Lecture Ten - Cell division Flashcards
What is the purpose of cellular division?
Growth, repair and reproduction.
Describe the process of mitosis (simple outline).
Asexual reproduction.
Occurs in somatic cells (non-germ cells).
Before replication - chromosomes (one copy).
After replication - a pair of chromatids (two copies held together by centromere).
Cell divides to produce two daughter cells.
DNA has been replicated then passed down with absolute fidelity - no genetic variation.
Mitosis divides the nucleus, while cytokinesis divides the cytoplasm.
Describe the processof meiosis (simple outline).
Sexual reproduction.
Allows for genetic variation between parent and daughter cells.
Describe how meiosis and mitosis change with relation to haploid and diploid cells.
Draw the cell cycle pie graph.
Alternates betwen interphae and mitosis/meiosis.
Cells spend the most time in interphase.
Mitosis or meiosis is brief compared to the other phases in the cell cycle.
In aldult organism most cells have exited cycle and are terminally differentiated.
G1 phase is the phase in which the cell grows.
S phase is the synthesis, in which the chromosomes are duplicated.
G2 phase is the second gap in which the cell grows more and prapares to beigin the process of mitosis.
Where are the check point merkers/proteins in the cell cycle?
What is non-disjunction?
Sometimes chromosomes do not segregate correctly, and end up with cells with extra chromosomes or schomosomes missing.
This is called non-disjunction.
Consequenses -
Responsible for ~ 50% of miscarriages.
If viable, causes disorders, e.g. down syndrome.
Describe the characteristics of diploid and homologous chromosomes, and sister chromatids.
Diploid chromosomes have two copies of each chromosome.
Homologous chromosomes carry the same genes - with unidentical DNA (different variations of the genes).
Sister chromatids are two copies of a newly replicated chromosome - identical.
How many pairs of chromosomes dows a human have?
23 pairs.
22 pairs of autosomes - same in both sexes.
1 pair of XX or XY sex chromosomes.
How are the sex chromosomes different?
X chromosome - like an autosome (no female specific qualities).
Y chromosome - very few genes, all male related.
Describe in more detail, each phase of mitosis.
How is cytokinesis different in plant and animal cells?
Draw the stages of meiosis.
What unique even occurs in meiosis I, metaphase I?
Homologous chromosomes pair in process of synapsis - paired homologous called bivalents.
Non sister chromatids exchange genetic information - called crossing over. Points at which this occurs are called chiasmata.
Pairs of homologues on metaphase plate, not individual chromosomes.
Homologous chromosomes segregate at anaphase I, but each is still a pair of sister chromatids.
What is independant assortment?
Generates more genetic diversity in gametes.
