2.7 Dividing to multiply through cell division. Flashcards
Who use meiosis and who use mitosis?
Mitosis involved in growth and is how asexually reproducing eukaryotes reproduce.
Meiosis is used alongside sexually reproducing eukaryotes.
What do all eukaryotic cells have in common?
They all have a nucleus which contains chromosomes and therefore DNA.
What is histone?
It is a protein found in chromosomes that help give chromosomes their shape.
Define diploid.
This term describes chromosomes in pairs.
Define haploid.
This term describes individual chromosomes that don’t belong to a pair.
What is mitosis used for?
growth
replacement
repair
asexual reproduction.
Why are the cells produced mitosis described as clones?
It is because they have identical genetic information.
What are the stages of mitosis?
Interphase: DNA replication occurs, alongside the growth of the cell, including replication of other organelles. During this stage, individual chromosomes cannot be seen under the microscope.
Mitosis: The nucleus divides, and then each chromosome is split by the centromere. Mitosis is made up of:
Prophase: Chromatin condenses and chromosomes become visible. The nucleus disappears (‘plump’).
Metaphase: Chromosomes line up along the middle of the cell at the equatorial plate (‘middle’).
Anaphase: Identical chromatids separate and each move to an opposite side of the cell (‘away’).
Telophase: Nuclear membranes reform around the chromatids (‘two’).
Cytokinesis: The cytoplasm splits, leading to the formation of two identical daughter cells. This involves the cell membrane pinching inwards so that a new membrane is formed, dividing the cell in two. In plate cells, a cell wall is also formed using a cell plate.
(thanks Jacplus)
Why do gametes only have one set (of 23) chromosomes?
So that they make an even 46 chromosomes when joining together in sexual reproduction.
What are the stages of Meiosis?
Prophase I: Chromosomes condense and become visible. The nuclear membrane disappears. Chromosomes find their homologous pair. (A special process known as crossing-over can also occur in which chromosomes may swap sections of DNA.)
Metaphase I: Chromosomes line up in their homologous pairs at the equatorial plate.
Anaphase I: The homologous pairs separate to opposite sides of the cell.
Telophase I: The nuclei in the two new cells reforms.
Cytokinesis: The cells split into two cells. These cells are now Haploid (half the chromosome number).
Prophase II: Chromatin condenses and chromosomes become visible. The nucleus disappears.
Metaphase II: Chromosomes line up along the middle of the cell at the equatorial plate.
Anaphase II: Identical chromatids separate and each move to an opposite side of the cell.
Telophase II: Nuclear membranes reform around the chromatids.
Cytokinesis: The cytoplasm splits, leading to four daughter cells being formed.
How is variation created within organisms?
Meiosis, only some chromosomes are passed on.
What are some ways variation occurs during meiosis?
Independent assortment: Chromosomes randomly split between the cells.
Crossing Over: When Homologous chromosomes swap genetic material (of the same location) with one another.
