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Chapter 11: Introduction to Genetics

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1 Chapter 11: Introduction to Genetics

2 11-1: The Work of Gregor Mendel
heredity: set of characteristics an organism receives from its parents genetics: study of heredity

3 Gregor Mendel

4 Reproduction in Pea Plants
pollen is the male sex cell eggs are the female sex cells Able to reproduce…. self pollination: pollen fertilizes an egg from the same plant cross pollination: pollen from one plant fertilizes an egg from another plant

5 Pea Plant Traits Seven traits with two options
Crossed plants with different characteristics of same trait tall with short green seeds with yellow seeds round seeds with wrinkled seeds alleles: different forms of a gene

6 True-Breeding True-breeding plants AA, bb
Only have one allele per trait AA, bb What is another name for a true-breeding plant? Only produce identical offspring TALL plants produce TALL plants Green seeded plants produce Green seeded plants

7 Mendel’s First Experiment
What did Mendel do in his experiments? Prevented self pollination Controlled cross pollination Removed male flower parts Pollen from plant A with egg from plant B used purebreds Seed color or plant height

8 Mendel’s Results offspring were hybrids: organisms produced by crossing parents with differing characteristics all hybrids had the characteristics of only one parent

9 Mendel’s Second Experiment
Crossed F1 hybrid plants P generation: purebred group F1 generation: hybrid group F2 generation: offspring of hybrids F2 plants - the recessive traits reappeared

10 Mendel’s Results Ratios of Mendel’s Crosses
phenotype: physical characteristics genotype: genetic makeup homozygous: two identical alleles for a particular trait TT, homozygous dominant tt, homozygous recessive heterozygous: having two different alleles for the same trait Tt

11 Genes and Alleles genes: unit that determines traits
alleles: different forms of a gene have two alleles for each trait one from each parent sex cells contain one allele when sex cells combine, create cells with two sets of genes

12 DO NOW DEC 8 Solve the following problem…
Cross a Heterozygous Long-clawed panther with a short-clawed panther. 1. List all of the possible genotypes and their phenotypes. 2. What percentage of panther cubs will have short claws?

13 Solution Dec 8 L l Ll ll L = LONG CLAW l = short claw
Genotype = Ll Phenotype = LONG claw ll short claw % Genotype ll L l Ll ll

14 Independent Assortment
Principle in which alleles separate independently of one another as they are passed down from parent to offspring. Interpret this statement. How does this process occur? Why is this process valuable to a species?

15 Independent Assortment
Interpret this statement. The passing down of alleles is a random process. How does this process occur? Meiosis Crossing over, Independent Association, Gamete Formation in Females Why is this process valuable to a species? Provides Genetic Variation to organisms. Necessary for survival.

16 Interpreting Genotypes and Phenotypes
Determine the possible genotypes of a pea plant that is Tall and has white flowers. TALL is dominant over short PURPLE is dominant over white flowers

17 Identifying Genotypes
Possible Genotypes TT pp where T = Tall P = Purple t = short p = white Tt pp

18 Dihybrid Crosses Perform a cross between two heterozygous round and heterozygous yellow seed plants. R = Round seed Y = Yellow seed r = wrinkled seed y = green seed What do you need to determine from the information you are given?

19 Dihybrid Crosses Solving for two different traits. Parents RrYy x RrYy
R = Round seed Y = Yellow seed r = wrinkled seed y = green seed

20 F=first O=outer I=inner L=last
Allele Combinations Use the FOIL method to determine all of the possible genotypes of the parents. F=first O=outer I=inner L=last

21 Allele Combinations Parent Genotypes – RrYy
Use FOIL Method to find parent allele combinations. F – RY O – Ry I – rY L – ry Allele Combinations RY Ry rY ry

22 Analyzing Results Answer the following question using your Punnett Square results. What is the ratio of offspring having a round and green seed?

23 Identifying the Phenotypes of the Offspring
Parent Allele Combinations RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy

24 Step by Step Procedure 1. Identify the parent genotypes
2. Assign letters to represent alleles 3. Use FOIL to determine allele combinations 4. Set up and Solve your Punnett Square 5. Identify information you need to answer questions. Write down genotypes / phenotypes 6. Analyze data from the results of your Punnett Square. Calculate genotypic and phenotypic ratios Answer questions using results

25 Punnett Square REVIEW A poodle that is heterozygous for white, curly fur is crossed with a poodle having black, straight fur. What are the chances one of their puppies will have white, straight fur?

26 WwCc x wwcc Parent Allele Combinations WC Wc wC wc WwCc Wwcc wwCc wwcc

27 Punnett Square REVIEW What are the chances one of their puppies will have white, straight fur? White Curly DOMINANT Genotypes for White, Straight fur WWcc or Wwcc 4/16 puppies

28 Mendel’s Conclusions 1. individual factors, called genes, control each trait 2. principle of dominance: some factors or alleles are dominant whereas others are recessive

29 11-2: Probability and Punnett Squares
probability applies to genetics because the formation of gametes depends on random events

30 Probability and Punnett Squares
probability: the likelihood that a particular event will occur # of times event occurs ÷ by the total # of occurrences

31 Predicting Averages Probabilities predict the average outcome of a large number of events. Cannot predict the precise outcome of a single event. Also true for genetics. Larger numbers of offspring will produce results closer to the expected values/ratios. Only 3 or 4 (F2) offspring may not equal the predicted ratio However, hundreds/thousands of offspring will produce ratios very close to results.

32 Segregation the separation of alleles during gamete formation
New random combinations formed through meiosis monohybrid cross: crossing one trait

33 Segregation What are the genotypes of the F1 plants?
When crossed, the recessive trait reappears in the F2 Gen

34 A Summary of Mendel’s Work
genes control heredity genes are inherited from each parent some forms of the gene may be dominant and others may be recessive segregation occurs during the formation of reproductive cells genes for different traits may sort independently of one another

35 Dihybrid Crosses Homework Review
Question 3 BE Be bE be BbEe Bbee bbEe bbee

36 Dihybrid Crosses Homework Review
Question 6 TP Tp TTPp TTpp tp TtPp Ttpp

37 11-3: A Closer Look At Heredity
Incomplete dominance: neither allele is completely dominant or recessive The phenotype for a heterozygous offspring is a blending of both alleles.

38 Incomplete Dominance Cross a Red Flowered plant with a White Flowered plant. What are the genotypes and phenotypes of the offspring? What percent of the offspring will have White Flowers?

39 Punnett Square Solution Incomplete Dominance

40 Codominance codominance: both alleles are expressed and contribute to the phenotype Example: Roan horse CWCW  White Coat CRCR  Red Coat CRCW  Roan Coat Cross a Roan Horse with a Red coated Horse.

41 Solution CR CW x CR CR  RW x RR How many horses have a white coat? R

42 Multiple Alleles Polygenic Traits
a trait that has more than two alleles eye color blood type traits that are controlled by more than one gene facial appearance

43 Multiple Alleles Polygenic Traits
Blood types in humans. A B AB O ALLELES: A, B, O Coat color in rabbits Four different alleles Skin color in humans Eye color is various organisms Fruit flies

44 BLOOD TYPES Controlled by 3 Alleles A and B are codominant
A (IA), B (IB) and O (ii) A and B are codominant Both dominant over O

45 Blood Type Punnett Squares

46 11-5 Gene Linkage Thomas Hunt Morgan conducted many experiments with the Drosophilia fruit fly. Many groups of genes were “linked” together. Reddish eyes and miniature wings Two conclusions. 1. Chromosomes are actually groups of linked genes 2. Chromosomes assort independently (not single genes)

47 11-5 Gene Mapping Crossing over can separate and exchange linked genes. Creates genetic diversity The farther apart 2 genes are from one another, the greater chance they would be separated by crossing over. Gene Locus – Location of a gene on a chromosome

48

49 Codominance A farmer has been told by his friend that white-coated horses are worth more money than red or roan coated horses. He decides to breed his own by crossing two Roan coat horses. Is he successful? List the genotypes and phenotypes of all the offspring. List the percentage of each phenotype.

50 Incomplete Dominance What is the genotype of a pink flower?
If two pink flowers were crossed, what are the possible genotypes and phenotypes of the offspring?


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