Heredity - Unit 6 Flashcards
What are homologous chromosomes?
The two copies of each autosome. (any chromosome that is not a sex chromosome.)
What is a diploid?
Cells with two copies of each chromosomes are diploid.
What is the abbreviation of Diploid?
Diploid is abbreviated as 2n.
In humans what is the 2n number?
In humans, the 2n number is 46.
What cells are haploid?
Sperm and egg cells are haploid.
What is the abbreviation of Haploid?
Haploid is abbreviated to n
What is the Haploid number in humans?
In humans, the n number is 23.
What results in a 2n new organism?
When a n sperm cell unites with a n egg cell, a 2n new organism results.
When does Meiosis occur?
Occurs during the formation of gametes(sperm and egg cells).
What happens during Meiosis?
The number of chromosomes is reduced by 1/2.
Diploid cell —> 4 haploid cells
How many steps does Meiosis occur in?
Meiosis occurs in 2 steps:
- Meiosis I
- Meiosis 2
What does Meiosis 1 result in?
Meiosis 1 results in 2 haploid daughter cells with duplicated chromosomes
What happens in Meiosis 2?
Haploid daughter cells from Meiosis I divide, resulting in 4 haploid gametes with un-doubled chromosomes.
What happens before Meiosis 1?
Interphase
What 3 things happen during Interphase?
- Cells increase in size
- Cells synthesize (make) proteins
- Cells replicate DNA
What are the 4 stages of Meiosis 1? (PMAT)
- Prophase 1
- Metaphase 1
- Anaphase 1
- Telophase 1
What happens during prophase 1?
Chromosomes condense, nuclear envelope breaks down, spindle forms.
When does Synapsis occur?
Prophase 1
What happens during Synapsis?
Homologous chromosomes come together to form a tetrad.
What is a Tetrad?
Tetrad is two chromosomes or four chromatids (sister and non-sister chromatids).
What happens during cross over?
Portions of chromatids break off and exchange places with corresponding portions of adjacent chromosomes.
What is mixed during cross over?
Mixes DNA from maternal and paternal chromosomes.
What happens during Metaphase 1?
Tetrads align on the metaphase plate.
What happens during Anaphase 1?
Homologous chromosomes separate and move towards the poles.
Sister chromatids remain attached at their centromeres.
What happens in Telophase 1?
New nuclear membranes are formed, chromosomes uncoil, and spindle breaks down.
What happens during Cytokinesis?
During Cytokinesis two haploid daughter cells are formed. (But they have duplicated chromosomes)
What happens during Anaphase 1?
Sister chromatids separate and they move towards the poles
What 3 things happen during telophase 2?
- Nuclei form
- Nucleolus reappears
- Spindle disappears
How many haploid daughter cells are produced during telophase 2?
Four haploid daughter cells are produced.
