Chapter 10 Flashcards
describe the cell cycle
G1 phase - cells grows, produces new proteins. S phase - cell makes exact copy of it’s DNA G2 phase - cell grows again M phase - cell divides to 2 daughter cells
Summarize Interphase
period between cell divisions, coversG1-G2 phases DNA doubles
Summarize prophase
cell nucleus disappears, two centrioles become visible, nucleolus disappears, nuclear membrane breaks down, chromatin threads tightly coil and are now chromosomes
Summarize metaphase
Chromosomes meet at the center of the cell, each centromere is attached to spindle fiber coming from centrioles
Summarize Anaphase
Chromosomes separate into chromatids, spindle fibers pull them to opposite poles of cell
Summarize telophase
Two sets of chromosomes form tight groups, nuclear membrane forms around each group and nucleolus appears, spindle fibers disappear, chromosomes uncoil to form chromatids.
What is cytokinesis
Separation of the cytoplasm, a furrow forms and deepens until it splits the cell
What is differentiation
Process by which cells become specialized; this occurs under the right conditions
What are stem cells
Cells that are not specialized and can divide repeatedly by mitosis
Name and describe the 3 types of stem cells
Totipotent stem cells-ability to form embryos and the membranes that surround and nourish it
Pluripotent-capable or giving rise to most tissue in organism
Multipotent-give rise to cells with specific function
What is the haploid number
Half the number of chromosomes, 23, daughter cells of meiosis have this number
What are homologous chromosomes
pairs of chromosomes that are identical in shape and carry genetic information that influences the same characteristics.
How many chromosomes does a gamete have
Haploid, 23
What happens during prophase I (meiosis)
chromosomes become visible as
long threads, each has already undergone DNA replication, consists of a pair of chromatids, homologous pairs form, DNA tightly coils. Meanwhile, spindles are forming at poles of cell
Describe metaphase I (meiosis)
homologous chromosomes are arranged at middle of cell and attach to spindle fibers
Describe anaphase I
homologous chromosomes separate (one member of each pair consisting of two chromatids), 23 chromosomes move to each pole
Describe telophase I
chromosomes decondense and nuclear membrane reforms. Cytokinesis then occurs with cytoplasm splitting and producing two separate cells
Describe the second meiotic division
New spindles form, chromosomes meet at middle, spindles pull chromatids to poles of cell (now chromosomes), nuclear membranes form and cytoplasm begins to split. Four total daughter cells are made
What is the main difference between mitosis and meiosis
mitosis produces identical diploid cells for growth and repair within the tissues,
whereas meiosis produces haploid gametes for sexual reproduction.
Do homologous chromosomes pair up in meiosis or mitosis?
They pair up in meiosis but not mitosis
Briefly outline the separation occurrences during first meiotic division and second meiotic division
At first meiotic division, members of homologous pairs separate so that new cells get a haploid set of chromosomes. At second division, chromatids separate, giving four haploid cells.
What is crossing over (meiosis)
Where chromatids may break, cross and exchange segments during homologous pairing (occurs during prophase I). This creates new combinations of genes
What is the chiasma
The point at which two chromatids cross
What is recombination
A new combination of alleles along the chromosome resulting from crossing over
