�      Intro

-          Gregor Mendel � father of modern genetics, used peas to study patterns of inheritance� used quantitative approach

1.      studied traits that were clear cut, no varieties

2.      collected data from a large sample (hundred of peas from several generations)

3.      applied statistical analysis to collected data

-          particulate inheritance � inherited characteristics are carried by discrete units called elements / genes

�      Meiosis � cell division

-          special cell division

-          occurs in sex organs called gonads

♀ovaries� ♂testes

-          reduction division

2n � n� ��monoploidy / haploidy

-          produces gametes (sex cells)

♀ ova = eggs, ♂sperm

-          Mitosis:

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����������� In mitosis, prophase�metaphase�anaphase �� 2 identical daughter cells (2n)

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-          Meiosis I:

Meiosis is a form of cell division that produces gametes (sex cells, or sperm and ova) with the haploid chromosome number (n). There are 2 stages in meiosis. Meiosis I (reduction division), is when homologous chromosomes separate. Meiosis II is like mitosis. In meiosis I, each chromosome pairs up with its homologue into a synaptonemal complex by a process called synapsis and forms a structure known as a tetrad or bivalent.

Prophase I � metaphase I � anaphase I � telophase I � cytokinesis I

End result: 4 monoploids

Boys: produce 4 gametes from 1 primary sex cell

Girls: during ovulation � egg is released, only 1 egg is produced, the other 3 are �polar bodies�

-          Meiosis II:

-          Genes contain information, when homologous = one from the mom and one from the dad

�      Law of Dominance

-          Mendel�s first law

-          When 2 organisms, each homozygous (pure) for 2 opposing traits are crossed the offspring will be hybrid (carry 2 different alleles) but will exhibit only the dominant trait and the remaining trait is hidden (recessive trait)�����������������������

According to the Law of Dominance all of the offspring will be tall

�      Law of Segregation

-          states that during the formation of gametes the 2 traits carried by each parent separate

-          During the formation of gametes, homologous genes (similar genes on a similar chromosomes) segregate and may not come back to the same combination in the next generation (a trait may skip a generation)

-          the cross that best exemplifies this law is the monohybrid cross. In the monohybrid cross, a trait that was not evident in either parent appears in the F₁ generation

�      Monohybrid cross

-          the crossing of the F₁ generation (Tt x Tt)

-          phenotype � appearance, results in a 3:1 ratio

-          genotype � type of genes, given in percentage is 25% homozygous dominant : 50% heterozygous : 25% homozygous recessive (1:2:1)

PR: 3:1

GR: 1:2:1

�      Backcross or Testcross

-          a way to determine whether an individual plant of animal showing the dominant trait is homozygous dominant (B/B) or heterozygous (B/b)

-          to determine the genotype, the individual in question (B/__) is crossed with a homozygous recessive (b/b)

-          if the individual is hybrid (B/b) = � of the offspring will show recessive trait

If the parent of the unknown genotype is hybrid there is a 50% chance that any offspring will be white

-          if homozygous dominant (B/B) = all offspring will be B/b

If the parent of the unknown genotype is BB, there can be no white offspring

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�      Law of Independent Assortment

-          applies when a cross is carried out between 2 individuals hybrid for 2 or more traits that are not on the same chromosome

-          Let Y = yellow seed color

�y = green

-          Let W = wrinkled seeds

������ w = smooth

-          During gamete formation, the alleles of a gene for one trait (Ww) segregate independently from the alleles of a gene for another trait (Yy)

-          These genes are not on the same chromosome and will assort independently. The only factor that determines how these alleles segregate of assort is how the homologous pairs line up in metaphase of meiosis I

-          During metaphase I if the homologous pairs happen to line up like this:

If the gene for Tall is linked to the gene for yellow and the gene for short is linked with the gene for green, the genes will not assort independently (ex: if the plant is tall it will have yellow seeds, if the plant is short it will have green seeds)

-          2 flowers are crossed that are homozygous for different traits and have the genes for height and seed color on different homologous chromosomes:

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-          The T/T� Y/Y parent ca produce gametes carrying only TY genes

-          The t/t� y/y parent can produce gametes carrying only ty genes

-          A punnett square is not needed b/c only one outcome is possible in the F₁: T/y� Y/y

-          The phenotype of all members of the F₁ generation is tall plants with yellow seeds, genotype = dihybrid

-          Dihybrid cross � a cross between 2 F₁ plants, it is a cross btwn individuals that are hybrid for 2 different traits such as �yellow and wrinkled

-          Dihybrid cross can produce 4 different types of gametes: WY, Wy, wY, wy

Dihybrid Cross:

PR: 9:3:3:1

Why? 9/16 tall, yellow����������� 3/16 tall, green����������� 3/16 short, yellow������ 1/16 short, green

A/a� B/b� C/c� D/D = genotype

2ⁿ�������� n = number of hybrids

2³ = 8

2⁴ = 16

4 x 4 = 16 gametes

�      Incomplete Dominance vs. Codominance

Skin Color � polygenic inheritance

-          skin color is controlled by 3 sets of alleles

-          A/A� B/B� C/C � all 6 dominant genes � darkest skin color

-          Cumulative effect � the more dominant the genes, the more darker the skin color, and the more pigment is being made

-          a/a� b/b� c/c � lightest skin color

-          A/a� B/b� C/c � intermediate skin color

-          64 box punnett square = 1/64 = all back, or all white

�      Multiple Alleles

-          allele � gene

-          multiple allelic trait � this is a trait that is controlled by more than 2 genes

�         ex: blood types

-          phenotypes:���������������������������������������������������� Serum (antibodies)

A�������� Antigen �A� on RBC������������������������ Anti-B Igs

B�������� Antigen �B� on RBC������������������������� Anti-A Igs

AB����� Antigens �A + B� on RBC���������������� None

O�������� No Antigens on RBC������������������������ Both

Why is �O� the universal blood type? Because it has no specific antigens on the RBCs.

What is the universal receiver? AB, because it has no specific antibodies, so it can receive from any blood type.

�         3 Alleles = I^a, I^b, i

O = i / i

A = I^a / i or I^a / I^a

����� B = I^b / i or I^b / I^b

����� AB = I^a / I^b

-    Is it possible for a husband and wife to have 4 kids with all different blood types? Yes. The husband and wife would have to both be I^a / i x I^b / i

�      Sex Linked Inheritance

-          Drosophila Melanogaster � fruit fly, have 8 chromosomes

2N = 8

2 sex chromosomes, 6 autosomes

-          Human = 46 chromosomes = 2N

-          Male determines gender

-          Some characteristics are only inherited through the X-chromosome and are said to be X-linked.

-          Some are only inherited through the Y-chromosome and are said to be Y-linked

�         Y-linked (Holandric)

-          If someone has a hairy pinna � X/Y^hp�

Can only be inherited from the Y-chromosome = only men can get it

�         X-linked

-          Colorblindness � retinal defect, missing cone cells (neurons that allow you to see color)

-          Hemophilia � bleeders disease, blood doesn�t clot, missing factor VIII and sometimes factor VII

-          Muscle Dystrophy

-          X/X � normal girl, X/Y � normal boy

X/X���������������������������������������������������� X/Y

X/X^C � carrier������������������������������������ X^C/Y � colorblind

Is she colorblind? No, she�s��������������� X^h/Y � hemophiliac

just a carrier, to have the genetic defect she would need to have it on both Xs, but males get the defect if they just have it on the X.���

X/X^h

X^C/X^C � colorblind, b/c homozygous

X^h/X^h � hemophiliac

-          X^h/Y� x� X/X � father has the defect

����������������������� �girls are carriers

����������������������� �boys are normal

����������������������� The defective gene is passed on to the girls not the boys

-          X/Y� x� X/ X^h

�only half the girls are carrier and the other 50% aren�t carriers but none of the girls display the disease = normal

�50% of the boys are hemophiliac and the other 50% are normal

�      PMN Cells � polymorphic Neutriphiles

-          �leukocyte� � WBC

-          Barr body � collapsed X

-          Male

44A +XXY �Klinefelters

1 Barr Body

-          Female

44A +XXX � 2 Barr bodies

44A +XXXX � 3 Barr bodies

44A +XXXXX � 4 Barr bodies

44A +X �Turner�s Syndrome (no Barr bodies)

�      Pedigree Analysis � family tree

�         Myopia � a trait = nearsighted

-          When the image falls short of the retina so people bring this closer to their eyes

-          Let M = Normal

������ m = myopic

1. Heterozygous M/m

2. Heterozygous M/m

3. homozygous dominant M/M

4. m/m recessive

5. heterozygous M/m � why? B/c the kids are myopic

6. m/m

7. Heterozygous M/m

8. m/m

9. M/m

-          Is the trait for myopia sex linked? No

-          Is myopia caused by a dominant gene? No because if it was dominant then the first generation parents would have had it. Since the parents didn�t show the trait it is a recessive trait.

-          Anything that is not sex linked is autosomal

Mutation

-          a mutation is a change in the genetic material of a sex cell �gametes are passed on to the offspring and the only way you can pass on a change is through gametes

�      Dominant Mutation � in order to have the trait only 1 mutant gene is required

1. polydactyly � six finger mutation

2. syndactyly � the finger or toes are fused

3. achrondroplasia � dwarfism

4. hypercholesterolemia � common in Ashkenaz Jews

5. Huntington�s Disease � a decline in motor skills (only experienced in adults not children � around age 40) �experience a lot of neurological problems and eventually die

�      Recessive Mutation � requires 2 genes

PKU � mental retardation, if it can be detected at birth, the child can get put on a non-phenylalanine diet until age 9-13 (until the brain develops)

�         Sickle cell anemia

-          There�s an error in one of the amino acids

-          The blood cell cant carry oxygen because its deformed and there�s an error in the hemoglobin

-          Hb/Hb � normal

Hb/s � resistant to malaria �people who have Hb/s have an advantage b/c they are resistant to malaria = usually people like these are found in Africa, South America, Asia and other tropical environments where malaria can be found

s/s � SCA �people with sickle cell anemia have very short lives

�      Change in Number �chromosomal mutation

�         Non-disjunction � the failure of a pair of chromosomes to separate during meiosis

-          Usually: sperm 22A +X��� ovum 22A +X � X/X��� 2N = 46

� Sperm 22A +Y��� ovum 22A +X � X/X��� 2N = 46

-          sperm 23A +X��� ovum 22A +X � 45 +X/X�� 2N = 47

EX: Trisomy 21 �on the 21^st pair of chromosomes / Down�s syndrome

� one extra chromosome, because it failed to separate in meiosis = inherited together and that results in 1 extra chr

Children with Down�s syndrome can survive and can live independent lives with proper medical care. One of the signs of Down�s syndrome is one crease across the hand � simian crease. Used to be referred to as Mongoloidism because they resemble orientals and Asians. Trisomy 21 is the result of non-disjunction

-          44A +XXX � 2 barr bodies / super female

1 non-disjunction

-          44A +XXXX � 3 barr bodies

2 non-disjunctions

-          44A +XXXXX � 4 barr bodies / penta-X female

2 non-disjunctions

-          44A +XYY � no barr bodies

The Y-chromosome is associated with males and people used to think that XYY = macho. Then a question arose as to why when some criminals went to jail they came out and returned to their life of crime? A study showed that most of these people had the XYY and they began associating XYY with increased aggression. But today that does not hold true, people with XYY just have larger hands and lower set ears.

-          44A +XXY

Klinefelter�s syndrome

Male is: sterile, has a short life expectancy, underdeveloped testes, low IQ

-          Turner�s syndrome

45X, X female: sterile, does not mature (short, underdeveloped, amenorrhea � no period), extra flap of tissue from neck, low hairline, simian crease, drooping eyelids, normal IQ

-          Amniocentesis � test for the fetus of a pregnant woman, a needle is inserted into the sac and withdraws amniotic fluid then the cells are examined and a karyotype is done to arrange and count the chromosomes

-          Chrorionic villus sampling � cells are taken form the chorion (part of the ambilical chord)� then examined and tested for Down�s syndrome (trisomy 21)

        Incid. Of

Down�s Synd.

�������������������� Maternal age

����������������������� Higher risk comes with age!!

�         Ploidy

-          Triploidy � when one sex cell doesn�t go through meiosis and has an extra set of chromosomes (only happens in plants)

2N + N � 3N

-          Tetraploid � when both sex cells don�t go through meiosis

2N + 2N � 4N

-          Polyploidy � a change in the number of chromosomes in plants that results in extra sets of chromosomes

�      Change in structure

�         Crossing-over

-          Tetrad � 2 sets of chromatids lined up on the metaphase plate

-          Crossing over � is the exchange of pieces of chromosome between homologous chromosomes. This creates new combination by break up old linkages and forming new one

�         Translocation

A piece broke off and attached itself to a non-homologous chromosome. Not as common as crossing-over

�         Inversion

-          A section broke off and then attached itself backwards. The key is that the chromosomes are read in a certain way. For example, you read Hebrew from right to left but if you read English that way it wouldn�t make any sense.

�         Deletion

�         Duplication

-          Fruit flies = #15 gene, if they have 1 then the eyes are normal but if there are 2 then the eyes change and develop into a rectangular shape then the fly cant see

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