1 / 64

Genetics Genetics – study of how traits are passed from parent to offspring

Genetics Genetics – study of how traits are passed from parent to offspring. GENETIC CODE. Organization. CHROMOSOMES – DNA packaging -humans have 46 in all somatic (body) cells – come in 23 pairs DNA –

bcole
Download Presentation

Genetics Genetics – study of how traits are passed from parent to offspring

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Genetics • Genetics – study of how traits are passed from parent to offspring

  2. GENETIC CODE

  3. Organization CHROMOSOMES – DNA packaging -humans have 46 in all somatic (body) cells – come in 23 pairs DNA – Nucleic Acids – made up of nucleotides (5-carbon sugar, nitrogenous base (ATCGs) and phosphate) Genes Sections on DNA that codes for traits and functional units (proteins) codes made of varying lengths of nitrogenous bases (ATCGs)- 300 to 1 million base pairs (bp) long.

  4. Chromosomes come in homologous pairs, thus genes also in pairs. • Homologous pairs – “corresponding” genes – one from female & one from male parent • Example: Humans have 46 chromosomes or 23 pairs. • One set from dad – 23 in sperm • One set from mom – 23 in egg

  5. One pair of Homologous Chromosomes: Gene for eye color(blue eyes) Homologous pair of chromosomes Gene for eye color (brown eyes) Alleles – different genes (possibilities) for the same trait – ex: blue eyes or brown eyes

  6. Genetics Notes Who is Gregor Mendel? Principle of Independent Assortment – Inheritance of one trait has no effect on the inheritance of another trait Principle of dominance – some traits “hide” other traits “Father of Genetics”

  7. Results for One Trait

  8. Dominant and Recessive Genes • Dominant -Gene that prevents the other gene from “showing” – • Gene that does NOT “show” even though it is present – recessive – unless not hidden • Symbol – Dominant gene – upper case letter – T • Recessive gene – lower case letter – t Recessive color Dominant color

  9. Example: Straight thumb is dominant to hitchhiker thumb T= straight thumb t = hitchhikers thumb (Always use the same letter for the same alleles— No S = straight, h = hitchhiker’s) Straight thumb = TT Straight thumb = Tt Hitchhikers thumb = tt * Must have 2 recessive allelesfor a recessive trait to “show”

  10. Both genes of a pair are the same – homozygous or purebred TT – homozygous dominant tt – homozygous recessive • One dominant and one recessive gene – heterozygous=hybrid Tt – heterozygous BB – Black Bb – Black w/ white gene bb – White

  11. Visualize Homologous Chromosomes Place the four chromosome number #2s in front of you. Look at the allele on each for a Lactase gene. • Move 2 in front of you to show homozygous dominant – What trait Would be expressed?2) Now, move 2 chromosomes in front of you to represent a heterozygous individual – what trait would be expressed? 3) Lastly, move 2 chromosomes in front of you to show a homozygous recessive individual. - What is expressed? Can this person drink milk?

  12. Genotype and Phenotype • Genotype Combination of genes (actual gene makeup) • Ex: TT, Tt, tt • Phenotype- Expression of gene (trait or protein)Ex: hitchhiker’s thumb or straight thumb • Ex: hair color Ex: hemoglobin, insulin, etc.

  13. Punnett Square and Probability • Used to predict the possible gene makeup of offspring – Punnett Square • Example:Black fur (B) is dominant to white fur (b) in mice • Cross a heterozygous male with a homozygous recessive female. Black fur (B) White fur (b) Heterozygous male Homozygous recessive female White fur (b) White fur (b)

  14. b b B b Male = Bb X Female = bb Female gametes – N (One gene in egg) Possible offspring – 2N Male gametes - N (One gene in sperm) Write the ratios in the following orders: Genotypic ratio homozygous : heterozygous : homozygous dominant recessive Phenotypic ratio dominant : recessive Genotypic ratio = 2 Bb : 2 bb 50% Bb : 50% bb Phenotypic ratio = 2 black : 2 white 50% black : 50% white

  15. Sickle Cell Anemia disease Autosomal recessive (ss) Mutation in hemoglobin protein in red blood cells Results in sickle cells Symptoms- tired, tissue damage

  16. Practice – Sickle Cell AnemiaInheritance Place the four chromosome 11s at the top of your desk. There are four alleles • Move two in front of you to show a homologous recessive genotype What is the trait being expressed? 2) Show homologous dominant genotype What trait is being expressed 3) Show a heterozygous genotype What trait is being expressed

  17. Sex Determination • People – 46 chromosomes or 23 pairs • 22 pairs are homologous (look alike) – called autosomes – determine body traits • 1 pair is the sex chromosomes – determines sex (male or female) • Females – sex chromosomes are homologous (look alike) – label XX • Males – sex chromosomes are different – label XY

  18. Cross 2 hybrid mice and give the genotypic ratio and phenotypic ratio. Black Fur (B) is dominant over white fur (b) BbX Bb B b B b Genotypic ratio = 1 BB : 2 Bb : 1 bb 25% BB : 50% Bb : 25% bb Phenotypic ratio = 3 black : 1 white 75% black : 25% white

  19. Incomplete dominance and Codominance • When one allele is NOT completely dominant over another (they blend) – incomplete dominance • Example: In carnations the color red (R) is incompletely dominant over white (W). The hybrid color is • pink. Give the genotypic and phenotypic ratio from a cross between 2 pink flowers. • RWX RW R W R W Genotypic = 1 RR : 2 RW : 1 WW Phenotypic = 1 red : 2 pink : 1 white

  20. When both alleles are expressed – Codominance Example: In certain chickens black feathers are codominant with white feathers. Heterozygous chickens have black and white speckled feathers.

  21. Sex – linked Traits • Genes for these traits are located only on the X chromosome (NOT on the Y chromosome) • X linked alleles always show up in males whether dominant or recessive because males have only one X chromosome

  22. Examples of recessive sex-linked disorders: • colorblindness – inability to distinguish between certain colors You should see 58 (upper left), 18 (upper right), E (lower left) and 17 (lower right). Color blindness is the inability to distinguish the differences between certain colors. The most common type is red-green color blindness, where red and green are seen as the same color.

  23. Colorblindness Inheritance Line up the four sex-chromosomes above • Place four X chromosomes and one Y chromosome at the top of your desk 2) Create a female that is a homozygous dominant genotype and put it in front of you? Colorblind or not? 3) Create a female that is heterozygous genotype. She is considered a carrier! Why? 4) Create a male with the phenotype for colorblindness! What genotype is this?

  24. 2. hemophilia – blood won’t clot

  25. Example: A female that has normal vision but is a carrier for colorblindness marries a male with normal vision. Give the expected phenotypes of their children. • N = normal vision • n = colorblindness XNXnXXN Y XN Xn XN Y Phenotype: 2 normal vision females 1 normal vision male 1 colorblind male

  26. Crazy Traits • The alleles you inherit from each parent are determined by chance. • In this investigation, you will play a game that will help you learn about inheritance.

  27. Your creature’s gender • Find the egg coin (x on both sides) • Find the sperm coin (x on one side, y on the other) • Flip the coins together to determine the gender of your creature. • Record this in the table provided – see next slide for example

  28. Determining trait genotypes for your creature • Members of this species have the following traits: main body, foot, leg, skin, arms, hands, beak, eyes, eyebrows, ears, wings, antenna. • You will flip sperm and egg coins to determine the allele for each trait your creature inherits from each parent.

  29. Determining trait genotypes for your creature • In this activity, we will assume that both parents have the same genotype for all traits (Tt). • The genotype of each parent could be Tt, TT, or tt. We are choosing to have parents with the Tt genotype for each trait.

  30. Determining the genotype for each trait • You will need the blue egg coin with a capital T on one side and a lower case t on the other side. • You will also need the green sperm coin with a capital T on one side and a lower case t on the other side.

  31. Determining the genotype for a trait • The first trait you will roll for is skin color. • Place the egg and sperm coins in the cup. • Shake the cup and toss the two coins onto the lab table. • The side that lands up on each coin represents the sperm and egg that unite during fertilization.

  32. Determining the genotype • Record the allele from each parent and genotype in columns 2, 3, and 4 of the first row of Table 1. • Repeat this procedure for traits 2 through 13. • See the next slide for an example.

  33. Stop and Think • What information do the letters on the sperm and egg coins indicate: alleles, genotype, or phenotype? Alleles. Both alleles together represent the genotype.

  34. Stop and Think b. For the sperm coin, what are the chances of getting a T or getting a t? State your answer as a fraction or a percent. 1/2 or 50%.

  35. Stop and Think c. For the egg coin, what are the chances of getting a T or getting a t? State your answer as a fraction or a percent. 1/2 or 50%.

  36. Stop and Think d. When both coins are flipped at once, what are your chances of getting each of the following combinations: TT, Tt, or tt? State your answer for each as a fraction and a percent.

  37. Building your creature • Once you have completed columns 2 through 4 of Table 1, use Table 2 (next page) to look up the phenotype for each trait. Record the phenotype for each trait in column 5 of Table 1.

  38. Building your creature • Once you have completed Table 1, select the correct body parts to build your creature. See parts list on next slide.

  39. Creature Building Tips • Orient the body for either male or female (which orientation do you think is male? Female?) • Place the skin on the smooth side of the body. • Attach the head. • Attach the leg. • Place foot on the stand. • Insert the leg into the foot and stand. • Attach the rest of the body parts.

  40. Thinking about what you observed a. Examine the creatures. Do any of them look exactly alike? Why or why not? • Some look similar, but no two are alike. For two to look exactly alike, every single flip of all three coins would have to be the same for both creatures. That seems very unlikely.

  41. Thinking about what you observed b. How does this investigation explain why siblings may resemble each other, but never look exactly alike (unless they are identical twins)? • Since siblings share the same parents they will likely share many of the same traits. With the huge amounts of traits possible for humans the probability of all of them matching from sibling to sibling is very small.

  42. Thinking about what you observed c. Count the number of males and number of females. Does the number of each match the chances of getting a male or female in the game? Why or why not? • Not exactly because the sample is small. Larger samples yield results that are closer to the average.

  43. Thinking about what you observed d. Which trait(s) are examples of complete dominance? • Eyebrows, beak, ears, leg, foot, arms, hands, antennae, antenna shape, wings, and gender. e. Which trait(s) are examples of incomplete dominance? • Skin color and tail. f. Which trait(s) are examples of codominance? • Eye color.

  44. Adaptation Survivor • Environment Cards will be displayed on this screen. For each card, your creature can: thrive (+1 point); be pushed closer to extinction (-1 point); or have no effect (0). • Watch out for Catastrophe Cards! • When you earn a score of -3, you become extinct! • Play until there is one survivor left.

More Related