Meiosis The Diploid Cell with 2 sets of
- Slides: 33
Meiosis
The Diploid Cell with 2 sets of chromosomes Contains chromosomes for each homologous pair Somatic Cells = Body Cells: Diploid All human cells except sex cells are diploid Fertilization restores the diploid number 2 n, where n is the number of chromosomes an individual has Humans: n = 23, 2 n = 46
The Haploid Cell containing one of each kind of chromosome Ex. sperm and egg cells (gametes) 1 set of chromosomes Half the number of chromosomes of diploid n Sperm + Egg = Zygote
Haploid = one of each kind Diploid = two of each kind + • 2 n = diploid or n = haploid
• Mitosis vs. Meiosis Mitosis: t = two: Diploid 2 n=46 • Meiosis: o = one: Haploid • n= 23
Meiosis Gametes are produced in specialized body cells Sperm and Egg Cells 2 divisions: Meiosis I and Meiosis II Meiosis occurs in sex cells, not body cells 4 daughter cells Each cell has half the chromosomes of the parent
Meiosis I Interphase occurs: the cell grows and DNA replicates Meiosis I begins Original cell produces two new cells Like Mitosis
Prophase I DNA Coils tightly into chromosomes Spindle fibers appear Each chromosome lines up next to the homologue Synapis occurs: pairing of homologous chromosomes Tetrad: Each pair of homologous chromosomes
Crossing Over: why we do not look exactly like our parents. • Portions of the chromatid breaks off and attaches to adjacent chromatids on the homologous chromosome Permits the exchange of genetic material between maternal and paternal chromosomes • Occurs during Prophase
Genetic Recombination Crossing over produces a new mixture of genetic material
Causes of Variation Chromosomes are assorted randomly Crossing over may occur Cells do not have identical genetic info as each other or the parent + more chance of survival and evolution - mistakes more likely
Metaphase I Tetrads line up randomly along the mid-line Spindle fibers attach to centromeres
Anaphase I Homologous chromosomes move to the opposite poles Random separation or Independent Assortment results in separation of maternal and paternal chromosomes.
Telophase I Chromosomes reach opposite ends of cell Cytokinesis begins Cell is now haploid
Meiosis II Occurs in each cell formed in Meiosis I Interphase does not occur again
Prophase II Spindle fibers form and move the chromosomes to the mid-line of the dividing cell
Metaphase II Chromosomes move to the midline of the dividing cell facing opposite poles of the dividing cell
Anaphase II Chromatids separate and move to opposite poles of the cell
Telophase II Nuclear membrane forms around the chromosomes in each of 4 new cells
Cytokinesis II Cytoplasm divides Cell membrane closes off
End Result: Four new cells that contain half of the original cells number of chromosomes Creates sex cells = gametes
What exactly is a gamete? Formed by meiosis Haploid reproductive cells In humans, meiosis occurs in the testes and ovaries
Meiosis Animation • Meiosis Animation
Why do we need haploid gametes? Female gamete 23 • EGG Male gamete 23 SPERM
Fertilization restores the diploid number 1 n fertilization 1 n meiosis 2 n 2 n Mitosis and cell growth 2 n
Mitosis vs. Meiosis • Mitosis vs. Meiosis Animation
Nondisjunction • • Failure of homologous chromosomes to separate properly during meiosis. Both chromosomes of a homologous pair move to the same pole of the cell. • 1 gamete has an extra chromosome • • Or 1 gamete is missing a chromosome
Nondisjunction Animation • Nondisjunction Animation
Chromosome Pop Quiz! • Chromosome: • Rod-shaped coiled and compact DNA • “Colored body” • Found in the nucleus • Looks like X • Humans have 23 pairs of chromosomes • Female = XX, Male = XY (23 rd pair)
Trisomy: Extra Chromosomes • Trisomy 13: Patau’s Syndrome • Trisomy 21: Down’s Syndrome • XXX: Trisomy X • XYY: Jacob’s Syndrome • XXY: Klinefelter’s Syndrome
Monosomy: Missing Chromosomes • • • Most do not survive Turner XO : develop as girls, but infertile OY: lethal
- Diploid contains 2 sets of chromosomes
- Are diploid cells produced in meiosis
- Why is meiosis important?
- What is the difference between somatic and gamete cells
- Mitosis and meiosis escape room answer key
- Number of divisions in mitosis
- Diploid cell
- Iaaba
- Anaphase meaning
- Chromosome sets (=n) in mitosis and meiosis
- Meiosis and genetic variation answer key
- Difference between meiosis 1 and 2
- Mitosis vs meiosis
- Chapter 10 section 1: meiosis
- Concept mapping chapter 10 meiosis 1 and meiosis 2
- Meiosis 1 vs meiosis 2
- Meiosis prophase 2
- Four chromosomes going through mitosis
- Egg cell meiosis
- Cell division mitosis and meiosis
- Meiosis 1 and 2 diagram
- Meiosis
- Concept map mitosis
- Genotypic ratios
- Diploid vs haploid number
- If a diploid egg was produced by mitosis
- What is diploid
- Primary oocyte haploid or diploid
- Parthenogenese
- Number of chromosomes in animals and plants
- Gametes
- Diploid cells
- Primary oocyte haploid or diploid
- Haploid vs diploid