Midterm 2 (2.2) Flashcards
Meiosis
Type of eukaryotic cell division that produces sperm and eggs.
Meiosis reduces 2n to n
– Diploid to haploid
Meiosis makes cells genetically different from the parent cell AND each other
3 events unique to MEIOSIS (occur during MEIOSIS I)
-1. Synapsis and crossing over (during prophase I)
-2. Homologous pairs positioned at metaphase
plate
-3. Homologues separated
Genome
Genetic material of an organism
Chromosome
Packages DNA
Somatic cells
All body cells except reproductive cells.
In humans: 46 chromosomes (two sets of 23)
Gametes
Reproductive cells
Humans: 23 chromosomes (one set)
Chromatids
Joined copies of original chromosome
Centromere
Chromosomal DNA where sister chromatids most closely attached
Arm of the chromatid
Portion of chromatid to either side of centromere
Mitosis
Nuclear division in eukaryotic cells
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Cytokinesis overlaps with latter stages, completes mitotic phase
Cytokinesis
-Division of cytoplasm
-One cell becomes two
Interphase
-G1 phase: cell grows
-S phase: cell grows and chromosomes replicated
-G2 phase: grows more, prepares for cell division
Mitotic phase
Cell divides
-mitosis
-cytokinesis
Interphase: G2
- Centrosome duplicated
>2 centrosomes each with 2
centrioles - Chromosomes have been duplicated
Prophase (mitosis)
Chromosomes condense
- two identical sister chromatids joined at centromere
Nucleoli disappear
Mitotic spindle forms
-centrosomes and microtubules
Centrosomes pushed away from each other
Prometaphase (mitosis)
Nuclear envelope fragments
Each of the two chromatids now have a kinetochore
Microtubules attach to kinetochore
Kinetochore
Protein structure at centromere
Metaphase (mitosis)
Centrosomes at opposite poles
Chromosomes at metaphase plate
- Plane equidistant between two poles
- Centromeres at metaphase plate
- Kinetochore of each sister chromatid attached to microtubules from opposite poles
Anaphase (mitosis)
Two sister chromatids pulled appart
-Each chromatid becomes a chromosome
Daughter chromosomes moved to opposite ends of cell as microtubules shorten
Cell elongated
-two ends of cell have complete copies of chromosome
Telophase (mitosis)
2 daughter nuclei form
Nucleoli reappear
Chromosomes decondense
Spindle breaks down
Mitosis is finished
Cytokinesis
Division of cytoplasm (starts during telophase)
Animal cells: cell pinches in two
- Occurs by CLEAVAGE
- Microfilaments contract until cell splits in two
Plant cells
- No cleavage furrow
- Cell plate produced by vesicles from Golgi during telophase.
- Cell plate develops into cell wall
Aster
Radial array of shorter microtubules that extend from the centrosomes
Metaphase plate
A plane that is equidistant between the spindle’s two poles.
Asexual reproduction
Single individual is sole parent.
Parent passes copies of all its genes to offspring
No fusion of gametes
Some multi-cellular organisms can produce asexually
Sexual reproduction
Two parents give rise to offspring that have unique combinations of genes inherited from both parents
Offspring vary genetically from siblings and parents
Karyotype
Image of a cell’s chromosomes laid out in pairs
Locus
Gene’s specific location along length of a chromosome (plural: loci)
Homologous chromosomes OR homologues
Two chromosomes making up a pair have the same length, centromere position, staining pattern
Both carry genes controlling the
same inherited characters
- If gene for eye colour is at a
particular LOCUS on a certain chromosome. its homologue will have version of gene to specify eye colour (at same locus)
Autosomes
Rest of the chromosomes that aren’t sex chromosomes
Sex chromosomes
X and Y
Females (XX)
Males (XY)
- Most genes on x do not have counterparts on Y
- Y has genes X does not have
Diploid cell
Any cell with 2 chromosome sets
- Has diploid number of chromosomes (2n)
n
Number of chromosomes in a single set
Haploid cell
Single set of chromosomes (gametes)
Haploid number of chromosomes (n)
Fertilization
Union of haploid gametes to produce diploid zygote
Allele
Different versions of genes in homologues
- Allele for freckles on one
chromosome and allele for absence of freckles at same locus
on the homologue
Synapsis
Paired homologues become physically attracted
Form tetrads
Chiasmata
Where a crossover has occurred
Mutations
Original sources of genetic variation
Changes in nucleotide sequence of an organism’s DNA or RNA of a virus
Mutations created different versions of genes called alleles
Recombinant chromosomes
Chromosomes that carry genes derived from 2 different parents
