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Meiosis & Genetics

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  1. Meiosis & Genetics

  2. Mitosis Review LT 1 When a cell gets too big or when cells need replaced, they will go through MITOSIS. Mitosis the division of the nuclear material (DNA) and takes place after Interphase (when DNA is replicated) Mitosis is followed by Cytokinesis, when the cytoplasm is divided and two new daughter cells are formed.

  3. Mitosis Review Interphase-DNA is in the form of chromatin (unorganized DNA) Prophase-chromatin sister chromatidsand nuclear envelope breaks down Metaphase-sister chromatids line up in the middle of the cell. Spindle fibers attach to sisters at the centromere Anaphase-sisters are pulled apart by the spindle fibers to the poles of the cell Telophase- sisters  independent chromosomes; one copy to each new daughter cell. Nuclear envelope reforms

  4. Mitosis Review Products 2 daughter cells Identical to parent cell Parent cell divides one time Kind of asexual reproduction (because genetic info is not exchanged) Parent and daughter cells are diploid-have a full set of chromosomes for that species. Done by all body or SOMATIC cells.

  5. Meiosis-Making Sex Cells Meiosis – is the process by which sex cells or gametes are made. Male Gamete -Sperm Female Gamete -Egg • The process will make… • 4 daughter cells or gametes • The cells will be genetically DIFFERENT than the parent cell • The cells will contain ½ the number of chromosomes in somatic (body) cells

  6. Meiosis Meiosis occurs in TWO parts or divisions: Meiosis I and Meiosis II Meiosis I Interphase I Prophase I Metaphase I AnaphaseI Telophase I Meiosis II NO Interphase !!!! Prophase II Metaphase II Anaphase II TelophaseII and Cytokinesis Meiosis I Meiosis II

  7. Mitosis v. Meiosis Mitosis 2 daughter cells Identical to parent cell Parent cell divides one time Kind of asexual reproduction Parent and daughter cells are diploid Done by all body or SOMATIC cells. Meiosis 4 daughter cells Genetically different from parent cell Parent cell divides two times Kind of sexual reproduction Parent cell = diploid, daughter cell = haploid-having ½ the number of chromosomes as a body cell Done only by sex cells/gametes

  8. LT 2 Homologous Pairs Let’s Watch This

  9. A HYPOTHETICAL ORGANISM HAS 10 CHROMOSOMES FOR EACH OF ITS BODY CELLS. • Skin cells are continuously being rubbed off and replaced. How many chromosomes will be contained in each new skin cell that is replaced? ____________ • This replacement occurs through the process of _____________. • Each somatic cell of this organism has how many chromosomes? __________ • The zygote divides many times to form all of the cells of the new “baby.” This type of division is called____________.

  10. A HYPOTHETICAL ORGANISM HAS 10 CHROMOSOMES FOR EACH OF ITS BODY CELLS. • The cell that starts Mitosis is Diploid/Haploid • The cell that starts Meiosis is Diploid/Haploid • The cell that results from Mitosis is Diploid/Haploid • The cell that results from Meiosis is Diploid/Haploid • If the organism above went through Meiosis each gamete would contain ____ chromosomes. • The gametes would be same as/different from the parent cell

  11. Crossing Over LT 3 Crossing Over-the process where portions of the homologous pairs swap segments of their chromosomes Occurs in Prophase I Creates genetic variation (The resulting pairs are neither entirely dad or entirely mom any longer) Chiasma-every point where HP’s overlap or intertwine for crossing over Synapsis-when the HP’s come together before crossing over Watch This

  12. Since there are more chances for a break to occur between two genes that lie on the chromatid, it is more likely that one gene will stay on the original chromosome, while the other crosses over. • So, genes that lie far apart are likely to end up on two different chromosomes. • Genes that lie very close together are less likely to be separated by a break and crossing-over. • Genes that tend to stay together during recombination are said to be linked Two linked traits in humans are Hemophilia and Red-Green Colorblindness

  13. Gametogenesis LT 2 So Meiosis is the process by which sex cells are made and we get 4 genetically different gametes from the parent cell with ½ the number of chromosomes…right? Well sort of…the process is slightly different for males and females. Males = Spermatogenesis Females = Oogenesis

  14. Spermatogenesis In males, the process is IDENTICAL to regular Meiosis They will get 4 gametes Each gamete will be haploid Each gamete will be genetically different

  15. Oogenesis In females, the process is slightly different then Meiosis Only 1 gamete or egg is actually produced. This is due to an uneven splitting of the cytoplasm during Meiosis I and II. NOTE…the chromosomes are evenly split. The smaller “cells” are called - polar bodies and will disintegrate One large egg is best as a source of food for the zygote. Having the extra mass means more nutrients until other structures can develop (think umbilical cord)

  16. Dwight Schrute

  17. Mono- and Dihybrid Crosses LT 4 & 5 Please see the notes and examples given on the board during class! Monohybrid Cross Dihybrid Cross P p Q q P q p q

  18. Other Forms of Inheritance LT 6 Fortunately for Mendel, peas show simple dominant-recessive inheritance or complete dominance. That is EASY!! Are there other ways to inherit traits? YES • Co-Dominance • Multiple Alleles • Sex-Linked Inheritance • Polygenic Traits

  19. Complete Dominance The presence of one dominant allele will mask (hide or recess) the recessive allele.

  20. Co-Dominance • When neither allele is dominant or recessive • Both traits show at the same time and equally. • The offspring has a phenotype that shows BOTH parents’ phenotypes Ex: AB Blood Type or Spotted Coat Color (Roan in cattle)

  21. Multiple Alleles Traits where there are more than two alleles (gene options) found in nature (Recall in dom-rec inheritance there are only two alleles-the dominant and recessive) Dom-Rec Inheritance Option 1: W = Widow’s Peak Option 2: w = no Widow’s Peak Multiple Alleles: Human Blood Types Option 1: A allele Option 2: B allele 3 options exist in nature Option 3: O allele **Note… despite having many alleles, any individual ONLY INHERITS 2 of the 3!! Ex: ABO Blood Types, Human Leukocyte Antigen (HLA), Fruit Fly Eye Color, Chicken combs

  22. Multiple Alleles • 400 alleles found in all humans in the population, but… • you can only inherit 1 of the 3 from mom (1 of the 2 she carries) • and 1 of the 3 from dad (1 of the 2 he carries) • A allele and B allele are dominant to O allele • O allele is recessive • A allele is equally dominant to B allele- or co-dominant

  23. Multiple Alleles-Practice Problem TRY THIS… Could you please help me? I have a question that is NOT a homework question. I am a Junior in High School. "Could a man with type B blood and a woman with type AB produce a child with type O blood?" I think not, because type O is recessive, and the B's seem to be dominant. My cousin thinks yes. Thank you for your help. -- Vicki • Possible • Not possible

  24. Sex-Linked Inheritance Traits that are carried on and inherited from the sex chromosomes Recall 22 pairs of autosomes(body chromosomes) 1 pair of sex chromosomes (X and Y) Females are XX Males are XY

  25. Sex-Linked Inheritance • Not only genes for male or female traits, but other genes are carried on the X and Y chromosome. • Females are only affected by X-linked traits • Males affected by both X- and Y-linked traits • X-linked traits might not be observable in women if they only have one copy because they have a second X to overcome the harmful gene. • X-linked traits will ALWAYS affect a male because they DO NOT have the other X to compensate. How could a women GET an X-linked disorder?

  26. Sex-Linked Inheritance Examples of Sex-Linked Traits • Colorblindness • Hemophilia • Duchenne Muscular Dystrophy • Fragile X Syndrome The female carries the recessive trait. The male is unaffected. What portion of male and female offspring will have the trait? The female is unaffected. The male has the trait and is a carrier of it.. What portion of male and female offspring will have the trait?

  27. Sex-Linked Trait-Practice Problem Crossing a white-eyed female and red-eyed male fly In a cross between a white-eyed female fruit fly and red-eyed male, what percent of the female offspring will have white eyes? (White eyes are X-linked, recessive) A. 100%XrXr B. 25% C. 50% XR D. 75% E. 0% Y

  28. Sex-Linked Trait-Answer Crossing a white-eyed female and red-eyed male fly In a cross between a white-eyed female fruit fly and red-eyed male, what percent of the female offspring will have white eyes? (White eyes are X-linked, recessive) A. 100%XrXr B. 25% C. 50% XR D. 75% E. 0%Y XRXr XRXr XrY XrY

  29. Sex-Linked Traits Quiz Solve this problem using a Punnett Square. I have a daughter who carries the allele for colorblindness, a sex-linked trait, but is NOT colorblind. Her genotype is XBXb; where B is normal vision and b is colorblindness. Her husband is NOT colorblinded (XBY). Will any of their children be able to inherit colorblindness? If so which SEX child and at what ratio?

  30. Answer XBXb XB Y Yes!! A male child, with a 25% chance overall (or 50% for all males) XBXB XBXb XBY XbY

  31. Polygenic Traits Traits that are controlled by more than one gene. Appearance depends on alleles on many different genes. Traits that are polygenic often show a range of characteristics like height, hair color, shoe size, etc. Let’s Watch This

  32. The Stren Line company recently sponsored a swimsuit competition. The only requirement was that the swimsuit be held up by fishing line. This year's winner ...... 2009 ... World's smallest (legal) swimsuit. Here is the winner:   It's held in place with clear fish line. I love the look on the girl's face holding the camera! Smart fisherman rely on Stren Line for all of their tackle needs Height S S S S S S S S S S T S S S S S S S S S T T S S S S S S S S T T T S - Short Gene S S S S S S S T T T T S S S S S S T T T T T T - Tall Gene S S S S S T T T T T T S S S S T T T T T T T S S S T T T T T T T T S S T T T T T T T T T S T T T T T T T T T T

  33. The Stren Line company recently sponsored a swimsuit competition. The only requirement was that the swimsuit be held up by fishing line. This year's winner ...... 2009 ... World's smallest (legal) swimsuit. Here is the winner:   It's held in place with clear fish line. I love the look on the girl's face holding the camera! Smart fisherman rely on Stren Line for all of their tackle needs Blood Pressure L L L L L L L L L L H L L L L L L L L L H H L L L L L L L L H H H L - Low BP Gene L L L L L L L H H H H L L L L L L H H H H H H - High BP Gene L L L L L H H H H H H L L L L H H H H H H H L L L H H H H H H H H L L H H H H H H H H H L H H H H H H H H H H

  34. The Stren Line company recently sponsored a swimsuit competition. The only requirement was that the swimsuit be held up by fishing line. This year's winner ...... 2009 ... World's smallest (legal) swimsuit. Here is the winner:   It's held in place with clear fish line. I love the look on the girl's face holding the camera! Smart fisherman rely on Stren Line for all of their tackle needs Blood Glucose Level L L L L L L L L L L H L L L L L L L L L H H L L L L L L L L H H H L - Low BG Gene L L L L L L L H H H H L L L L L L H H H H H H - High BG Gene L L L L L H H H H H H L L L L H H H H H H H L L L H H H H H H H H L L H H H H H H H H H L H H H H H H H H H H

  35. The Stren Line company recently sponsored a swimsuit competition. The only requirement was that the swimsuit be held up by fishing line. This year's winner ...... 2009 ... World's smallest (legal) swimsuit. Here is the winner:   It's held in place with clear fish line. I love the look on the girl's face holding the camera! Smart fisherman rely on Stren Line for all of their tackle needs ASD - Autism Spectrum Disorder L L L L L L L L L L T L L L L L L L L L T T T T T L L L L L L L L L - Loose Synapse Gene T T T T L L L L L L L L L L L L L T T T T T T - Tight Synapse Gene L L L L L T T T T T T L L L L T T T T T T T L L L T T T T T T T T L L T T T T T T T T T T T T T T T T L T T T

  36. SYNAPTIC CONNECTIONS Thought to result from over 300 genes AUTISM

  37. Pedigrees LT 7 Often times traits can be followed through families and the form of inheritance can be followed. • We can use the known phenotypes or genotypes of individuals to predict the phenotypes or genotypes of other family members. • Sometimes we can guess based on other family members.

  38. Pedigree Symbols Generation #