Presentation is loading. Please wait.

Presentation is loading. Please wait.

5/11/20151. Who is the GREATEST BIOLOGIST EVER? 5/11/20152.

Similar presentations


Presentation on theme: "5/11/20151. Who is the GREATEST BIOLOGIST EVER? 5/11/20152."— Presentation transcript:

1 5/11/20151

2 Who is the GREATEST BIOLOGIST EVER? 5/11/20152

3 Why Gregor Mendel is the GREATEST BIOLOGIST EVER… Even though he wasn’t really a biologist 5/11/20153

4 4 Ch 14 Mendelian Genetics

5 5/11/20155 Pre-Mendel Predominate belief in “blending”, child is a mix of parents problem with this was traits skipping generations Terms early genetic study Character = detectable, inherited feature, ex. color Trait = variant of an inheritable character, ex. green or red color True-Breeding = always produce plants with same traits as parents, self fertilization Cross-Breeding = cross parents with different traits to create hybrids

6 5/11/20156 Generations are named P = parental F1= results of PxP F2= results of F1 x F1

7 5/11/20157 Mendel’s experiment Mendel looked at 7 characteristics, each had 1 alternate form that did not “blend” when cross-bred His experiment– if a cross of purple & white P’s gives all purple, then a cross between F 1 ’s, self-pollinating, would produce white again in F 2 generation results – 3:1 ratio of purple to white flowers, conclusions – ?

8 5/11/20158 Mendel’s experiment Mendel looked at 7 characteristics, each had 1 alternate form that did not “blend” when cross-bred His experiment– if a cross of purple & white P’s gives all purple, then a cross between F 1 ’s, self- pollinating, would produce white again in F 2 generation results – 3:1 ratio of purple to white flowers, conclusions  Heritable trait for whiteness is masked  Purple trait is dominant Extension  If 2 purple P’s were mated, what ratio of traits would you expect to observe?

9 The ratio does not match the ideal. Create a plan to test if this difference is acceptable. 5/11/20159

10 10 So… there are alternate forms of the same gene = alleles, p265 we inherit one allele from each parent if alleles are different, one is dominant (noted by capital letter), one is recessive (lowercase letter) When do alleles segregate?

11 5/11/201511 So… there are alternate forms of the same gene = alleles, p265 we inherit one allele from each parent if alleles are different, one is dominant (noted by capital letter), one is recessive (lowercase letter) When do alleles segregate? Anaphase I

12 5/11/201512 More Terms homozygous – 2 identical alleles for a trait, ex. DD, dd heterozygous – 2 different alleles for a trait, carrier, ex. Dd phenotype – organism’s expressed traits, ex. color, height genotype – organism’s genetic makeup, letters, ex. PP, Pp

13 5/11/201513 Testcross – a cross between a recessive and an unknown  tells if it is homo or heterozygous monohybrid cross – dealing with 1 trait dihybrid cross – 2 traits Trihybrid – 3 traits

14 5/11/201514 Mendel’s first postulate: Law of Segregation = allele pairs separate randomly during meiosis, p. 266 There are 2 alleles for flower color, if 1 purple and 1 white: there is a 50% chance of getting either allele Punnett square used to predict the results

15 5/11/201515 Mendel’s secondpostulate: Law of Mendel’s secondpostulate: Law of Independent Assortment when dealing with 2 or more traits, each allele of the different genes segregates independently of each other WHY? If cross 2 dihybrid heterozygotes, get 9:3:3:1 ratio

16 5/11/201516 Probability = mathematical chance of an event happening Rule of multiplication- probability of 2 events occurring at the same time = product of their individual probabilities  Ex: 2 coins both coming up heads = ?  Ex: If DdRr x DdRr what is probability of getting DDRR is ?

17 5/11/201517 Probability = mathematical chance of an event happening Rule of multiplication- probability of 2 events occurring at the same time = product of their individual probabilities  Ex. 2 coins both coming up heads = ½ x ½ = ¼  Ex: If DdRr x DdRr what is probability of getting DDRR is ? chance of DD = ¼, chance of RR = ¼ so ¼ x ¼ = 1/16

18 5/11/201518 Rule of addition –p.270, probability that either of two or more mutually exclusive events will occur is calculated by adding the individual probabilities. What are the chances you will get heads or tails when you flip a coin? Ex. cross of 2 heterozygotes, what are chances of result being hetero? Use → trihybrid AaBbCc x AaBbCc ? chance of AabbCC?

19 5/11/201519 Rule of addition –p.270, probability that either of two or more mutually exclusive events will occur is calculated by adding the individual probabilities. What are the chances you will get heads or tails when you flip a coin? ½ + ½ = 1 Ex. cross of 2 heterozygotes, what are chances of result being hetero?  Chance of recessive egg + dominant sperm = ½ x ½ = ¼  Chance of dominant egg + recessive sperm = ½ x ½ = ¼  chance of hetero child is ¼ + ¼ = ½ Use → trihybrid AaBbCc x AaBbCc ? chance of AabbCC?

20 5/11/201520 Extensions: Mendel’s laws were not perfect, in fact, he was lucky (or wise) that he choose peas which have simple inheritance (except pod shape) Incomplete dominance = 1 allele is not completely dominant over the other thus, there is a 3 rd phenotype, intermediate, ex.Carnations/snapdragons p. 271

21 5/11/201521 Codominance = both alleles are expressed Level of expression varies at different levels ex: Tay-sachs  at the molecular level – looks codominant – both alleles transcribed  at the biochemical level – looks like incomplete→ a partial level of lipid-metabolizing activity  at the organismal level – heterozygotes are symptom free, homoygote recessives express disorder

22 5/11/201522 Multiple Alleles = genes that have more than 2 alleles Ex. blood groups A, B, AB, O (surface carbohydrates)  blood type is the antigen present on the RBC, p. 273 also contains Rh factor, + or – with standard Mendelian rules

23 5/11/201523

24 5/11/201524 Pleiotropy = a single gene has multiple effects ex: sickle-cell

25 5/11/201525 Epistasis = one gene affects the expression of another gene, Ex. pigments in mice

26 5/11/201526 Polygenic inheritance = many genes affect the same trait Ex: skin color, very dark to very light, p. 274

27 5/11/201527 Environment plays an important part in gene expression, how much is dependent on the gene, nature vs. nurture argument Norm of Reaction = The phenotypic range for a genotype, p.275

28 5/11/201528 Humans Pedigree – family tree that shows inheritance over many generations, shows patterns  = male, O = female, ●= affected, ○= non-affected

29 5/11/201529 - usually caused by a defective protein - heterozygotes are carriers Why more common than dominant disorders? Examples Cystic Fibrosis – most common amongst Europeans (4% carry), membrane protein that controls Cl ⁻ traffic, causes increase mucus in lungs  infections persist Cystic Fibrosis Tay-Sachs – higher in Ashkenazic Jews, can’t break down a type of lipid. How can it be high in a particular pop? Sickle cell – substitution in one hemoglobin, causes RBC to sickle and clog, carriers are immune to malaria, p. 278  In which pop. would sickle cell predominate? ConsanguinityConsanguinity – mating with relatives, increases expression of recessive disorders. Why? Recessive human disorders

30 5/11/201530 – rarer than recessive. Why? Examples Achondroplasia – type of dwarfism Achondroplasia Huntington's – late acting degeneration of nervous system, due to single allele on tip of chromosme #4Huntington's  Knowledge of this makes disease detectable. many different factors affect onset, but genetic predisposure present ex. Heart disease, diabetes, cancer Dominant inherited disorders Multifactorial disorders

31 5/11/201531 Genetic testing and counseling 1) carrier recognition - help make decisions about whether or not to reproduce  Can test for Tay-Sachs, sickle-cell, and cystic fibrosis, etc. 2) fetal tests  amniocentesis – take amniotic fluid from around fetus, do karyotype  chorionic villus sampling (CVS) – take villi, do karyoptype, fast, earlier, more risk, p. 280  ultrasound – imagery using sound waves, look for physical problems  fetoscopy – fiber optics  Culturing escaped fetal blood cells in mother’s blood 3) Newborn screening – ex. PKU

32 5/11/201532

33 Big Picture of Inheritance… must be looked in integrated light…i.e. it is a product of genes working collectively and is influenced by environmental cues  Must view emergent properties of organism as a whole, not a reductionist view of single genes acting in isolation

34 So, why is Gregor Mendel the GREATEST BIOLOGIST EVER ? Even though he wasn’t really a biologist 5/11/201534

35 5/11/201535 Ch 15 Chromosomes and Inheritance

36 5/11/201536 Chromosome theory of inheritance: genes are located on chromosomes, they segregate and independently assort

37 5/11/201537 T.H.Morgan rediscovered Mendel’s work 1900’s, specific genes on specific chromosomes? work on fruit fly, why?  fast repro., easy to handle, 4 pairs of chromosomes (1 pair are sex chromosomes) gene symbol is based on the mutant or recessive ex. curly is recessive = Cy, if normal then Cy+ wild type is the type seen in nature = +

38 5/11/201538 Experiment- p 289 white eyed male (♂)→ crossed with a red eyed female (♀)→ in F2 only males had white eyes ?  how is no independent assortment possible?

39 5/11/201539 Experiment- p 289 white eyed male (♂)→ crossed with a red eyed female (♀)→ in F2 only males had white eyes ? → eye color and sex are linked Linked genes = when genes are on the same chromosome, so they are inherited together

40 5/11/201540 Sex linked traits = located on a sex chromosome, p. 290, ex. Hemophilia  few genes on the Y, thus most sex-linked diseases are seen in males b/c on the X (not masked), females often carriers, p. 290 few genes on the Y  X-inactivation = females inactivate one of their X’s (see cat diagram) inactive X becomes a Barr body Typically both chromosomes’ genes are expressed

41 Examining 2 genes: How could you determine if a two genes were “linked”? How could you tell distance between two genes? 41

42 Examining 2 genes: How could you determine if a two genes were “linked”? How could you tell distance between two genes? 5/11/201542

43 5/11/201543 Recombination = offspring with different combinations of traits than the parents, caused by crossing over or mutations Parental types – same phenotype as a parent Recombinants – differ from parents, *p. 293-294  What is % of recombination of the peas?

44 5/11/201544 Recombination = offspring with different combinations of traits than the parents, caused by crossing over or mutations Parental types – same phenotype as a parent Recombinants – differ from parents, *p. 293-294  What is % of recombination of the peas? 50% - one-half of the offspring are expected to inherit either of the two phenotypes

45 5/11/201545 Recombination What would a recombination of 25% tell you about the chromosomal location of two given genes?

46 5/11/201546 Recombination What would a recombination of 25% tell you about the chromosomal location of two given genes?  The genes’ loci are on the same chromosome Why is the recombination % not 0? What would a recombination of 0.5% tell you about their respective locations?

47 5/11/201547 Recombination What would a recombination of 25% tell you about the chromosomal location of two given genes?  The genes’ loci are on the same chromosome Why is the recombination % not 0?  Crossing-over separates them What would a recombination of 0.5% tell you about their respective locations?  That their respective loci are in close proximity on the same chromosome

48 5/11/201548 Sturtevant and gene mapping use recombination frequency to determine distance of genes The farther apart two genes are, the higher the probability that crossover will occur between them and ∴ the higher the recombination frequency made chromosome maps  find relative distance between farthest genes, find distance of an end and a middle, fill in other genes  double crossovers can occur too, throw # off a little  Made distance unit: 1 map unit = 1% recombination

49 5/11/201549

50 Final product: a genetic (linkage) map 5/11/201550

51 HUMAN GENETIC DISORDERS 5/11/201551

52 5/11/201552 Nondisjunction –two chromosomes stuck together or not present  Why and when would this occur?

53 5/11/201553 Nondisjunction –two chromosomes stuck together or not present  Why and when would this occur? Aneuploidy = having an abnormal # of chromosomes  Trisomy – 3 copies of 1 chromosome  Monosomy – 1 copy of the chromosome Polyploidy = more than normal chromosome set  Triploidy – 3 chromosome sets (3N)

54 5/11/201554 Nondisjunction –two chromosomes stuck together or not present  Why and when would this occur? Aneuploidy = having an abnormal # of chromosomes  Trisomy – 3 copies of 1 chromosome  Monosomy – 1 copy of the chromosome Polyploidy = more than normal chromosome set  Triploidy – 3 chromosome sets (3N)

55 5/11/201555 Basic Mutations Deletion – chromosome loses a piece, p. 298 Duplication – double of gene Inversion – chromosome is in reverse Translocation – gene moves to another chromosome →caused by UV light, chemicals or random →effects can be silent, lethal or in between

56 5/11/201556 Down Syndrome – trisomy 21, female age makes more frequent? Klinefelters – XXY, XXXY male, sterile, some female features XYY – male, usually normal, XXX- female, usually normal Turner syndrome – X, female, sterile, few sexual features Some effects of chromosomal abnormalities depend on what parent inherited by (genomic imprinting, p.300) - Prader–Willi disorder– deletion of part of #15 from dad - Angelman syndrome– deletion of same part of # 15 from mom, motor issues Human aneuploid conditions

57 Genomic Imprinting is the activation or deactivation of a gene depending upon whether it was inherited from mom or dad  Mechanism is typically methylation (adding of methyl group, –CH 3 ). Methyl group acts as an on/off switch. Key player in epigenetics 5/11/201557

58 Organelles and their genes Do not follow Mendelian rules of inheritance.  Why? 5/11/201558

59 Organelles and their genes Do not follow Mendelian rules of inheritance.  Why? They do not undergo meiosis 5/11/201559

60 Study tip of the day: always be able to explain text chapter concepts Concept 15.1: Mendelian inheritance has its physical basis in the behavior of chromosomes Concept 15.2: Sex-linked genes exhibit unique patterns of inheritance Concept 15.3: Linked genes tend to be inherited together because they are located near each other on the same chromosome Concept 15.4: Alterations of chromosome number or structure cause some genetic disorders Concept 15.5: Some inheritance patterns are exceptions to standard Mendelian inheritance 5/11/201560

61 Chapter 14 & 15 Quiz

62 pedigree charts 5/11/201562

63 5/11/201563 Pedigree Practice Problems : Identify each pedigree as autosomal recessive, autosomal dominant, X-linked, or Y-linked

64 5/11/201564 Pedigree Practice Problems : Identify each pedigree as autosomal recessive, autosomal dominant, X-linked, or Y-linked ANSWERS a. autosomal recessive b. autosomal dominant

65 5/11/201565

66 5/11/201566 ANSWERS c. autosomal dominant d. autosomal recessive e. x-linked recessive

67 5/11/201567

68 5/11/201568 ANSWERS f.autosomal dominant g.autosomal recessive

69 1. If a plant with purple flowers produces only the same variety as the parent plant over many generations, what is the plant said to be? 2. What is Mendel’s law that states that the two alleles for a heritable character separate from each other during gamete formation? Chapter 14

70 1. True-breeding plants 2. Law of Segregation Chapter 14

71 5/11/201571 3. If two heterozygous purple flowers produce offspring, what are the odds that the offspring will have white flowers? 4. The child’s mother has blonde hair, and their father is heterozygous and has brown hair. If blonde hair is a recessive trait, what are the odds that the child would have blonde hair? 5. When red snapdragons are crossed with white snapdragons their offspring is pink. What type of dominance is this?

72 5/11/201572 3. 25% 4. 50% 5. Incomplete

73 1. The law that states that alleles of genes on nonhomologous chromosomes assort independently during gamete formation is? 2. Who has a greater chance to receive X- linked recessive disorders? Males or females? 3. Genes located near each other on the same chromosome tend to be inherited together in genetic crosses are called? Chapter 15

74 1. Law of Independent Assortment 2. Males 3. Linked Genes Chapter 15

75 5/11/201575 4. When the members of a pair of homologous chromosomes do not move apart properly during meiosis I they can alter the chromosome structure. What is this error called? 5. What are the four types of changes that can occur to chromosome structure?

76 5/11/201576 4. Nondisjunction 5. Deletion, duplication, inversion, translocation

77 Try your luck at… practice pedigree problems Or more on following pages  5/11/201577

78 Dominant or recessive? autosomal, x-, or y-linked? 5/11/201578 ?

79 5/11/201579

80 5/11/201580

81 5/11/201581 A

82 5/11/201582


Download ppt "5/11/20151. Who is the GREATEST BIOLOGIST EVER? 5/11/20152."

Similar presentations


Ads by Google