DRILL #14
description
Transcript of DRILL #14
![Page 1: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/1.jpg)
DRILL #14Quote: You will never leave where you
are, until you decide where you'd rather be.
~Dexter Yager
Agenda: Meiosis Notes
Warm-up:1. Describe interphase.
2. After a bacterial cell has undergone binary fission, how many chromosome copies will each daughter cell contain?
![Page 2: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/2.jpg)
Meiosis NotesCH 11
Go to Section:
![Page 3: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/3.jpg)
Meiosis• The form of cell division by which gametes,
with half the number of chromosomes, are produced.
• Diploid (2n) haploid (n)
• Meiosis is sexual reproduction.
• Two divisions (meiosis I and meiosis II).
![Page 4: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/4.jpg)
Meiosis• Sex cells divide to produce gametes (sperm
or egg).• Gametes have half the # of chromosomes.
• Occurs only in gonads (testes or ovaries).Male: spermatogenesisFemale: oogenesis
• Meiosis is similar to mitosis with some chromosomal differences.
![Page 5: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/5.jpg)
Spermatogenesis
2n=46
humansex cell
diploid (2n)
n=23
n=23
meiosis I
n=23
n=23
n=23
n=23
sperm
haploid (n)
meiosis II
![Page 6: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/6.jpg)
Interphase I• Similar to mitosis interphase.
• Chromosomes replicate (S phase).
• Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres.
• Centriole pairs also replicate.
![Page 7: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/7.jpg)
Meiosis I (four phases)• Cell division that reduces the chromosome
number by one-half.
• four phases:a. prophase Ib. metaphase Ic. anaphase Id. telophase I
![Page 8: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/8.jpg)
Prophase I• Longest and most complex phase (90%).• Chromosomes condense.
• Synapsis occurs: homologous chromosomes come together to form a tetrad.
• Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).
![Page 9: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/9.jpg)
Prophase I - Synapsis
Homologous chromosomes
sister chromatids sister chromatidsTetrad
![Page 10: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/10.jpg)
Homologous Chromosomes• Pair of chromosomes (maternal and paternal) that are
similar in shape and size.• Homologous pairs (tetrads) carry genes controlling
the same inherited traits. Having two copies of every gene can be an advantage. For example, if the one gene from Dad was damaged, Mom’s good gene could take over.
• Each locus (position of a gene) is in the same position on homologues.
• Humans have 23 pairs of homologous chromosomes.
a. 22 pairs of autosomesb. 01 pair of sex chromosomes
![Page 11: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/11.jpg)
Homologous Chromosomes
Paternal Maternal
eye color locus
eye color locus
hair color locus
hair color locus
![Page 12: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/12.jpg)
Crossing Over• Crossing over (variation) may occur between
nonsister chromatids at the chiasmata.
• Crossing over: segments of nonsister chromatids break and reattach to the other chromatid.
• Chiasmata (chiasma) are the sites of crossing over.
![Page 13: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/13.jpg)
Crossing Over - variation
nonsister chromatids
chiasmata: site of crossing over
variation
Tetrad
![Page 14: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/14.jpg)
Sex Chromosomes
XX chromosome - female XY chromosome - male
![Page 15: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/15.jpg)
Prophase I
centriolesspindle fiber
asterfibers
![Page 16: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/16.jpg)
Metaphase I• Shortest phase• Tetrads align on the metaphase plate.• INDEPENDENT ASSORTMENT OCCURS:
1. Orientation of homologous pair to poles is random.2. Variation3. Formula: 2n
Example: 2n = 4then n = 2
thus 22 = 4 combinations
![Page 17: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/17.jpg)
Metaphase I
metaphase plate
OR
metaphase plate
![Page 18: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/18.jpg)
Question:• In terms of Independent Assortment -
how many different combinations of sperm could a human male produce?
![Page 19: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/19.jpg)
Answer• Formula: 2n
• Human chromosomes: 2n = 46 n = 23
• 223 = 8,388,608 million combinations
• Any one of these assortments can combine with any one of the 8,388,608 combinations of his partner!
![Page 20: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/20.jpg)
Anaphase I• Homologous chromosomes separate and
move towards the poles.
• Sister chromatids remain attached at their centromeres.
![Page 21: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/21.jpg)
Anaphase I
![Page 22: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/22.jpg)
Telophase I• Each pole now has haploid set of
chromosomes.
• Cytokinesis occurs and two haploid daughter cells are formed.
![Page 23: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/23.jpg)
Telophase I
![Page 24: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/24.jpg)
Meiosis II• No interphase II
(or very short - no more DNA replication)
• Remember: Meiosis II is similar to mitosis
![Page 25: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/25.jpg)
Prophase II• same as prophase in mitosis
![Page 26: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/26.jpg)
Metaphase II• same as metaphase in mitosis
metaphase platemetaphase plate
![Page 27: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/27.jpg)
Anaphase II• same as anaphase in mitosis• sister chromatids separate
![Page 28: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/28.jpg)
Telophase II• Same as telophase in mitosis.
• Nuclei form.
• Cytokinesis occurs.
• Remember: four haploid daughter cells produced.
gametes = sperm or egg
![Page 29: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/29.jpg)
Telophase II
![Page 30: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/30.jpg)
Meiosis
2n=4
sex cell
diploid (2n)
n=2
n=2
meiosis I
n=2
n=2
n=2
n=2
sperm
haploid (n)
meiosis II
![Page 31: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/31.jpg)
In males, four sperm are produced and flagella soon develop.
In females, one large egg survives and three smaller eggs die.
![Page 32: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/32.jpg)
Fertilization• The fusion of a sperm and egg to form a zygote.• A zygote is a fertilized egg
n=23egg
sperm n=23
2n=46zygote
![Page 33: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/33.jpg)
Variation• Important to population as the raw
material for natural selection.
• Question:What are the three sexual sources ofgenetic variation?
![Page 34: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/34.jpg)
Answer:
1. crossing over (prophase I)
2. independent assortment (metaphase I)
3. random fertilization
Remember: variation is good!
![Page 35: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/35.jpg)
Question:• A cell containing 20 chromosomes (diploid)
at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?
![Page 36: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/36.jpg)
Answer:• 10 chromosomes (haploid)
![Page 37: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/37.jpg)
Karyotype• A method of organizing the chromosomes of a
cell in relation to number, size, and type.
![Page 38: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/38.jpg)
Question:• A cell containing 40 chromatids at the
beginning of meiosis would, at its completion, produce cells containing how many chromosomes?
![Page 39: DRILL #14](https://reader035.fdocuments.us/reader035/viewer/2022062323/56816598550346895dd87284/html5/thumbnails/39.jpg)
Answer:• 10 chromosomes