BIOL 1001 Lecture Notes - Lecture 5: Homologous Chromosome, Sister Chromatids, Seminiferous Tubule

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lavenderelephant707

20 Oct 2016

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Meiosis

1. a tetrad(bivalent) forms because of all chromosomes duplicate during Interphase I

-Then the homologous chromosomes line up

2. during meiosis I, homologous chromosomes separate

3. during meiosis II, sister chromatids separate. Meiosis I similar to mitosis

4. crossing over occurs during Meiosis I

Homologous Chromosomes

· are a pair of chromosomes that resemble eachother in size, shape, and the genes they carry

Human Chromosome Number

· diploid= 46

· haploid=23

· 23 pair of bivalents form

· ½ of each set for father. ½ from mother

· mitosis occurs in somatic cells and produces cells with 46 chromosomes-two of each type.

Random Alignment of Homologous Chromosomes During Meiosis I

· either maternal or paternal member of a homologous pair can end up at either pole of a cell

· homologues can go up or down in the previous figures

· the chromosomes in a gamete are a mix of chromosomes form the 2 parents

· our gametes almost always contain both maternal and paternal chromosomes

· all gametes normally contain only 23 chromosomes.

Possible Chromosomal Combos

· 2^n or 2^23, or 8.5 million combos

· for a cell with 8 chromosomes or 4 pairs, the haploid number is 4. The possible combos are

2^4 or 16.

· THIS IS IN THE ABSENCE OF CROSSING OVER

8 Possible Chromosome Combos

· 2n=6 and n=3

Crossing Over During Meiosis I

· each chromosome becomes zipper to its homologue

· all 4 chromatids are closely aligned and form a chiasma

· nonsister chromosomes exchange segments

· occurs during prophase I of Meiosis I **TEST QUESTION*8

Effect of Crossing Over

· each homologous chromosome contains both maternal and paternal segments

1. creates new allele combos in offspring

2. allows for genetic mixing

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Document Summary

Meiosis: a tetrad(bivalent) forms because of all chromosomes duplicate during interphase i. Then the homologous chromosomes line up: during meiosis i, homologous chromosomes separate, during meiosis ii, sister chromatids separate. Meiosis i similar to mitosis: crossing over occurs during meiosis i. Are a pair of chromosomes that resemble eachother in size, shape, and the genes they carry. Mitosis occurs in somatic cells and produces cells with 46 chromosomes-two of each type. Random alignment of homologous chromosomes during meiosis i. Either maternal or paternal member of a homologous pair can end up at either pole of a cell. Homologues can go up or down in the previous figures. The chromosomes in a gamete are a mix of chromosomes form the 2 parents. Our gametes almost always contain both maternal and paternal chromosomes. All gametes normally contain only 23 chromosomes. 2^n or 2^23, or 8. 5 million combos. For a cell with 8 chromosomes or 4 pairs, the haploid number is 4.

Related Questions

1. only one chromosome of a homologous pair is present in a cell

2. sister chromatids seperate

3. homologous chromosomes pair up

4. parent cell and daughter cells are genetically identical to each other

5. chromosomes replicate before nuclear division

6. crossing over

7. involved in growth and repair

8. homologous chromosomes separate

9. synthesis of sister chromatids before division

10. independent assortment

Answer Choices:

A. occurs ONLY in meiosis

B. occurs in BOTH mitosis and meiosis

C. occurs ONLY in mitosis

harlequineel895

-Complete the following sentences: metaphase of mitosis, prophase II of meiosis, crossing over, anaphase I of meiosis, variable, random fertilization, identical, random orientation, metaphase I of meiosis, prophase I of meiosis, metaphase II of meiosis, reduction division

Two processes that occur during meiosis produce genetically ____________ cells.

In a process called ____________ , paired homologous chromosomes align randomly at the cell equator. This occurs during this stage of cell division: ____________ .

In a process called ____________ , genetic material is exchanged between homologous chromosomes. This occurs during this stage of cell division: ____________ .

-Complete the following paragraph to describe nondisjunction and the resulting effects on chromosome number.

words: euploidy, primary nondisjunction, nomal, nondisjunction, secondary nondisjunction, homologous chromosomes, abnormal, trisomy, monosomy, sister chromatids, aneuploid

1.During meiosis I, ____________ separate and move towards opposite ends of the poles.

2.During meiosis II, ____________ separate and move towards opposite ends of the poles.

3.During meiosis I, if both members of a homologous pair go into the same daughter cell, ____________ is said to occur and no normal gametes are produced.

4.During meiosis II, if the sister chromatids fail to separate and both daughter chromosomes go into the same gamete, ____________ is said to occur. Half the gametes are aneuploid while the other half are euploid.

5.If an egg that contains 24 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

6.If an egg that contains 22 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

Determine whether the following applies to mitosis, meiosis, orboth; also identify the specific stage of cell division thatapplies (e.g. mitosis prophase, meiosis anaphase II, etc)

1) chromosomes pairs line up across the center of the cell

2) sister chromatids seperate

3) spindle fibers separate homologous chromosomes

4) 4 haploid daughter cells are produced

5) a cell 1st undergoes DNA replication

6) chromosomes line up single file across the middle of thecell

7) sister chromatids separate from each other

8) 2 haploid daughter cells form

9) the nuclear membrane re forms

10) spindle fibers attach to pairs of homologous chromosomes

11) the nuclear membrane begins to dissolve

12) centrosomes duplicate

13) synapsis and crossing over occurs

14) 2 diploid daughter cells form

turquoiseporpoise808

BIOL 1001 Lecture Notes - Lecture 5: Homologous Chromosome, Sister Chromatids, Seminiferous Tubule

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