Mitosis
Genetically identical
Asexual reproduction
Growth & repair
_______
a single parent cell divides, resulting in two daughter cells
The daughter cells are ________ to each other (and to the parent cell)
Unicellular organisms
_______ accomplishes ________
Multicellular organisms
_______ accomplishes _________
Meiosis
Gametes (eggs/sperm)
Genetically unique
Sexual reproduction
_______
a single parent cell divides, resulting in four daughter cells
The daughter cells are ________
Gametes are _____ from each other (and from the parent cell)
______ accomplishes _______
DNA
Chromosomes
____ is the inherited information- containing molecule located in the nucleus of cells
Genes are discrete segments of _______ that code for specific proteins ( and therefore for particular traits)
________ exists as very long molecular strands called ________
Each ______ consists of thousands of genes
46
cells within individuals of the same species have the same number of chromosomes
Human cells have ___ chromosomes
Chromatin
When the cell is not dividing:
chromosomes exist in a diffuse state called ______
Spread throughout the nucleus
Individual chromosomes cannot be distinguished
Centromere
Histone
Chromatin
As the cell is preparing to divide:
each chromosome is duplicated
Chromosomes now consist of two sister chromatids attached at a _____
Chromosomes wrap and coil around ______ proteins
Chromosomal DNA becomes tightly compacted
Chromosomes are no longer in the diffuse _____ state
Individual condensed chromosomes can now be distinguished
Separate
Distributed
While the cell is dividing:
sister chromatids ______ and are ______ to the two daughter cell
Each new chromosome is identical to each other (and to the parent chromosome)
The daughter cells therefor receive identical genes
When a cell is first produced by cell division
When it in turn divides
The cell cycle is the sequence of stages between when _________ and _________
Interphase
Not dividing
G1, S, G2
90% of the cell cycle is spent in the ______
The cell is not ______ during this time
_____ is separated into its own three stages
______, ______, and ______
G1
Growth
Cytoplasm
Chromatin
Interphase
_____ phase (first gap)
the cell performs its normal functions
Cell ______ occurs
New ______ (organelles and cytosol) is produced
Chromosomes are in the diffuse _____ state
Chromosomes have not yet duplicated and therefore do not yet consist of sister chromatids
S
Two sister chromatids
Interphase
____ phase (DNA synthesis)
chromosomes duplicate
Each chromosome now consists of _______ attached at their centromere
G2
Chromatin
Chromatids
Interphase
____ phase (second gap)
cells continue to perform their usual functions
Cells continue to grow
Chromosomes still exist as _______
Each chromosome is now two _______, so the amount of DNA has doubles
Mitotic phase
Nucleus
Cytoplasm
10% of the cell cycle is spent in the _______
Cell division occurs during this time
The _____ consists of mitosis and cytokinesis
Mitosis = division of the ______
Cytokinesis = division of the ______
Prophase, metaphase, anaphase, telophase
Telophase
The four continuous stages of mitosis are:
_____, ______, ______, and _______
(Cytokinesis occurs simultaneously with ______)
Prophase
Centrosomes
Microtubules
Mitosis
______
chromosomes (consisting of sister chromatids) coil tightly around histones and become individually distinct
Two organelles called ______ (each with a pair of centrioles) move toward opposite poles of the cell
Centrioles manufacture the miotic spindle
Made of ______
The miotic spindle extends from each centrosome
Nuclear envelope
Kinetochores
Mitosis: Prophase
the ________ breaks down
Some of the spindle microtubules attach to the chromosomes at their centromeres
At specific centromere proteins called _______
Other spindle microtubules span across the entire cell
From one centrosome to the other, now at opposite poles of the cell
Metaphase
Metaphase plate
Mitosis
________
the mitotic spindle aligns the chromosomes (each with two chromatids) at the equator of the cell
Called the ________
Anaphase
Spindle microtubules
Mitosis
_______
the spindle microtubules attached to the chromosomes centromeres shorten
Pulling the chromatids apart, toward opposite poles of the cell
Once seperated, chromatids are now individual chromosomes
The _________ extend across the entire cell membrane
Pushing the poles farther apart, elongating the cell
Telophase
Nuclear envelope
Mitosis
________
chromosomes have now reached opposite poles of the cell
A ________ forms around each pole
Chromosomes (no laonger consisting of sister chromatids) return to the chromatin state
The mitotic spindle breaks down
Cleavage furrow
Micro filaments
Genetically identical
Cytokinesis
Animal cells
A _______ forms
A ring of ______ that begins shallow but deepens as it contracts
The elongated cell is cleaved down its center
Pinching the parent cell into two _______ daughter cells
Cell plate
Genetically identical
Cytokinesis: plant cells
A _______ forms
Vesicles with cell wall material are deposited in the center of the elongated cell
The vesicles fuse to form a _____
The ______ then fuses with the cell wall of the parent cell
Separating the parent cell into two _____ daughter cells
Homologous chromosomes
Locus
Chromosomes occur in pairs called ______
a gene for a particular trait is found at the same location on both ______
Called the genes ______
Somatic
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23
An organisms body cells are called ______ cells
human ______ cells contain ___ chromosomes
Human ______ cells therefore contain ___ pairs of homologous chromosomes
Autosomes
Sex chromosomes
22 pairs (44 chromosomes) are called ______
Genes for traits other than gender are located on these
1 pair (2 chromosomes) are called ______
These can determine gender
They are called X and Y
Half
Meiosis separates chromosomes of a homologous pair, producing cells (gametes) with _____ the number of chromosomes
The adults of one generation
The adults of the next generation
The human life cycle is the sequence of stages between ________ and ________
44 & 2
2(23)=46
22 & 1
23
human somatic cells are diploid (2n)
Diploid cells have both members of each homologous pair of chromosomes
___ autosomes & ___ sex chromosomes
Humans have 2n= _____
Gametes are haploid (n)
Haploid cells have just one member of each homologous pair of chromosomes
___ autosomes & ___ sex chromosome
Humans have n= _____
Haploid
Diploid
_______ gametes (egg and sperm) are produced by meiosis only in the gonads (ovaries and testes)
Fertilization is the fusion of gametes
Fertilization produces a single cell called a zygote
A zygote receives one member of each homologous pair from the egg and the other member of each homologous pair from the sperm
Zygotes are therefore _______
Meiosis
Fertilization
Sexual reproduction
______ (reducing the chromosome number from diploid to haploid) and ______ (reestablishing the diploid chromosome number form the basis of ______
Chromatin
Centromeres
Haploid
Cell division during which a diploid cell gives rise to four haploid gametes
Interphase (prior to meiosis)
Chromosomes are in the _____ state (They duplicate to form sister chromatids attach at their _____)
Meiosis I
A diploid cell divides producing two _____ cells
Meiosis II
The two _____ cells divide producing four _____ cells (gametes)
Histones
Synapses
Tetrad
Crossing over
Meiosis I: Prophase I
Chromosomes (consisting of sister chromatids) coil tightly around ______ and become individually distinct
Homologous chromosomes pair up in ______
2 homologous chromosomes + 2 sister chromatids = ________
______ occurs
Microtubules
Nuclear envelops
Meiosis I: Prophase I
two centrosomes move toward opposite poles of the cell
Centrioles manufacture a spindle of ______, which extends from each centrosome
The ______ breaks down
Kinetochores
Meiosis I: Prophase I
some spindle microtubules attach to the chromosomes at their centromeres
At the ______
Each attaches to only one member of each homologous pair
Others span across the entire cell
Tetrads
Metaphase plate
Meiosis I: Metaphase I
homologous pairs of chromosomes (______) are aligned at the equator of the cell (_______)
Centromeres
Lengthen
Meiosis I: Anaphase I
the spindle microtubules attached to the chromosomes’ _______ shorten
The spindle microtubules that extend across the entire cell ________
Nuclear envelope
Meiosis I: Telophase I
homologous chromosomes have reached opposite poles of the cell
New ________ forms
Spindle breaks down
Two daughter cells are haploid with half the number of chromosomes as the parent cell
Cleavage furrow
Cell plate
Meiosis I: Cytokinesis
animals = _______
Plants = _______
Haploid
Diploid
Meiosis II
Prophase II, metaphase II, anaphase II, & telophase II
All same except:
In meiosis II, each cell begins and ends with a ____ chromosome number
In mitosis, each cell begins and ends with a ____ chromosome number
Evolution by natural selection
Genetically identical
Genetically unique
Genetic variation is essential for ________
asexual reproduction produces _______ offspring
Mitosis
Sexual reproduction produces _______ offspring
Meiosis & fertilization
Crossing over
Independent assortment of chromosomes
Random fertilization
23
8
orientation of homologous pairs of chromosomes during metaphase I is random
number of possible chromosome combinations gamete can receive is 2^n
N = haploid number
Humans = ______
2^23 = ______ million possible combinations
8 million x 8 million = 64 trillion
A random egg is fertilized by a random sperm
resulting c=zygote has ___ x ___ = ___ possible chromosome combinations
Recombinant
Chiasma
Crossing over adds genetic variation
produces _______ chromosomes with genetic information distinct from the parental chromosomes
Site of crossing over is called the ______
Nondisjunction
Homologous
Sister
______ is a failure of chromosomes to separate during meiosis, which results in gametes with an abnormal number of chromosomes (n +/- 1)
______ chromosomes fail to separate during anaphase I
______ chromatids fail to separate during anaphase II
Trisomy
Monosomy
Nondisjunction
zygotes will have abnormal chromosome numbers
2n + 1 (______)
2n - 1 (______)
Abnormality is passed by mitosis to all somatic cells as zygote grows
Spontaneous abortion/miscarriage
Down syndrome
Nondisjunction
typically results in _______ early on during pregnancy
Trisomy 21
Extra 21st chromosome
Condition: _______
Risk increases as mothers age increases
Normal male
Nondisjunction of sex chromosomes
XYY _______
Normal female
Nondisjunction of sex chromosomes
XXX _______
Klinefelter syndrome
Nondisjunction of sex chromosomes
XXY _______
Turner syndrome
Nondisjunction of sex chromosomes
XO _______