Mitosis
What is the main purpose of mitosis?
Growth, repair, and replacement of cells.
What is the main purpose of meiosis?
To produce haploid reproductive cells.
What does diploid (2n) mean?
A cell has two sets of chromosomes.
What type of reproduction generally requires only one parent?
Asexual reproduction.
Which cell type lacks a membrane-bound nucleus?
Prokaryotic.
How many daughter cells result from mitosis, and how do they compare genetically?
Two genetically identical daughter cells, assuming no mutations.
How many cells are produced after meiosis II?
Four haploid cells.
What does haploid (n) mean?
A cell has one set of chromosomes.
What is binary fission?
A form of asexual reproduction in which one prokaryotic cell divides into two cells.
Name two structures found in eukaryotic cells but not prokaryotic cells.
A nucleus and membrane-bound organelles such as mitochondria.
During which phase of mitosis do sister chromatids separate?
Anaphase
What is the difference between what separates in anaphase I and anaphase II?
Homologous chromosomes separate in anaphase I; sister chromatids separate in anaphase II.
An organism has 18 chromosomes in its body cells. How many are in its gametes?
9
What happens during fertilization?
Two haploid gametes fuse to form a diploid zygote.
A diagram shows one cell dividing twice to produce four cells. What process is shown?
Meiosis.
A skin cell has 24 chromosomes. How many chromosomes will each daughter cell have after mitosis? Explain.
24. Mitosis maintains chromosome number.
What is a tetrad, and during which stage does it form?
A paired set of homologous duplicated chromosomes, containing four chromatids, formed in prophase I.
If a sperm cell has 12 chromosomes, how many chromosomes would the resulting zygote normally have?
24, assuming the egg also contains 12.
Explain one advantage of sexual reproduction over asexual reproduction.
Sexual reproduction produces genetic variation, which may help populations adapt to changing conditions.
Describe the difference between homologous chromosomes and sister chromatids.
Homologous chromosomes have genes for the same traits, one from each parent; sister chromatids are duplicated copies of one chromosome.
Explain how spindle fibers help ensure that daughter cells receive chromosomes during mitosis.
They attach to chromosomes and help separate sister chromatids toward opposite poles.
Why is there no second round of DNA replication between meiosis I and II?
The chromosomes are already duplicated, and a second replication would interfere with producing haploid cells.
An organism has 30 chromosomes in its liver cells. Predict the chromosome numbers in its skin cells, gametes, and daughter cells after mitosis.
Skin cells: 30; gametes: 15; daughter cells after mitosis: 30.
Explain how crossing over and independent assortment produce genetically different gametes.
Crossing over exchanges DNA between homologous chromosomes; independent assortment distributes maternal and paternal homologs into gametes in different combinations.
Explain three differences between mitosis and meiosis, including the processes and their final products.
Mitosis has one division vs. two in meiosis; produces two cells vs. four; maintains chromosome number and usually identical cells vs. haploid genetically different cells.