Chromosomes Flashcards
Define Cells
Cells are the structural and functional unit of life.
define Cytokinesis
Cytokinesis is defined as the division of the cytoplasm of a cell
In what stage of karyokinesis is the shape and size of a chromosome best seen?
Metaphase
Define Crossing Over?
It is the process of exchange of genetic material between non-sister chromatids of the homologous chromosomes . it occurs during meiosis
What is karyokinesis?
it is the division of the nucleus of the cell.
What is mitosis?
It is the division of the cell into two identical daughter cells with each cell having the same number of chromosomes as the parent cell.it occurs in somatic (body) cells. aka equational divison.
What is meiosis?
Meiosis occurs in the reproductive cells to produce the gametes. In meiosis the chromosome number is reduced to half. aka reductional division. It occurs in germ cells or reproductive cells.
What is Synapsis?
During meiosis the pairing between the homologous chromosomes is called synapsis and the pair is called bivalent.
What are the two phases of the cell cycle?
The Interphase and the mitotic phase (m1 phase )
What are the three phases of Interphase?
- First Growth Phase : Cells grows to the same size as parent cell. RNA and proteins are synthesized for Dna replication.
- Synthesis Phase : Replication of DNA takes place. chromosomes are duplicated.
- Second Growth Phase: More RNA and Proteins are Synthesized. (pre-mitotic phase) increase in volume of nucleus.
What are the stages of mitosis?
- Karyokinesis
Prophase
Metaphase
Anaphase
Telophase - Cytokinesis
How many chromosomes do humans have?
46 (23 pairs)
What are the two types of chromosmes?
- Autosomes - 44
- Sex Chromosomes or Allosomes - 2
What are the 4 types of Chromatids on the basis of the centromere?
- Telocentric
- Acrocentric
- Submetacentric
- Metacentric
Define Gene
Genes are the specific sequence of nucleotides on a chromosome that encode particular proteins which express in the form of some particular feature of the body .
Who proposed the double helical structure of DNA?
Watson and Crick. Nobel Prize 1962
descibe nucleotide?
pentose (sugar)
phosphate (above 2 form backbone of DNA molecule)
Nitrogenous base joined to complimentary nitrogenous base by hydrogen bond.
What is chiasmata?
The points of attachment where crossing-over occurs.
What is crossing over?
exchange of chromatid parts between the paternal and maternal chromatids of a pair of homologous chromosomes during meiosis.
What are the four nitrogenous bases of DNA? what do they combine to?
Adenine, guanine, thymine and cytosine
A=T
G=_C
in what stage of meiosis does crossing over occur?
in the pachytene stage
