14 - Meiosis Flashcards
Heredity
the transmission of traits from one generation to the next
Gametes
Reproductive cells, such as sperm and eggs
Somatic cells
All body cells EXCEPT reproductive cells (gametes)
Asexual reproduction
A single individual (like yeast or amoeba) is the sole parent and passes copies of all its genes to its offspring WITHOUT the fusion of gametes
Sexual production
Two parents give rise to offspring that have unique combinations of genes inherited from the two parents
Sex chromosomes
X and Y chromosomes
Autosomes
chromosomes that are not involved in determining a person’s sex
Ploidy
refers to the number of sets of chromosomes in a cell
Diploid
any cell with two chromosomes sets (2n)
Haploid
single set of chromosomes (n)
Zygote
resulting fertilized egg, diploid cell
Fertilization
the union of gametes, culminating in fusion of their nuclei
Meiosis
special type of cell division that produces cells with half the chromosome of the parent cell. Occurs in cells of testes and ovaries in humans
Meiosis 1
Homologs are separated
Prophase 1
Duplicated homologous chromosomes pair up and exchange segments (2n=6)
Metaphase 1
chromosomes line up by homologous pairs
Anaphase 1
The two homologous chromosomes of each pair separate
Telophase 1 and cytokinesis
Two haploid cells form; each chromosome still consists of two sister chromatids
Meiosis 2
sister chromatids are separated
prophase 2
- spindle apparatus forms
- chromosomes, each still composed of two chromatids associated at the centromere. are moved by MTs toward metaphase 2 plate
Metaphase 2
- chromosomes align at metaphase plate
- due to crossover in meiosis 1, sister chromatids are not genetically identical
- kinetochores of the sister chromatids attach to MTs from opposite poles, preparing for their separation
Anaphase 2
Breakdown of proteins holding sister chromatids together at centromere allows chromatids to separate and move toward opposite poles
- each chromatid has now become an individual chromosome
Telophase 2
- nuclei form, chromsomes begin decondensing and cytokinesis occurs
- four daughter cells are produced, each with a haploid set of (unduplicated chromosomes)
- Four daughter cells are genetically distinct from one another and from the parent cell
Chromosomes
structures that carry genetic information
Sister chromatids
joined copies of the original chromosome
Homologous chromosomes
(or homologs) are pairs of chromosomes that have the same genes in the same order, but they may have different versions of those genes
Duplicated chromosomes
chromosomes that have been copied to prepare for cell division
Chromatin
material consisting of DNA and proteins; visible in a dividing cell as individual condensed chromosomes
Crossing over
is a process that happens during meiosis where homologous chromosomes exchange pieces of genetic material
Synapsis
the process during meiosis where homologous chromosomes pair up tightly
Chiasmata
(singular, chiasma) where crossovers have occurs
Independent assortment
is a process during meiosis where the pairs of homologous chromosomes are randomly distributed to the daughter cells
Random fertilization
refers to the idea that any sperm cell can fertilize any egg cell
Nondisjunction
a mishap, in which the members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2
Aneuploidy
an abnormal chromosome number
Monosomy
(2n-1) a type of aneuploidy where a cell is missing one chromosome from a pair. Turner syndrome is a cause of this.
Trisomy
(2n+1), a condition where a cell has an extra chromosome, resulting in 3 copies instead of 2. This can lead to down syndrome.
