Molecular Biology & Genetics 2 - Meiosis & Mitosis Flashcards
What is included in acellular RNA?
Viruses
How does acellular RNA store genetic information?
Double stranded or single stranded DNA or RNA
What is prokaryotic?
Bacteria
How do prokaryotic organisms store genetic information?
Circular, single copy, naked double stranded DNA
What is included in eukaryotic organisms?
Protists, fungi, plants and animals
How is genetic information stored in eukaryotic organisms?
Linear, at least a single copy, his tone-bound DNA; sexual cycle
What is a karyotype?
An ordered, visual representation of the chromosomes in a cell
How are chromosomes ordered in a karyotype?
Homologous chromosomes are paired together, ordered in decreasing size and in groups
What are autosomes?
Chromosomes which don’t determine gender while x and y do. Y chromosome means male
What is a locus?
A place on a chromosome where a particular gene is found
What is an allele?
Alternative forms of genes
What is meant by a homozygote?
Having the same alleles at a particular locus
What is meant by a heterozygote?
Having different alleles at a particular locus
What is the cell cycle needed for?
Development from a fertiliser cell, growth to adult and repair
What is G1?
Growth 1
What is S?
Synthesis (when replication of DNA occurs)
What is G2?
Growth 2
What is included in interphase?
Growth 1, synthesis and growth 2
What is included in the mitotic phase?
Mitosis and cytokinesis
What are duplicated chromosomes?
Two sister chromatids which later separate during mitosis
What is the centromere?
Pinched part in the middle of duplicated chromosomes
What is the chromosome arms?
Parts of the chromosomes which are found either side of the centromere
How are duplicated chromosomes formed?
Single chromosomes turn into a pair during duplication. Sister chromatids have identical information most of the time
What happens during mitosis?
Two genetically identical daughter cells are produced
How many phases are in mitosis?
5
What is the first phase of mitosis?
Prophase
What happens during prophase?
Chromosomes condense and become visible. The mitotic spindle also forms
What is the second phase of mitosis?
Prometaphase
What happens during prometaphase?
The nuclear envelope dissolved and the mitotic spindle attaches to the sister chromatids at the centromere
What is the kinetichore?
Attachment between the chromosome and microtubules
What are kinetichore microtubules?
Microtubules which attach to the chromosomes
What are non-kinetichore microtubules?
Microtubules which don’t attach to the chromosomes
What is the third phase of mitosis?
Metaphase
What happens during metaphase?
All the chromosomes line up at the centre of the cell in a plane (metaphase plate). Centrosomes have moved to opposite ends (poles) of the cell
What are centrosomes?
Where mitotic spindles spread from
What happens during anaphase?
Kinetichore microtubules get shorter and tear apart the pairs of sister chromosomes to form daughter chromosomes. This means each side of the cell will have the same information. Non- kinetichore microtubules become longer to help push the two poles apart
What is the fifth phase of mitosis?
Telophase and cytokinesis
What happens during telophase and cytokinesis?
Each new cell has a single copy of each chromosome. Nuclear envelope forms in each cell and in cytokinesis the cytoplasm of the two cells is separated
How do single felled organisms usually reproduce?
Binary Fission
How do multicellular plants and animals reproduce?
Vegetative means
What are some single celled organisms?
Amoeba, paramecium, yeasts, algae
What are some multi-cellular plants and animals?
Runners, bulbs, tubers, rhizomes, hydra, anemone, sponge and starfish
What is the sexual cycle found in?
Most eukaryotes
What is the process of the sexual cycle?
Meiosis»>Haploid gametes (sperm-n and egg-n (n=23))»>fertilisation»>diploid zygote (2n=46)
What would happen if garnered were produced by mitosis?
They would be 2n and resulting embryos would be 4n. A cell division process which halves the number of chromosomes going into gametes (n), so that the diploid number (2n) is retained in the zygote
What occurs during interphase of meiosis?
Chromosomes duplicate
What happens during Meiosis l?
Homologous chromosomes separate
What happens during Meiosis lol?
Sister chromatids separate
What happens at prophase l?
Spindle apparatus (microtubules) forms joining the centrosomes together, the nuclear envelope dissolved, homologous chromosomes align and synapse and crossing over also occurs
What happens during crossing over?
It occurs at the chiasmata of non-sister chromatids and results in the chromatids being a mix of pieces from each homologous chromosome
What is the chiasmata?
Where non-sister chromatids touch during crossing over
What happens during Metaphase l?
Paired homologous chromosomes which are still connected at the chiasmata move to the metaphase plate and the chiasmata line up there
What happens during anaphase l?
Recombined homologous chromosomes separate (disjoin)- it is random as to which direction the maternal and paternal chromosomes go
What is the difference between anaphase in meiosis l compared to mitosis?
Sister chromatids remain attached in meiosis l which is different to mitosis where they separate
What happens in telophase l and cytokinesis?
Haploid cells with duplicated chromosomes (the pairs of sister chromatids) form
Why are cells formed in meiosis called haploid?
Because they only have half they genetic information
What happens during Meiosis ll?
Sister chromatids are separated in the same process as meiosis l except crossing over doesn’t occur
What is the result of meiosis?
4 daughter cells which each contain half the genetic information of the original cells
What is unique to mitosis?
Chromosomes align independently, no chiasmata so no crossing over, centromeres on metaphase plate, chromatids disjoin, 2n to 2n
What is unique to Meiosis l?
Homologous chromosomes synapse, chiasmata are present and they align on the metaphase plate, chromosomes disjoin, 2n to n
How does sexual reproduction cause genetic diversity?
Independent assortment of chromosomes, crossing over and random fertilisation of gametes
What does genetic diversity allow selective responses to?
Spatially variable environments, changing environments and sibling-sibling competition
What is segregation and independent assortment?
Homologous pairs of chromosomes line up independently of each other. Therefore when segregation occurs there is many possible combinations of chromosomes in the daughter cells
What is the number of possible gametes?
2 ^n where n is the haploid number. This is without crossing over
What does crossing over result in?
Four different gametes which are all genetically different from each other therefore creating genetic diversity