Session 6 - Introduction To Embryology And Gametogenesis Flashcards
What happens during interphase in mitosis?
- DNA replicates
- Chromatin network coils, contracts and condenses to prepare for prophase
What happens during prophase in mitosis?
- Chromosome are present
- Cytoskeleton breaks down
- Centrioles move to opposite poles
What happens during prometaphase in mitosis?
- Nuclear membrane breaks down
- Microtubules attach to centrioles to centromeres
What happens during metaphase in mitosis?
- Chromosomes align at the middle of the cell
What happens during anaphase in mitosis?
- Chromosome pairs split and sister chromatids move to opposite sides
What happens during telophase in mitosis?
- Chromatids uncoil and lengthen
- New membranes form
- Cytoplasm splits
What happens during cytokinesis in mitosis?
- A ring around centre shrinks and splits cell into two
- Each daughter cell has the same number of chromosomes as the parent cell
What happens during interphase in meiosis?
- DNA is replicated
What happens in prophase 1?
- Homologous chromosome align and pair up
- There is fusion of homologous chromosomes at the chiasma and there is a possibility of crossing over taking place which leads to genetic variation
What happens during prometaphase 1?
- Nuclear membrane disappears
- Microtubules attach centrioles to centromeres
What happens during metaphase 1?
- Chromosomes align at the equator and the law of independent assortments comes into effect
- Spindle apparatus form
What happens during anaphase 1?
Pairs of homologous chromosomes split and move to the opposite poles
What happens during telophase 1?
- New nuclear membrane forms
- Cytokinesis cleaves cell in 2
What happens during prophase 2?
- Chromatids condense
- Nuclear membrane disappears
- Centrioles move to opposite poles
What happens during metaphase 2?
Chromosomes align at the equator of the cell
What happens during anaphase 2?
Chromosomes split and sister chromatids move to the opposite poles
What happens during telophase 2?
Sister chromatids reach opposite poles and nuclear membrane forms.
Cytokinesis cleaves each cell into 2
What is the end result of meiosis?
- 4 non-identical daughter cells each with 23 chromosomes making them haploid cells.
What is cell trisomy?
When a cell has one extra chromosome
What is monosomy?
When a cell have one missing chromosome
What is non-disjunction?
Ineffective separation of chromosomes or chromatids during meiosis 1 or 2
What are the consequences and chromosomal abnormalities?
- Birth defects
- Spontaneous abortions
What are the 2 types of chromosomal abnormalities?
- Structural
- Numerical
What are the possible results of non-disjunction of sex chromosomes?
- XXX
- XXY or XXXY
- XO
- YO