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Cellular Reproduction and DNA
 Offspring receive their traits from their parentsbut sometimes the child looks nothing like the
parents
Cellular Reproduction and DNA
 Offspring receive their traits from their parentsbut sometimes the child looks nothing like the
parents
 Lamarkian biology- characteristics such as
height, strength, and weight are determined by the
activities of the parents. (FAIL.)
The Father of Modern Genetics
 Gregor Mendel (1822-1884): an
Austrian monk
 Gave first real explanation for
how traits are passed on to
offspring
 Conducted meticulous
experiments on 29,000 pea plants
 Mendel's work was rejected
during his lifetime, and it wasn't
widely accepted until the 1930's
and 1940's
 Genetics- the science that studies
how characteristics get passed
from parent to offspring
Genes, Chromosomes, and DNA
 DNA governs an organism's
traits and characteristics
 DNA's main function is to tell
the cell what proteins to make
Genes, Chromosomes, and DNA
 DNA governs an organism's
traits and characteristics
 DNA's main function is to tell
the cell what proteins to make
 Not every organism's traits
are completely determined by
a person's genes
 Genetic tendency- a range of
possible characteristics set by
DNA
Genetic Tendencies
 People have a certain capacity for musical ability, or athletic ability
 Some people choose to fight against genetic predispositions such as
alcoholism and obesity
 Consider an alcoholic whose father is also an alcoholic- you could
argue that the son learned this through father, or that alcoholism is in
his genes, or it's a combination of both
Genetic Tendencies
 People have a certain capacity for musical ability, or athletic ability
 Some people choose to fight against genetic predispositions such as
alcoholism and obesity
 Consider an alcoholic whose father is also an alcoholic- you could
argue that the son learned this through father, or that alcoholism is in
his genes, or it's a combination of both
 Gay rights activists are searching for a “gay gene” in order to justify
their behavior
 However, many defects are transmitted through genes (eg. Down
Syndrome, cystic fibrosis, color blindness)
 Even if a “gay gene” were found, a gene cannot force a person into a
homosexual lifestyle- he is able to choose how to live, just like an
alcoholic can choose not to drink alcohol
Developmental Factors
 Characteristics completely from DNA: hair color, blood type
 DNA alone does not determine who you are or what you will
become
 DNA provides the general framework within which you decide
who you will become
Developmental Factors
 Characteristics completely from DNA: hair color, blood type
 DNA alone does not determine who you are or what you will
become
 DNA provides the general framework within which you decide
who you will become

Genetic factors- traits determined by DNA

Environmental factors- nonbiological factors that are
involved in a person's surroundings (family, friends,
school, choices they make)

Spiritual factors- factors in a person's life determined
by the quality of their relationship with God
 There is still much debate over how much influence each of
these factors has over a person's development
Genes and DNA
 Gene- a section of DNA that
codes for the production or
portion of protein, thereby
causing a trait
Genes and DNA
 Gene- a section of DNA that
codes for the production or
portion of protein, thereby
causing a trait
 The tasks that a cell can
complete depend upon the
proteins it produces
 If a cell produces certain
proteins, it's a nerve cell, if it
make other proteins, it's a
blood cell
Genes and DNA
 Gene- a section of DNA that
codes for the production or
portion of protein, thereby
causing a trait
 The tasks that a cell can
complete depend upon the
proteins it produces
 If a cell produces certain
proteins, it's a nerve cell, if it
make other proteins, it's a
blood cell
 A cell knows what proteins it
should produce because the
DNA tells it what to make
DNA and RNA
DNA and RNA
DNA
RNA
 Sugar: deoxyribose
Sugar: ribose
 Structure: double helix
Structure: single strand
 Nucleotides: adenine,
guanine, cytosine, thymine
Nucleotides: adenine,
guanine, cytosine, thymine
 More stable, less likely to
experience changes during
duplication (less mutations)
Less stable
Protein Synthesis- Part 1:
Transcription
 1. Transcription- building an
RNA strand from a section of DNA
 RNA copies DNA by attaching
corresponding nucleotide bases
 RNA is like a camera that produces
a negative image (light in places it
should be dark)
 T- A
 C- G
 A- U
Protein Synthesis- Part II: Translation
 2. Translation: the process
of translating the nucleotide
bases into amino acid
sequences
Protein Synthesis- Part II: Translation
 2. Translation: the process
of translating the nucleotide
bases into amino acid
sequences
 Messenger RNA (mRNA)RNA that performs
transcription and then goes
to the ribosomes
Protein Synthesis- Part II: Translation
 2. Translation: the process
of translating the nucleotide
bases into amino acid
sequences
 Messenger RNA (mRNA)RNA that performs
transcription and then goes
to the ribosomes
 Transfer RNA (tRNA)contains an anticodon
bonded to an amino acid
 Anticodon- three nucleotide
base sequence on tRNA
Protein Synthesis- Part II: Translation
 Codon- a sequence of three
nucleotide bases on mRNA that
refers to specific amino acid
Protein Synthesis- Part II: Translation
 Codon- a sequence of three
nucleotide bases on mRNA that
refers to specific amino acid
 Translation repeats until all amino
acids that are called for by codons
are linked together
 DNA → RNA → protein
Protein Synthesis- Part II: Translation
 Codon- a sequence of three
nucleotide bases on mRNA that
refers to specific amino acid
 Translation repeats until all amino
acids that are called for by codons
are linked together
 DNA → RNA → protein
 A given amino acid can be “called
for” by several different codons.
eg. cysteine can be called by UGC
or UGU
 However, a single codon cannot
call for more than one amino acid
(eg. UGU is only for cysteine)
 Protein Synthesis
DNA and RNA
 Exons- part of DNA with instructions for making a protein
 Introns- separates exons, must be removed before it becomes mRNA
DNA and RNA
 Exons- part of DNA with instructions for making a protein
 Introns- separates exons, must be removed before it becomes mRNA
 Introns are also known as “junk DNA” because they don't appear to
serve any purpose
 DNA is very thin- .0000002mm
 If all the DNA from one cell we strung together end to end, it would
be six feet long. All DNA in body: 67 billion miles (16x distance of
Pluto to Sun)
How DNA is Packaged
 Histones- proteins that act as
spools which wind up small
stretches of DNA
 Nucleosomes- beads of DNA
wrapped around histone
How DNA is Packaged
 Histones- proteins that act as
spools which wind up small
stretches of DNA
 Nucleosomes- beads of DNA
wrapped around histone
 Chromosome- network of DNA
coils and proteins

In nucleus
How DNA is Packaged
 Histones- proteins that act as
spools which wind up small
stretches of DNA
 Nucleosomes- beads of DNA
wrapped around histone
 Chromosome- network of DNA
coils and proteins

In nucleus
 Chromatin- strands of
chromosomes, RNA, and proteins
 Condensed chromosome- most
compact version of DNA
 Humans: 46 chromosomes horse:
64, crayfish: 200
Mitosis and Interphase
 Mitosis- a process of asexual
reproduction in eukaryotic cells
 Interphase- time interval
between cellular reproduction
 Chromosomes not condensed
 Cell spends most of its time in this
stage
 DNA remains in its chromatin form,
except when making proteins
 Cell cycle- cycle between interphase and mitosis
Mitosis
-In order to reproduce,
chromosomes must duplicate
-Sister chromatids- duplicate
chromosomes
-The centrioles also duplicate,
then mitosis starts
1. Prophase
-duplicated chromosomes coil into
their condensed form
Centromere- the region that joins two
sister chromatids
-aster- microtubules extended from
centrioles
-as centrioles migrate, the
microtubules grow, producing spindle
fibers
- Spindle fibers make up the mitotic
spindle
2. Metaphase
-chromosomes are lined up
along equatorial plane
2. Metaphase
-chromosomes are lined up
along equatorial plane
3. Anaphase
-microtubules separate the sister
chromatids from each other
-sister chromatids are pulled
to opposite sides
2. Metaphase
-chromosomes are lined up
along equatorial plane
3. Anaphase
-microtubules separate the sister
chromatids from each other
-sister chromatids are pulled
to opposite sides
4. Telophase
-spindle begins to disintergrate
-plasma membrane begins to
constrict along equatorial plane
4. Telophase
-spindle begins to
disintergrate
-plasma membrane begins to
constrict along equatorial
plane
-two cells begin to form
-nuclear membrane forms
around each chromosome
- chromosomes uncoil from
their condensed form back
into chromatin
-the end result is two
identical daughter cells
More About Mitosis
•Each daughter cell gets at least one of each organelle
•If the two cells have only one organelle between them, the
organelle is split
•DNA can build up or make new organelles as needed
•The mitochondria has its own DNA so it can replicate itself
More About Mitosis
•Each daughter cell gets at least one of each organelle
•If the two cells have only one organelle between them, the
organelle is split
•DNA can build up or make new organelles as needed
•The mitochondria has its own DNA so it can replicate itself
•Mitosis is a form of asexual reproduction
•Every eukaryotic organism performs mitosis
•Mitosis produces new cells as the organism grows, and
replaces dead cells
•Millions of red blood cells die every minute
More About Mitosis
• Plant mitosis: due to cell wall, the plasma membrane
can’t constrict
• Cellulose is formed in the middle, producing the cell
well
• Also no centrioles are in the plant cells
Chromosomes
Karyotype- the figure produced
when chromosomes of a species
during metaphase are arranged
according to their homologous pairs
-Homologous pairs- chromosomes
that are very similar but not identical
-Sex chromosomes- a pair of
chromosomes which can be used to
distinguish between the sexes
- XX: female
- XY: male
Diploid and Haploid Cells
•each homologue has exactly
the same number of genes as
its partner
•For example, the gene for
blood type can be found on
chromosome #9- on one
homologue, the gene might be
for blood type A and on the
other, O.
•Diploid cell- a cell with
chromosomes that come in
homologous pairs
•Haploid cell- a cell that has
only one representative of each
pair
Diploid and Haploid Cells
•Even species that
have diploid cells will
have some haploid
cells
•Diploid number (2n)total number of
chromosomes in a
diploid cell
•46 for human
•Haploid number- (n)
number of
homologous pairs in a
diploid cell
•23 for human
Sexual Reproduction
Meiosis – the process by which a diploid (2n) cell forms gametes (n)
-each parent contributes 23 chromosomes
-In meiosis, diploid cells get split into haploid cells called gametes
-Gametes- haploid cells produced by
diploid cells for purpose of sexual
reproduction
-Female: egg (ovum)
Male: sperm
-Two gametes join together to form a|
diploid cell that has 23 homologous
pairs of chromosomes- zygote
Meiosis I
Meiosis I- one diploid cell forms
two haploid cells
-two begin meiosis, cell must
duplicate DNA and centrioles
-Prophase I- centrioles move to
opposite sides of cell
-DNA is exchanged between
homologous chromosomes (cross
over)
-Mitotic spindle forms
-Metaphase I- single microtubule
for each pair- chromatids stay
intact
Meiosis I
Anaphase I- homologous pairs
are pulled to either side
Telophase I- plasma membrane
constricts along equatorial plane
-two haploid cells are formed
-though each cell has 46
chromosomes, the cells are
considered haploid because the
chromosomes are paired with an
exact duplicate, leaving 23
unique chromosomes
Meiosis
Prophase II- both cells have their centrioles duplicate and form a
spindle
Metaphase II- chromosomes line up
along equatorial plane
-chromosomes attach to each
chromatid
Anaphase II- the microtubules pull
the chromosomes away from
their duplicates
Telophase II- plasma membrane constricts along equatorial plane,
forming two pairs of haploid cells
Mitosis vs. Meiosis
Mitosis: one diploid cell forms
two duplicate diploid cells
Meiosis: diploid to haploid
-One diploid cell forms 4
haploid cells
Spermatogenesis
-In males, meiosis produces
sperm cells
- At the end of meiosis II,
flagella emerges on each of
the four haploid cells
Oogenesis
Oogenesis: meiosis in females
-at the end of telophase I, one of
the two cells produced takes most
of the cytoplasm and organelles
-After meiosis II, one of the big
cells from Meiosis I takes most of
the cytoplasm and organelles
-the end result is one large gamete
(Egg cell) and three smaller polar
bodies
- when the sperm burrows into the
egg, it forms a diploid cell called
a zygote
Viruses
Virus- non-cellular infectious
agent
1. has genetic material
(RNA or DNA) inside a
protective protein coat
2. cannot reproduce on its
own
-a virus hijacks a cell in
order to reproduce
-because a virus cannot
reproduce on its own, it’s not
alive
Lytic Pathway
1. Virus attaches to bacterium
2. Virus injects own genetic
material
3. Virus DNA instructs bacteria to
make viral proteins and genetic
material
4. Viruses form in cell
5. Cell ruptures, releasing several
viruses
Viruses
•Some viruses, like HIV, can
inject genes into the cell and
lie dormant for several years
before the lytic pathway starts
•Viruses: chicken pox, flu,
mumps, cold, mumps, measles,
AIDS, cold sores, some forms
of cancer
•Viruses affect plants, animals,
and bacteria
The Immune System
Phagocytic cells- purpose is to
engulf and destroy pathogens (eg.
White blood cells)
Lymph nodes- a place for
phagocytic cells to gather
-lymph carries pathogens
through the lymph nodes, where
the phagocytic cells destroy them
Antibodies- specialized proteins
that aid in destroying infectious
agents
Antibodies
-some antibodies can destroy many
kinds of pathogens, others can only
fight one kind
-when the body is infected, it
produces antibodies that will
destroy the pathogen
-the body remembers which
antibodies will fight a particular
disease
Vaccine- a weakened or inactive
version of a pathogen that
stimulates the body’s production of
antibodies which can aid in
destroying a pathogen