Lecture 5 Flashcards
What are the four main differences between prokaryotes and eukaryotes?
- ) Pro: No membrane bound nucleus or organelles, single and circular chromosome, single cell organisms
- ) Eu: All have membrane bound nucleus, number of chromosomes varies by species (humans have 23 pairs of chromosome but chicken may have different), membrane-bound organelles. can be single or multi-celled organisms
What determines the sex of cells?
X and Y are sex chromosomes (22 pairs of autosomal chromosomal and 1 pair of sex chromosomes)
XX= Female
XY= Male
After S phase how many alleles are there after S phase? and before S phase?
After S phase = 4 Alleles
ANY other times is ONLY 2 allele
True/False: Eu and Pro have the same reasons for wanting to undergo cell division
Largely False: But do share one similarity- REPRODUCTION
Eukaryote: Also go through cell division for tissue growth and to repair damaged tissues
What are the two main stages of mitosis?
Inter[hase (DAND replication happens in the S phase)
Mitosis and cytokinesis (nuclear division and the production of two identical daughter cells)
What stage does a cell spend most of its life?
Interphase
What stage in interphase does the replication of organelles happen?
G1 Phase
True/False: The growth of RNA and protein stops after S phase ?
FALSE
Which stage in interphase is the longest?
G1 phase
What are the stages in mitosis?
Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis
At which part during mitosis are sister chromatids classified as chromosomes?
During Anaphase as the sister chromatids are pulled apart
How many chromosomes and chromatids are there at the beginning of mitosis?
Chromosomes: 46
Chromatids: 92
How many chromosomes and chromatids are there at the end of anaphase?
Chromosomes: 92
Chromatids: 92
How many chromosomes and chromatids are there during telophase of mitosis?
Chromosomes: 92
Chromatids: 92
How many chromosomes and chromatids are there after cytokinesis of mitosis?
Chromosomes: 46
Chromatids: 46
How many chromosomes and kinetochores are there on a chromosome in mitosis?
2 kinetochores and 2 chromosomes
True/ False: The frequency of cell division varies with cell type
True
What happens when a checkpoint requirement is not met?
If there is something wrong, the cell waits till the error is corrected and if can’t be corrected, the cell undergoes apoptosis *programmed cell death)
What are the four main checkpoints during cell division?
G1 (Cell growth, and env), S (DNA replication), G2 (Cell growth and env), and metaphase (chromosome alignment on spindle)
What are the three main reasons for a checkpoint?
The checkpoints are programmed BUT can also be triggered. Save energy and resources that does not need to be wasted. Looking at internal env (kinetochores and microtubules formation), and external factors (such as hormones, and growth factors)
What two things does a successful cell division require?
DNA replicating only once - must not try to divide until replication is complete
Cell mass must increase- must not be able to replicate until cell mass is sufficient as have to make two daughter cells
What happens when one of two factors is wrong?
The cell undergoes cardiac arrest
What is the solution to preserving information while making it variable at the same time?
Sexual reproduction (fusion of gametes) and meiosis (production of gametes)
What happens during anaphase I?
Separation homologous chromosomes
How many chromosomes and chromatids are there during anaphase I?
Chromosomes: 46
Chromatids: 92
How many chromosomes and chromatids are there during Telophase I?
Chromosomes: 23
Chromatids: 46
How is variability created?
- ) Independent assortment of homologous chromosomes in meiosis - 2*n
- )Crossing ober during prophase I
How many chromosomes and chromatids are there during Anaphase II?
Chromosomes: 46
Chromatids: 46
How many chromosomes and chromatids are there during Telophase II?
Chromosomes: 23
Chromatids: 23
What is the difference between non-disjunction and aneuploidy?
Non-disjunction: Failure of linked homologs or chromatids to separate during anaphase of mitosis or meiosis
Aneuploidy is often as a result of non-disjunction- a state where a cell has an abnormal number of chromosomes
What are three instances where non-disjunction can occur?
Mitotic divisions of the primordial germ cells from which the gametes form
Mitotic divisions of the embryo following fertilization
Meiotic divisions of an oocyte or sperm (most times maternal meiosis)
What are the two important factors that affects non-disjunction?
Metaphase checkpoint, cohesins
Size and shape of chromosomes, acrocentric chromosomes more prone to forming vulnerable bivalent
