Classical Genetics Flashcards
prophase
early prophase and late prophase
the beginning of mitosis when the chromatin begins to form chromosomes
- centrioles split up and move to opposite poles - condensation of chromatin into chromosomes - nuclear membrane breaks down
metaphase (and prometaphase)
Alignment (ie meeting of the chrms)
- spindle fibres form - chromosomes align on metaphase plate - spindle fibres attach to centromeres
Prometa: discrete chrms visible; the nuclear envelope fragments
anaphase
the shortest phase of mitosis
- spindle fibres contract - sister chromatids separate to become daughter chromosomes - daughter chromosomes are pulled to opposite poles.
telophase
the chromosomes start to unravel
- chromosomes decondense back into chromatin - new nuclear membranes form
cytokinesis
after mitosis is complete (ie when 2 identical nuclei have formed) 2 daughters cells separate
euploidy and aneuploidy
having the correct number of chromosomes;
having the incorrect number
prophase 1 (very important); prophase 2
PROPHASE I
LEPTOTENE - condensation commences
ZYGOTENE - further condensation, pairing commences
PACHYTENE - further condensation, end of pairing, crossing over ( = chiasma formation)
DIPLOTENE/DIAKINESIS - further condensation, nuclear membrane breaks down
PROPHASE 2 -
metaphase 1; metaphase 2
METAPHASE I
-bivalents align on metaphase plate ie in pairs of homologous chrms (cf meta in mitosis in which indiv chrms line up on meta plate)
anaphase 1; anaphase 2
ANAPHASE I
- bivalents separate and move toward opposite poles
(disjunction)
telophase 1; telophase 2
TELOPHASE I - chromosomes reach poles and new nuclear membranes form
meiosis (meiosis 1 and 2)
produces gametes; involves 2 separate divisions, btwn which there is no interphase ie they are back to back
DIVISION II - phrophase II - telphase II are all identical to their mitotic counterparts but involve half the number of chromosomes.
Consequences:
(I) Production of haploid gametes
(II) New combinations of paternally and maternally derived chromosomes
(III) Produces genetic recombination via chiasma formation
This brings about a huge range of variation which allows for natural selection
metaphase 1; metaphase 2
METAPHASE I -bivalents align on metaphase plate
recombination (also “crossing over” or chiasma/ta)
changes the combination of genes on the chromosomes; with one crossover four possible gene combinations can be produced; one of the mechanisms of maintaining and propagating change and genetic variation
inheritance
the heritability of traits
allele
a version of a gene; linked with variation
uses of genetics
Disease diagnosis and cure (eg haemophilia, cystic fybrosis, sickle cell anaemia, Rh incompatability)
Crop and stock improvement (wheat, figs, peas, dogs, sheep)
Forensics (identity and paternity testing)
Conservation
Systematics (cf phylogeny)
Making sense of the Evolution module
systematics
concept of the relationships between species;
based on evolutionary history, in a modern sense; molecular systematics based on genetic features are more reliable
chromosome
(literally ‘coloured bodies’ in Latin); a condensed form of proteins and nucleic acids carrying genetic information; visible only during cell division.
the gene
from ‘pangen’, a shortening of Darwin’s name for a factor that conveys traits from parent to offspring, a gene is the smallest particle representing one hereditary characteristic; the fundamental physical and functional unit of heredity (from 1909)
chromatin
made of nucleic acids and proteins, like chromosomes, but looks different; it is spread out in the nucleus, relaxed
(sister) chromatid; daughter chromosome
one of two strands of the chromosome, joined by the centromere;
after they are pulled apart in Anaphase, they become daughter chromosomes
centromere
protein that joins that two sister chromatids
telomere
the ends of the chromatids; their degradation after many cells divisions links with aging and cancer formation
shapes of chromosomes: metacentric, acrocentric, telocentric
meta: chromatids joined roughly in the middle by the centromere
acro: joined nearer one end
telo: joined at the end, ie the telomeres