16. Cell Division Flashcards
In cell cycle which phase accounts for 90-95% of time?
Interphase
In eukaryotic cells the amount of DNA in a cell doubles during the
S phase
What is the number of chromosomes in human cells formed by mitotic cell division and meiotic cell division respectively?
46,23
Indicate number of chromosomes in a human egg and sperm cell
23 and 23
Meiotic division is process leading to formation of specific cells in animals. What are these cells called???
Sex cells or gametes
After DNA replication and before anaphase of mitosis, a chromosome has
two chromatids which have identical copies of DNA.
Meiosis and mitosis have a number of features common. However only meiosis has the following feature:
The pairing up of homologous chromosomes
Meiosis produces four cells that are
Haploid and are genetically different from each other
Meiosis
Produces new combinations of genes
Chromatids of homologous chromosomes ( crossing over) may exchange genetic material
during Prophase 1 meiosis
At the end of telophase II of meiosis each of the four resulting cell contains
one full set of chromosomes, each a single chromatid.
In animal cells cytokinesis
Starts at poles and pinches inwards
Two copies of each chromosome are called??
Homologous chromosomes
Meaning of haploid and diploid
Haploid: 1 father set, 1 mother set
Diplom: 1 set of chromosomes
MITOSIS (3)
- Purpose: growth and repair
- Occurrence: ALL BODY CELLS
- 1 division, produce 2N daughter cells
MEIOSIS (3)
- Purpose: gamete production
- Occurrence: ALL SEX ORGAANSSS
- 2 divisions produce 1N daughter cells
Give 3 examples of activities in interphase
Interphase = metabolic activity to pro for next division
- Copy of DNA
- Protein and organelle synthesis
Identify 5 stages in MITOTIC CELL DIVISION with support
- INTERPHASE: chromosomes invisible
- PROPHASE: chromosomes visible
- METAPHASE: chromosomes line up MIDDLE
- ANAPHASE: sister chromatids of each chromosome pulled apart TOWARD OPP POLE via contracting SF
- TELEPHASE: new cell wall formed on new cells that teared apart.
Describe how sister chromatids move via SF in cell
- Centresome= control microtubles
- Microtubles: contracts
- Chromosome moves towards Centresome
Describe what happens when cell cycle gets uncontrolled
Mechanisms regulate how often and how many times diff cells in body divide. If mechanism breakdown.
Cells divide uncontrollably-> tumour -> cAncers
In cell cycle what are checkpoints??
Where cell cycle stops until ahead signal RECIEVED
Important checkpoints:
G1, g2 ,M
Know sequence and order of MEIOSIS!!! (8 steps)!!!!!!
- PROPHASE 1: Chromosome visible
- METAPHASE 1: SF form(HORIZONTAL, HOMOLOGOUS CHROMOSOMES, move to middle cell, attached to SF by centromere)
- ANAPHASE 1: SF contract. HOMOCHROM pulls APART (vertical position)
- TELEPHASE 1: nuclear membrane around chromosomes
- PROPHASE 2: nuclear membrane break down
- METAPHASE 2: SP (VERTICAL) and chromosomes line up MIDDLE, attach to SF VIA centromere ( horizontal position)
- ANAPHASE 2: sister chrimatids PULL apart as SF CONTRACTS
- TELEPHASE 2:
1-nuclear membrane around each set chromosomes
2—-> after cytoplasmic division: 4 haploid daughter cells formed EACH WITH ONE MEMBER OF EACH HOMO PAIR
3- chromosome uncoil to chromatin again
Explain how MEIOTIC cell division gives rise to genetic variation in offspring
Genetic variations= pairing up of HOMO CHROMOSOMES at prophase 1
Where would transcription happen… PHASE????
In INTERPHASE (Z)
Z: transcription–> mRNA —> protein
protein synthesis occurs in interphase
