week 5 - lab quiz 2 Flashcards
Define coarse adjustment
moves stage up and down to get a rough focus
Define fine adjustment
moves stage up and down to get a fine focus
Define ocular/eyepiece
part to look into microscope, contains lenses to increase magnification
Define objectives
contains lenses of different magnification on a revolving nose piece
Define stage
supports specimen, has opening which allows light to come through from light source underneath, mechanical stage knobs control positioning of slide
Define iris diaphragm
opening underneath stage whose size can be regulated in order to regulate amount of light passing through specimen
Define condenser
focuses light on specimen, adjusts contrast
How is total magnification found
product of magnification of eyepiece times magnification of objective
Which two parts of microscope magnify
the eyepiece and objective
Define parfocal
all objectives are adjusted to the same plane of focus
what is the growth of a multicellular organism due to
division and multiplication of its somatic celles by mitosis
name the 2 types of reproduction
asexual and sexual
Describe asexual reproduction
a single parent splits or buds by mitosis to produce two or more individuals
What is the result of asexual reproduction
Daughter cells which are genetically identical to each other and the parent, same number of chromosomes
What type of individual does asexual reproduction produce
adapted individual to produce more adapted individuals
Describe sexual reproduction
2 parents, gametes unite during fertilization to form zygote, chromosome number is reduced by half, 1n+1n=2n
What is the result of sexual reproduction
not identical to each other or parents
What type of individual does sexual reproduction produce
evolved individuals in response to demands of their environment
For sexual reproduction what doe chromosomes usually exist as
homologous pairs, 2 kinds of each chromosome
define homologous pair
similar in length, shape, size and carries genes that control the same characters
what is a diploid cell
2n
what is a haploid cell
n
what does mitosis produce
2 daughter nuclei which are exact replicas of parent
what is mitosis responsible for
Asexual reproduction like fission, budding, regeneration, how a multicellular organism grows and how mature organisms replace damaged or old somatic cells
which phase are cells in most of the time
interphase
define interphase
period between one nuclear division and the next
what happens during g1
growth of cytoplasmic material, like organelles
what happens during s
duplication of DNA, chromosomes become condensed during prophase they will each have 2 identical daughter chromosomes called chromatids attached at centromere
what happens during g2
structures involved with mitosis, like spindle fibres are synthesized
for animal cells, centrioles undergo cell division to produce 2 pairs of centrioles
What happens in prophase
Individual chromosomes become distinguishable
chromosome = 2 chromatids attached at centromere
nuclear membrane breaks down
centriole pairs outside nuclear membrane move to opposite ends of cell
what happens in metaphase
chromosome moves back and forth along spindle fibre
chromosomes line up at equator of cell
spindle fibres attach to the kinetochore of each chromosome
what happens in anaphase
kinetochores divide and 2 identical sets of chromosomes (previously chromatids) move to opposite poles
what happens in telophase
chromosomes reach opposite poles
cytokinesis begins =
- animal cell = cleavage furrow is created and 2 daughter cells are formed
- plant cell = form cell plate
spindle apparatus disperses and nuclear envelope reforms, chromosomes become indistinct
what cells result from meiosis
haploid cells
What is meiosis
spermatogonia and oogonia are germ cells, some of which develop into primary spermatocytes and oocytes, these are diploid cells which undergo meiosis to produce sperm and egg cells
What does kind of divisons does meiosis have
2 successive divisions, meiosis I and meiosis II
what results from meiosis
4 haploid nuclei, not identical and have half the chromosomes as parent cells
Before meiosis I what happens
Chromosomes are duplicated during interphase
What happens before meiosis II
2 nuclei undergo meiosis II BUT THERES NO DUPLICATION OF DNA
what happens in prophase I
2 homologous chromosomes join together through synapsis to form a tetrad, diploid cell of 4 has 2 tetrads, crossing over takes place between 2 non sister chromatids
Where is the 1st source of variation
crossing over between 2 non sister chromatids
where is the 2nd source of variation
Independent assortment occurs
what happens in metaphase I
tetrads align along metaphase plate, independent assortment occurs
what happens in anaphase I
homologous chromosomes separate and move to each pole
what happens in telophase I
cytokinesis forms 2 non identical haploid cells
are there any more homologues present at the end of meiosis I
NOOO
what happens in prophase II
as mitosis
what happens in metaphase II
individual chromosomes align (mitosis like) perpendicular to spindle fibres
what happens in anaphase II
sister chromatids separate and move to each pole
what happens in telophase II
meiosis yields 4 non identical haploid cells
Spermatogenesis = 4 haploid sperm cells
Oogenesis = one ovum and 3 polar bodies which eventually degenerate
spermatogenesis: describe undifferentiated germ cells
round cells at edge of seminiferous tubules
spermatogenesis: describe primary spermatocytes
large cells just to the inside of germ cells
spermatogenesis: describe secondary spermatocytes
slightly smaller cells to the inside of primary spermatocytes
what are secondary spermatocytes produced by
meiosis I
spermatogenesis: describe spermatids
smaller cells to the inside of secondary spermatocytes
what are spermatids produced by
meiosis II
What do spermatids mature into
sperm cells
What do sperm cells look like
elongated cells in central portion of the seminiferous tubule
Oogenesis: where do ova develop
within minute vesicular follicles
Oogenesis: what happens to oogonial cells
they differentiate into primary oocytes during prenatal development and progress to prophase I by the time of birth
Oogenesis: When does meiotic division of primary oocytes occur
only after puberty, a couple cells a month
Oogenesis: What produces the large and functional secondary oocyte and the small non functional first polar body
the unequal division of the cytoplasm
Oogenesis: what happens to first polar body
rapidly degenerates
sometimes can undergo meiotic division forming 2 functionless polar bodies
Oogenesis: What does secondary oocyte do
progresses to metaphase and stops developing till it is fertilized
Oogenesis: When is second meiotic division completed
only after developing ovum has been expelled from the ovary and fertilization has occurred
Oogenesis: what happens to the mature follicle
graafian follicle
it ruptures and the ovum is expelled out of the ovarian surface in a stream of follicular fluid
Oogenesis: what happens once ovulation has occurred
definite changes take place within ovary
Oogenesis: what is corpus luteum
cells lining the ruptured follicle multiply and create a cell mass
Oogenesis: what is the corpus albicans
if ovum is not fertilized the corpus lutuem degenerates and forms an area of scar tissue
