12.6 - Cell Cycle + Cell Division Flashcards
What happens in each of the three stages of the cell cycle?
1) Interphase
2) Nuclear Division
3) Cytokinesis
1) Interphase
3 parts =
- G1 phase = cell increases in size and new biomass is made (proteins) [majority of cell life spent here ]
- S phase = Semi conservative DNA replication
- G2 phase = cell prepares for division, synthesises and stores of ATP + neew organelles synthesised.
2) Nuclear division (meiosis or mitosis)
- Nucleus divides into two or four.
3) Cell division - cytokinesis
- Division of the cytoplasm where cytoplasm divides to produce two cells or four cells.
1) What is a chromosome?
2) In DNA replication, 2 gene.ident. copies of the DNA molecule are made, where do they attach?
3) What does n mean?
4) What is a homologous pair of chromosomes?
5) What is the number of homologous PAIRS of Cs in a diploid cell?
6) What cells only have one copy of each chromosome?
7) Why is it important that these are haploid?
1) an independent DNA molecule which has been supercoiled into a condensed form
2) At a central point called the centromere - 2
identical sister chromatids.
3) The number of different chromosomes possessed by an organism (chromosome no.)
4) Two chromosomes that carry the same genes in the same loci but may have different alleles of the genes.
5) 23 pairs (46)
6) Haploid cells - gametes - sperm + egg
7) So that they restore the chromosome number when gametes fuse to make a zygote (fertilised egg cell)
MITOSIS - PMAT
1) What are the three functions of mitosis?
2) Describe the features of prophase. (4)
3) Describe the features of metaphase. (3)
4) Describe the features of anaphase. (4)
5) Describe the features of telophase. (2)
6) What happens in cytokinesis?
1) TO increase cell numbers and growth of an organism, to repair damaged tissues, replace worn out/dead cells.
2) [This is where you first see the chromosomes PROperly = PROphase]
- Nuclear membrane starts to break down
- The centrioles move to the poles of the cell and make spindle fibres
- The chromosomes supercoil and condense (become visible)
- Each chromosome appears as 2 identical sister chromatids joined at the centromere.
3) [ This is where the chromosomes look like they line up in the Middle = Metaphase ]
- The centrioles complete production of spindle fibres
- The chromosomes attach to the spindle fibres at their centromere
- The chromosomes align at the equator of the cell
4) [where the chromosomes are pulled Apart = Anaphase / look V shaped ]
- The spindle fibres contract / shorten
- The centromere splits
- The identical sister chromatids are pulled to opposite poles
- Making a V shape.
5) [where the chromosomes have split and clustered into Two nuclei = Telophase]
- A nuclear membrane starts to reform around each set of chromosomes
- The chromosomes unwind/uncoil and become thinner + invisible.
6) Once the nuclear material has divided, the cell surface membrane pinches together, the cytoplasm divides forming two daughter cells.
Describe the appearances and behaviour of chromosomes during mitosis. (7)
1) Prophase, chromosomes supercoil and condense to become visible
2) Chromosomes appear as 2 identical sister chromatids joined by a centromere
3) Metaphase, chromosomes align at the equator of the cell
4) Chromosomes attach to the spindle fibres by their centromeres
5) Anaphase, centromere splits.
6) Identical sister chromatids are pulled to opposite poles of the cell, making a V shape
7) Telophase, chromatids uncoil and become thinner.
UNREGULATED MITOSIS AND CANCER
1) Once tissues have been formed, cell division..
2) What control genes switch cell division on and off?
3) If a mutation occurs in one of these control genes…
4) This is rapid and the cells produced are abnormal. A __ develops. Which is?
5) If the cells start to spread into the tissue, the tumour is regarded as..
6) What is one method to treat cancer?
1) stops.
2) Tumour suppressor genes = code for proteins that SLOW DOWN the cell cycle
Proto-onco genes = code for proteins that SPEED UP the cell cycle.
3) Cell division continues, uncontrolled.
4) Tumour. A mass of abnormal cells / Uncontrolled cell division
5) A cancer.
6) To give drugs that inhibit cell division. They may stop DNA replication, spindle fibre formation, cytokinesis..
BINARY FISSION
1) This occurs in…
2) Replication of the…
3) Division of the..
4) How does the cytoplasm divide?
VIRUSES [extra]
1) What is their strategy?
2) What are the four stages of this?
1) prokaryotic cells
2) circular DNA and plamids
3) cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable no. of copies of plasmids.
4) The cell elongates in the middle, separating the two DNA molecules, which are attached to different parts of the cell membrane. A new cell wall (murein) is formed down the middle of the elongated cell which eventually meets, dividing the cell into two.
1) Use the host cell enzymes to replicate and transcribe viral DNA and translate viral proteins, making more virus particles which then burst out of the cell.
2) - virus attaches to cell
- virus enters cell and injects nucleic acid into the host cells DNA
- The cell replicates the viral DNA
- new viral nucleic acids are packaged into viral particles (virions) and released from the cell. Host cell may be destroyed.
How do you calculate the mitotic index? (proportion of cells undergoing cell division)
What is the formula for SERIAL DILUTION?
( Number of cells with condensed chromosomes [cells in PMAT ] / total number of cells ) x 100
M1 x V1 = M2 x V2
desired conc. x desired vol = orig. conc. x unknown vol.
[when you’ve got the volume, fill the rest of it with water ]
MEIOSIS
1) Meiosis is used to produce….for…
2) Results in…
3) Important as it halves…
4) There are two…
5) In the first, In the second..
6) Meiosis increases genetic variation between the daughter cells via two processes during meiosis 1:
1) haploid gametes for sexual reproduction
2) four genetically different daughter cells
3) the chromosomes number (so each egg or sperm only has one copy of each chromosome (n)) before fertilisation to restore the full chromosome number at fertilisation (2n). Ensures chromosomes number in the cell remains constant from one gen to the next.
4) nuclear divisions (each has a PMAT)
5) the homologous chromosomes pair up and are separated. 2=the chromatids are separated.
6) Crossing over between non-sister chromatids of `H.Cs
Independent segregation of H.Cs during meiosis.
[also random fertilisation of haploid gametes causes variation, also arise through mutations ]
Meiosis results in cells that have the haploid no. of chromosomes and show genetic variation. Explain how. (7)
1) Homologous chromosomes pair up
2) Maternal and paternal chromosomes are arranged in any order
3) Independent segregation
4) Crossing over
5) Equal portions of chromaids are swapped between chromosomes
6) Produces new combo of alleles
7) Chromatids separated at meiosis II
Meiosis results in cells that have the haploid no. of chromosomes and show genetic variation. Explain how. (7)
1) Homologous chromosomes pair up
2) Maternal and paternal chromosomes are arranged in any order
3) Independent segregation
4) Crossing over
5) Equal portions of chromaids are swapped between chromosomes
6) Produces new combo of alleles
7) Chromatids separated at meiosis II
Describe the process of crossing over and explain how it increases genetic diversity. (4)
What is independent segregation?
How to work out the possible no. of different combos of chromosomes?
Why is variation in gametes important?
Q- Describe and explain the processes that occur during meiosis that increase genetic variation (5) - process of crossing over and independent segregation.
1) Homologous pairs of chromosomes associate (form a bivalent)
2) Chaismata form (chromosomes entangle / twist)
3) Equal lengths of non-sister chromatids are exchanged
4) Producing new combos of alleles.
I.S = during metaphase I = homologous chromosomes attach to the spindle fibres and they pair up side by side and can be reshuffled in any comvination.
2 to the power of n. n= no. of chromosomes.
Produces new combos of characteristics, meaning members of species will have advantageous alleles that will allow them to survive if the environment changes.
Differences between mitosis and meiosis. (7)
- One division V two divisions
- Daughter cells genetically identical V genetically different
- Two cells produced V four cells
- Diploid to diploid/haploid to haploid V diploid to haploid
- separation of homologous chromosomes, crossing over, and IS = only in meiosis.
Describe how the process of meiosis results in haploid cells. (w/o genetic variation) (5)
1) DNA replication in interphase
2) Two divisions
3) Separation of homologous chromosomes in first division
4) Separation of sister chromatids in second division
5) Produces 4 haploid cells
Describe binary fission in bacteria. (3)
1) Replication of circular DNA
2) R of plasmids
3) Division of cytoplasm to produce daughter cells
