CSB429H1 Lecture Notes - Lecture 2: Germ Plasm, Germplasm, Oogenesis

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blueox941

19 Apr 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB429H1

Professor

Dorothea Godt

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Document Summary

Might be to maintain synchronization, so the y are all at same stage of development. Another model: during meiosis, dna is replicated and split, and then splits again. In this case, remaining connected during first meiotic division has an advantage because the protein product of gene x will still be created even if one copy of gene x is not functional. If they were to separate, 2/4 of the sperm will die because they have a bad copy of gene. X: so this is why they remain connected during meiotic divisions, although why they remain connected in mitotic is still a mystery. This applies to the sex chromosomes, the y copy of the gene is pretty small, by remaining connected, the. X copy will still be abl to make gene product so the sperm can survive (if they split, you"d have 2 daughter cells (of a total 4) that have only y.

Related Questions

The smooth and rough endoplasmic reticulum

A. are connected, and connected to the outer leaflet of the nuclear envelope

B. have different functions: the smooth is involved in lipid synthesis, the rough is a site of protein synthesis

C. are not connected, but have different functions

D. are connected but have the same functions

E. are both connected to the Golgi and the nucleus

fuchsiadog167

Nondisjuction is a cell division error in which either homologous chromosomes or sister chromatids fail to separate and thus do not migrate to opposite poles. It is responsible for conditions such as monosomy (one member of a chromosome pair is missing) and trisomy (three copies of a chromosome is present rather than two).

Nondisjunction can occur during the first or second meiotic division.

Part A- Jill is heterozygous for gene A and is going to have a child with Jack, who is homozygous recessive for gene A.

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an egg that had undergone nondisjunction in meiosis I?
Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

I put AAa, Aaa, Aa, but it was not correct

Part B-

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an oocyte that had undergone nondisjunction in meiosis II?

Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

Part E-

If Jack and Jill have a child with an aaa genotype, during which meiotic division, and in which parent, could nondisjunction have occurred?

Check all that apply.

1) Meiosis I in the mother

2 Meiosis II in the mother

3) Meiosis I in the father

4) Meiosis II in the father

The answer is not Meisis I in the mother

One non disjunction event has occurred during the second meiotic division. Explain how chromosomes are in 2 gametes affected at the end of telophase 2?

CSB429H1 Lecture Notes - Lecture 2: Germ Plasm, Germplasm, Oogenesis

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