1. Genetics

2. History of Genetics
: Gregor Mendel (Austrian monk) presented results of 10 yrs. of experimentation on pea plants
2. Late 1800’s: increased research in microscopy and cytology (study of cells) · recognized each chromosome (“colored-body”) transferred (contribution from parent)
: chromosomes in gametes (sex cells) found to be involved in reproductive cycle

3. History of Genetics
: fruit fly began to be used for genetic research because of very short generation span 5.
1940’s: chemical techniques developed to reveal association between genes in chromosomes and proteins made in the cell
1944: DNA’s responsibility is to code for production of proteins (acts like a recipe book) one gene codes for production of only one protein
: Watson and Crick proposed model of DNA structure to be coiled spiral ladder (double helix)

4. 7. 1960’s: genetic code deciphered
’s: description of how a gene produces a protein (how nucleotide bases can create recipe for specific order of amino acids to build specific proteins
: scientists in United States organized Human Genome Project (HGP), an international effort to completely map & sequence the human genome (~ genes on 46 chromosomes) • Feb HGP published working draft of 3 billion base pairs of DNA

5. Mendel’s Experiments
1. chose garden pea: self-pollinating plant, annual, “true-breeding” (offspring always resemble parents) a. gametes: sex cells- egg or sperm pollen grains produced on stamen contain sperm, ovules produced in pistils contain eggs

6. Mendel’s Experiments
b. fertilization: eggs & sperm combine to form zygote • in peas, zygote develops into embryo inside of seed c. pollination: transfer of pollen from stamen to pistil    • self-pollination: pollen of plant is transferred to pistil of same plant • cross-pollination: sperm in pollen from one plant fertilizes eggs in ovules of another plant

7. Monohybrid Crosses
a. hybrid: offspring of parents having different forms of a trait • monohybrid cross: cross pollinating two parent organisms are only different from each other by one trait • dihybrid cross: cross pollinating two parent organisms are only different from each other by two traits

8. Monohybrid Crosses
b. Generations • P1: Parent generation • F1: first Filial generation (filial = son or daughter) • F2: second Filial generation, “grandchildren” of original parent generation

9. Monohybrid Crosses
c. alleles: different forms or versions of a gene for a trait • Rule of Unit Factors: each trait controlled by 2 factors (alleles) located on different copies of a chromosome (1 copy from each parent)

10. Dominance of Alleles
a. dominant: trait will be expressed (show up) any time the allele is inherited e.g. tall plant, red flower color, freckles, brown (hazel) eyes · Symbol for trait is a CAPITAL letter when writing genotype, e.g. TT, Tt

11. Dominance of Alleles
b. recessive: trait that only shows its effect (expressed) when two alleles of the trait are inherited e.g. short plant, white flower, no freckles, blue (green) eyes · Symbol for trait is the lower case letter of the matching dominant trait when writing genotype e.g. tt, rr (short plant, white flowers) * recessive alleles can be hidden, but passed on to offspring

12. 3. Parent to Offspring
a. law of segregation: offspring receive one of two copies of allele for a trait (in egg or sperm)
b. law of independent assortment: traits (on different chromosomes) are inherited independently

13. C. Predicting Genotype Outcomes
Draw diagram of possible gametes
AaBbCc
ABc
abc
ABC
Abc
abC
AbC
aBC
aBc

14. C. Predicting Genotype Outcomes
1. homozygous genotype: 2 identical alleles for a trait (purebred or true-breeding) e.g. AA, aa
2. heterozygous genotype: 2 different alleles for a trait (hybrid) e.g. Aa
3. phenotype: physical traits that are expressed (show up)

15. 4. Punnett square
Punnett square: model used to predict possible combinations of alleles inherited by offspring
1st Filial
Generation
Parent
Generation
TT X tt

16. 4. Punnett square P1
TT X tt T T t Tt Tt Tt t Tt

17. 4. Punnett square F1
Tt X Tt t T T TT Tt Tt t tt

18. D. Dihybrid cross
1. Possible genotypes for offspring from parents heterozygous for two traits e.g. heterozygous Red flowered heterozygous Tall pea plant genotype: RrTt

19. RrTt X RrTt RT Rt rT rt

20. RrTt X RrTt RT Rt rT rt
RRTT
RRTt
RrTT
RrTt
RRtt
Rrtt
rrTT
rrTt
rrtt

21. Genotypes of offspring:
RRTT, RrTT, RrTt, rrTT, rrTt, rrtt
Phenotype ratio: Red+Tall : Red+short : white+Tall : white+short
9 : 3 : 3 : 1

22. Mendelian Exceptions A. Complex Patterns of Inheritance
1. Incomplete Dominance: e.g. Red x white = pink
2. Codominance: e.g. Black-feathers x White-feathers = Black-and-white feathers

23. III. When Heredity Follows Different Rules
3. Multiple Phenotypes from Multiple alleles: e.g. coat color in rabbits
4. Sex determination Sex Chromosomes in humans: XX is female, XY is male X Y

24. Sex Determination in HumansXX Y XY

25. 5. Sex-linked Traits
a. traits carried on the sex chromosomes b. leads to an unequal occurrence of the trait in the sexes e.g. hemophilia or color-blindness in humans e.g. eye color in fruit flies See Fig **different from sex-influenced traits, such as male pattern baldness, that are expressed differently in males vs. females due to the environmental effects of sex hormones (estrogen & testosterone)

26. 6. Polygenic Inheritance
a. multiple genes coding for one trait b. leads to a spectrum of traits e.g. skin color and hair color in humans e.g. stem length in plants

27. Pleiotropy
a. a single gene controls multiple traits e.g. the gene for pigment production in humans inheritance is by complete dominance recessive allele leads to no pigment production - albinism

28. B. Environmental Influences
both external and internal (including age) 1. There are external(temperature, nutrition, light) and Internal (hormones) influences on genetics. 2. Knowing the genotype at birth determines only the organism’s potential to develop and function.

29. IV. Complex Inheritance of Human Traits
A. Codominance in Humans
1. Sickle Cell Anemia
2. Multiple Alleles Govern Blood type: 2 traits- ABO blood type and Rh factor a. A and B alleles are co-dominant (neither one can mask the other), and o is recessive

30. IV. Complex Inheritance of Human TraitsIB i IA IA IB i IB i IA

31. IV. Complex Inheritance of Human TraitsIB i IA
IAIB
IAi IA IB i
IAi
IBi IB i IA
IAIB
IAi
IBi ii

32. V. Meiosis
1. Haploid: having 1 set of chromosomes (1/2 normal number), 1 set of alleles for a trait • gametes are haploid (23 chromosomes in humans)
2. Diploid: having 2 sets of chromosomes (normal number), 2 sets of alleles for a trait • body cells are diploid (46 chromosomes in humans) • Some plants exhibit polyploidy: having multiple copies of each gene

33. Meiosis
3. Homologous Chromosomes: two chromosomes containing matching genes, one received from each parent
4. mitosis: cell division where daughter cells have same number of chromosomes as parent cell • used to form new body cells with same genetic information, asexual reproduction

34. meiosis
5. meiosis: (“reduction division”) cell division where resulting cells get half the normal number of chromosomes (one from each chromosome pair) to form gametes (egg or sperm cells) Diagram on pg

35. Meiosis

36. Meiosis Interphase Prophase I Metaphase I Anaphase I Telophase I
Telophase II
Prophase II
Metaphase II
Anaphase II

37. B. Meiosis Provides Genetic Variation
1. Crossing Over: arms of non-sister chromatids wind around each other and genetic material may be changed

38. 2. Nondisjunction
Nondisjunction: Failure of homologous chromosomes to separate during meiosis resulting in a. trisomy: three copies of a chroromsome per cell b. monosomy: one copy of a chromosome per cell c. polyploidy: Many copies of each chromosome per cell

39. VI. Karyotypes A. How does it work?
1. A sample of cells are taken from a person. A picture of chromosomes during Metaphase is taken. It is then enlarged and arranged in order of size

40. Karyotype Useful in identifying unusual chromosome numbers in cells
Chromosome 21 trisomy- Down Syndrome
# 23 monosomy- Turner syndrome

41. Down Syndrome

42. Turner Syndrome