1. Introduction to Genetics
Chapter 11
Introduction to Genetics

2. IV. MEIOSIS
Mendel’s principles require 2 things-1)each organism inherits a single copy for every gene from each parent.
2)When an organism produces its own gametes,those 2 sets of genes must be separated from each other so that each gamete has only 1 set.

3. Analyzing Inheritance
Interest Grabber
Analyzing Inheritance
Section 11-1
Offspring resemble their parents. Offspring inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals.
In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.

4. I. The work of Gregor Mendel
_____________________=The scientific study of heredity.
genetics

5. Interest Grabber continued
Section 11-1
Parents
Long stems  short stems
Red flowers  white flowers
Green pods  yellow pods
Round seeds  wrinkled seeds
Yellow seeds  green seeds
First Generation
All long
All red
All green
All round
All yellow
Second Generation
787 long: 277 short
705 red: 224 white
428 green: 152 yellow
5474 round: 1850 wrinkled
6022 yellow: 2001 green
1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
2. How do the characteristics of the second generation compare to the characteristics of the first generation?

7. A. Gregor Mendel’s Peas
Austrian monk whose statistical work w/ pea plants yielded a greater understanding of biological inheritance
He knew each flower produces pollen,containing the male reproductive cells-sperm and female portion produces egg cells.During sexual reproduction,male and female cell join in ________-making a new cell that develops into an embryo
Pea plants self-pollinating
fertilization

8. identical
He started w/ true-breeding plants-meaning that if they are allowed to self-pollinate,they make offspring _________ to themselves.
1 group ____ plants
1 group ______
1 made only ______ seed
1 made ______ seeds
tall
short
green
yellow

9. Mendel wanted to produce seeds from male and female reproductive cells from 2 different plants,preventing self-pollination by cross-pollination,with 2 different plants as parents….This allowed him to cross- breed characteristics

10. Mendel studied different characteristics.
B. Genes and Dominance
Traits
Mendel studied different characteristics.
These characteristics are called ______________-such as seed or flower color or height in humans
Studied 7 traits-see p.264-and he studied the offspring
The offspring are called F1(“first filial”…Filius and filia are Latin words for son and daughter)
__________________are the offspring of crosses of parents w/different traits.
Mendel expected characteristics to blend-like red+white=pink-This was not the outcome
hybrids

11. 2 conclusions:
1) biological inheritance is determined by factors carried by one generation to another.we now call these chemical factors that determine traits___________________.
Different forms of a gene are called ___________________
genes
alleles

12. 2 alleles of that trait must be present for _______________traits.
2) The Principle of Dominance states some alleles are ________________and some are recessive
Alleles occur in pairs and only one allele w/ a certain trait needs to be present for a _________________trait
2 alleles of that trait must be present for _______________traits.
Tall plants were dominant and short recessive.
dominant
dominant
recessive

14. Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants
Section 11-1
Seed Shape
Seed Color
Seed Coat
Color
Pod
Shape
Pod Color
Flower Position
Plant Height
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Smooth
Green
Axial
Tall

15. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

16. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

17. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

18. Interest Grabber
Section 11-2
If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin
ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.
Tossing Coins

19. 4. How do the expected results differ from the observed results?
1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?
2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?
3. If you compiled the results for the whole class, what results would you expect?
4. How do the expected results differ from the observed results?

20. C. Segregation
Mendel wondered if the recessive alleles had disappeared or were they still present in the F1 plants .He allowed all 7 kinds of F1 hybrids to produce an F2 generation by self-pollination

21. F1 cross-recessive traits reappeared(~ ¼ F2 showed recessive trait)
Mendel said the alleles for tall and short segregated(separated) during formation of sex cells
Each gamete (Sex cell) carries a single copy of each gene
F1 produces 2 types of gametes-one has short allele and one has tall allele.
______________letter stands for dominant allele and lower case letter for __________________.example:Tt T stands for tall and lower case for short.
recessive
big

22. Probability and Punnett Squares
Likelihood for occurrence for a particular event is __________________________
PAST OUTCOMES DO NOT AFFECT FUTURE OUTCOMES
Probability is used to determine genetic occurrences using a diagram called a ___________________-which can predict and compare genetic variations that will result from a cross.
probability
Punnett square

23. ____________________means the organism has the same 2 alleles for a trait---TT—also called true-breeding
_______________means the organism has 2 different alleles for a certain trait---Tt-also called hybrid.
______________is the observed physical trait----example:tallness or shortness
________________=genetic makeup or actual alleles----example:TT or Tt
homozygous
heterozygous
genotype
phenotype

24. Tt X Tt Cross
Section 11-2

25. Tt X Tt Cross
Section 11-2

26. Punnett squares Genotypes:___TT__Tt_____tt1
Genotypes:___TT__Tt_____tt
Phenotypes:____tall _____short 2 1 3 1
Punnett squares

27. Larger the # of offspring ,the closer to_________________
Each offspring will have the same probability of a genotype and phenotype because each is ____________or a single occurrence
Larger the # of offspring ,the closer to_________________
predicted ratio.
segregated

29. III.Mendelian Genetics
Mendel wondered if the segregation of one pr of alleles affected another(?)
A) Independent Assortment
To answer his questions ,he performed a ______________.
1)Two-Factor Cross F1
Crossed truebreeders w/ only round yellow peas (genotype RRYY) x plants w/wrinkled green peas(rryy)
Offspring were round yellow,establishing the dominance of RRYY
Resulting genotype RrYy
2 factor cross experiment

30. rryy x RRYY ry RY
RrYy

31. 2) The Two factor Cross:F2
All F1 plants were ______.He wanted to see how the alleles will segregate when F1’s are crossed w/ each other to make an F2 generation
F2 produced 556 seeds-315 round 7 yellow and 32 were wrinkled and green
______seeds had a combination…Therefore seed shape separated separately from color.
This is known as ______________________-genes segregate independently during formation of gametes.This accounts for much of the variation in color
Heterogeneous for seed shape and color
The Principle of Independent Assortment
209

33. Summary of Mendel’s Principles
Inheritance of biological characteristics is controlled by genes from the parents
When there are 2 or more alleles of a gene,then one is dominant and one is recessive
Most sexually reproducing organisms have 2 adults w/ 2 copies of each gene-one from each parent.
Alleles usually segregate independently.

34. C. Beyond Dominant and Recessive alleles
Exceptions to the rules
Majority of genes have more than 2 alleles.
Some are neither dominant nor recessive and multiple genes and alleles or genes control traits
1 ) Incomplete dominance-one allele is not completely dominant over another one

46. 2) ____________-both alleles contribute to the phenotype—example –in chickens the allele for black feathers is codominant with white---this results in __________offspring
3) _______________-more than 2 possible alleles exist in a population(not in one organism-example-rabbits have 1 gene for coat color,but 4 possible alleles for that gene….also an example is genes for human blood type
4)_____________-traits controlled by 2 or more genes’ INTERACTION-4 different genes cover probably control human skin color
MULTIPLE ALLELES
CODOMINANCE
SPECKLED
POLYGENIC TRAITS

47. Applying Mendel’s principles
_____________________started using fruit flies to study genetics-______________________________________They are easy to study because they produce many offspring quickly….Mendelian genetics applied to them
MORGAN
Drosophilia melanogaster

48. E. Genetics and the Environment
Traits not determined solely by genes
Traits determined by ____________________________
Interaction of the genes and the environment they are in.

49. IV. MEIOSIS
Mendel’s principles require 2 things-1)each organism inherits a single copy for every gene from each parent.
When an organism produces its own gametes,those 2 sets of genes must be separated from each other so that each gamete has only 1 set

50. Chromosome #
The sets of chromosomes will be homologous,meaning that one from male corresponds w/ one from female
A cell w/ both sets of homologous chromosomes is _______________,meaning 2 sets(2N)---For Drosophilia,2N=8-2 complete sets of chromosomes and 2 complete sets of genes.
Gametes,however contain a __________________#-1 set of chromosomes-for Drosophilia N=4.
haploid
diploid

51. B. Meiosis=_______________________________________________________________________________________________
Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

52. 2 divisions-Meiosis I and Meiosis II

54. Meiosis I – tetrad Crossing-over Chromosomes are replicated 1st
Divide similar to mitosis,except in prophase I each chromosome pairs w/ its corresponding chromosome to make a __________________-which has 4 chromatids
They exchange portions of their chromatids in _______________________-resulting in a exchange of alleles between homologous chromosomes and produces new combinations of alleles.
Homomlogous chromosomes separate and 2 new cells are formed
Each cell has 4 chromatids,but they are separated
Crossing-over

56. Meiosis II-
No replication(of chromosomes) previous to Meiosis II-unlike w/ meiosis I
Each chromosome has 2 chromatids
4 daughter cells contain haploid # (N)

61. C. Gamete Formation-In female- 1 egg cell produced and 3 ______________________.
Male produces 4 sperm cells
D. Comparing Mitosis and meiosis
Mitosis produces 2 genetically alike diploid cells /also allows for growth
Meiosis produces 4 genetically different haploid cells/for sexual reproduction
Polar bodies

62. V. Linkage and Gene Mapping
A. Linkage
Morgan in 1910 discovered the principle of linkage-certain genes inherited together
Drosophilia had 4 linkage groups----CHROMOSOMES assort independently,not the genes

63. B. Gene Maps
.Crossing –over during meiosis separates genes on the same chromosome onto homologous chromosomes---This gives great genetic ____________________.
diversity

64. Crossing-Over