Transcript 2013-14 Academic Decathlon Science Component

2013-14 Academic Decathlon
Science Component Section I
Prepared by Ms. Aguilar
Section I History Overview
Early Hypothesis
Aristotle: Male provides a miniature individual through the
blood. Female provide the environment for growth.
Idea Persisted for >2000 years
Hippocrates: every organ in our body originated from a
“gemmule” that accumulate in the male & female
reproductive organs during sexual maturity. Pangenesis:
Upon conception gemmules combined & blended together
to form different parts of the new individual (Proposed by
Darwin)
Kolreuter: studies genetic crosses in tobacco plant & came up
with Blending Inheritance. Formed the basis for Darwin’s
theory of evolution
Mendel: 1850’s-60’s experimented with pea
plant. Formulated a set of principles &
described the “inheritance factor” later called
the gene.
Darwin: along with Wallace developed the
theory of “Natural Selection”
Note! neither men had knowledge of
chromosomes and so Mendel’s work was
ignored for decades
Major Discoveries WWI
• Genetics Blossomed
• 1900-1914 Mendel’s work was rediscovered &
Natural Selection validated.
• Correns, deVries, & Tschermak hybridized: mated
two different plant species to generate an
offspring with traits from both parents thereby
marking the rediscovery of Mendel’s work
• Sutton & Boveri: chromosomes in nucleus
segregate in meiosis. So Mendel’s “factor” was
linked to the chromosome.
• 1905 term “genetics” is coined by William
Bateson. Together with Reginald Punnett discover
linked genes.
• Stevens and Wilson discover chromosome
differences w/ male & female.
• 1902 Archibold Garrod notices 1st “inborn error in
metabolism” caused by the lack of an enzyme
due to a recessive trait.
• Morgan worked with Drosophila melanogaster
to study pattern of eye color inheritance and
realized it was a sex-linked carried on the X
since most males had white eyes.
Controversy
Late 19th century/ early 20th century
• Social Darwinism becomes popular; “Survival
of the Fittest”
• Eugenics Movement: R.A. Fisher becomes a
strong advocate for improving the genetic
composition of humans. NOTE!! Used during
WWII commit acts of genocide.
Discovery of Cells
• Microscope; most important tool that aided
humans in viewing the microscopic world.
• Robert Hook: 1st to observe cork cells and call
them “cells”
• Anton van Leeuwenhoek was the 1st to
observe live cells.
• Robert Brown observed and coined the
“nucleus”
• Father of Taxonomy, Carolus Linnaeus (1700’s) was the first to
classify everything living into 3 kingdoms: Vegetable, Animal or
Mineral
• Today we use a system derived from the rRNA comparison of
organisms. (molecular biology)
Live in extreme
conditions; very
hot, salty, acidic,
methane rich
places.
Large diversity of
bacteria some can
perform
photosynthesis
Conditions of Early Earth
• 1923: Hypothesis by Oparin suggested that the
atmosphere only contained ammonia, hydrogen gas,
water vapor, & methane.
- This gases reacted under extreme temperatures &
conditions to form simple organic compounds.
• 1953: Miller & Urey set up an experiment to
test Oparin’s hypothesis.
- The experiment produced a variation of
organic compounds, including amino
acids and nucleotides.
1953: Miller & Urey
set up an experiment
to test Oparin’s
hypothesis.
- The experiment
produced a variation
of organic
compounds, including
amino acids and
nucleotides.
From Molecules to Cell-Like Structures
• Sidney Fox heated
amino acids to form
protein chains. When
allowed to cool selfassembled into small
spheres that were
selectively permeable.
• They were called
microspheres.
• Microsphere demonstrate
excitability, absorb
materials from their
surroundings & respond to
changes in osmotic
gradients
Cell Theory
Cells
Schleiden, Virchow, Schwann
• The Cell is the basic unit of life
• All living things are made of cells
• All cells arise from pre-existing cell
Eukaryote
Prokaryote
3.8 by First cells,
bacteria, lack a nucleus.
Have nucleoid region
and no membrane
bound organelles. Might
have cell wall, capsule,
pili or flagella
Highly organized membrane-bound organelles &
nucleus with specific functions. Have an outer
barrier, and a fluid filled space. Found in protist,
fungi animals & plants.
Animal
Round in shape have
centrioles, lysosomes, &
some have flagella.
Plant
Squared in shape, have
cell wall, chloroplast,
large vacuole.
Plasma Membrane
• Bilayer of phospholipids; charged phosphate heads and
hydrophobic fatty acid tail.
• Several proteins function as enzymes, transporters,
receptors, recognition sites or anchoring
Cytoplasm
• Fluid filled space w/ cell
membrane and nucleus.
• Initial breakdown of
glucose takes place here.
(glycolysis)
• All other reactions critical
to the cell take place in
specialized
compartments
(organelles)
Nucleus
Double membrane
• Delegates orders to
the rest of the
organelles.
• Stores genetic info
• DNA organized in
chromosomes.
• Has nucleolus inside;
rRNA synthesis
Ribosomes
•Composed > 70 proteins
•Can be free-floating or
attached to the rough ER
•Function is to synthesize
proteins
(50S)
•Proteins made by free
floating ribosome stay and
work inside the cell
•Proteins made by attached
ribosome go through an
assembly line, travel through
membrane system, & are
directed to various
destinations
(30S)
Endomembrane System
• Consists of the nuclear envelop, rough &
smooth ER, Golgi body and transport vesicles.
• Vesicles shuttle proteins from one location to
another through the endomembrane system.
• At each location the protein undergoes
modifications that prepare it for a specialized
function
Rough
ER
• Made of tightly compacted membranes
• Ribosomes attached to its surface
• Have many enzymes responsible for varied rxn’s
Golgi Complex
• Receives
proteins from
the Rough ER
• Process,
concentrate, &
modifies
proteins & sends
them to their
final destination.
Lysosome
• Digestive organelle
• Digests particles, gets
rid of aged and worn
out structures and
recycles the parts
• Lacking in plant cells,
use vacuole in its
place.
Vesicle
• Produced from the ER
or Golgi membrane,
but can also form
from the cell
membrane when the
cell takes IN material
• Section pinches off
producing a
membrane-enclosed
compartment.
• Temporarily store and
transport proteins to
their destination
Smooth ER
• Site of steroid, lipid, &
carbohydrate synthesis
• Has enzymes that
break-down toxins
• Detoxification of
drugs, alcohol,
pesticides and other
toxins
• Made of protein
fibers that provide
support, aid in
transport, anchor
organelles & act as
tracts for motor
proteins
-microtubules: largest,
provide support, form
tracks for
transportation & aid
in cell division
-Intermediate Filaments:
made of flexible
protein that keep
organelles in place
- Microfilaments:
thinnest, look like
string of beads, found
around the periphery
of the cell to provide
shape, strength &
motility. Play role in
cell taking in material.
Cytoskeleton
Centrioles
• Found in pairs near the
nucleus and only in
animal cells.
• Microtubule organizing
center
• Play an important role in
cell division.
• Divide during cell
division, move to
opposite poles and form
the spindle fibers
Cilia and Flagella
• External projections of the
plasma membrane
• Used in movement,
adhesion, & movement of
material outside cell
• Internally made of
microtubules
• Sperm: long tail that
propels a cell
• Cilia: small, numerous,
projections
Mitochondria
• Double membrane
• Generate energy:
Converts chemical
energy from food
into ATP
• Contains its own
DNA & ribosomes
• Believed to have
evolved from
prokaryotic cell
• Double Membrane
• Have own DNA &
ribosomes
• Produce & store
food material
• Contain chlorophyll
& carotenoids that
trap light for
photosynthesis
• Found only in plant
cells
• Believed to have
evolved from
prokaryotic cell
Chloroplast
Vacuole
•Found in plants and some
protist
•Help support the cell wall
•Store water, food, salts,
pigments & toxic byproducts
•Help eliminate excess water &
maintains proper salt content
in cytoplasm
• have similar role to lysosome
in animal cell
•Very small in animal cells but
large in plant cells (90% of
space)
Edosymbiosis
• Theory that explains the origin of the mitochondria &
chloroplast which are both double membrane bound
organelles with their own DNA.
• Evolved from prokaryotes that entered and began
living symbiotically within eukaryotic cells.
Organelles Involved in Cell Division
• Nucleus,
centrosomes,
microtubules, cell
membrane and cell
wall.
• Microtubules
organized by newly
formed centrosomes
move and transport
chromosomes.
Life Cycle
• All living systems must reproduce to maintain the
survival of the specie
•All cellular reproduction involves replication of the
genetic material & even distribution of it to daughter cells
• Reproduction can be sexual or asexual
• Asexual = Binary Fission
- In Prokaryotes: bacteria have a single circular
chromosome that replicates itself to form 2 rings these
rings then anchor themselves to the cell membrane.
Membrane grows, pinches inward and splits forming 2
identical cells clones to the parent cell.
• Bacteria divide every 20 min if conditions are good.
• Sexual Reproduction in bacteria is called conjugation
and it’s a process that generates diversity.
• 90% of time is spent
preparing for Mitosis in
interphase (G1, S, G2)
• 10% of time in Mitosis
• G1: the cell grows and
RNA and protein
synthesis because all
organelles must replicate
• S: diploid genome
doubles = DNA
replicates. Chromosomes
double and each end up
with 2 sister connected
chromatids
• G2: building blocks for
organelles are assembled
Cell Cycle
Interphase: chromatin
duplicates, sister
chromatids are formed
Early Prophase: sister
chromatids condense &
joined at centromere,
spindle microtubules
appear
Late Prophase: nuclear
envelop disintegrates,
spindle microtubules
connect to sister
chromatids in
kinetochore,
centrosomes with
anchored spindle fibers
migrate to opposite
poles
Mitosis
Metaphase: chromosomes line up along the
metaphase plate
Anaphase: adhesive connecting the sister
chromatids disintegrates. The 2 centromere
splits separating the sisters. The kinetochore
shorten, pulling the chromosomes to opposite
poles
Telophase: reverse of prophase. Chromosomes
start to unwind, nucleoli reassemble, nuclear
envelop reforms, & spindle microtubules and
centromeres disintegrate & recycled.
Cytokinesis: point in which cytoplasm divides.
-Animals: a cleavage furrow forms halfway w/
the 2 new cells & the cells split.
-Plants: require preformed vesicles with cell
wall & cellulose material to form a plate
Sexual Reproduction
• evolved 2 billion years ago
• unicellular eukaryotes use
mitosis under normal
conditions but sexually under
unpredictable environments.
• germ cells: specialized cells
like sperm and egg pass on
hereditary information
through meiosis.
- Gametogenesis: the
formation of the egg and
sperm
- spermatogonia: diploid
immature male gamete
- oogonia: diploid immature
female gamete
• Similar to mitosis in phases.
• Differences:
- 2 cell divisions, 1st necessary for crossing
over and creating genetic diversity and the
second one dividing the chromosome # by
half.
IMPORTANT
•Prophase I: Homologous Chromosomes
pair up along their length forming a tetrad
then crossover to synapse. Genes from the
maternal and paternal chromosomes
exchange genes leading to genetic diversity.
Meiosis
Fertilization
• Sperm + Egg = zygote or
n (haploid)+ n (haploid) = 2n (diploid)
• Zygote divides numerous times through mitosis reaching 50 trillion cells
• Stem Cells: calls that divide infinitely and can be induced to become any cell type
•NOTE! very important to scientist because they can be used to replace damaged cells
that do not divide (brain and heart) also some of the genes that program stem cells
have been identified so in the future stem cells may be reprogrammed into Pluripotent
cells.
• cells can be
-Totipotent: cell that can become any of 260 cell types
-Pluripotent: cells that can differentiate into any cells that we find in an adult human
-Multipotent: can only form a small # of specialized cells.
Sources of Genetic Variation
Mutation: ultimate source of genetic variation. Change
in DNA.
Crossing Over & genetic recombination: cell can
undergo up to 60 crossing over events. Reason we
have traits from mom & dad.
Independent Assortment: independent shuffling of
chromosomes. 46 chromosomes in humans can yield
up to 64 trillion possible combinations
Random Mating & Fertilization: 1 of 50 million sperm
and 1 of 1 million eggs randomly combine during
fertilization.
Types of Somatic Cells
Not all cells divide in our body because the process consumes
too much ATP
Dividing Cells: needed to replace cells that die. Commonly
found in cells lining external & internal structures & go
through mitosis often.
Non-Dividing Cells: cells that have vital functions and
therefore cannot be interrupted with cell division. These cells
stay in the G0 phase. Ex: nerve cells, cardiac, hair cells in the
ear, & lens cells
Reproductively Dormant Cells: cells in the G0 phase but are
induced to enter the cell cycle under certain conditions. Ex:
embryos in seeds, when organ needs to heal
Controls of the Cell Cycle
• Needed to make sure cells do not divide
indefinitely because this would lead to
cancer
• Mitosis Inhibiting Proteins provide the
checkpoints in the cell cycle.
• Mutations in any of these proteins can
cause cells to proliferate
• Mutations in the Mitosis Promoting
Proteins can also cause cells to proliferate