Transcript RW - My CCSD

Who was Gregor Mendel?
• Father of Genetics
• Austrian monk, teacher, scientist and
gardener who formulated basic laws of
heredity in the early 1860’s video
What did he study?
Worked with garden peas
Easy to grow and had a
short generation time video
Mendelian Genetics p68
Warm up: why did Mendel choose pea plants
to study?
 Mendel cross pollinated
parent (P1) plants to
produce new hybrids.
 He crossed tall plants with
short ones and the
offspring (F1) were all tall.
 Then he allowed the
hybrids to self pollinate
and got 3 tall and 1 short
offspring (F2)
Conclusions? p68
 Rule of unit factors: we have 2 alleles
(different gene forms) for each of our
traits. (1 from each parent)
 Rule of Dominance: one of our alleles
is dominant (T) and one is recessive (t).
 Law of segregation & Independent
Assortment: during fertilization, both
alleles from each parent randomly
separate and combine in new ways.
Mendel’s Conclusion
Paragraph p67
 Explain how Mendel came up with each
of his 3 conclusions from his work with
pea plants.
Examples of
dominant
and
recessive
traits in
humans!
p70
More terminology: p70
warm up: describe some dominant and recessive
traits you have.
Genotype refers to the alleles an individual receives
at fertilization
Phenotype refers to the physical appearance
of the individual.
Homozygous dominant genotypes =
two dominant alleles for a trait. (BB)
Homozygous recessive genotypes =
possess two recessive alleles for a trait (bb)
Heterozygous genotypes =
one of each allele for a particular trait (Bb)
Punnett Squares p70
 Monohybrid Cross: 1 trait, 2 parents
P1= Pure Tall x Pure Short
TT=Tall
tt =short
T
T
t
Tt
Tt
t
Tt
Tt
F1=100%
Tall
T
t
T
t
TT
Tt
Tt
tt
F2=25% pure tall
50% hybrid tall
25% pure short
Dihybrid Cross: 2 traits, parents
p72
 Warm up: how many boxes are in a
monohybrid cross and what % does each
box represent?
Dominant
Yy, YY = yellow
Rr, RR = round
Recessive
yy = green
rr = wrinkled
Each box is=6.25%
Recessive Allele Disorders p74
Warm up: Describe a genetic disease that you have
heard of or that someone you know has.
Disorder: PKU
 Facts: missing an enzyme that breaks down
Phenyalanine (in milk) it accumulates in the
central nervous system
 Caused by a point mutation
Symptoms: can cause mental retardation,
abnormal growth patterns
Incidence: rare in African Americans & Japanese;
more common in Irish
Treatments: test newborns- change diet
Recessive Disorders p74
Disorder: CF- Cystic Fibrosis
 Facts: mucus in lungs & digestive tract is
very thick ; caused by point mutation
Symptoms: makes breathing & digestion
difficult
Incidence: most common in
Caucasians(whites) 1 in 2000 white; 1 in 25
carry recessive allele.
Treatments: frequent lungs infections, daily
therapy is needed to loosen & remove
mucus
Recessive Disorders p74
Disorder: Tay-Sachs
 Facts: disorder of central nervous system,
brain & spinal cord
 missing an enzyme which breaks down
lipids; accumulates in brain
Symptoms: everything goes in reverse;
deteriorates
Incidence: 1 in 27 Jews, Cajuns(Lousiana), &
French-Canadians are carriers
Treatments: none; happens within 1st year
most children don’t live past 5
Defend your position p73
Q. If you were a scientist, which disease
would you want to cure and why? (half
page)
Q Explain why you agree or don’t agree
with the following statement: “We have
millions of genes, so a mutation in one
of them can’t cause very much
damage.”
Incomplete Dominance
p76
 Warm up: what does dominance
mean? Incomplete? Codominance?
 When 2 alleles blend for a new
phenotype:
 A homozygous red flower (RR)
crosses with a homozygous white
flower (WW), to make a Pink flower
(RW)
 Ex: Japanese Four o’clocks
RR = red WW = white RW = pink
 F1:
W
R
RW
RW
W
R
RW
RW
All Pink
F2:
R
R
W
RR
RW
RW
WW
W
1 red : 2 pinks : 1 white
Codominance p76
 When both alleles are expressed in a
cross.
 Ex. A chicken with black feathers (BB)
crosses with a chicken with white
feathers(WW) to make offspring with
black and white checkered feathers.
 Ex.Different blood types in humans: A,
B, AB, O
 Ex: Red Coat - RR
White Coat – WW
White & Red Mixed – RW (“roan”)
F1: R
W
R
RW
RW
RW
RW
W
All Roan – both red and white
hair
F2: R
R
W
RR
RW
RW
WW
W
1 red : 2 roan : 1 white
Codominance in humans
p76
Disorder: Sickle-Cell Anemia
 Facts: sickle-shaped blood cells block/clot
up blood vessels; point mutation
Symptoms: pain in joints, anemia, weakness
Incidence: 1 in 375 African Americans
Treatments: bone marrow transplants,
medicines
Dominance Cartoons p75
 Draw a cartoon that shows what
Codominance is. (half page)
 Draw a cartoon that shows what
incomplete dominance is.
Meiosis p78
• Warm up: What happens to cells during
interphase & mitosis?
• The production of sex cells (egg & sperm,
aka “gametes”) through a series of 2 cell
divisions. video
• Each gamete ends up with half its genetic
material in the end-haploid (23
chromosomes)
• After fertilization, the embryo (baby) gets its
full 46 chromosomes- diploid (or 23 pair)
http://www.palaeos.com/
Meiosis I
Interphase: genetic material is duplicated
(fill in on right page- Meiosis I)
First Phase meiosis: (46 pair) (p267)
– Prophase 1: The 2 sets of chromosomes
condense. Crossing over can occur.
– Metaphase 1: chromosome pairs align at
the center.
– Anaphase 1: pairs separate
– Telophase 1: Two daughter cells are
formed each containing 23 pair of
Chromosomes (diploid)
Crossing Over (Recombination)
p78
• Where a section of one chromosome
switches places with the same
section of another chromosome
• This causes variation of genes.
http://www.accessexcellence.org
Meiosis- Phase 2 (fill in right)
• Gamete formation:
– Prophase 2: DNA does not replicate.
– Metaphase 2: Chromosomes of each
daughter cell align in the centers
– Anaphase 2: Chromosomes divide and
migrate separately to each pole.
– Telophase 2: Cell division is complete. Four
gametes are obtained, each having only 23
chromosome (haploid)
• One parent cell produces 2 diploid daughter
cells and then 4 haploid sex cells.
Animation
http://www.johnkyrk.com/meiosis.
html
Draw & label fig 10.12, p273 on left page under this diagram
http://post.queensu.ca/
Animation
http://www.csuchico.edu/~jbell/Bio
l207/animations/meiosis.html
Sex Determination p80
 Warm up: How is the gender of a baby
determined?
 The 23rd pair of chromosomes are XX for a
female and XY for a male.
 Mom can only pass on her X chromosome, but
dad can pass X or Y.
 Dad determines if offspring is male or female.
 Dads give their Y to sons, Moms always give
their X to their sons
Sex linked traits-traits on this pair of
chromosomes, and can be traced back to a
mother or father.
Sex-linked Disorders p80
*most disorders are x-linked,
recessive
Disorder: Muscular Dystrophy (MD)
 Facts: recessive, x-linked; many types of
MD
 Symptoms: muscle loss & weakness
Incidence: mainly in males; all ethnic groups
have an equal chance of MD
Treatments: physical therapy , braces,
wheelchair
Sex-linked Disorders
p80
Disorder: Hemophilia
 Facts: recessive, x-linked; blood does
not have clotting factors
 Symptoms: bleed excessively or to
death
Incidence: mainly in males ; Royal
Family
Treatments: inject themselves with
purified clotting factors to prevent or
stop bleeding
Sex-linked Disorders p80
Disorder: Color-blindness
 Facts: recessive, x-linked disorder; Cones in
eyes(color receptors) are absent or lack of
pigment
 Symptoms: cannot tell difference between
certain colors
Incidence: mainly in males- passed from mother;
red-green color blindness most common
Seeing only black/white is rare
Treatments: none
A Difficult Decision p79
 If one day, you and your future
husband or wife were a carrier for a
sex linked disorder, would you still
have children? Back up your decision
using examples from today’s or
previous notes.
Nondisjunction p82 video
 Warm up: how many chromosomes do we have?
 when a chromosome pair fails to separate during
meiosis-can happen to any chromosome pair
2 types:
 1.Monosomy: when gamete has one less
chromosome than it should
 only 45 chromosomes
(need 46)
 Ex: Turner syndromeoccurs only in females
Nondisjunction p82
 2.Trisomy: when gamete has one more
chromosome than it should
• 47 chromosomes( need 46)
• Ex: Down’s syndrome, extra #21 video
Questions p81
Q. How can a nondisjunction occur? (1/3
page)
Q. What is the difference between
monosomy and trisomy? (1/3 page)
 Read p 273 about polyploidy and answer
question about the banana plant under
figure 10.17