Biology Chapter 7
Explain fertilization...
Fertilization involves the fusion of two haploid gamete cells, each containing a single set of n chromosomes, to give rise to a diploid zygote cell containing two sets of n chromosomes.
What are haploid cells?
Haploid cells have only one copy of each chromosome. Gametes are haploid.
In single-celled organisms, reproduction and cell division are equivalent. However, this is not true in multicellular organisms. Why not?
In single-celled organisms, every cell division results in a new individual organism. In multicellular organisms, cell division is required to generate many types of specialized somatic cells in the adult, and these cells are not involved in reproduction. Relatively few cell divisions give rise to cells that will undergo meiosis to produce gametes for reproduction.
What is DNA replication?
The dividing cell's genetic material (DNA) must be duplicated so that each of the two new cells will have a full complement of genetic information.
What is DNA segregation?
The replicated DNA must be distributed appropriately to the two daughter cells, so that each receives a copy of every chromosome.
What are gametes?
a reproductive cell of an animal or plant female gametes= egg cells male gametes= sperm both female and male gametes are haploid cells!
What are mutations?
alterations in DNA sequence
What is a somatic cell?
any cell in the body of a multicellular organism that is not specialized for reproduction
What are the 2 types of asexual reproduction?
binary fission and mitosis
Are somatic cells diploid or haploid?
diploid
What are the 3 different examples of the sexual life cycle?
diploid zygote immediately undergoes meiosis and essentially all of the life cycle is haploid haploid gametes immediately undergo fertilization and essentially all of the life cycle is diploid life cycles in which the organism spends significant time in both haploid and diploid stages all 3 involve meiosis and fertilization
Are gametes diploid or haploid?
haploid
What do all sexual life cycles involve?
meiosis and fertilization
What is the chromosome number for a diploid zygote? What is the chromosome number for a haploid gamete?
n= number of different chromosomes diploid zygote- 2n haploid gamete- n
What is an example of symmetrical cell division?
paramecium
What reproduces through mitosis?
single celled eukaryotes
What reproduces through binary fission?
single celled prokaryotes
What is a homologous pair?
the chromosomes in each pair are nearly identical in length and DNA sequence
What is an example of asymmetrical cell division?
yeast
What 4 events have to happen in order for any cell to divide
1) cell division signals 2) DNA replication 3) DNA segregation 4) Cytokinesis
What does mitosis produce?
2 genetically identical daughter cells
What does binary fission produce?
2 genetically identical daughter cells from a parent cell
What is cytokinesis?
The cytoplasm must divide to form the two new cells, each surrounded by a cell membrane and a cell wall in organisms that have one.
In terms of the genetic diversity produced, what is the main difference between sexual and asexual reproduction?
Asexual reproduction produces offspring that are clones of one another, meaning they are essentially identical genetically. Sexual reproduction involves fusion of haploid gametes, which are produces by meiosis and are genetically variable. The resulting offspring are thus highly variable genetically.
What are diploid cells?
Cells that have two sets of chromosomes. Human body cells are diploid.
Explain meiosis...
Meiosis involves the production of haploid cells from a diploid cell. In between these two events, there may be many mitotic cell divisions in either the diploid stage (a diplontic life cycle), the haploid stage (a haplontic life cycle), or both stages (a haplo-diplontic life cycle).
Describe the 2 events that characterize a sexual, meiotic, life cycle.
Meiosis is a cell division in a diploid cell that produces haploid cells. Fertilization is the fusion of haploid gamete cells, resulting in a diploid zygote.
What are cell division signals?
One or more signals are required to initiate cell division. The signals may originate from either inside or outside the cell.
What is the difference between symmetrical and asymmetrical cell division?
Symmetrical: a mother cell divides and produces two daughter cells that are essentially identical and can't be distinguished Asymmetrical: mother and daughter cells can be distinguished from one another by size or their functions