BIO 160 Chapter 8 Flashcards
cell division
the two daughter cells that result are genetically identical to each other
asexual reproduction
does not involve the fertilization of an egg by a sperm
sexual reproduction
requires fertilization of an egg by a sperm
gametes
egg and sperm
meiosis
cell division which occurs in reproductive organs
histones
small proteins used to package DNA
nucleosome
are proteins used to package DNA in
eukaryotes
centromere
narrow “waist” that joins sister chromatids,holds the sister chromatids
together
cell cycle
A cell cycle is the ordered sequence of events that lead to cell division • Interphase • Mitosis – Prophase – Metaphase – Anaphase – Telophase – Cytokinesis
interphase
a time when a cell performs is normal functions within an organism
mitotic phase
part of the cell cycle when the cell is actually dividing
cytokinesis
the cytoplasm is divided into two
eukaryotic cells
• most genes are located on chromosomes in the cell
nucleus and
• a few genes are found in DNA in mitochondria and
chloroplasts.
• Nucleus contains lots of DNA and genes
• Number of chromosomes in a eukaryotic cell depends
species.
chromatin
fibers composed of roughly equal amounts
of DNA and protein molecules and
– not visible in a cell until cell division occurs
when is DNA replicated?
DNA is replicated during s-phase, resulting in
sister chromatids containing identical genes
what happens during interphase?
During interphase, a cell:
• Functions normally
• Duplicates everything in cytoplasm
• Grows in size
what happens during mitotic phase?
• Mitosis: when nucleus and its contents divide evenly
into 2 daughter nuclei
• Cytokinesis: when cytoplasm is divided into two
mitosis
– Results in two identical daughter cells
– Functions:
• replaces damaged or lost cells (tissue repair)
• permits growth (growth)
• allows for reproduction (asexual)
interphase
each chromosome replicates in late interphase, resulting in two sister chromatids connected at the centromere, chromosomes are loosely gathered at the nucleus
prophase
replicated chromosomes begin to coil up
nuclear membrane begins to disassemble
protein fibers of mitotic spindle begin to form
prometaphase
chromosomes condense to shorten them, making it easier to separate
spindle fibers attach to chromosomes on both sides at the centromere region
metaphase
spindle fibers from opposite sides begin to pull on chromosomes
chromosomes are aligned along middle of cell
anaphase
spindle fibers shorten and pull sister chromatids to opposite ends of the cell
telophase
an identical set of chromosomes reaches each pole
spindle fibers disassemble
nuclear membrane forms around each set of chromosomes, forming the daughter cell nuclei
cytokinesis
• During cytokinesis, the cell membrane pinches in to
completely surround each new daughter cell.
• The cell cycle starts over with two newly formed identical
daughter cells in interphase. Each daughter cell has the same
number of chromosomes as the parent cell
how does cytokinesis differ in plants and animals?
– In animal cells
• known as cleavage
• begins with the appearance of a cleavage furrow, an
indentation at the equator of the cell.
– In plant cells
• cytokinesis begins when vesicles containing cell wall
material collect at the middle of the cell and then fuse
– forms membranous disk called the cell plate.
What happens when cell cycle goes
out of control?
Specialized cell cycle factors normally regulate cell
proliferation by sending “stop” or “go”signals.
• Tumor suppressor genes lose ability to regulate cell
division
• Oncogenes gain ability to always be active
Tumor suppressor genes
Tumor suppressor genes lose ability to regulate cell BRAKES
division
oncogenes
Oncogenes gain ability to always be active GAS
What is cancer?
– Uncontrolled cell proliferation
– Cancer cells can form tumors, abnormally growing
masses of body cells.
– If the abnormal cells remain at the original site,
the lump is called a benign tumor
tumor
abnormally growing mass of body cells
metastasis
The spread of cancer cells beyond their original
site of origin is metastasis
malignant tumor
• spread to other parts of the body and
• interrupt normal body functions.
– Patients w malignant tumor have cancer
cancer treatment
– Resection: removal of tumor
– Radiation therapy: damages DNA and disrupts cell
division
– Chemotherapy: uses drugs to disrupt cell division
resection
removal of tumor
radiation therapy
damages DNA and disrupts cell
division
chemotherapy
uses drugs to disrupt cell division
meiosis
– Results in four haploid gametes
– Functions:
• To increase genetic diversity (ie offspring have slightly
different genetic makeup compared to parents)
• Allows sexual reproduction
• Keeps the chromosome number from doubling every
generation.
somatic cell
– A human somatic cell
• is a typical body cell
• has 46 chromosomes
karyotype
A karyotype is an image that reveals an orderly
arrangement of chromosomes.
homologous chromosome
- are matching pairs of chromosomes
* can possess different versions of the same genes
sex chromosomes
X or Y
autosomes
matching chromosomes
life cycle
The life cycle of a multicellular organism is the
sequence of stages leading from the adults of one
generation to the adults of the next.
diploid organism
Humans are diploid organisms with
• body cells containing two sets of chromosomes
• Haploid gametes that have only one member of each
homologous pair of chromosomes
diploid zygote
In humans, a haploid sperm fuses with a haploid egg
during fertilization to form a diploid zygote
meiosis process
– Haploid daughter cells are produced in diploid
organisms.
– Interphase is followed by two consecutive
divisions, meiosis I and meiosis II.
– Genetic diversity increases through DNA
recombination (crossing over) and independent
assortment
mitosis vs meiosis
– Chromosomes duplicate only once (in S-phase of
Interphase)
– The number of cell divisions varies:
• Mitosis: one division and produces two diploid cells.
• Meiosis: two divisions and produces four haploid cells.
– All the events unique to meiosis occur during
meiosis I.
origins of genetic variations
– Offspring of sexual reproduction are genetically
different from their parents and one another.
– Mechanisms
• DNA recombination (Prophase I of Meiosis)
• Independent assortment (Metaphase I of Meiosis)
• Random fertilization
DNA recombination
– In crossing over,
• nonsister chromatids of homologous chromosomes
exchange corresponding segments
• Genetic recombination, the production of gene
combinations different from those carried by parental
chromosomes, occurs
independent assortment
• Homologous chromosomes align at Metaphase I
randomly
• Homologous chromosome pairs align independently of
other chromosomes
• Total number of chromosome combinations that can
appear in gametes due to independent assortment is 2
n
,
where n is the haploid number
– For humans: 2
23
, there are 8,388,608 different chromosome
combinations possible in a gamete
random fertilization
• Fertilization between egg and sperm is random
• If each gamete is 1 in 8,388,608 different
chromosome combinations, humans have >70 trillion
(8,388,608x8,388,608) different chromosome
combinations
nondisjunction
• Occurs when members of a chromosome pair fail to
separate at anaphase
• produces gametes with an incorrect number of
chromosomes
• Can occur during meiosis I or II
what happens when errors occur in meiosis?
If nondisjunction occurs, and a normal sperm
fertilizes an egg with an extra chromosome, the
result is a zygote with a total of 2n + 1
chromosomes.
– If the organism survives, it will have
• an abnormal karyotype and
• probably a syndrome of disorders caused by the
abnormal number of genes.
down syndrome
– Trisomy 21
– A condition where an individual has an extra
chromosome 21
– Affects ~1 in 700 children
– The incidence of Down syndrome in the offspring
of normal parents increases markedly with the age
of the mother.
roles of cell division in living organisms
cells must divide to replace damaged or ost cells, growth and reproduction
describe structure of a chromosome
helix. histones, nucleosome, centromere
explain how and when chromosomes are duplicated
before the cell divides and DNA molecule is copied and proteins attach as needed, each chromosome consists of two copies called sister chromatids.
describe key events of the cell cycle
interphase- doubles everything in cytoplasm, increases supply of proteins, increases number of organelles.. duplicates chromosomes
mitotic phase- 2 daughter nuclei formed
cytokinesis- cytoplasm splits
s phase
DNA replication
g phases
gap phases between s phase G1 G2
how are tumor cells different than healthy cells of the body?
tumor abnormally growing in body, healthy cells have gas or brakes…
benign vs malignant
benign stays at original site, malignant spreads to surrounding tissue
slash burn and poison
remove tumor, radiate “burn” cells, poison, drugs used to disrupt cell division
sex chromosomes vs autosomes
sex chomosomes, non matching pair,
autosome all match
somatic cells vs gametes
somatic cells have 46 chromosomes somatics go through mitosis, gametes go through meiosis
diploid vs haploid
diiploid - homologous chromosomes
haploid - a single chromosome set
