genetics--nuclear division & inheritance mitosis & meiosis
TRANSCRIPT
![Page 1: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/1.jpg)
Genetics--Nuclear Division & Inheritance
Mitosis & Meiosis
![Page 2: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/2.jpg)
Introduction
• What is Genetics?
• What level of organization is being examined?– molecular, cellular, species, or population
• What is the purpose of this lab?
![Page 3: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/3.jpg)
Somatic versus Reproductive Cells
• Somatic cells:– all except the reproductive
cells
– 2 copies of each chromosome
– diploid
– example: in humans, the diploid number is 46
• Reproductive or sex cells:– haploid
– 1 copy of each chromosome
![Page 4: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/4.jpg)
Nuclear Division
• Mitosis– prior to mitosis chromosomes are duplicated– nuclear division in somatic cells– genetic info from “parent” to daughters– cancer: uncontrolled cell division
![Page 5: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/5.jpg)
Nuclear Division
• Meiosis– prior to meiosis: chromosomes are duplicated– nuclear division in the sex cells– genetic diversity
![Page 6: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/6.jpg)
Cytokinesis
• division of the cytoplasm• occurs at the end of mitosis• occurs at the end of meiosis I• occurs at the end of meiosis II
![Page 7: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/7.jpg)
Interphase
Mitosis
![Page 8: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/8.jpg)
Interphase
• no nuclear or cell division
• DNA replication, chromosome duplication, and cell growth
• “chromosomes,” not visible inside nucleus
• but can see nucleolus inside nucleus
![Page 9: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/9.jpg)
Mitosis
• Four phases of mitosis:
– prophase
– metaphase
– anaphase
– telophase
• End result of mitosis: 2 daughter cells
![Page 10: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/10.jpg)
Prophase
• Duplicated chromosomes condense and become visible as sister chromatids joined at the centromere
• nuclear membrane disintegrates; neither the nucleus nor the nucleolus is distinct
• spindle apparatus of the cell is formed
![Page 11: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/11.jpg)
Early prophase
Prophase
Prophase
• Chromatin condenses into discrete chromosomes– two identical “sister
chromatids”
– joined at the centromere
![Page 12: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/12.jpg)
Metaphase
• Chromosomes are aligned along the cell’s equator at their centromeres
• spindle fibers are visible
![Page 13: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/13.jpg)
MetaphaseChromosomes convene on the metaphase plate, an imaginary “equator” located between the two poles of the spindle. Centromeres are aligned, and sister chromatids of each chromosome straddle the metaphase plate.
Metaphase plate
Spindle fibers
![Page 14: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/14.jpg)
Anaphase
• Migration of the chromosomes: – centromeres split – move along the spindle fibers towards opposite
poles – pulling the sister chromatid
• Each chromatid -- a chromosome
![Page 15: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/15.jpg)
AnaphaseThe sister chromatids separate from each other and move along the spindle fibers towards opposite poles. Each chromatid is now considered a chromosome.
Early anaphase
Anaphase
Spindle poles
![Page 16: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/16.jpg)
Anaphase
Late anaphase
By the end of anaphase, each pole has an equivalent and complete set of chromosomes.
![Page 17: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/17.jpg)
Telophase
• Chromosomes are aggregated at the poles and begin to thin out and extend in length
• new nuclear membrane forms; nucleolus and nucleus begin to reappear
• spindle disintegrates
• cytoplasm divides (cytokinesis occurs); daughter cells begin to form
![Page 18: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/18.jpg)
Telophase
Late telophase
Cytokinesis begins, separating the cytoplasm into 2 “daughter cells”.
Telophase
• The “daughter” nuclei begin to form at the two poles
• Nuclear membranes begin to form
• chromosomes lose their distinct appearance.
![Page 19: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/19.jpg)
Daughter Cells
Telophase
• formation of 2 daughter cells
• Each daughter cell has same genetic material as parent
![Page 20: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/20.jpg)
Meiosis: Reproductive or Sex Cells• Gametes
– female gametes: “eggs” or “ova” (ovum, singular)
– male gametes: “sperm”
– HAPLOID, have 1 copy of each chromosome (i.e., 1/2 as many chromosomes as somatic cells)
– example, in humans, the haploid number is 23.
![Page 21: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/21.jpg)
Meiosis in the Lily Anther
• Lily anther:
– male reproductive organ in flowering plants.
– meiosis takes place
– result: haploid pollen grains
![Page 22: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/22.jpg)
Meiosis in the Lily Anther• A very thin cross-section of a lily anther
• stain it
• examine with a compound light microscope:
![Page 23: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/23.jpg)
Meiosis in the Lily AntherEach anther contains 4 pollen sacs where meiosis takes place.
![Page 24: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/24.jpg)
Meiosis in the Lily Anther
• Study the various phases of meiosis in prepared slides of the lily anther.
• look at the cells inside the pollen sacs
• locate the different phases.
![Page 25: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/25.jpg)
Stages of Meiosis
Meiosis consists of meiosis I and meiosis II and both have 4 stages leading up to the actual cell division.
Meiosis I: Meiosis II:
Prophase I Prophase II
Metaphase I Metaphase II
Anaphase I Anaphase II
Telophase I Telophase II
![Page 26: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/26.jpg)
Meiosis: Prophase I
Chromatin condenses into discrete chromosomes. Chromosome is actually composed of 2 sister chromatids.
Homologous chromosomes come together as pairs.
![Page 27: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/27.jpg)
Meiosis: Metaphase I
Metaphase plate
Spindle fibers
• Chromosomes are arranged on the metaphase plate, still in homologous pairs.
• Spindle fibers from each pole attach to one chromosome of each pair of the homologue.
![Page 28: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/28.jpg)
Meiosis: Anaphase I
• each homologous pair of chromosomes separate and move toward opposite poles.
• each chromosome still consists of 2 sister chromatids joined together at the centromere.
![Page 29: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/29.jpg)
Meiosis: Telophase I
Haploid
Haploid
• Chromosomes have moved to opposite poles.
• Cytokinesis separates the cytoplasm into 2 daughter cells.
• Each cell is now haploid.
![Page 30: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/30.jpg)
Meiosis: Prophase IIIn prophase II, the chromatin again condenses so the chromosomes have a distinct shape.
![Page 31: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/31.jpg)
Meiosis: Metaphase II
In metaphase II, chromosomes align on the metaphase plate.
![Page 32: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/32.jpg)
Meiosis: Anaphase II
• sister chromatids separate, and move towards opposite poles
• sister chromatids are now individual chromosomes.
![Page 33: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/33.jpg)
Meiosis: Telophase II
Haploid
Haploid Haploid
Haploid
• nuclei begin to form at opposite poles, and cytokinesis occurs
• 4 daughter cells, each with the haploid number of chromosomes.
![Page 34: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/34.jpg)
Meiosis I: Review
Prophase I Metaphase I
Telophase IAnaphase I
![Page 35: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/35.jpg)
Review: Meiosis II
Prophase II Metaphase II
Anaphase II Telophase II
![Page 36: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/36.jpg)
Chromosomes and Genes• one long strand of
DNA• associated proteins
– “chromatin”
• thousands of genes• gene
– discrete unit of heredity
• locus– physical location of a
gene
![Page 37: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/37.jpg)
Homologous Chromosomes, Genes, and Alleles
• Chromosome pair:– “homologous
chromosomes”
• pair has genes at the same loci– “alleles”
– may be the same or different
![Page 38: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/38.jpg)
Human Genetics
• Genotype– heterozygous– homozygous
• Phenotype
• Observe traits and identify which form you possess
• Make a table
![Page 39: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/39.jpg)
Extra 21st chromosome
Heredity and Genetic Disorders
• Video, “Healthy, Heredity, and Genetic Disorders”
![Page 40: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/40.jpg)
Mechanics of Mitosis
• Answer questions– use instructional materials available
• video: Mechanics of Mitosis
• posters
• Photo Atlas of Biology
![Page 41: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/41.jpg)
Mitosis in the Onion Root Tip
• Today’s lab exercises
– examine the tip of an onion root
– find and identify the 4 different phases of mitosis.
• Root tips are useful material because the cells are frequently dividing as the root grows.
![Page 42: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/42.jpg)
Growth and Mitosis in Onion Root Tips
A) Examine onion (Allium) root tip under low power objective (10x)– answer questions
B) Examine same slide under high power objective (40x)– follow instructions
![Page 43: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/43.jpg)
Meiosis: The basis of Genetic Inheritance and Sexual
Reproduction
• Mechanics of Meiosis– Answer questions
• use instructional materials available– video: Mechanics of Meiosis
– posters
– Photo Atlas of Biology
![Page 44: Genetics--Nuclear Division & Inheritance Mitosis & Meiosis](https://reader036.vdocument.in/reader036/viewer/2022081505/55156a6855034691418b4e50/html5/thumbnails/44.jpg)
Meiosis and Gamete Formation in Lily Anthers
• Observe first and second meiotic division in demonstration slides
Note:
•DO NOT move the slides out of position
•Use only FINE focus