Meiosis Flashcards
heredity
continuity of biological traits from one generation to the next
heredity results from
transmission of herediart units from parent to offspring
variation is due to
- crossing over
- mutations
variation
inherited differences among individuals of the same species
genetics
study of heredity and heredity variation
DNA
type of nucleic acid that is a polymer of 4 different kinds of nucleotides
consist of a single long and highly folded DNA molecules that are coiled along proteins
chromosomes
locus
specific location on a chromosome that contains a gene
contain genetic information arranged in a linear sequence and coded by genes
chromosome
sexual reproduction occurs ONLY in
eukaryotes
during the formation of gamates, chromosome number is
reduced in half
gametes are
haploid
somatic cells are
diploid
gametes return to being diploid when
two gametes fuse in fertilization
ploidy
number of sets of chromosomes
haploid organisms have
one set of chromosomes
diploid organisms have
two sets of chromosomes
meiosis
segregates one copy of each homologous chromosome into each new gamete
meiosis is a specialized type of
nuclear division
somatic cells in the human body are produced by
mitosis
germ line cells are produced by
meiosis
meiosis is restricted to the
gonads
the vast majority of cell division in human body are
mitotic
human somatic cells have ____ pairs of chromosomes
23
karyotype
ordered display of chromosomes pairs from a cell
the two chromosomes in each pair are
homologous chromosomes (homologs)
chromosomes in a homologous pair are the
same length, shape and carry the same genes
sex chromosomes
determine the sex of an individual
X and Y chromosomes are
sex chromosomes
human female phenotype
homologous pair of X chromosomes (XX)
human male phenotype
have one X and Y chromosome
autosomes
remaining 22 pairs of chromosomes
homologous chromosome pairs include
one chromosome inherited by each parnet
46 chromosomes in somatic cells are two sets of
23; one from each parent
diploid number for humans
46
sister chromatids
a pair of the SAME parent
non-sister chromatids
a pair from DIFFERENT parents (one from each parent)
karyotypes can be used to screen for
defective or abnormal chromosome numbers
how are karyotypes prepared
isolated somatic cells
genetic link to our parents
genes
what is the genetic program language made from
DNA
vehicle that transmit genes from one generation to the next
gametes
where is DNA mostly packed
nucleus
where else can DNA be packed
mitochondria or chloroplast
diploid is represented by
2n
haploid is represented by
n
is the cell still diploid after undergoing DNA synthesis
YES
when does the human life cycle begin
haploid sperm from father fuses with haploid egg from mother
fertilization
union of gamates
results in a fertilized egg known as a zygote
fertilization
the zygote is
diploid
what generates all the somatic cells in the body
mitosis of the zygote
only cells not produced by mitosis
gametes
how to gametes develop
from germ cells in the gonads
gonads in males
testes
gonads in females
ovaries
meiosis does what to the number of chromosomes
reduces from two to one in the gametes
_______ and _______ maintain a constant number of chromosomes in each species from different generations
fertilization and meiosis
what is common to ALL organisms that reproduce sexually
alternation of meiosis and fertilization
Is this sexual or asexual reproduction
single individual is the sole parent
asexual
Is this sexual or asexual reproduction
two parents give rise to offspring
sexual
Is this sexual or asexual reproduction
single parent passes on ALL its genes to the offspring
asexual
Is this sexual or asexual reproduction
each parent passes on HALF its genes to offspring
sexual
Is this sexual or asexual reproduction
offspring are genetically identical to the parent
asexual
Is this sexual or asexual reproduction
offspring are unique from both parents and each other
sexual
Is this sexual or asexual reproduction
results in a clone
aseuxal
Is this sexual or asexual reproduction
results in genetic variation in offspring
sexual
clone
genetically identical individual with rare genetic differences from mutations
____ can divide by mitosis depending on the type of life cycle
haploid OR diploid
______ can undergo meiosis
diploid cells ONLY
In meiosis, the single duplication stage is followed by
TWO consecutive cell divisions
what does meiosis result in
4 daughter cells with ONE set of chromosomes each
the only animal haploid ccell
gametes
what process produces gametes
meiosis
do gametes undergo more cell division before fertilization
NO
what is formed when gametes fuse
diploid zygote
what results in a multicellular organism
dividing gametes by mitosis
what show alternation of generations
plants and some algae
alternation of generations includes
both a diploid and haploid multicellular stage
what is the diploid organism called in alternation of generations
sporophyte
what part of alternation of generations makes the haploid spores
the sporophyte by meiosis
how do the spores grow into the haploid organism in alternation of generations
by mitosis
what is the haploid organisms known as in alternation of generations
gametophyte
how do gametophytes make haploid gametes
by mitosis
what does fertilization of gametes result in for the alternation of generations
a diploid sporophyte
what is the only diploid stage in most fungi and some protists
single-celled zygote
is there a multicellular stage in most fungi and some protists
NO
what does the zygote produce in fungi
haploid cells by meiosis
how do each haploid cell grow into the organism in fungi
by mitosis
how do the haploid adults produce gametes in fungi
mitosis
is the multicellular organism in fungi diploid or haploid
haploid
meiosis I is also known as
reductional division
meiosis 2 is also known as
equational division
what happens to chromosomes in meiosis I
homologous chromosomes seperate
what separates in meiosis II
sister chromatids
allele
different versions of genes at corresponding loci
what meiosis phase does this represent?
centrosomes begin to seperate
prophase 1
what meiosis phase does this represent?
spindle begins to form
prophase 1
what meiosis phase does this represent?
nuclear envelope begins to break down
prophase 1
what meiosis phase does this represent?
each centrosome pairs with its homologue
early prophase 1
how are homologous pairs aligned during prophase 1
allele by allele
what meiosis phase does this represent?
crossing over occurs
early prophase 1
crossing over
DNA molecules of NON-SISTER chromatids are broken and rejoined to each other
x shaped region where crossing over has occurred
chiasmata
what meiosis phase does this represent?
microtubules from one pole will attach to the two kinetochores
late prophase 1
where do the microtubules attach in late prophase 1
one at the centromere of each homologue
what meiosis phase does this represent?
pairs of chromosomes are at the metaphase plate
metaphase 1
how are the chromosomes arranged in metaphase 1
one chromosome of each pair facing each pole
what meiosis phase does this represent?
both chromatids of one homologue are attached to kinetochore microtubules
metaphase 1
what meiosis phase does this represent?
sister chromatid cohesion along the chromatid arm breaks apart= homologues seperate
anaphase 1
what meiosis phase does this represent?
sister chromatid cohesion continues at the centromere
anaphase 1
what meiosis phase does this represent?
each half of the cell has a complete haploid set of duplicated chromosomes
telophase 1
what occurs at the same time as telophase 1
cytokinesis
what forms during cytokinesis in animals
cleavage furrow
what forms during cytokinesis in plant cells
cell plat forms
what does NOT occur between meiosis 1 and 2
chromosome duplication
chromosomes do what throughout prophase 1
condense progressively
what meiosis phase does this represent?
spindle apparatus forms
prophase 2
what meiosis phase does this represent?
chromosomes move toward metaphase 2 plate
late prophase 2
what are the chromosomes made up of during late prophase 2
two chromatids associated at the centromeres
what meiosis phase does this represent?
chromosomes are positioned at the metaphase plate
metaphase 2
what meiosis phase does this represent?
kinetochores of sister chromatids are attached to microtubules from opposite poles
metaphase 2
what meiosis phase does this represent?
breakdown of proteins holding sister chromatids together
anaphase 2
what meiosis phase does this represent?
chromatids separate
anaphase 2
what meiosis phase does this represent?
move to opposite poles as individual chromosomes
anaphase 2
what is the result of crossing over in meiosis 1
sister chromatids are NOT genetically identical
what meiosis phase does this represent?
nuclei forms
telophase 2
what meiosis phase does this represent?
the chromosomes begin decondensing
telophase 2
what is the final product of meiotic division
four daughter cells
what does each daughter cell have
haploid set of chromosomes
what has been done to chromosomes after interphase
they have been duplicated
how are sister chromatids held together after interphase
proteins called choesins
synaptonemal complex
zipper-like structure that holds one homologue tightly to the other
what must occur for homologous pairs to remain together as they move to the metaphase 1 plate
at least ONE crossing over
is this meiosis or mitosis?
reduces the number of chromosomes from diploid to haploid
meiosis
is this meiosis or mitosis?
produces cells that are genetically different
meiosis
is this meiosis or mitosis?
conserves the number of chromosomes
mitosis
is this meiosis or mitosis?
produces cells that are genetically identical
mitosis
is this meiosis or mitosis?
occurs in both haploid and diploid cells
mitosis
is this meiosis or mitosis?
one division
mitosis
is this meiosis or mitosis?
synopsis of homologous chromosomes doesn’t occur
mitosis
is this meiosis or mitosis?
two daughter cells
mitosis
is this meiosis or mitosis?
enables multicellular plant or animal to arise from a single cell
mitosis
is this meiosis or mitosis?
produces cells for growth, repair, asexual reproduction
mitosis
is this meiosis or mitosis?
produces gametes in the gametophyte plant
mitosis
is this meiosis or mitosis?
occurs ONLY in diploid cells
meiosis
is this meiosis or mitosis?
two divisions
meiosis
is this meiosis or mitosis?
synapsis of homologous chromosomes occurs
meiosis
is this meiosis or mitosis?
four daughter cells
meiosis
is this meiosis or mitosis?
produces gametes in animals
meiosis
is this meiosis or mitosis?
produces spores in sporophyte plant
meiosis
is this meiosis or mitosis?
introduces genetic variability in gametes and spores
meiosis
what does DNA replication take place in BOTH meiosis and mitosis
interphase
3 events unique to meiosis (occur in meiosis 1)
- synapsis and crossing over
- alignment of homologous pairs at metaphase plate
- separation of homologues
synapsis and crossing over occur in
prophase 1
synapsis and crossing over
duplicated homologues pair up and crossing over occurs
does synapsis and crossing over happen in mitosis
NO
alignment of homologous pairs at the metaphase plate occurs
metaphase 1
how is the position of chromosomes at the metaphase plate different in meiosis than in mitosis
in meiosis = pairs of homologues
in mitosis = individual chromosomes
separation of homologues occurs
anaphase 1
separation of homologues
Duplicated chromosomes of each homologous pair move toward opposite poles
what happens to sister chromatids during separation of homologues
remain attached
what happens to sister chromatids in mitosis
seperate
what is the original source of genetic diveristy
mutations
mutations
changes in organism’s DNA that create different versions of alleles
most of the variation between each generation during SEXUAL reproduction
behaviour of chromosomes during meiosis and fertilization
Three mechanisms that contribute to the genetic variation from sexual reproduction
Independent assortment of chromosomes
Crossing over
Random fertilization
Independent assortment of chromosomes
random orientation of pairs of homologous chromosomes at metaphase of meiosis 1
the orientation of maternal and paternal chromosomes is
random
the first meiotic division results in
each pair of chromosomes sortings its maternal and paternal chromosomes independently of each other
The number of possible combinations when chromosomes sort independently is represented by
2n
crossing over produces
recombinant chromosomes
recombinant chromosomes
Individual chromosomes that carry genes (DNA) from two different parents
the chromosomes after crossing over have
new combinations of maternal and paternal alleles
The different possible arrangements of non-identical sister chromatids during meiosis II increases with the
number of genetic types of daughter cells
The individuals best suited to the environment leave the
most offspring and transmit their genes
original source of different alleles
mutations
When does sexual reproduction seem to be less advantageous than asexual reproduction
stabe environment
Why is sexual reproduction universal in animals
Ability to produce genetic diversity is the common explanation for evolutionary processes
Gregor Mendel
a theory of inheritance that helps explain genetic variation
Darwin could not explain why
offspring resemble their parents but are NOT identical
gametogenesis
process of forming gametes from diploid cells of the germ line
types of gametogenesis
- spermatogenesis
- oogenesis
spermatogenesis
process of forming sperm cells by meiosis
spermatogenesis in plants
by mitosis
where does spermatogenesis happen
in specialized organs known as gonads
what happens after division in spermatogenesis
cells undergo differentiation to become sperm cells
Oogenesis
process of forming an ovum by meiosis
where does Oogenesis happen
in specialized gonads known as ovaries
in Oogenesis where does most of the cytoplasm go
into one large egg
polar bodies
the three other cells in Oogenesis that do not develop
what happens to the meiotic products in spermatogenesis
all 4 are developed into gamates
who brings the genetic material AND the needed support for the cell
ovum
