0
Chapter  14. Beyond Mendel’s Laws of Inheritance
Extending Mendelian genetics <ul><li>Mendel worked with a simple system </li></ul><ul><ul><li>peas are genetically simple ...
Incomplete dominance <ul><li>Heterozygotes show an intermediate phenotype </li></ul><ul><ul><li>RR = red flowers </li></ul...
Incomplete dominance true-breeding red flowers true-breeding  white flowers X 100% 100%  pink flowers F 1 generation (hybr...
Incomplete dominance <ul><li>C R C W   x  C R C W </li></ul>C R C R C R C W C W C W C R C W 1:2:1 1:2:1 % genotype % pheno...
Co-dominance <ul><li>2 alleles affect the phenotype in separate, distinguishable ways </li></ul><ul><ul><li>ABO   blood gr...
Blood type universal donor universal recipient __ __ status no oligosaccharides on surface of RBC both type A & type B oli...
Blood compatibility <ul><li>Matching compatible blood groups  </li></ul><ul><ul><li>critical for blood transfusions  </li>...
Blood donation
Pleiotropy  <ul><li>Most genes are  pleiotropic   </li></ul><ul><ul><li>one gene affects more than one phenotypic characte...
Acromegaly: André the Giant
Pleiotropy  <ul><li>It is not surprising that a gene can affect a number of organism’s characteristics </li></ul><ul><ul><...
Epistasis  <ul><li>One gene masks another </li></ul><ul><ul><li>coat color in mice =  2 genes </li></ul></ul><ul><ul><ul><...
Epistasis in Labrador retrievers <ul><li>2 genes:  E  &  B </li></ul><ul><ul><li>pigment ( E ) or no pigment ( e ) </li></...
Polygenic inheritance <ul><li>Some phenotypes determined by additive effects of 2 or more genes on a single character </li...
Albinism Johnny & Edgar Winter albino Africans
Nature vs. nurture <ul><li>Phenotype is controlled by both  environment & genes </li></ul>Color of Hydrangea flowers is in...
It all started with a fly… <ul><li>Chromosome theory of inheritance </li></ul><ul><ul><li>experimental evidence from impro...
Thomas Hunt Morgan <ul><li>embryologist at Columbia University </li></ul><ul><ul><li>1 st  to associate a specific gene wi...
Morgan’s first mutant… <ul><li>Wild type fly = red eyes </li></ul><ul><li>Morgan discovered a mutant  white-eyed male </li...
Discovery of sex linkage all red eye offspring How is this possible? Sex-linked trait! red eye female white eye male x 75%...
Sex-linked traits <ul><li>Although differences between women & men are many, the chromosomal basis of sex is rather simple...
Sex chromosomes autosomal chromosomes sex chromosomes
Genes on sex chromosomes <ul><li>Y chromosome </li></ul><ul><ul><li>SRY: sex-determining region </li></ul></ul><ul><ul><ul...
Human X chromosome <ul><li>Sex-linked </li></ul><ul><ul><li>usually  X-linked </li></ul></ul><ul><ul><li>more than 60 dise...
Map of Human Y chromosome? <ul><li>< 30 genes on  Y chromosome </li></ul>SRY
Sex-linked traits Hh  x  HH sex-linked recessive X H Y male / sperm X H X h female / eggs X H X H X H Y X H X h X H X h X ...
Sex-linked traits summary <ul><li>X-linked </li></ul><ul><ul><li>follow the X chromosomes </li></ul></ul><ul><ul><li>males...
 
 
X-inactivation <ul><li>Female mammals inherit two X chromosomes </li></ul><ul><ul><li>one X becomes inactivated during emb...
X-inactivation & tortoise shell cat <ul><li>2 different cell lines in cat </li></ul>
Male pattern baldness <ul><li>Sex influenced trait </li></ul><ul><ul><li>autosomal trait influenced by sex hormones </li><...
Mechanisms of inheritance <ul><li>What causes the differences in alleles of a trait? </li></ul><ul><ul><li>yellow vs. gree...
Mechanisms of inheritance <ul><li>What causes dominance vs. recessive? </li></ul><ul><ul><li>genes code for polypeptides <...
How does dominance work: enzyme =  allele coding for functional enzyme = allele coding for non-functional enzyme = 100% no...
How does dominance work: structure = allele coding for functional structural protein = allele coding for non-functional st...
Prevalence of dominance <ul><li>Because an allele is dominant  does  not  mean… </li></ul><ul><ul><li>it is better </li></...
Polydactyly  individuals are born with extra fingers or toes dominant  to the recessive allele for 5 digits recessive alle...
Hound Dog Taylor
Any Questions??
Upcoming SlideShare
Loading in...5
×

Beyond Mendel's Laws of Inheritance

2,205

Published on

0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
2,205
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
135
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide
  • The genes that we have covered so far affect only one phenotypic character, but most genes are pleiotropic
  • The relative importance of genes &amp; the environment in influencing human characteristics is a very old &amp; hotly contested debate a single tree has leaves that vary in size, shape &amp; color, depending on exposure to wind &amp; sun for humans, nutrition influences height, exercise alters build, sun-tanning darkens the skin, and experience improves performance on intelligence tests even identical twins — genetic equals — accumulate phenotypic differences as a result of their unique experiences
  • Duchenne muscular dystrophy affects one in 3,500 males born in the United States. Affected individuals rarely live past their early 20s. This disorder is due to the absence of an X-linked gene for a key muscle protein, called dystrophin. The disease is characterized by a progressive weakening of the muscles and loss of coordination.
  • Hemophilia is a sex-linked recessive trait defined by the absence of one or more clotting factors. These proteins normally slow and then stop bleeding. Individuals with hemophilia have prolonged bleeding because a firm clot forms slowly. Bleeding in muscles and joints can be painful and lead to serious damage. Individuals can be treated with intravenous injections of the missing protein.
  • Transcript of "Beyond Mendel's Laws of Inheritance"

    1. 1. Chapter 14. Beyond Mendel’s Laws of Inheritance
    2. 2. Extending Mendelian genetics <ul><li>Mendel worked with a simple system </li></ul><ul><ul><li>peas are genetically simple </li></ul></ul><ul><ul><li>most traits are controlled by a single gene </li></ul></ul><ul><ul><li>each gene has only 2 alleles, 1 of which is completely dominant to the other </li></ul></ul><ul><li>The relationship between genotype & phenotype is rarely that simple </li></ul>
    3. 3. Incomplete dominance <ul><li>Heterozygotes show an intermediate phenotype </li></ul><ul><ul><li>RR = red flowers </li></ul></ul><ul><ul><li>rr = white flowers </li></ul></ul><ul><ul><li>Rr = pink flowers </li></ul></ul><ul><ul><ul><li>make 50% less color </li></ul></ul></ul>
    4. 4. Incomplete dominance true-breeding red flowers true-breeding white flowers X 100% 100% pink flowers F 1 generation (hybrids) F 2 generation 1:2:1 P 25% white 25% red self-pollinate 50% pink
    5. 5. Incomplete dominance <ul><li>C R C W x C R C W </li></ul>C R C R C R C W C W C W C R C W 1:2:1 1:2:1 % genotype % phenotype C R C W male / sperm C R C W female / eggs 25% 25% 50% 25% C R C R C R C W C R C W C W C W 25% 50%
    6. 6. Co-dominance <ul><li>2 alleles affect the phenotype in separate, distinguishable ways </li></ul><ul><ul><li>ABO blood groups </li></ul></ul><ul><ul><li>3 alleles </li></ul></ul><ul><ul><ul><li>I A , I B , i </li></ul></ul></ul><ul><ul><ul><li>both I A & I B are dominant to i allele </li></ul></ul></ul><ul><ul><ul><li>I A & I B alleles are co-dominant to each other </li></ul></ul></ul><ul><ul><li>determines presences of oligosaccharides on the surface of red blood cells </li></ul></ul>
    7. 7. Blood type universal donor universal recipient __ __ status no oligosaccharides on surface of RBC both type A & type B oligosaccharides on surface of RBC type B oligosaccharides on surface of RBC type A oligosaccharides on surface of RBC phenotype type O i i type AB I A I B type B I B I B I B i type A I A I A I A i phenotype genotype
    8. 8. Blood compatibility <ul><li>Matching compatible blood groups </li></ul><ul><ul><li>critical for blood transfusions </li></ul></ul><ul><li>A person produces antibodies against oligosaccharides in foreign blood </li></ul><ul><ul><li>wrong blood type </li></ul></ul><ul><ul><ul><li>donor’s blood has A or B oligosaccharide that is foreign to recipient </li></ul></ul></ul><ul><ul><ul><li>antibodies in recipient’s blood bind to foreign molecules </li></ul></ul></ul><ul><ul><ul><li>cause donated blood cells to clump together </li></ul></ul></ul><ul><ul><ul><li>can kill the recipient </li></ul></ul></ul>Karl Landsteiner (1868-1943) 1901 | 1930
    9. 9. Blood donation
    10. 10. Pleiotropy <ul><li>Most genes are pleiotropic </li></ul><ul><ul><li>one gene affects more than one phenotypic character </li></ul></ul><ul><ul><ul><li>wide-ranging effects due to a single gene: </li></ul></ul></ul><ul><ul><ul><li>dwarfism (achondroplasia) </li></ul></ul></ul><ul><ul><ul><li>gigantism (acromegaly) </li></ul></ul></ul>
    11. 11. Acromegaly: André the Giant
    12. 12. Pleiotropy <ul><li>It is not surprising that a gene can affect a number of organism’s characteristics </li></ul><ul><ul><li>consider the intricate molecular & cellular interactions responsible for an organism’s development </li></ul></ul><ul><ul><ul><li>cystic fibrosis </li></ul></ul></ul><ul><ul><ul><ul><li>mucus build up in many organs </li></ul></ul></ul></ul><ul><ul><ul><li>sickle cell anemia </li></ul></ul></ul><ul><ul><ul><ul><li>sickling of blood cells </li></ul></ul></ul></ul>
    13. 13. Epistasis <ul><li>One gene masks another </li></ul><ul><ul><li>coat color in mice = 2 genes </li></ul></ul><ul><ul><ul><li>pigment (C) or no pigment (c) </li></ul></ul></ul><ul><ul><ul><li>more pigment (black= B ) or less (brown= b ) </li></ul></ul></ul><ul><ul><ul><li>cc = albino, no matter B allele </li></ul></ul></ul><ul><ul><ul><li>9:3:3:1 becomes 9:3:4 </li></ul></ul></ul>How would you know that difference wasn’t random chance? Chi-square test!
    14. 14. Epistasis in Labrador retrievers <ul><li>2 genes: E & B </li></ul><ul><ul><li>pigment ( E ) or no pigment ( e ) </li></ul></ul><ul><ul><li>how dark pigment will be: black ( B ) to brown ( b ) </li></ul></ul>
    15. 15. Polygenic inheritance <ul><li>Some phenotypes determined by additive effects of 2 or more genes on a single character </li></ul><ul><ul><li>phenotypes on a continuum </li></ul></ul><ul><ul><li>human traits </li></ul></ul><ul><ul><ul><li>skin color </li></ul></ul></ul><ul><ul><ul><li>height </li></ul></ul></ul><ul><ul><ul><li>weight </li></ul></ul></ul><ul><ul><ul><li>eye color </li></ul></ul></ul><ul><ul><ul><li>intelligence </li></ul></ul></ul><ul><ul><ul><li>behaviors </li></ul></ul></ul>
    16. 16. Albinism Johnny & Edgar Winter albino Africans
    17. 17. Nature vs. nurture <ul><li>Phenotype is controlled by both environment & genes </li></ul>Color of Hydrangea flowers is influenced by soil pH Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fox influenced by heat sensitive alleles
    18. 18. It all started with a fly… <ul><li>Chromosome theory of inheritance </li></ul><ul><ul><li>experimental evidence from improved microscopy & animal breeding led us to a better understanding of chromosomes & genes beyond Mendel </li></ul></ul><ul><ul><ul><li>Drosophila studies </li></ul></ul></ul>A. H. Sturtevant in the Drosophila stockroom at Columbia University
    19. 19. Thomas Hunt Morgan <ul><li>embryologist at Columbia University </li></ul><ul><ul><li>1 st to associate a specific gene with a specific chromosome </li></ul></ul><ul><ul><li>Drosophila breeding </li></ul></ul><ul><ul><ul><li>prolific </li></ul></ul></ul><ul><ul><ul><li>2 week generations </li></ul></ul></ul><ul><ul><ul><li>4 pairs of chromosomes </li></ul></ul></ul><ul><ul><ul><li>XX=female, XY=male </li></ul></ul></ul>1910 | 1933
    20. 20. Morgan’s first mutant… <ul><li>Wild type fly = red eyes </li></ul><ul><li>Morgan discovered a mutant white-eyed male </li></ul><ul><ul><li>traced the gene for eye color to a specific chromosome </li></ul></ul>
    21. 21. Discovery of sex linkage all red eye offspring How is this possible? Sex-linked trait! red eye female white eye male x 75% red eye female 25% white eye male x
    22. 22. Sex-linked traits <ul><li>Although differences between women & men are many, the chromosomal basis of sex is rather simple </li></ul><ul><li>In humans & other mammals, there are 2 sex chromosomes: X & Y </li></ul><ul><ul><li>2 X chromosomes develops as a female: XX </li></ul></ul><ul><ul><ul><li>redundancy </li></ul></ul></ul><ul><ul><li>an X & Y chromosome develops as a male: XY </li></ul></ul><ul><ul><ul><li>no redundancy </li></ul></ul></ul>
    23. 23. Sex chromosomes autosomal chromosomes sex chromosomes
    24. 24. Genes on sex chromosomes <ul><li>Y chromosome </li></ul><ul><ul><li>SRY: sex-determining region </li></ul></ul><ul><ul><ul><li>master regulator for maleness </li></ul></ul></ul><ul><ul><ul><li>turns on genes for production of male hormones </li></ul></ul></ul><ul><ul><ul><ul><li>pleiotropy! </li></ul></ul></ul></ul><ul><li>X chromosome </li></ul><ul><ul><li>other traits beyond sex determination </li></ul></ul><ul><ul><ul><li>hemophilia </li></ul></ul></ul><ul><ul><ul><li>Duchenne muscular dystrophy </li></ul></ul></ul><ul><ul><ul><li>color-blind </li></ul></ul></ul>
    25. 25. Human X chromosome <ul><li>Sex-linked </li></ul><ul><ul><li>usually X-linked </li></ul></ul><ul><ul><li>more than 60 diseases traced to genes on X chromosome </li></ul></ul>
    26. 26. Map of Human Y chromosome? <ul><li>< 30 genes on Y chromosome </li></ul>SRY
    27. 27. Sex-linked traits Hh x HH sex-linked recessive X H Y male / sperm X H X h female / eggs X H X H X H Y X H X h X H X h X H Y X h Y X H X h X H X h X H Y Y X H X H X H X H Y X H X h X h Y
    28. 28. Sex-linked traits summary <ul><li>X-linked </li></ul><ul><ul><li>follow the X chromosomes </li></ul></ul><ul><ul><li>males get their X from their mother </li></ul></ul><ul><ul><li>trait is never passed from father to son </li></ul></ul><ul><li>Y-linked </li></ul><ul><ul><li>very few traits </li></ul></ul><ul><ul><li>only 26 genes </li></ul></ul><ul><ul><li>trait is only passed from father to son </li></ul></ul><ul><ul><li>females cannot inherit trait </li></ul></ul>
    29. 31. X-inactivation <ul><li>Female mammals inherit two X chromosomes </li></ul><ul><ul><li>one X becomes inactivated during embryonic development </li></ul></ul><ul><ul><ul><li>condenses into compact object = Barr body </li></ul></ul></ul>
    30. 32. X-inactivation & tortoise shell cat <ul><li>2 different cell lines in cat </li></ul>
    31. 33. Male pattern baldness <ul><li>Sex influenced trait </li></ul><ul><ul><li>autosomal trait influenced by sex hormones </li></ul></ul><ul><ul><ul><li>age effect as well: onset after 30 years old </li></ul></ul></ul><ul><ul><li>dominant in males & recessive in females </li></ul></ul><ul><ul><ul><li>B_ = bald in males; bb = bald in females </li></ul></ul></ul>
    32. 34. Mechanisms of inheritance <ul><li>What causes the differences in alleles of a trait? </li></ul><ul><ul><li>yellow vs. green color </li></ul></ul><ul><ul><li>smooth vs. wrinkled seeds </li></ul></ul><ul><ul><li>dark vs. light skin </li></ul></ul><ul><ul><li>Tay sachs disease vs. no disease </li></ul></ul><ul><ul><li>Sickle cell anemia vs. no disease </li></ul></ul>
    33. 35. Mechanisms of inheritance <ul><li>What causes dominance vs. recessive? </li></ul><ul><ul><li>genes code for polypeptides </li></ul></ul><ul><ul><li>polypeptides are processed into proteins </li></ul></ul><ul><ul><li>proteins function as… </li></ul></ul><ul><ul><ul><li>enzymes </li></ul></ul></ul><ul><ul><ul><li>structural proteins </li></ul></ul></ul><ul><ul><ul><li>hormones </li></ul></ul></ul>
    34. 36. How does dominance work: enzyme = allele coding for functional enzyme = allele coding for non-functional enzyme = 100% non-functional enzyme • normal trait is not exhibited = 50% functional enzyme • sufficient enzyme present • normal trait is exhibited • NORMAL trait is DOMINANT carrier = 100% functional enzyme • normal trait is exhibited aa Aa AA
    35. 37. How does dominance work: structure = allele coding for functional structural protein = allele coding for non-functional structural protein = 100% non-functional structure • normal trait is not exhibited = 50% functional structure • 50% proteins malformed • normal trait is not exhibited • MUTANT trait is DOMINANT = 100% functional structure • normal trait is exhibited AA Aa aa
    36. 38. Prevalence of dominance <ul><li>Because an allele is dominant does not mean… </li></ul><ul><ul><li>it is better </li></ul></ul><ul><ul><li>it is more common </li></ul></ul>Polydactyly: dominant allele
    37. 39. Polydactyly individuals are born with extra fingers or toes dominant to the recessive allele for 5 digits recessive allele far more common than dominant  399 individuals out of 400 have only 5 digits  most people are homozygous recessive (aa)
    38. 40. Hound Dog Taylor
    39. 41. Any Questions??
    1. A particular slide catching your eye?

      Clipping is a handy way to collect important slides you want to go back to later.

    ×