D2.1 Cell and Nuclear Division

D2.1.1— Generation of new cells in living organisms by cell division. ​List implications of the idea that new cells are only produced from a pre-existing cell. D2.1.2— Cytokinesis as splitting of cytoplasm in a parent cell between daughter cells. Define cytokinesis. State the difference between mitosis and cytokinesis. Compare and contrast cytokinesis in plant and animal cells. Describe the formation of the cleavage furrow in animal cell cytokinesis. Describe the formation of the cell wall in plant cell cytokinesis. D2.1.3- Equal and unequal cytokinesis. State that cytokinesis usually, but not always, results in equal division of the cytoplasm. State the reason why daughter cells must receive at least one mitochondria during cytokinesis. Outline unequal cytokinesis in yeast budding. Outline unequal cytokinesis during human oogenesis D2.1.4- Roles of mitosis and meiosis in eukaryotes. State that mitosis is nuclear division resulting in continuity of the chromosome number and genome. State that meiosis is nuclear division that results in reduction of the chromosome number and diversity between genomes. Outline the cause and consequence of anucleate cells. D2.1.5— DNA replication as a prerequisite for both mitosis and meiosis. State that DNA replication occurs before both mitosis and meiosis. State that DNA replication occurs in S-phase of interphase. ​ Explain how replicated DNA molecules are held together, with reference to chromatid, replicated chromosome, centromere and cohesin. D2.1.6- Condensation and movement of chromosomes as shared features of mitosis and meiosis. Explain how and why chromosomes condense during mitosis and meiosis. State the role of microtubules and kinetochore motor proteins. ​​​​D2.1.7- Phases of mitosis. State the names of the four phases of mitosis. Draw typical eukaryotic cells as they would appear during the interphase and the four phases of mitosis. Outline four events that occur during prophase. Outline the process of metaphase, inclusive of the role of microtubules and the kinetochore. Outline the process of anaphase. Outline four events that occur during telophase. D2.1.9- Meiosis as a reduction division. Explain what it means for chromosomes to be “homologous.” Define diploid. State the human cell diploid number. Define haploid. State the human cell haploid number. List example haploid cells. Given a diploid number (for example 2n=4), outline the movement and structure of DNA through the stages of meiosis. Explain why meiosis I is a reductive division. State that cells are haploid at the end of meiosis I. Compare meiosis with mitosis. ​Outline the events of prophase, metaphase, anaphase and telophase in meiosis I and meiosis II. D2.1.10- Down syndrome and nondisjunction. Define nondisjunction. State the result of nondisjunction during anaphase I and anaphase II. Describe the cause and symptoms of Down syndrome. D2.1.11- Meiosis as a source of variation. Explain how meiosis leads to genetic variation in gametes. Define bivalent. Describe the process and result of crossing over during prophase I of meiosis. Draw a diagram to illustrate the formation of new allele combinations as a result of crossing over. Describe the process and result of random orientation of bivalents during metaphase I of meiosis. Draw a diagram to illustrate the formation of different chromosome combinations that result from random orientation during meiosis. State that the number of chromosome combinations possible due to random orientation is 2^n. page 19 link: https://mlcsyd.instructure.com/courses/5314/pages/unit-4-d2-dot-1-cell-and-nuclear-division

Define DNA replication. When does it occur?

DNA replication is the semi-conservative process whereby DNA makes new copies of itself.

It occurs in the interphase stage, specifically the S phase of the cell cycle and is necessary before mitosis or meiosis can occur.

necessary for mitosis and meiosis because it ensures that each daughter cell receives a complete set of genetic information

Chromosome vs Chromatid

chromosome is the condensed form of DNA visible during mitosis & meiosis. when DNA replicates, it coils up and the 2 DNA strands are called sister chromatids and are held together by a centromere. In the final stage of mitosis, anaphase, the sister chromatids are pulled apart. Each DNA strand is still called a chromosome.

Homologous Chromosomes

in eurkaryotes, chromosomes that exist in pairs, similar in structure and carry the same genes in the same order, but they may have different alleles (similar. but not identical) for those genes one from each parent

Define cytokenesis and identify where it occurs

the process of cytoplasmic division, where the cell splits into two identical daughter cells.

occurs concurrently with the final stage of mitosis (telophase) and is different in plant and animal cells

the difference between mitosis and cytokinesis.

mitosis: division of the nucleus and dna into two different daughter cells

cytokenesis: division of the cell and organelles into two different daughter cells

they can occur simultaneously

Cytokinesis in animal cells

plasma membrane pulled inwards at the equator of the cell to form a cleavage furrow which is achieved by contractile proteins such as myosin.When the cleavage furrow reaches the centre, the cell splits forming 2 daughter cells

Cytokinesis in plant cells

vesicles are moved to the equator of the cell and fuse to form a tubular structure across the cell which will then form a cell plate, they develop into the membrane by forming 2 new cells already connected to existing membranes by pectins and other substances deposited by exocytosis and forms the middle lamella which link them and both daughter cells secrete cellulose to create cell wall.

Cytokenises equality and inequality

cytokinesis usually, but not always, results in equal division of the cytoplasm. typically, both daughter cells receive at least one of the organelles that were made from the division from pre-existing structures such as the mitochondrion.

an example of this is yeast budding and oogenesis

Oogenesis