Bio Chapter 8

Front 1

Living organisms reproduce by two methods

Back 1

Asexual reproduction
Sexual reproduction

Front 2

Asexual reproduction

Back 2

– Offspring are identical to the
original cell or organism
– Involves inheritance of all
genes from one parent

Front 3

Sexual reproduction

Back 3

– Offspring are similar to
parents, but show variations
in traits
– Involves inheritance of
unique sets of genes from
two parents

Front 4

Virchow’s principle states

Back 4

“Every cell from a cell”

Front 5

Roles of cell division
– Asexual reproduction

Back 5

– Reproduction of an entire single-celled organism
(e.g. amoeba, bacteria)
– Growth of a multicellular organism (e.g. humans)
– Growth from a fertilized egg into an adult (e.g.
developing fetus)
– Repair and replacement of cells in an adult (e.g. if
you get burn, cut etc.)

Front 6

Roles of cell division
– Sexual reproduction

Back 6

– Sperm and egg production

Front 7

Binary fission means

Back 7

“dividing in half”

Front 8

Binary fission

Back 8

– Occurs in prokaryotic cells
– Two identical cells arise from one cell

Front 9

Steps of binary fission

Back 9

– A single circular
chromosome duplicates,
and the copies begin to
separate from each other
– The cell elongates, and
the chromosomal copies
separate further
– The plasma membrane
grows inward at the
midpoint to divide the
cells

Front 10

Eukaryotic chromosomes are composed of

Back 10

chromatin

Front 11

Chromatin=

Back 11

DNA + proteins

Front 12

To prepare for division, the
chromatin

Back 12

becomes highly
compact, and the chromosomes
are visible with a microscope

Front 13

Early in the division process,
chromosomes duplicate

Back 13

-Each chromosome appears as two sister chromatids containing identical DNA molecules
-Sister chromatids are joined at the centromere, a narrow region

Front 14

Cell cycle

Back 14

ordered sequence of
events for cell division
-It consists of two stages
- Interphase and Mitosis

Front 15

Interphase

Back 15

duplication of cell
contents
– G1—growth, increase in
cytoplasm
– S—duplication of
chromosomes
– G2—growth, preparation
for division

Front 16

Mitotic phase

Back 16

division
– Mitosis—division of the
nucleus
– Cytokinesis—division of
cytoplasm

Front 17

Mitosis progresses through a series of stages

Back 17

– Prophase
8.6 Cell division is a continuum of dynamic
changes
– Prometaphase
– Metaphase
– Anaphase
– Telophase

Front 18

Cytokinesis often overlaps

Back 18

telophase

Front 19

mitotic spindle

Back 19

required to divide
the chromosomes
– The mitotic spindle is composed of
microtubules
– It is produced by centrosomes

Front 20

centrosomes

Back 20

structures in the cytoplasm that
– Organize microtubule
arrangement
– Contain a pair of centrioles in
animal cells
– The role of centrioles in
cell division is unclear

Front 21

Interphase
– In the cytoplasm

Back 21

– Cytoplasmic
contents double
– Two centrosomes
form

Front 22

Interphase
- In the nucleus

Back 22

In the nucleus
– Chromosomes
duplicate during the
S phase
– Nucleoli, sites of
ribosome assembly,
are visible

Front 23

– How many chromosomes are present in one cell?
– How many chromatids are present in one cell?

Back 23

-46 chromosomes
-96 chromatids

Front 24

Prophase
– In the cytoplasm

Back 24

– Microtubules begin
to emerge from
centrosomes,
forming the spindle

Front 25

Prophase
– In the nucleus

Back 25

– Chromosomes coil
and become
compact
– Nucleoli disappear

Front 26

Prometaphase

Back 26

– Spindle microtubules
reach chromosomes,
where they
– Attach at kinetochores
on the centromeres of
sister chromatids
– Move chromosomes to
the center of the cell
through associated
protein “motors”
– Other microtubules
meet those from the
opposite poles

Front 27

Metaphase

Back 27

– Spindle is fully formed
– Chromosomes align at the cell
equator
– Kinetochores of sister chromatids
are facing the opposite poles of
the spindle

Front 28

Anaphase

Back 28

– Sister chromatids separate at the
centromeres
– Daughter chromosomes are moved to
opposite poles of the cell
– Motor proteins move the
chromosomes along the
spindle microtubules
– Kinetochore microtubules
shorten
– The cell elongates due to lengthening
of nonkinetochore microtubules

Front 29

Telophase

Back 29

– The cell continues to elongate
– The nuclear envelope forms
around chromosomes at each
pole, establishing daughter
nuclei
– Chromatin uncoils
– Nucleoli reappear
– The spindle disappears

Front 30

Cytokinesis

Back 30

– Cytoplasm is divided into separate cells

Front 31

cleavage furrow

Back 31

– A cleavage furrow
forms from a contracting
ring of microfilaments,
interacting with myosin
– The cleavage furrow
deepens to separate the
contents into two cells

Front 32

cell plate

Back 32

– A cell plate forms in the
middle from vesicles
containing cell wall
material
– The cell plate grows
outward to reach the
edges, dividing the
contents into two cells
– Each cell has a plasma
membrane and cell wall

Front 33

Factors that control cell division

Back 33

– Presence of essential
nutrients
– Growth factors, proteins
that stimulate division
– Presence of other cells
causes density-dependent
inhibition
– Contact with a solid surface;
most cells show anchorage
dependence

Front 34

Cancer cells escape controls on the cell cycle

Back 34

– Cancer cells divide rapidly, often in the absence of growth factors
– They spread to other tissues through the circulatory
system
– Growth is not inhibited by other cells, and tumors
form

Front 35

Tumors

Back 35

– Benign tumors remain at the original site
– Malignant tumors spread to other locations by
metastasis

Front 36

Cancer treatments

Back 36

– Localized tumors can be treated with surgery or radiation
- Chemotherapy is used for metastatic tumors

Front 37

Classification of cancer by origin

Back 37

– Carcinomas arise in external or internal body coverings
– Sarcomas arise in supportive and connective tissue
– Leukemias and lymphomas arise from blood-forming tissues

Front 38

Somatic cells

Back 38

(body cells) have pairs of
homologous chromosomes, receiving
one member of each pair from each
parent

Front 39

homologous chromosomes
(homologs)

Back 39

The two chromosomes composing a pair
- matched in
– Length, Centromere position and
Gene locations
– They will both carry genes
controlling the same inherited
characteristics.
– For example, if a gene that
determines whether a person has
freckles is located at a particular
place or locus, e.g on one
chromosome within the narrow
orange band. Then the other chromos of the
homologous pair also has a gene for
freckles at that locus
– However the two homologs my have
different version of the freckles gene,
perhaps one promotes freckles the other
do not

Front 40

locus

Back 40

(plural, loci) is the
position of a gene

Front 41

Different versions of a gene may
be found at the same _____on
maternal and paternal
chromosomes

Back 41

locus

Front 42

The two distinct chromosomes
called ______ are in an
important exception to general
pattern of homologous
chromosomes

Back 42

X and Y

Front 43

Females have a homologous pair
of... males have....

Back 43

X chromosome (XX)
one X and one Y (XY)

Front 44

Because they determine the
individual sex, the X and Y are
called

Back 44

sex chromosomes
(although they carry genes that
perform other functions as well

Front 45

Only small parts of the X and Y
are homologous

Back 45

Most genes carried on the X
chromosomes do not have
counterparts on the tiny Y

Front 46

The other 22 pairs of
chromosomes are called

Back 46

autosomes

Front 47

Having two sets of chromosomes,
one inherited from each parent is a...

Back 47

key factor in human life cycle

Front 48

Meiosis

Back 48

process that converts
diploid nuclei to haploid nuclei

Front 49

Diploid cells

Back 49

have two
homologous sets of
chromosomes; total number
of chromosomes is called a
diploid (2n), which is 46 for
humans; 2n = 46

Front 50

Almost all cells humans are
diploid except the...

Back 50

egg and
sperm cells (gametes)

Front 51

Each gamete has a single set
of chromosomes;

Back 51

22 autosomes plus a single sex
chromosome, either X or Y

Front 52

Haploid cell

Back 52

A cell with a single
chromosome is a Haploid
cell (have one set of
chromosomes)

Front 53

Humans haploid number
is

Back 53

23; n = 23

Front 54

In humans, sexual
intercourse allows...

Back 54

a
haploid sperm from the
father to reach and fuse
with a haploid egg cell of
the mother during
fertilization

Front 55

zygote

Back 55

has a diploid
chromosome number, one set
from each parent

Front 56

Meiosis occurs in

Back 56

the sex
organs, producing
gametes—sperm and eggs

Front 57

Fertilization

Back 57

the union of
sperm (haploid, n) and egg
(haploid, n)

Front 58

zygote has a diploid...

Back 58

(2n) chromosome number,
one set from each parent

Front 59

Mitotic (mitosis) cell division
is then used thereafter:

Back 59

from
zygote stage to complete
development of an adult

Front 60

Because of this all somatic
(body) cells of the human
body has ___chromosomes

Back 60

46

Front 61

Meiosis is a type of cell division that produces...

Back 61

haploid gametes in a diploid
organism

Front 62

Like mitosis, meiosis is preceded by...

Back 62

Interphase
-chromosomes duplicate during the S phase

Front 63

Unlike mitosis, meiosis has...

Back 63

two divisions
– During meiosis I, homologous chromosomes separate
– The chromosome number is reduced by half
– During meiosis II, sister chromatids separate
– The chromosome number remains the same
– (note. meiosis II is similar to mitosis)

Front 64

Events in the nucleus during meiosis 1 Prophase 1

Back 64

– Chromosomes coil and
become compact
– Homologous chromosomes
come together as pairs by
synapsis
– Each pair, with four
chromatids, is called a tetrad
– Nonsister chromatids
exchange genetic material by crossing over

Front 65

Each pair, with four
chromatids, is called

Back 65

tetrad

Front 66

– How many chromosomes are present in one cell?
– How many chromatids are present in one cell?

Back 66

46 chromosomes
92 chromatids

Front 67

Meiosis 1 Metaphase 1

Back 67

– Tetrads align at the cell
equator

Front 68

Meiosis 1 Anaphase I

Back 68

Homologous pairs
separate and move
toward opposite poles of
the cell

Front 69

Meiosis I Telophase I

Back 69

Duplicated chromosomes have reached the poles
– A nuclear envelope forms around chromosomes in some species
– Two daughter cells are formed
– Each nucleus has the haploid number of chromosomes

Front 70

Meiosis II

Back 70

follows meiosis I
without chromosome duplication
(no interphase); sister chromatids
will separate

Front 71

Meiosis II Prophase II

Back 71

Chromosomes coil
and become
compact

Front 72

Meiosis II Metaphase II

Back 72

Duplicated chromosomes
align at the cell equator

Front 73

Meiosis II Anaphase II

Back 73

Sister chromatids
separate and
chromosomes move
toward opposite poles

Front 74

Meiosis II Telophase II

Back 74

– Chromosomes have reached
the poles of the cell
– A nuclear envelope forms
around each set of
chromosomes
– With cytokinesis, four haploid
cells are produced

Front 75

Which characteristics are similar for mitosis and
meiosis?

Back 75

One duplication of chromosomes

Front 76

Which characteristics are unique to meiosis?

Back 76

– Two divisions of chromosomes
– Pairing of homologous chromosomes
– Exchange of genetic material by crossing over

Front 77

What is the outcome of each process?

Back 77

– Mitosis: two genetically identical cells, with the same
8.15 Mitosis and meiosis have important
similarities and differences
g y ,
chromosome number as the original cell
– Meiosis: four genetically different cells, with half the
chromosome number of the original cell

Front 78

Independent orientation at metaphase I

Back 78

– Each pair of chromosomes independently aligns at
the cell equator
– There is an equal probability of the maternal or
paternal chromosome facing a given pole
– The number of combinations for chromosomes
packaged into gametes is 2n where n = haploid
number of chromosomes

Front 79

Random fertilization

Back 79

The combination of each unique sperm with each
unique egg increases genetic variability

Front 80

Separation of homologous chromosomes during
meiosis can lead to genetic differences between
gametes

Back 80

– Homologous chromosomes may have different
versions of a gene at the same locus
– One version was inherited from the maternal parent,
and the other came from the paternal parent
– Since homologues move to opposite poles during
anaphase I, gametes will receive either the maternal
or paternal version of the gene

Front 81

Genetic recombination is...

Back 81

the production
of new combinations of genes due to
crossing over seen in Meiosis I -prophase

Front 82

Crossing over involves

Back 82

exchange of
genetic material between homologous
chromosomes

Front 83

chiasma

Back 83

Nonsister chromatids join at a
chiasma (plural, chiasmata), the
site of attachment and crossing
over
– Corresponding amounts of
genetic material are exchanged
between maternal and paternal
(nonsister) chromatids

Front 84

karyotype

Back 84

shows stained and
magnified versions of chromosomes
– Karyotypes are produced from
dividing white blood cells,
stopped at metaphase
– Karyotypes allow observation of
– Homologous chromosome
pairs
– Chromosome number
– Chromosome structure

Front 85

Trisomy 21

Back 85

involves the inheritance of
three copies of chromosome 21
– Trisomy 21 is the most common
human chromosome abnormality

Front 86

Down syndrome

Back 86

– An imbalance in chromosome
number causes Down
syndrome, which is
characterized by
– Characteristic facial
features
– Susceptibility to disease
– Shortened life span
– Mental retardation
– Variation in characteristics
– The incidence increases with the
age of the mother