Chapter Three: Chromosomes Flashcards
the first human genetic disorder attributable to an abnormal number of chromosomes rather than a gene mutation
down syndrome
chromosomes transmit ___
genetic information
the ___ and ___ of genetic material is important for normal development
type and amount
genes reside in ___ in the ___
chromosomes
nucleus
the first observations of fertilization of nuclei occurred with ___ looking at ___
the naked eye
frog and sea urchin eggs and sperm
from observing the fusion of nuclei in frog and sea urchin eggs, scientists concluded that ___
something in the nucleus must contain hereditary material
in the 1880s, ___ and ___ were highly improved, and ___ could be visualized in the ___ and followed through ___
microscopy
staining techniques
chromosomes
nucleus
cell division
nuclear division that generates two daughter cells containing the same number and type of chromosomes as parent cell
mitosis
nuclear division that generates gametes (egg and sperm) containing half the number of chromosomes found in other cells
meiosis
body cells are ___and gametes are ___
diploid
haploid
diploid human cells have ___ chromosomes
46
haploid human cells have ___ chromosomes
23
the union of haploid gametes to produce diploid zygotes
fertilization
for each pair of chromosomes, zygotes have one from ___ and one from ___
mom
dad
how many cells are in an average adult human
100 trillion
to get from 1 to 100 trillion cells, ___ rounds of cell division are needed
60
metaphase chromosomes can be classified by ___, ___, and ___
size, banding pattern, and centromere position
location where sister chromatids are attached
centromere
centromere is in the middle of sister chromatids
metacentric chromosome
centromere is near one end of sister chromatids
Afrocentric chromosome
centromere is at the end of sister chromatids
telocentric chromosome
identical copies of a replicated chromosome
sister chromatids
chromosomes that contain the same set of genes, but can have different alleles for some genes
homologs/homologous chromosomes
chromosomes that carry completely unrelated sets of genes
nonhomologs/nonhmologous chromosomes
there are about ___ genes in the human genome, and about ___ genes per chromosome
20,000
1,000
___ of human DNA codes for something
1.5%
micrograph of stained chromosomes arranged in homologous pairs
karyotype
homologous chromosomes have the same ___, ___, and ___
size, shape (centromere location), and banding
the study of genetic anomalies
cytogenetics
every species has a characteristic number of ___
chromosomes
all chromosomes except X and Y
autosomes
unpaired X and Y
sex chromosomes
chromosomes are made of ___, ___, and ___
DNA, histone protein, and non-histone protein
a long thread primarily made of DNA with some protein scaffolding, what chromosomes usually exist as
chromatin
chromatin only duplicated and condenses into visible chromosomes when ___
cell division is about to occur
duplicated chromosomes (chromatids) are joined at the ___
centromere
a repeating pattern of cell growth and division
cell cycle
passes of the cell cycle
G1
S
G2
mitosis
cytokinesis
period of cell growth and chromosome duplication between divisions
interphase
microtubule organizing center near the nuclear envelope
centrosome
centrosome is also called the ___
“MTOC” (microtubule organizing center)
___ come from the centrosome
microtubules / spindle fibers
the centrosome divides to form ___
two centrioles
most of cell growth occurs during ___ and ___
G1 and G2
some terminally differentiated cells stop dividing and arrest in ___ stage
G0
___ and ___ stop in G0
mature neurons
muscle cells
chromosomes replicate to form sister chromatids during ___
S phase
which phase do most defects happen that cause cancers
G1
when do chromosomes form from chromatin
end of G2, right before mitosis
3 steps in prophase
- chromosomes condense and become visible
- centrosomes move apart toward opposite poles
- nucleoli begin to disappear
2 steps of prometaphase
- nuclear envelope breaks down
- spindle forms and sister chromatids attach to microtubules from opposite centrosomes
2 steps of metaphase
- chromosomes align on the metaphase plate with sister chromatids facing opposite poles
- forces pushing and pulling chromosomes to or from each pole are in balanced equilibrium keeping chromosomes in place
2 steps of anaphase
- centromeres of all chromosomes split simultaneously
- kinetochore microtubules shorten and pull separate sister chromatids to opposite poles
4 steps of telophase
- nuclear envelope forms around each group of chromatids
- nucleoli re-form
- spindle fibers disappear
- chromosomes uncoil and reform as chromatin
three kinds of microtubules and their functions
- astral = anchor to cell membrane
- kinetochore = push against chromosome
- polar = pull chromosome toward centrosome
cytokinesis begins during ___ but is not completed until after ___
anaphase
telophase
cytokinesis
cytoplasm of parent cell split into two daughter cells with identical nuclei
in animal cytokinesis, a ___ contracts to form ___
contractile ring
cleavage furrow
in plant cytokinesis, a ___ forms near the equator of the cell
cell plate
in all cytokinesis, ___ are distributed to each daughter cell
organelles
does cytokinesis always occur after mitosis?
NO
a cell with multiple nuclei
syncytium
a syncytium is a result of ___
cytokinesis not occurring
there are ___ in the cell cycle that have to occur before the cell moves on to the next stage
checkpoints
make up the vast majority of cells in an organism
somatic cells
somatic cells are either in stage ___ or ___
G0
actively going through the cell cycle
precursors to gametes
germ cells
germ cells are set aside during ___
embryogenesis
germ cells become incorporated into ___
reproducing organs
only cells that undergo meiosis to produce haploid gametes
germ cells
meiosis has ___ of cell division
two rounds
in meiosis, chromosomes duplicate ___ and nuclei divide ___
once
twice
meiosis one reduces chromosomes from ___ to ___
2n
n
meiosis two produces ___
four haploid nuclei
meiosis one separates ___, meiosis two separates ___
chromosomes
sister chromatids
in meiosis one, homologs ___, ___ and then ___
pair, cross over, segregate
___ remain intact through meiosis one
sister chromatids
in meiosis one, maternal and paternal homologs ___ and create new combinations of alleles
recombine
homologous chromosomes pair together in prophase one and are held together by ___
synaptonemal complex
crossing over occurs during ___ resulting in ___ of genetic material
prophase one
recombination
the outer chromatids of homologous pairs are ___ and the inner chromatids are ___
parental
recombinant
after recombination, the synaptonemal complex ___ and chromatids in each ___ become visible
dissolve
tetrad
in metaphase one and anaphase one, ___ are separated
homologs
in metaphase one and anaphase one, ___ do not divide and ___ do not separate
centromeres
sister chromatids
meiosis one is a ___ division
reductional
phase after meiosis one in which no chromosomal duplication takes place
interkinesis
during meiosis two, ___ separate
sister chromatids
in meiosis two, haploid nuclei progress through a process similar to ___ to create ___
mitosis
four haploid daughter cells
meiosis two is an ___ division
equational
four haploid cells that result from meiosis two each have unique ___
genomes
homologs of a chromosome pair do not separate during meiosis one
nondisjunction
nondisjunction may result in ___ or ___
inviable gametes or embryos
abnormal chromosome numbers in viable individuals
independent assortment of nonhomologs creates different combinations of alleles in ___
gametes
crossing-over between homologs creates different combinations of alleles in ___
each chromosome
two ways meiosis contributes to genetic diversity
independent assortment of nonhomologs
crossing-over between homologs
in 1903, ___ determined that chromosomes carry Mendel’s units of heredity
Walter Sutton
does the movement of chromosomes prove or disprove Mendel’s laws
proves
