Everything You Need To Know Bout Meiosis Flashcards
(25 cards)
What is Meiosis?
A type of cell division that produces four haploid daughter cells
💁🏻♀️Recall: Haploid cells contain half the number of chromosomes of the parent cell.
Where does Meiosis occur?
Reproductive cells only
In humans & animals: testes (males) ovaries (females)
In plants: pollen(anther) ovule(ovary)
Importance of Meiosis #1
It results in formation of cells that are not identical
This ensures that each daughter cell has a different combination of genes
This leads to variation
Variation is a survival advantage as it allows species to adapt to changing environments.
Importance of Meiosis #2
Ensures that the chromosome number for the species is restored after fertilization and formation of zygote
Importance of Meiosis #3
Some genetic traits are transferred from parent to offspring. This means a parent of inferior quality can produce offspring of superior quality.
Homologous
2 pieces of DNA within a diploid organism that carries the same genes, one from each parent.
Homozygous
Homozygous describes a gene with identical alleles
Heterozygous
Describes genotype with different or varying alleles
Allele
One or more forms of a gene
Genotype
Composition of genes within cell
Phenotype
Observable characteristics of organism as a result of its genotype and environment.
Meiosis Phases
2Cycles: Meiosis 1 and Meiosis 2
Interphase [Meiosis 1] Prophase 1 Metaphase 1 Anaphase 1 Telophase 1
[Meiosis 2] Prophase 2 Metaphase 2 Anaphase 2 Telophase 2-> Cytokinesis
Interphase
G1 phase- cell grows
S phase- copies all chromosomes
G2 phase- prepares for division
Prophase 1
Chromosomes begin to condense
Each chromosome lines up with homologous partner so that meet up at corresponding positions along their full length.
A chiasma forms between adjacent chromatids of different homologs
Breakage and rejoining at the chiasma results in recombinant chromatids
The DNA is broken at the same spot on each homologous and reconnected in criss-cross pattern so they exchange part of their DNA.(crossing over- process where homologous chromosomes exchange parts)
Metaphase 1
These homologous pairs line up along the equator
Orientation for each pair is random
Anaphase 1
Homologues are pulled apart
Move towards opposite sides of cell
Sister chromatids remained attached and don’t come apart
Telophase 1
Two cells each with the haploid number are formed
Review of Meiosis 1
Start with ONE parent cell
Homologous chromosomes pair up
Crossing over occurs to exchange gene segments on chromosomes(recombination)
Homologous chromosomes separate and move to ends of cell
Cell divides
End with TWO daughter cells
Meiosis 2
Cells move from meiosis 1 to 2 without copying their DNA.
They are haploid cells with one chromosome from each homologous pair
The chromosomes still consist of 2 sister chromatids
Period between meiosis 1 and 2 known as interkinesis
Prophase 2
Chromosomes in each cell condense
Nuclear envelope breaks down
Centrosomes move apart
Spindle forms between them and begin to capture chromosomes from opposite poles of cell
Metaphase 2
Chromosomes line up along equator
Anaphase 2
Sister chromatids separate
They are pulled away from each other at different ends of the cell
Telophase 2
Nuclear membranes form around each set of chromosomes.
Chromosomes unravel
Cytokinesis
Cytokinesis splits the chromosome sets into new cells
