Mitosis And Meiosis Flashcards
Chromosome structure
Each replicated chromosome consists of 2 chromatids
Each replicated chromosome contains 2 identical DNA molecules
One chromosome = one DNA molecule before replication
After replication one chromosome -= 2 DNA molecules 2 chromatids
P arm = short
Q arm = long
Metacentric
Equal sized p and q arm
Submetacentric
P is shorter than q
Acrocentric
P arm is almost non existent
Telocentric
No p arm
What are homologous chromosome
They have the same DNA sequence and have the same genes located on them
Genes on homologous chromosomes maybe be different varients- alleles
Mitosis
Cell division for somatic cells
Production of 2 identical daughter ells
-with some chromosome content as parental cell
50 mitosis rounds during early development
Mitotic growth also necessary for some tissue
-epidermis , mucosae,bone marrow and spermatogonia
Prophase
Spindles appear
Chromosome condense
Prometaphase
Spindle attach to chromosome
Chromosomes condense further
Metaphase
Chromosome align
Anaphase
Centromeres divide
Sister chromatids move to opposite poles
Telophase
Nuclear membrane reforms
Chromosome decondense
Spindle fibres disappear
Cytokinesis
Cytoplasm divides
Parent cell becomes 2 daughter cells with identical genetic information.
No disjunction
Missegregtion of chromosomes
Leads to aneuploidy- unusual amount of chromosome
Meiosis
Special cell division
Chromosome number reduced- one round of replication and 2 rounds of division
Consequences of meiosis
Generation of genetic diversity
- crossing over of genetic material in prophase 1
- random assortment of chromosomes in metaphase 1
Maintaining constant chromosome number from generation to generation
What is the different between meiosis 1 ans 2
Homologous pairs of chromosomes lien up ad separate in meiosis 1 and in meiosis 2 chromosomes line up and chromatids separate
Spermatogenesis
Cell division to produce male gametes
When a spermatogonium undergoes meiosis it becomes a spermatocytes
From spermatocyte (2n) to 4 sperm (n) in approximately 60 days
Oogenesis
Cell division to produce female gametes
The oocyte arrests into meiosis 1 during prophase 1 and stays thee until puberty and there is the menstrual cycle
Every time we have the menstrual cycle - the oocyte is released from the arrest in prophase 1
From 1 oocyte (2n) to 1 egg (n) plus 3 polar bodes in 12-50 years
what is nondisjunction
missegregation of chromosomes
leads to aneuploidy
which leads to monosomy- 1 chromatid
trisomy- 3 chromatids
