Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chapter 11: Introduction to Genetics

Similar presentations


Presentation on theme: "Chapter 11: Introduction to Genetics"— Presentation transcript:

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 are plants that only carry one allele for a trait. If these plants are allowed to self-pollinate, they will produce offspring identical to themselves. TALL plants produce TALL plants Green seeded plants produce Green seeded plants

7 DO NOW DEC 12 If you crossed a wrinkled seeded pea plant with a round seeded pea plant, how would you predict the offspring produced?

8 DO NOW ANSWERED You would need to know which trait was dominant.
It is also necessary to identify the alleles from each parent that may be passed down to an offspring. This dominant trait will most likely be expressed.

9 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

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

11 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

12 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

13 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

14 Punnett Square Practice
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

15 Punnett Square Practice
Possible Genotypes TT pp where T = Tall P = Purple t = short p = white Tt pp

16 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

17 11-2: Probability and Punnett Squares
probability applies to genetics because the formation of gametes depends on random events

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

19 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.

20 Punnett Square Practice DEC 15
Solve the following problem… Cross a Heterozygous Long-clawed panther with a short-clawed panther. List all of the possible genotypes and their phenotypes. What ratio of panther cubs have short claws? What percentage?

21 Solution Dec 15 L = LONG CLAW DOMINANT l = short claw L l Ll ll

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

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

24 Independent Assortment
process by which genes separate independently of one another Crossing of multiple traits Dihybrid Cross

25 Dihybrid Crosses Solving for two different traits.
Parents --- RrYy and RrYy R = Round seed Y = Yellow seed Capital Letters = DOMINANT TRAITS Use the FOIL method to determine all of the possible genotypes of the parents. F=first O=outer I=inner L=last

26 Dihybrid Crosses Parent Genotypes – RrYy
Use FOIL Method to find possible allele combinations. F – RY O – Ry I – rY L – ry Allele Combinations – RY Ry rY ry

27 Dihybrid Crosses RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy

28 Review of Mendel’s Work
What information did Mendel’s experiments reveal about genetics? Write your answers in your notebooks. BE READY TO SHARE YOUR ANSWERS!

29 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

30 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.

31 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?

32 Punnett Square Solution

33 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.

34 DO NOW Answered DEC 17 CR CW x CR CR  RW x RR
NO. 0 out of 4 horses have a WHITE Coat. What genotype identifies a WHITE Coat? R RR W RW

35 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)

36 Polygenic Traits traits that are controlled by more than one gene
facial appearance

37 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

38

39 Dihybrid Cross Cross a homozygous Tall, heterozygous yellow seeded pea plant with a short, green seeded pea plant. What percentage of the offspring will be tall and green seeded?

40 DO NOW ANSWER DEC 18 TY Ty ty TtYy Ttyy

41 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.

42 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?


Download ppt "Chapter 11: Introduction to Genetics"

Similar presentations


Ads by Google