Download Document

Another example: Flower color
For example, flower color:
P = purple (dominant)
p = white (recessive)
If you cross a homozygous Purple (PP) with a
homozygous white (pp):
PP

Pp
pp
ALL PURPLE (Pp)
Cross the F1 generation:

Pp
P
p
Pp
P
p
PP
Pp
Pp
pp
Genotypes:
1 PP
2 Pp
1 pp
Phenotypes:
3 Purple
1 White
Mendel’s Principles
• 1. Principle of ___________________:
One allele ________________ another,
one allele was _________________ over the
other in the F1 generation.
• 2. Principle of ____________________:
When ______________ are formed, the
pairs of hereditary factors (_________)
become ________________, so that each sex
cell (egg/sperm) receives only ________ kind
of gene.
Human case: CF
• Mendel’s Principles of Heredity apply
universally to all organisms.
• Cystic Fibrosis: a lethal genetic disease affecting
_________________.
• Caused by mutant ______________ gene carried
by 1 in 20 people of European descent (12M)
• One in 400 Caucasian couples will be both
carriers of CF – 1 in ____ children will have it.
• CF disease affects ______________
in tissues – mucus is accumulated
in lungs, causing infections.
Inheritance pattern of CF
IF two parents ___________ the recessive
gene of Cystic Fibrosis (c), that is, they are
___________________ (C c), one in four of
their children is expected to be
__________________ for CF and have the
C
c
disease:
C C = normal
C c = carrier, no symptoms
c c = has cystic fibrosis
C
CC
Cc
c
Cc
cc
Probabilities…
• Of course, the 1 in 4 probability of getting the
disease is just an expectation, and in reality,
any two carriers may have normal children.
• However, the greatest probability is for 1 in 4
children to be affected.
• Important factor when prospective parents are
concerned about their chances of having
affected children.
• Now, 1 in 29 Americans is a symptom-less
carrier (Cf cf) of the gene.
Gaucher Disease
• Gaucher Disease is a rare _______________
disease. It causes _____________-storage disorder
(lipids accumulate in spleen, liver, bone marrow)
• It is the most common genetic disease affecting
_____________ people of Eastern European
ancestry
(1 in 500 incidence; rest of pop. 1 in 100,000)
Principle of Independent Assortment
• Based on these results, Mendel postulated the
3. Principle of __________________________:
“Members of one gene pair
_______________ independently from other gene
pairs during ______________ formation”
Genes get ______________ – these many
combinations are one of the advantages of sexual
reproduction
Relation of gene segregation to
meiosis…
• There’s a ________________ between the
movement of chromosomes in meiosis and
the segregation of __________ that occurs
in ___________
Beyond Mendelian Genetics:
Incomplete Dominance
Mendel was lucky!
Traits he chose in the
pea plant showed up
very clearly…
One allele was _______________ over another,
so ________________ were easy to
recognize.
But sometimes phenotypes are not very
obvious…
Summary of Genetics
• Chromosomes carry _________________ info (genes)
• Chromosomes (and genes) occur in __________
• New _________________ of genes occur in sexual
reproduction
• Monohybrid vs. Dihybrid crosses
• Mendel’s Principles:
– _____________________: one allele masks another
– _________________: genes become separated in gamete
formation
– ________________ Assortment: Members of one gene pair
segregate independently from other gene pairs during gamete
formation
Meiosis
Genes
• Tens of thousands of genes
• Lined up on chromosomes
Chromosomes
• Occur in ___________
(Male, Female)
• _____________—A
cell with two of each
kind of chromosome is
said to be diploid, or
_______, number of
chromosomes
Gametes
• Male (__________) and Female
(_________)
• Contain one of each kind of
chromosomes.
• A cell with one of each kind of
chromosome is called a
________________ and is said to
contain a haploid, or _____, number of
chromosomes.
Homologous Chromosomes
• Pair chromosomes are
called
__________________
chromosomes—
determine
__________________.
• Gene for same trait
– same order,
– chromosomes in a
homologous pair are not
always identical.
• (Chromosome 4
contains 3 traits
Mendel Studied)
Meiosis
From the Greek word meioun,
meaning “to diminish”.
Cell division that results in a
_____________ containing
___________ the number of
chromosomes of its parents.
Meiosis
• Divisions: Meiosis ____ and Meiosis ______
• Begins with
one diploid (___) cell
four haploid (___)
cells.
• Sex cells (_________________) haploid.
• Sperm fertilizes an egg-results in zygote
(diploid)
• Zygote develops by ______________ into a
multi-cellular organism.
• Reproduction —Production and subsequent
fusion of haploid sex cells.
Interphase
• Chromosomes _____________
• Chromosome
– two identical sister ________________ held
together by a ____________________
Prophase I
• Chromosomes coil up and a
_______________ forms.
• Homologous chromosomes
comes together, matched
gene by gene, to form a
four-part structure called a
_____________.
• Chromatids pair so tight
that sometimes non-sister
chromatids from
homologous chromosomes
sometimes exchange
genetic material in a
process known as
___________________.
Crossing Over
•
•
•
•
Exchange of ______________ material
Any location
Several locations at once
Humans-Two to three crossovers for each pair of
homologous __________________.
Metaphase I
• ___________________ attaches to a spindle
fiber
• ____________________________ pull the
tetrads into the middle, or equator, of the spindle.
• Chromosomes are lined up side by side as
tetrads.
Anaphase I
• Chromosomes
__________________ and
move to opposite ends of the
cell.
• Centromeres holding the sister
chromatids together do not
___________ like they do in
anaphase of mitosis.
• Ensures that each new cell
have only one chromosome
from each ______________
pair.
Telophase I
• ______________ is
broken down
• Chromosomes
_______________
• Cytoplasm divides  2
new cells.
• ____________ of genetic
information of original
cell (one chromosome
from each homologous
pair)
• Another cell division
needed
Meiosis II
• Newly formed cells go through short
_______________ (*chromosomes don’t replicate*)
• _______________ II—Spindle forms in each of the
two new cells and the spindle fibers attach to the
chromosomes.
• _______________ II—The chromosomes, still made
up of sister chromatids, are pulled to the center of the
cell and line up randomly at the equator.
• _______________ II—Centromere of each
chromosome splits, allowing sister chromatids to
separate and move to opposite poles.
• _______________ II—Nuclei reform, spindles break
down, and cytoplasm divides.
Meiosis Results
• Four ______________ sex cells have
been formed from one original
_____________ cell.
• Each haploid cell contains one
____________________ from each
homologous pair.
• Haploid cells become ______________,
transmitting the genes they contain to
offspring.
The History of DNA
Early Work
Friedrich Miescher, 1869, first isolates a
substance from the nucleus of cells that
he calls “______________.” His student,
Richard Altmann, calls the substance
“___________________________.”
Biochemists identify two types of
nucleic acids, later called ____________ and
________________.
In 1929, ____________________________________
at the Rockefeller center identifies the
four bases of DNA.
What Does DNA Do?
Though early researchers knew that DNA
was found in chromosomes, they doubted
that it was the hereditary material. There
were only four bases. How could four bases
code for all sorts of proteins?
Some researchers, including Linus Pauling,
thought that the protein also found in
chromosomes was probably the hereditary
factor.
Frederick Griffith
In 1928, Frederick Griffith carried out
experiments on pneumonia
_________________________ in _____________.
Discovery: something in
__________________________________ virulent
bacteria could be transferred to live,
harmless bacteria and make them
virulent.
Griffith’s Experiment
Oswald Avery
Avery continued working with
Griffith’s findings in hope of
discovering what factor in bacteria
carried the trait of virulence.
Isolated proteins, carbohydrates,
nucleic acids and applied them to nonvirulent bacteria. Only
__________________________________ (DNA)
caused a change.
Avery’s Work
Erwin Chargaff
Chargaff studied DNA itself, in
hopes of providing some clues
about its _______________________.
Discovered that there are always
_____________________ amounts of the
bases Adenine and Thymine, and
equal amounts of Cytosine and
Guanine.
Chargaff proposed that these
bases _______________ with one
another in some way.
Wilkins and Franklin
Rosalind Franklin and Maurice Wilkins
worked with __________________
crystalography to find more clues about
the ________________________ of DNA.
Franklin’s X-ray images suggested a
______________________ structure.
Franklin and Wilkins
Watson and Crick
James Watson and Francis Crick were also
working on discovering the structure of DNA.
Applied Chargaff’s rule, assumed that _________
always pairs with _______, ______ with __________.
Watson was not entirely convinced of the
helical structure that _____________________ had
suggested, and his critique of her work led her
to doubt herself.
Watson and Crick
Wilkins consulted with
Watson and Crick.
Without Franklin’s
knowledge, he handed
them the data that he and
Franklin had worked on.
Watson immediately
recognized the
significance. He and Crick
went to work on a model
of DNA.
The First DNA Model
DNA structure
DNA is made up of _________ bases. RNA also has four bases, but has
_______________ instead of ________________.
DNA structure
Across the DNA double-ladder, _______ always pairs with ______, _________
always pairs with _______ because of the number of hydrogen bonds the
bases form.
DNA structure
The DNA ladder forms a ___________________, or helical, structure, with
the two sides held together with _______________________ bonds.