Lecture 17 Gametogenesis at the Chromosomal level Mitosis
- Slides: 26
Lecture 17 Gametogenesis at the Chromosomal level: Mitosis and Meiosis Animal Science 434 John J. Parrish
Definitions Chromosome - linear DNA molecule Centromere - special region of spindle attachment Homologous Chromosomes • Have the same kind of genes in the same order • 1 from father, 1 from mother Sister chromosomes (X, Y)
Definitions Homologous Chromosomes DNA Replication Chromatids A chromatid pair has an identical sequence of DNA
Cell Cycle M Go MPF MPF G 2 MPF MPF Interphase S G 1
M - Phase l l l Prophase Metaphase Anaphase Telophase Cytokinesis
Grand Scheme Mitosis Meiosis 2 N 2 N Replicate Division 2 N 2 N Division N N
Go Mitosis G 1 M - phase Prophase S G 2 Chromatids Metaphase Homologous chromosomes pair along side of each other Centromere Spindles (microtubules) MPF high
Mitosis Anaphase MPF decreases Chromatids pull apart
Mitosis Anaphase MPF decreases Chromatids pull apart
Mitosis Telophase Chromosomes pull apart further Microtubules Disappears Nuclear envelopes reform
Mitosis Telophase Chromosomes pull apart further Microtubules Disappears Nuclear envelopes reform
Mitosis Cytokinesis
Mitosis Cytokinesis 2 N 2 N
Meiosis 2 N Go G 1 Primary Spermatocyte Primary Oocyte 4 N S G 2 Prophase
The Five Phases of Meiotic Prophase 4 N Leptotene • Chromosomes condense Zygotene 4 N • Homologous chromosomes begin to pair • Bivalents
The Five Phases of Meiotic Prophase Pachytene 4 N • Pairing is completed • Crossing over of homologues occur Diplotene/Dictyatene • Oocytes stop here before puberty 4 N • Homologous chromosomes pull apart but remain attached at crossover points (chiasma) • RNA synthesis is possible
The Five Phases of Meiotic Prophase Diakinesis • RNA synthesis stops 4 N Homologous chromosomes linked at chiasma Chromatids linked at centromere • The chromatids become visible Crossover (chiasma) Centromere
Metaphase I of Meiosis 4 N Homologous chromosomes move toward opposite poles and pair across from one another Homologous chromosomes held together via chiasma
Anaphase I of Meiosis 4 N Recombination as a result of crossing over
Telophase I 4 N
Telophase I 4 N Cytokinesis 2 N 2 N Secondary Spermatocyte or Secondary Oocyte
Meiosis Metaphase II 2 N 2 N 2 N No Replication Rest Same As Mitosis 2 N Oocytes stop here until fertilized
Meiosis Anaphase II This does not exist for oocyte Telophase II Cytokinesis N N 2 N Spermatid N 2 N N
Abnormalities l Anueploidy – Not an exact multiple – Hyper or hypo – Example: 2 N - 1 or 2 N + 1 l Euploidy – Exact multiple of haploid – Example: 3 N, 4 N, etc. l Non-disjunction – Causes aneuploidy and occurs in meiosis – Example: N - 1 or N + 1
Abnormalities Non-disjunction XXYY XY XXYY X XXYY O XX YY XY XY O O XX O Y Y XXY XO XO XXX XO XY XY Kleinfelter’s Syndrome Turner’s Syndrome
Down’s Syndrome l Non-disjunction l Extra copy of chromosome 21 l Probability increases with age – Age 35, 2 per 1000 births – Age 40, 6 per 1000 births – Age 45, 16 per 1000 births
- Bioflix activity: mitosis -- events of mitosis
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- Syndrome triple x
- Chromosomal mutation deletion
- Deletion chromosomal mutation
- Cri du chat chromosomal abnormalities
- Mutations are any mistake or change in the...
- Cri du chat chromosomal abnormalities
- Chromosomal crossover
- Chromosomal mutation images
- Chromosomal mutation
- Chapter 15 the chromosomal basis of inheritance
- Chromosome numbers
- Chromosomal abnormalities miscarriage
- Chromosomal mutation
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- The chromosomal basis of inheritance chapter 15
- Ap biology chapter 15
- Introductiondefinition
- Substitution mutation
- Mizzz foster
- Function of
- Chromosome deletion definition
- Duplication chromosomique
- Chromosomal mutation
- Chromosomal mutation
- Chromosomal mutations