Who was Gregor Mendel?

1
Who was Gregor Mendel?

• Father of Genetics
• Austrian monk, teacher, scientist and gardener
  who formulated basic laws of heredity in the
  early 1860s video

2
What did he study?

• Worked with garden peas
• Easy to grow and had a
• short generation time video

3
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)

4
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.

5
Mendels Conclusion Paragraph p67

• Explain how Mendel came up with each of his 3
  conclusions from his work with pea plants.

6
Examples of dominant and recessive traits in
humans! p70
7
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)

8
Punnett Squares p70

• Monohybrid Cross 1 trait, 2 parents

P1 Pure Tall x Pure Short TTTall tt short
F225 pure tall 50 hybrid tall 25
pure short
F1100 Tall
9
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
10
Each box is6.25
11
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

12
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

13
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 dont live past 5

14
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 dont agree with the
  following statement We have millions of genes,
  so a mutation in one of them cant cause very
  much damage.

15
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)

16

• Ex Japanese Four oclocks
• RR red WW white RW pink

• F1 F2

R W
R R
R W
W W
RW
RW
RR
RW
RW
RW
RW
WW
All Pink
1 red 2 pinks 1 white
17
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

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• Ex Red Coat - RR
• White Coat WW
• White Red Mixed RW (roan)

F1 R R
F2 R W
RW
RW
RW
R W
RR
W W
RW
RW
RW
WW
All Roan both red and white hair
1 red 2 roan 1 white
19
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

20
Dominance Cartoons p75

• Draw a cartoon that shows what Codominance is.
  (half page)
• Draw a cartoon that shows what incomplete
  dominance is.

21
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)

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http//www.palaeos.com/
23
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)

24
Crossing Over (Recombination) p78

• Where a section of one chromosome switches places
  with the same section of another chromosome
• This causes variation of genes.

25
http//www.accessexcellence.org
26
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.

27
Animation

• http//www.johnkyrk.com/meiosis.html

28
Draw label fig 10.12, p273 on left page under
this diagram
29
http//post.queensu.ca/
30
Animation

• http//www.csuchico.edu/jbell/Biol207/animations/
  meiosis.html

31
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.

32
Sex-linked Disorders p80most 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

33
Sex-linked Disordersp80

• 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

34
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

35
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 todays or previous notes.

36
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 syndrome-
• occurs only in females

37
Nondisjunction p82

• 2.Trisomy when gamete has one more chromosome
  than it should
• 47 chromosomes( need 46)
• Ex Downs syndrome, extra 21 video

38
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