section 11.4. chromosome number an organism with 2 parents must inherit a single copy of every gene...
TRANSCRIPT
![Page 1: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/1.jpg)
Section 11.4
![Page 2: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/2.jpg)
Chromosome Number
• An organism with 2 parents must inherit a single copy of every gene from each parent.
• When gametes are made, the 2 sets of genes must be separated so that each gamete has 1 set of genes.
![Page 3: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/3.jpg)
Chromosome Number
• Diploid Cells (2)– When a cell has both sets of homologous
chromosomes.• Body cells
• Haploid Cells (1)– When a cell has one set of chromosomes• Gametes
![Page 4: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/4.jpg)
Phases of Meiosis
• Meiosis is when the number of chromosomes is cut in half.
• Has two divisions.
![Page 5: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/5.jpg)
Meiosis I
• Chromosomes replicate prior to meiosis I.• Each chromosome has 2 sister chromatids,
joined at the center by a centromere.
![Page 6: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/6.jpg)
Meiosis I• ***Prophase I– Each replicated chromosome pairs with its
homologous chromosome.– Pair forms a tetrad– Crossing-over occurs between tetrads.• Makes new combos of alleles.
![Page 7: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/7.jpg)
Meiosis I
• Metaphase I: paired homologous chromosomes line up across the middle.
• Anaphase I: chromosomes pulled to opposite ends of the cell.
• Telophase I:nuclear envelope reforms • Cytokinesis I: cytoplasm divides, forms 2
diploid cells.
![Page 8: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/8.jpg)
Meiosis I
![Page 9: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/9.jpg)
Meiosis II
• Each daughter cell undergoes a second meiotic division.
• Chromosomes are NOT replicated before this.
![Page 10: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/10.jpg)
Meiosis II
• Prophase II– Chromosomes become visible– DO NOT form tetrads• Homologous pairs were separated during meiosis I.
![Page 11: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/11.jpg)
Meiosis II
• Metaphase II, Anaphase II, Telophase II, Cytokinesis II.
• Stages just like meiosis I.• Results in 4 haploid cells
![Page 12: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/12.jpg)
![Page 13: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/13.jpg)
Gametes to Zygotes
• 4 haploid cells are gametes– Sperm in males– Eggs in females
• When an egg is fertilized (by a sperm), it is called a zygote.– Zygote forms a new organism
![Page 14: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/14.jpg)
Comparing Meiosis and Mitosis
• Replication and Separation of Genetic Material– Mitosis: each daughter cell has one complete set of
chromosomes. (Body Cells)– Meiosis: daughter cells contain 1/2 the number of
chromososmes. (Gametes)
![Page 15: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/15.jpg)
Comparing Meiosis and Mitosis
• Changes in Chromosome Number– Mitosis: Normally doesn’t change chromosome #• Diploid
– Meiosis: Chromosome number is halved• Haploid
![Page 16: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/16.jpg)
Comparing Meiosis and Mitosis
• Number of Cell Divisions:– Mitosis• 2 cells; genetically identical; diploid
– Meiosis• 4 cells; genetically different; haploid
![Page 17: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/17.jpg)
Gene Linkage
• Thomas Morgan used fruit flies.• He determined that genes located on the
same chromosome segregate together.
![Page 18: Section 11.4. Chromosome Number An organism with 2 parents must inherit a single copy of every gene from each parent. When gametes are made, the 2 sets](https://reader035.vdocuments.us/reader035/viewer/2022062305/5697bfb51a28abf838c9d960/html5/thumbnails/18.jpg)
Gene Maps
• If genes are farther apart, the more likely it is that they will cross-over.
• If genes are close together, cross-overs are rare.
• Use frequency of crossing-over to determine distance.