Meiosis Day 2

Thursday February 21^st

During meiosis 1, what pairs up in the nucleus? Homologous Chromosomes (It is important that you know it's the homologous chromosomes and not JUST chromosomes.  Chromosomes line up during Mitosis - but during meiosis this first step of homologous chromosomes pairing is VERY important!!!)

During this time, the legs of chromosomes can swap DNA in a process known as Crossing Over. (keep in mind, this is not what we would call a mutation because it is swapping DNA from the same section of a chromosome.  It just results in some of your moms dna being found on your dads chromosome.)

In order for meiosis to create four, genetcially different gametes, DNA replication must occur.  Which of these best describes when DNA replication would occur during meiosis?

A.  Interphase of meiosis I                 

B.  Anaphase I in meiosis I      

C. Interphase in meiosis II  

D.  Anaphase II in meiosis II

DNA replication will ALWAYS occur before mitosis OR meiosis begins

Which statement BEST describes the relationship between an allele and a gene?

A.  An allele is a variation of a gene that can be expressed as a phenotype.

B.  An allele is the part of a gene that attaches to messenger RNA molecules

C.  An allele is a segment of a DNA molecule that controls replication of a gene

D.  An allele is the primary protein made by a gene found in a developing embryo.

We spent the rest of the period walking through meiosis I and II using our magnet boards and clay models.

Prophase 1 - Homologous chromosomes pair up with each other

then you guys made some of your own
chromosomes with clay so I could show you
crossing over

Sometimes the legs of homologous chromosomes will "cross over"
each other

The DNA is swapped on those sections so know the sister
chromatids are no longer identical

During Metaphase 1 these homologous chromosomes
will line up in the middle of the cell

During AnaphaseI then these homologous chromosomes Pull
apart from each other.

During Telophase I the nuclear envelop closes back in and
now you have two cell with different combinations of
the mothers and fathers DNA

 Meiosis II involved cutting apart the chromosomes which is what we spent the rest of the period doing.  Catch more pics of meisosis II tomorrow! (AFTER our DQQ!!)