but I can't access it right now) $\endgroup$
    – user25568
    Oct 13, 2016 at 4:37
  • $\begingroup$ @Qwerty Thanks for your appreciation. glad to write something helpful $\endgroup$
    – user25568
    Oct 14, 2016 at 1:23

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