Genetics

1. Genetics Biology Chapter 10-12

4. Gregor Mendel- the Father of Genetics Austrian monk worked in gardens in monastery studied pea plants studied heredity- passing on of traits or characteristics from parents to offspring

5. genetics – the branch of biology that studies heredity • traits- characteristics that are inherited • gametes- sex cells; sperm and egg cells

6. fertilization- when sperm unites with egg cell forming a 1 celled structure called a zygote • in plants, achieved thru pollination

7. 2 types of reproduction: • Asexual reproduction- when there is NO exchange of genetic information between organisms ex: mitosis in paramecium 2. sexual reproduction- where there is an exchange of genetic info between org ex: meiosis

8. in unicellular organisms, MITOSIS is form of asexual reproduction • won’t go thru MEIOSIS • in multicellular organisms, (plants, animals, us, etc) MITOSIS is how more cells are formed • MEIOSIS is how sperm & egg cells are formed

9. on chromosomes, there are segments that code for specific traits; segments are called GENES • genes are the factors that offspring have received from mom & dad

10. SISTER CHROMATIDS chromosome chromatid child receives one chromosome from mom and one from dad for each DNA molecule in species

11. genes code for traits traits are characteristics that are inherited • alleles- alternate forms of genes

12. receive 1 allele from mom & 1 allele from dad for each trait • represent alleles by using LETTERS • dominant allele is represented by a CAPITAL LETTER • represents the trait that is stronger or dominant • (usually will use the 1st letter of the dominant trait)

13. for ex: rolling tongue is a dominant trait in humans • usually use R to represent ability to roll tongue

14. recessive alleles are represented by a small letter • represents the weaker or hidden trait

15. for example, not being able to roll your tongue is a recessive trait • represented by r

16. terms we have to learn: • phenotype- physical appearance of the trait in the organism

17. genotype- gene or allele combination of an organism for that trait • ex: RR or Rr or rr • got 1 from mom; 1 from dad • use the combo of letters to represent genotype

18. more terms to learn: • homozygous dominant- means 2 capital letters (dominant trait) • homo= same • aka: pure dominant • for ex: RR= can roll tongue

19. homozygous recessive- 2 little letters ( 2 recessive alleles) • aka: pure recessive • for ex: rr = can’t roll tongue

20. heterozygous- have 1 capital letter (dominant trait) & 1 little letter (recessive trait) • hetero= different (means size here or trait) • aka: hybrid • for ex: Rr What does this genotype mean? • can roll tongue Why?

21. Dominant: • L k e M r O d S E • Recessive: • M p Q t r D K n s • Homozygous Dominant: • BB Hhgg TT Rr • Homozygous Recessive: • ff Aa Cc tt KK Ll mm

22. Offspring combinations in which dominant trait must show: • BB DdeeJjRr ii • Offspring combinations in which recessive phenotype must show: • Ee ff Hh ii LlnnOo

23. Dominant: • L k e M r O d S E • Recessive: • M p Q t r D K n s • Homozygous Dominant: • BB Hhgg TT Rr • Homozygous Recessive: • ff Aa Cc tt KK Ll mm

24. Offspring combinations in which dominant trait must show: • BB DdeeJjRr ii • Offspring combinations in which recessive phenotype must show: • Ee ff Hh ii LlnnOo

25. to figure out traits organisms inherit: • use a Punnett square • perform monohybrid crosses • use a 4 box square

27. Karotype

29. Meiosis • in multicellular org, there are 2 types of cells: • body cells (somatic) stomach, bone, nervous, etc • sex cells (gametes)- sperm, egg inside somatic cells, you’ll find 2 of each kind of chromosome= DIPLOID (2n) inside sex cells, you’ll find only 1 of each kind of chromosome= HAPLOID (n)

30. chromosomes occur in pairs called homologous chromosomes • have genes for the same traits located in the same positions • they are not genetically identical (we got 1 from mom, 1 from dad)

32. we have 23 pairs of these homologous chromosomes • somatic cells (body) have 46 chromosomes in them • in sex cells (sperm or egg) we have just 23 chromosomes • this is IMPORTANT WHY?

33. different organisms have different numbers of chromosomes in their cells • look p. 265 • chromosome # does NOT indicate complexity • if an org has 24 chromosomes in its body cells, how many chromosomes will be in the sex cells?

34. What would happen in humans if the sperm and egg cells each contained 46 chromosomes? • the resulting zygote would have 92 • SOMETHING has to occur to prevent too many chromosomes • Meiosis- process of nuclear division that reduces chromosome # by half

36. meiosis is involved in sexual reproduction • results in haploid cells – makes sperm & egg cells • in order to happen, there has to be 2 nuclear divisions

37. similar to mitosis, but divides twice • divided into Meiosis I & Meiosis II • same names as mitosis (easier) • Interphase-chromosomes are replicated, but aren’t visible yet

38. Prophase I • chromosomes become visible • nucleus/ nucleolus disapppears • UNIQUE to meiosis: • homologous chromosomes form TETRAD • chromatids are paired tightly; genetic material is exchanged= CROSSING OVER

40. Metaphase I • tetrads line up at equator (middle) • UNIQUE: • homo chromos are lined up as PAIRS

41. Anaphase I • homo chromos separate & move to opposite ends of cell • UNIQUE: centromeres do NOT split- this ensures that each new cell only receives ONE chromosome from each parent

42. Telophase I • spindles break down chromosomes uncoil • cytoplasm divides to 2 cells • each new cell has ½ genetic info of parent cell • another division must occur because chromosomes were copied

43. Prophase II • new spindle fibers form • chromosomes are visible again

44. Metaphase II • chromosomes line up individually at middle of cell

45. Anaphase II • centromeres split • sister chromatids separate & move to opposite ends of cell

46. Telophase II • spindles break down • nuclei reforms • cytoplasm divides

47. Results of meiosis • 4 haploid cells formed from original diploid cell • they become gametes- sperm and egg cells