INQUIRY Q2 Flashcards
(43 cards)
DNA
Stands for Deoxyribose Nucleic Acid, a molecule composed of two strands that coil around each other to form a double helix carrying genetic instructions.
- Essential for the development, functioning, growth and reproduction of all known organisms and many viruses.
Chromatin
The general packaging of DNA around histone proteins, decondensed as a long thin string.
For most of the cell cycle, DNA is packaged in the form of chromatin.
Chromosomes
An additional level of organisation of chromatin that occurs during mitosis and meiosis.
- Located inside the nucleus of animal and plant cells
- Contains genes which has code for proteins
- Exist in duplicated or unduplicated states
Autosomal Chromosomes
No. 1 - 22 chromosomes are the pair of chromosomes that regulate the somatic characteristics.
Sex Chromosome
No. 23 chromosomes are the pair of chromosomes that regulate the sex-linked traits.
Cell Cycle
A series of events that takes place in a cell as it grows and divides.
A cell spends most of its time in interphase and prepares for cell division by replicating its chromosomes (genetic material).
* The cell cycle is a 4 stage process, consisting of G1, Synthesis, G2 and Mitosis (or Meiosis).
Cell cycle:
Gap 1 (G1)
The period in the cell cycle after cell division and before the start of DNA replication.
* Cells grow and monitor their environment to determine whether another round of cell division can be intiated.
Cell cycle:
Synthesis
The period in the cell cycle of DNA synthesis.
* Cells replicate their chromosomes.
Cell cycle:
Gap 2 (G2)
The period in the cell cycle between the end of DNA replication and start of cell division.
* Cells check DNA replication has sucessfully completed and make any necessary repairs.
Allele
- Each of two or more alternative forms of a gene that are found at the same place on a chromosome.
Chromatid
- One of two genetically identical halves of a replicated chromosome.
After DNA replication, a chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.
Sister Chromatid
One of two chromatids of the same chromosome joined together by a common centromere.
Non-sister Chromatid
One of the two chromatids of paired homologous chromosomes, the pairing of a paternal chromosome and a maternal chromosome.
Genes
A distinct sequence of nucleotides on a chromosome which code for some characteristic which is transferred from parent to offspring.
Dominant and recessive alleles: An allele of a gene is said to be dominant when it effectively overrules the other (recessive allele).
Mitosis
The process of nuclear division in which a single parent cell divides once to produce two genetically identical daughter cells.
Main purpose of mitosis is to accommodate grotwth of the organism and to replace damaged cells.
Mitosis:
Interphase
- Nuclear DNA remains in a semi-condensed chromatin configuration.
- DNA is replicated and results in the formation of sister chromatids, an identical pair of DNA molecules, that are firmly attached to the centromeric region.
- Centrosomes replicate and move to opposite ends of the cell’s pole.
Mitosis:
Prophase
- Chromatin condenses into chromosomes and becomes visible under a microscope.
- Miotic spindle fibres start to form from microtubules within the centroles.
- Nuclear membrane dissolves to allow spindle fibres to attach to chromosomes.
- Spindle fibre attaches to the area of centromere on eah sister chromatid.
Mitosis:
Metaphase
- Centosomes are at the opposite end of the cell’s pole.
- Spindle fibres attach to the centromere of each pair of sister chromatids.
- Sister chromatids line up at the equator of the cell.
- Spindle fibres ensure that sister chromatids will seperate and go to different daughter cells when the cell divides.
Mitosis:
Anaphase
- Sister chromatids are pulled to opposite ends of the cell by the shortening of the spindle fibres.
- At the end of anaphase, each pole has a full set of chromosomes.
Mitosis:
Cytokinesis
- Division of the cytoplasm to form two new cells each with their own cell membrane.
- Cytoplasm splits equally between the two cells.
- Chromosomes unravel to become chromatin.
Meiosis
The process where a single parent cell divides twice to produce genetically different four daughter cells containing half the amount of orignal genetic information.
- Resulting cells are sex gametes.
Homologous Chromosomes
A pair of chromosomes that consists of one maternal and one paternal chromosome that are the same length and carry genes at the same locations.
Meiosis I:
Interphase
- DNA in the cell is copied resulting in two identical full sets of chromosomes.
- Two centrosomes are located outside of the nucleus in the cell.
- During interphase, microtubules extend from these centrosomes.
Meiosis I:
Prophase I
- Replicated chromosomes condense into X-shaped structures.
- Chromosomes organise in homologous pairs so that both copies of chromsomes form together as a tetrad.
- Any pairs of chromatid arms overlap at a point of contact (chiasma), causing them to break and recombine to produce new combinations of genes, known as “crossing over”.
- At the end of Prophase I, the nuclear membrane dissolves away.
