Mitosis And Meiosis Flashcards
Cause of Down syndrome?
Non-disjunction during meiosis causing trisomy of chromosome 21.
Symptoms of Down syndrome
Delayed growth
Characteristic facial features
Mild intellectual disability
Arms of a chromosome
P (short) arm
And q (long) arm
What is a telomere?
Found at the end of chromosome. They are repeat sequences at the end of each chromosome/chromatid.
Four types of centromere and where they are
Metacentric - centromere at centre of chromosome
Submetacentric - centromere between the middle and end of chromosome
Acrocentric - centromere at end of chromosome (but still creating short and long arms)
Telocentric - centromere is the end of the chromosome (only one set of arms)
MSAT
Turner syndrome
One X chromosome is missing
Compare sister and non-sister chromatids
Sister - identical copies of genes (same alleles)
Non-sister - not identical (different alleles - derived from maternal and paternal genomes)
Mitosis
Examples of tissues that mitosis is necessary for?
Cell division that occurs in somatic cells, producing two identical daughter cells with the same chromosome content as parent cell.
Epidermis, mucosae, bone marrow, spermatogonia
Phases of cell cycle
G1 - metabolic changes prepare cell for division - cellular contents, besides DNA, duplicates
S - DNA synthesis replicates genetic material
G2 - metabolic changes assemble cytoplasmic materials necessary for mitosis/cytokinesis
M - mitosis (nuclear division)
(Interphase) - period between mitotic divisions
G0 - resting or quiescent phase
Phases of mitosis
Prophase - breakdown of nuclear membrane; spindle fibres appear; chromosomes condense
Prometaphase - spindle fibres attach to chromosomes; chromosomes condense
Metaphase - chromosomes align on metaphase plate
Anaphase - chromosomes divide; sister chromatids move to opposite poles
Telophase - nuclear membrane reforms; chromosomes decondense; spindle fibres disappear
Cytokineses - cytoplasm divides; parent cell becomes two daughter cells
Meiosis
Special type of cell division for germline cells. It produces four non-identical daughter cells with half the chromosome content of the parent cell.
Meiosis 1 - phases
Prophase 1 - nuclear membrane dissolves; chromosomes condense; crossing over of homologous chromosomes occurs, forming recombinant chromosomes
Metaphase 1 - spindle fibres form; pairs of chromosomes line up on metaphase plate;
Anaphase 1 - random assortment of chromosomes as they are pulled to opposite ends of cell
Telophase 1 - nuclear membrane reforms; chromosomes decondense
Cytokineses occurs
-> 2 daughter cells so far
Meiosis 2 - phases
Prophase 2 - chromosomes condense; nuclear membrane dissolves
Metaphase 2 - pairs of chromatids line up at metaphase plate
Anaphase 2 - random assortment of non-sister chromatids; chromatids pulled to either end of cell
Telophase 2 - nuclear membrane forms; chromatids decondense
Cytokineses occurs
-> four non-identical haploid daughter cells
What are the consequences of meiosis?
Maintain constant number of chromosomes from generation to generation
Generates genetic diversity, from random assortment and crossing over
What is meiosis in males called and how long does it take?
What does it produce?
Spermatogenesis
60 days
Four mature sperm
What is meiosis on females called and how long does it take?
What does it produce?
Oogenesis
12-50 years
1 ovum and 3 polar bodies
Define non-disjunction
Unequal distribution of chromosomes due to failure to separate properly during meiosis.
Define aneuploidy
What is it caused by?
The condition of having an abnormal number of chromosomes in a haploid organism
Caused by non-disjunction in meiosis or mitosis.
Name 3 human diseases that non-disjunction during meiosis can lead to.
Down syndrome
Patau syndrome
Edwards syndrome
