Who was Gregor Mendel? Father of Genetics Austrian monk, teacher, scientist and gardener who formulated basic laws of heredity in the early 1860’s videovideo

What did he study? Worked with garden peas Easy to grow and had a short generation time video video

Mendelian Genetics p68  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) Warm up: why did Mendel choose pea plants to study?

ConclusionsConclusions? p68 Conclusions  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 = Homozygous recessive genotypes = possess two recessive alleles for a trait (bb) Heterozygous genotypes = Heterozygous genotypes = one of each allele for a particular trait (Bb)

Punnett Squares p70  Monohybrid Cross : 1 trait, 2 parents Monohybrid Cross Monohybrid Cross P1= Pure Tall x Pure Short TT=Tall tt =shortT t t Tt TtTt TT Tt tt F1=100% Tall F2=25% pure tall 50% hybrid tall 25% pure short

Dihybrid Cross: 2 traits, parents p72 Dominant Yy, YY = yellow Rr, RR = round Recessive yy = green rr = wrinkled  Warm up: how many boxes are in a monohybrid cross and what % does each box represent?

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 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)

 F1: F2:  Ex: Japanese Four o’clocks RR = red WW = white RW = pink RR W W RW RWRW R W RRRW WW All Pink1 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 Coat – WW White & Red Mixed – RW (“roan”) White & Red Mixed – RW (“roan”) F1: R R W W F2: R W R W RW RR RW WW All Roan – both red and white hair 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. videovideo 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)

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.

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 html

Draw & label fig 10.12, p273 on left page under this diagram

Animation l207/animations/meiosis.html

Sex Determination p80  Warm up: How is the gender of a baby determined?  The 23 rd 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 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

Nondisjunction p82  2.Trisomy: when gamete has one more chromosome than it should 47 chromosomes( need 46)47 chromosomes( need 46) Ex: Down’s syndrome, extra #21 videoEx: Down’s syndrome, extra #21 videovideo

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