genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.
genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles.
sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles.
nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles.
one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles.
the cells can differentiate.
the fertilized egg has half the genetic material of the parents.
the number of chromosomes is cut in half in gametes.
genetic disorders are prevented.
genetic diversity is reduced.
0
1
2
3
4
synapsis.
crossing-over.
tetrad formation.
disjunction.
nondisjunction.
homologous; autosomes
autosomes; homologous
diploid; haploid
homologous: sex
sex; autosomes
a zygote with trisomy.
a zygote with disomy.
a zygote with monosomy.
a zygote with normal chromosome number.
nondisjunction during subsequent mitosis.
0
1
2
3
4
two homologous chromosomes consisting of two sister chromatids.
two homologous chromosomes consisting of two nonsister chromatids.
one duplicated chromosome consisting of two nonsister chromatids.
one duplicated chromosome consisting of two sister chromatids.
two homologous chromosomes consisting of a single DNA strand each.
anaphase of mitosis
anaphase I, anaphase II, and anaphase of mitosis
anaphase I and anaphase II
anaphase I and anaphase of mitosis
anaphase II and anaphase of mitosis
in metaphase I, tetrads align together at the spindle equator.
in metaphase II, tetrads align separately at the spindle equator.
in metaphase of mitosis, tetrads align separately at the spindle equator.
in metaphase II, dyads align separately at the spindle equator.
in metaphase I, dyads align separately at the spindle equator.
crossing over occurs in prophase of meiosis I but not in prophase of meiosis II.
sister chromatids are separated during meiosis I while homologous chromosomes are separated during meiosis II.
the resulting cells at the end of meiosis I are diploid while the cells at the end of meiosis II are haploid.
in telophase of meiosis I four daughter cells form from the parent cell and in telophase of meiosis II each parent cells gives rise to two daughter cells.
in meiosis I there is no pairing of chromosomes while homologues pair in meiosis II.
DNA is duplicated during interphase, but not during interkinesis.
DNA is duplicated during interkinesis, but not during interphase.
homologous chromosomes separate during interkinesis, but not during interphase.
homologous chromosomes separate during interphase, but not during interkinesis.
interkinesis only occurs during mitosis, while interphase occurs during both meiosis and mitosis.
Meiosis involves 2 divisions and produces 4 non-identical daughter nuclei.
Meiosis involves 1 division and produces 2 non-identical daughter nuclei.
Mitosis involves 1 division and produces 2 non-identical daughter nuclei.
Mitosis involves 2 divisions and produces 4 identical daughter nuclei.
Meiosis involves 2 divisions and produces 4 identical daughter nuclei.
nondisjunction during meiosis I in the female parent.
nondisjunction during meiosis I in the male parent.
nondisjunction during meiosis II in the female parent.
nondisjunction during meiosis II in the male parent.
normal disjunction during meiosis, but deletion of portion of the Y chromosome in the male parent.
two chromosomes with two sister chromatids each.
two sister chromatids with separate centromeres.
four chromosomes with two sister chromatids each.
four sister chromatids with a common centromere.
four sister chromatids attached at a common centromere.
16
32
64
80
128
Chromosomes are classified into two categories, the sex chromosomes that determine gender and autosomes that determine non-gender related traits.
Homologous chromosomes differ in banding patterns, the traits they code for and size.
While sex chromosomes determine different genders they look the same until they are stained.
In humans all 46 chromosomes have an identical match called the homologue.
Chromosomes are classified into two categories, autosomes that determine gender and the sex chromosomes that determine non-gender related traits.
homologous chromosomes line up separately, with sister chromatids facing the same spindle pole.
chromosomes line up separately, with sister chromatids facing opposite spindle poles.
chromosomes line up separately, with sister chromatids facing the same spindle pole.
homologous chromosomes line up separately, with sister chromatids facing opposite spindle poles.
homologous chromosomes line up together, with sister chromatids facing opposite spindle poles.
Half of the gametes from nondisjunction during meiosis I will have normal chromosome number.
Half of the gametes from nondisjunction during meiosis II will have normal chromosome number.
Gametes from nondisjunction during meiosis I will have an extra chromosome, while gametes from nondisjunction during meiosis II will have a missing chromosome.
Gametes from nondisjunction during meiosis II will have an extra chromosome, while gametes from nondisjunction during meiosis I will have a missing chromosome.
Nondisjunction during meiosis I results in only two gametes, while nondisjunction during meiosis II gives four gametes, half of which have extra or missing chromosomes.
adults who are haploid and produce diploid gametes, these gametes fuse to produce a haploid zygote which grows into an adult.
zygotes who are haploid fuse to produce a diploid gamete which grows into an adult.
gametes that are diploid and produce haploid zygotes, these grow into haploid adults.
adults who are diploid and produce haploid gametes, these gametes fuse to produce a diploid zygote which grows into an adult.
adults that are diploid who produce zygotes that are also diploid.
1
2
3
4
8
allele – gene – chromosome
gene – allele – chromosome
allele – chromosome – gene
chromosome – gene – allele
gene – chromosome – allele
47, XXY
47, XXX
46, XY
47, XY, trisomy 21
45, XO
0
35
70
140
280
Turner syndrome
Klinefelter syndrome
Down syndrome
Swyer syndrome
Barr body syndrome
1
2
3
4
8
47, XXY
47, XXX
46, XY
47, XY, trisomy 21
45, XO
sister chromatids have the same alleles while non-sister chromatids have different ones.
sister chromatids have the same genes while non-sister chromatids have different ones.
sister chromatids have the same alleles but different genes while non-sister chromatids have different alleles but the same genes.
non-sister chromatids have the same alleles while sister chromatids have different ones.
non-sister chromatids have the same genes while sister chromatids have different ones.
diploid chromosomes; haploid chromosomes
autosomes; sex chromosomes
homologues; autosomes
karyotype; sex chromosomes
karyotype; autosomes
face the same spindle pole.
face both spindle poles.
face opposite spindle poles.
do not face spindle poles, but are aligned at the spindle equator.
undergo separation of sister chromatids.
The two homologous chromosomes of a tetrad separate into different daughter nuclei.
The sister chromatids of each chromosome separate into different daughter nuclei.
The nonsister chromatids of each tetrad separate into different daughter nuclei.
The two homologous chromosomes of a tetrad separate into one of two daughter nuclei.
The two homologous chromosomes of a tetrad are duplicated and separate into each daughter nucleus.
Meiosis involves 2 divisions and produces 4 non-identical daughter nuclei.
Meiosis involves 1 division and produces 2 non-identical daughter nuclei.
Mitosis involves 1 division and produces 2 non-identical daughter nuclei.
Mitosis involves 2 divisions and produces 4 identical daughter nuclei.
Meiosis involves 2 divisions and produces 4 identical daughter nuclei.
an individual with Swyer syndrome has a Barr body, while an individual with Klinefelter syndrome does not.
an individual with Klinefelter syndrome has a functional SRY gene on his Y chromosome, whereas an individual with Swyer syndrome does not.
both individuals have a functional SRY gene, but the extra X chromosome makes the individual with Klinefelter syndrome appear female.
neither individual has a functional SRY gene, but the X chromosome of the individual with Swyer syndrome has a functional SRY and appears male.
an individual with Swyer syndrome lacks a functional SRY gene, but appears male because it has moved to the X chromosome as in an individual with Klinefelter syndrome.
separation of tetrads – anaphase II
synapsis – metaphase I
separation of sister chromatids – anaphase I
synapsis – prophase II
separation of sister chromatids – anaphase II
meiosis produces haploid gametes, and fertilization creates a diploid cell that divides by mitosis to produce a new individual.
mitosis produces haploid gametes, and fertilization creates a diploid cell that divides by meiosis to produce a new individual.
diploid gametes reproduce by meiosis to produce haploid daughter cells that divide by mitosis to produce a new individual.
diploid gametes reproduce by mitosis to produce diploid daughter cells that divide by meiosis to produce a new individual.
a haploid zygote reproduces by meiosis to produce diploid daughter cells that divide by mitosis to produce a new individual.
crossing-over
independent assortment of chromosomes
pairing of homologous chromosomes
interkinesis
different alleles of the same gene
cause an organism to grow
create genetic variability
reduce the chromosome number in gametes
keep chromosome number constant from one generation to the next
produce gametes
1
2
3
4
8
her DNA is damaged through an accumulation of replication errors.
her DNA stops checking for replication errors.
fertilization no longer occurs correctly with older eggs.
the contents of the egg contains the wrong signals for the correct development of the fetus.
the possibility of nondisjunction increases.
30; 120
30; 60
60; 120
60; 240
30; 240
trisomy
diploidy
monosomy
polyploidy
Crossing over is preceded by a process known as synapsis where homologous chromosomes attach to each other.
Crossing over results in greater genetic variability in offspring.
Crossing over is only detectable when it occurs between sister chromatids.
Crossing over occurs during Prophase I when homologous chromosomes line up prior to separation.
In humans, crossing over occurs an average of approximately two events per chromosome.
