2 - Mitosis And Meiosis Flashcards
What is the structure of a chromosome with two DNA molecules?
When looking at a eukaryotic cell under the microscope, why might there be no nuclear envelope?
Cell may be undergoing mitosis or meiosis
What are the four types of centromere?
How are chromosomes classified and what are X and why?
- Based on their size and centromere type
- Go in descending size from 1-22
- Grouped A-G
- X is C and Y is G
How does DNA polymerase proof-read?
- Contains a restriction endonuclease
What is the proccess and outcome of mitosis?
Outcome: 2 identical diploid daughter cells, somatic cell replication for growth and repair
Prophase: nuclear envelope disintegrates, chromosomes condense, centrioles move to opp ends
Prometaphase: spindle attach by kinetochore
Metaphase: chromosomes line up randomly on the equator
Anaphase: spindles contract, centromere splits, sister chromatids go to opposite poles of cell and they appear v-shaped
Telophase: two groups of chromosomes, new nuclear envelope surrounds each group. chromosomes uncondense.
Cytokenesis: from cleavage furrow
Where are chromosomes during interphase?
In their own territories in the nucleus as chromatin
What is a metaphase spread?
- Where chromosomes are analysed when the cell is arrested during metaphase as the chromosomes are highly condensed
What are non-sister chromatids and what do they have in common?
Chromsomes in the same tetrad
Both have same genes but different alleles
What is the outcome of meiosis and why is it carried out?
- 4 haploid non-identical daughter cells
- Used to create genetic diversity and maintain the chromosome number throughout generations
What is the process of meiosis?
What is crossing over?
- Homologous chromosomes in a bivalent
- Non sister chromatids form chiasmata and swap genetic information
- Essential, if didn’t occur may lead to both chromosomes ending up in one cell
What is a karyotype?
- Can physically see all the bands and chromosomes
OR
- Chromosome number:
47,XY,+21
(no spaces, just commas)
Why is the ova larger than the sperm?
Ova contains all the organelles and cytoplasm for cell growth but sperm just needs genetic material
What generates genetic diversity?
- Independent assortment
- Crossing over
What is the importance of G0?
- Stops cells over replicating
- If they recieve a signal, they can reenter the cell cycle for tissue repair
(neurones never can, liver can)
How do autosomes pair up in meiosis?
- Contain similar DNA sequences so they pair up
What is anaphase lag?
- Where chromosomes dont attach to the spindle fibre or they get left behind in the cytoplasm
- DNA lost as degraded in cytoplasm
- Aneuploidy
Compare and contrast mitosis and meiosis?
Mitosis
- One division , one replication
- 2 identical diploid cells
- Has prometaphase
Meiosis:
- Two divisions, one replication
- 4 haploid non-identical daughter cells
- Crossing over
- Independent assortment
- Homologous chromosomes pair up
What is the nucleolus and why isn’t it visible during mitosis?
- Contains DNA from five chromosomes. Used to produce ribosomal RNA
- During mitosis all DNA is condensed into chromosomes and they are on the equator of the cell
What is the process of oogenesis?
What is the process of spermogenesis?
What is the SRY gene?
The gene that codes for male development
If crossing over occurs in a male, and SRY passed to X chromosome, daughter can inherit this and be intersex
- She has XX but no female development as presence of SRY gene
- Intersex children
