Mitosis and Meiosis Flashcards
What is a Karyotype?
An ordered, visual representation of the chromosomes in a cell
What is a locus?
Location of gene on chromosome
What is an allele?
Alternative forms of a gene
What is a homozygote?
Two identical alleles at a locus on a gene
What is a heterozygote?
Two different alleles at a locus on a gene
What do multicellular organisms depend on for cell division?
Development from a fertilised cell, growth and repair
What is interphase in the cell cycle?
Longest part of cell cycle broken up into stages, where chromosomes are replicated (DNA must be duplicated before replication occurs)
What is G1 phase in the cell cycle?
Metabolic activity and growth
Single copy of DNA
What is S Phase in the cell cycle?
Metabolic activity, growth and DNA synthesis where DNA replication occurs
What is G2 Phase in cell cycle?
Metabolic activity, growth and preparation for cell division. Two copes of DNA
What is a duplicated chromosome?
Two sister chromatids which later separate during mitosis
What are the five stages of mitosis?
PMAT
P- prior Prophase
Prometaphase
M- move to middle Metaphase
A- apart Anaphase
T- two new cells Telophase
What happens in Prophase?
(MITOSIS)
chromatin condenses into chromosomes, and the nuclear envelope begins to break down, spindle begins to form
What happens in Prometaphase?
(MITOSIS)
Nuclear envelope fragmented
Kinetochore forms at centromeres
Microtubules attach to kinetochore
Non microtubules interact and lengthen towards opposite poles
What happens in Metaphase?
(MITOSIS)
Duplicated chromosomes arrive at metaphase plate
Microtubules attached to all kinetochore
Centrosomes at opposite poles
What happens in Anaphase?
(MITOSIS)
Sister chromatids separates, now a singular chromosome
Kinetochores shorten pulling cell
Non-kinetochores lengthen
What happens in telophase and cytokinesis?
(MITOSIS)
Nuclear envelope reappears from fragments
Chromosomes become less condensed
Spindle disappears
Cytoplasm divides into two
What are the stages involved in meiosis?
PMAT
Prophase I and II
Metaphase I and II
Anaphase I and II
Telophase I and II
Cytokinesis
What happens at Prophase I?
(MEIOSIS I)
Chromosomes duplicated and condensed
Nuclear envelope broken down/fragmented
Homologous pairs of chromosomes align and crossing over occurs
Meiotic spindle forms
Microtubules begin to attach to kinetochore
What happens at Metaphase I?
(MEIOSIS I)
Homologous pair of chromosomes arranged at metaphase plate
Chiasmata lie on metaphase plate
Microtubules attached to kinetochores
What happens at Anaphase I?
(MEIOSIS I)
Homologous pairs seperate at chiasmata
Sister chromatids still attached at centromere
Kinetochores shorten
Non kinetochores lengthen
What happens at Telophase & Cytokinesis?
(MEIOSIS I)
Each half of the cell has one set of duplicated chromosomes
Sister chromatids not identical due to crossing over, attached at centromere
Cytokineses: cytoplasm divides into two
What happens at meiosis II?
Prophase II: Microtubules move sister chromatids towards metaphase plate
Metaphase II: sister chromatids line up
Anaphase II: sister chromatids separate, become independent chromosomes
Telophase II and Cytokinesis: Haploid daughter cells begin to form, cytoplasm divides into two
How does sexual reproduction produce diversity?
- Independent assortment of chromosomes
- Segregation
- Crossing Over
- Random and independent fertilisation of gametes
What is independent assortment?
Chromosomes move randomly to separate poles during meiosis I, metaphase
What is crossing over?
Two chromosomes — one from the mother and one from the father — line up, parts of the chromosome can be switched in meiosis I prophase
What is segregation?
the separation of allele pairs during meiosis so that they can transfer specifically to separate gametes
What is the end result of mitosis?
Two genetically identical unreplicated daughter cells, diploid (2n)
What is the end result of meiosis I?
2 haploid, non identical cells, individual chromosomes
What is the end result of meiosis II?
Four haploid cells that are genetically different to each other
