Analyzing Inheritance

1
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.

2
Section 11-1

• 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?

3
Section Outline
Section 11-1

• 111 The Work of Mendel
• A. Gregor Mendels Peas
• B. Genes and Dominance
• C. Segregation
• 1. The F1 Cross
• 2. Explaining the F1 Cross

4
Section 11-1

• 111 The Work of Mendel
• Gregor Mendel (1822-1884) was a monk at a
  monastery in Brunn, Austria
• He taught school and did other chores, but in his
  spare time he set out to study plant breeding
• He started breeding pea plants about 1855
• He wanted to learn the rules of heredity so that
  better varieties could be produced

5
Section 11-1

• 111 cont.
• Mendels original pea plants were true-breeding.
• When allowed to self-pollinate they produced
  offspring identical to themselves
• Mendel wanted to cross-pollinate the plants and
  study the results
• Mendel studied seven different pea plant traits
  (specific characteristic that varies from
  individual to individual) with 2 contrasting
  characteristics

6
Figure 11-3 Mendels Seven F1 Crosses on Pea
Plants
Section 11-1
Seed Shape
Flower Position
Seed Coat Color
Seed Color
Pod Color
Plant Height
Pod Shape
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Smooth
Green
Axial
Tall
7
Section 11-1

• 111 cont.
• Mendel called each original pair of plants the
• P Generation (parental) and the offspring of
  these the F1 generation (first filial)
• Mendel produced hybrids when he crossed parents
  with different traits and to his surprise the
  offspring only resembled one of the parents

8
Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
9
Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
10
Section 11-1

• 111 cont.
• Mendel drew 2 conclusions from this experiment
• Biological inheritance is determined by factors
  that are passed from one generation to the next
  today known as genes
• Principle of Dominance which states that some
  alleles (different forms of a gene) are dominant
  and others are recessive

11
Section 11-1

• 111 cont.
• Dominant alleles will always exhibit that form of
  the trait and is represented with a capital
  letter
• ex. (T) - Tall
• Recessive alleles will only exhibit that form of
  the trait if the dominant allele is not present
  and is represented with a lower case letter
• ex. (t) - short

12
Section 11-1

• 111 cont.
• Mendel then allowed his F1 hybrid plants to
  self-pollinate to produce an F2 generation
  (second filial)
• Traits controlled by the recessive alleles
  reappeared in ¼ of the F2 generation
• Mendel explained that the dominant allele masked
  the recessive allele in the F1 generation and due
  to the segregation of alleles during gamete
  formation reappeared in the F2 generation

13
Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
14
Section 11-1
15
Tossing Coins
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.

16
Section 11-2
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 partners
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?
17
Section Outline
Section 11-2

• 112 Probability and Punnett Squares
• A. Genetics and Probability
• B. Punnett Squares
• C. Probability and Segregation
• D. Probabilities Predict Averages

18
Section 11-2

• 112 Probability and Punnett Squares
• Probability is the likelihood that a particular
  event will occur and Mendel realized that the
  principles of probability could be used in
  predicting the outcomes of genetic crosses

19
Section 11-2

• 112 cont.
• Punnett Squares can be used to predict and
  compare the genetic variations that will result
  from a cross
• The gametes are shown along the top and left side
• Possible gene combinations of the offsping appear
  in the boxes

20
Tt X Tt Cross
Section 11-2
21
Tt X Tt Cross
Section 11-2
22
Section 11-2

• 112 cont.
• Homozygous organisms are true-breeding which
  means they have two identical alleles for a
  particular trait
• Ex. TT
• Heterozygous organisms are hybrids that have two
  different alleles for the same trait
• Ex. Tt

23
Section 11-2

• 112 cont.
• Genotype vs. Phenotype
• The genotype is the actual genetic makeup of the
  traits, while the phenotype is the actual
  physical characteristics of an organism

24
Section Outline
Section 11-3

• 113 Exploring Mendelian Genetics
• A. Independent Assortment
• 1. The Two-Factor Cross F1 2. The Two-Factor
  Cross F2
• B. A Summary of Mendels Principles
• C. Beyond Dominant and Recessive Alleles
• 1. Incomplete Dominance 2. Codominance
• 3. Multiple Alleles 4. Polygenic Traits
• D. Applying Mendels Principles
• E. Genetics and the Environment

25
11-3 Exploring Mendelian Genetics

• After proving that alleles segregate in the
  formation of gametes, Mendel wanted to know if
  they did so independently did the segregation
  of one pair of alleles affect the segregation of
  other pairs?
• Two-Factor Cross F1
• - Mendel crossed homozygous round yellow peas
  (RRYY) with wrinkled green peas (rryy).
• - F1 were all round yellow (RrYy)

26

• Two-Factor F2
• - Mendel knew F1s were heterozygous for both
  traits
• - when allowed to self-fertilize the F1 gave rise
  to F2s w/ a
• definite ratio
• - this led Mendel to his Principle of Independent
  Assortment
• - alleles for different characteristics segregate
  independently of
• each other so as long as genes for two traits
  are on
• different chromosomes every combination of
  alleles is possible.

27
Figure 11-10 Independent Assortment in Peas
Section 11-3
28
Concept Map
Section 11-3
Gregor Mendel
concluded that
experimented with
which is called the
which is called the
29
Incomplete Dominance

• when neither allele is dominant over the other
• - heterozygotes differ phenotypically from either
  
• homozygote
• Ex. Four Oclock plants
• - RR red
• - WW white
• - RW pink
• this is not blending because red and white
• flowers will reappear.

30
Figure 11-11 Incomplete Dominance in Four
OClock Flowers
Section 11-3
31
Figure 11-11 Incomplete Dominance in Four
OClock Flowers
Section 11-3
32
Codominance

• situation in which both alleles contribute to
  the phenotype
• - both are expressed if present
• Ex. chickens white and black feathers are
  codominant
• - heterozygotes produce both white and black
  feathers
• A and B alleles in human blood types

33
Multiple Alleles

• when a gene has more than two alleles
• - each individual still only gets two of the
  possible alleles that exist in the population
• Ex. Human blood groups
• - three alleles A, B, O
• - A and B are codominant
• - O is recessive

34
Polygenic Traits

• traits which are influenced by several genes
• - results in a wide range of phenotypes
• Ex. Human height, skin color, color in eyes of
  fruitflies

35
Height in Humans
Section 11-3

• Height in pea plants is controlled by one of two
  alleles the allele for a tall plant is the
  dominant allele, while the allele for a short
  plant is the recessive one. What about people?
  Are the factors that determine height more
  complicated in humans?

36
Section 11-3

• 1. Make a list of 10 adults whom you know. Next
  to the name of each adult, write his or her
  approximate height in feet and inches.
• 2. What can you observe about the heights of the
  ten people?
• 3. Do you think height in humans is controlled by
  2 alleles, as it is in pea plants? Explain your
  answer.

37
Applying Mendels Principles

• Mendels principles apply to all organisms
• - Thomas Hunt Morgan began use of fruitflies
• - ideal organism
• - fast breeder
• - lots of young
• - many observable traits
• - small size
• - Environment also affects development of
  organisms

38
Sex Linkage

• - genes located on autosomes behave as we have
  studied
• - genes located on the sex chromosomes often
  exhibit a unique
• pattern of inheritance.
• - in mammals females have two X-chromosomes (XX)
• - in mammals males have an X and a Y chromosome
  (XY)
• - the Y chromosome has a gene (SRY) that makes
  the
• embryo male
• - but Y has fewer genes than X and so males only
  get one
• copy of some genes on the Y
• - genes that males only get one copy of are
  sex-linked and are
• expressed more often in males than females
• - color-blindness, muscular dystrophy

39
(No Transcript)
40

• The most important fact of mitosis is that each
  daughter cell has the exact same genetic make-up
  as the original cell.
• Gregor Mendel The Father of Genetics
• - didnt know where genes were located
• - described in detail how genes must move in the
  
• formation of gametes and subsequent
  fertilization
• - each organism must inherit a single copy of
  every gene from both of its parents
• - each offspring therefore has two copies of
  each gene
• - these two copies must be separated to form
  the gametes of this organism

41

• Chromosome Number
• Normal body cells contain two copies of each
  chromosome
• one received from each of the two parents
• Homologous chromosomes
• Same shape, size, and contain the same genes in
  same order
• Diploid term used to describe a cell with
  homologous chromosomes
• Symbol 2N
• Found in all normal body (somatic) cells
• Haploid term describing a cell with a single
  copy of each chromosome
• Symbol N
• Found in gametes (sex cells)

42

• Phases of Meiosis
• Meiosis is a process of reduction division in
  which the chromosome number per cell is cut in
  half through the separation of homologous
  chromosomes in a diploid cell. (Diploid ?
  Haploid) (2N ? N)
• - requires two distinct divisions Meiosis I
  and Meiosis II
• - allows organisms to reproduce sexually and
  maintain the normal diploid number in the
  offspring
• Meiosis I Reduction Division (Figure 11.15, pg
  276)
• - prior to meiosis I the chromosomes replicate

43

• A. Prophase I
• - nucleolus, nuclear membrane break down
• - centrioles migrate to poles
• - homologous chromosomes pair up to form tetrads
  4
• chromatids
• - crossing-over occurs
• - homologous chromosomes exchange portions of
• themselves which results in a mixing of genes
  between the two chromosomes

44
Crossing-Over
Section 11-4
45

• B. Metaphase I
• - tetrads line-up at the equator of the cell
• C. Anaphase I
• - homologous pairs separate
• - sister chromatids stay connected at their
  centromeres
• D. Telophase I
• - nuclear membranes reform around the
  chromosomes and cytyokinesis takes place
• - each cell is now haploid

46

• No DNA replication takes place before Meiosis
  II
• 2. Meiosis II (Figure 11.15, page 277)
• - each cells chromosomes consist of two
  chromatids connected at the centromere
• A) Prophase II
• - just like prophase in mitosis
• B) Metaphase II
• - chromosomes align at center of cell
• C) Anaphase II
• - sister chromatids are separated at the
  centromere and are pulled to opposite poles
• D) Telophase II
• - new nuclear envelopes appear
• - cytokinesis occurs

47
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
48

• Results of Meiosis Four haploid cells which are
  genetically unique
• Gamete formation (Figure 11.17, page 278)
• - in male animals and the pollen grains of plants
  the haploid gametes are called sperm cells
• - in female animals generally only one of the
  cells formed by meiosis develops into an egg
• - in female animals uneven cytokinesis at the
  end of Meiosis I and Meiosis II result in a
  large egg and 3 polar bodies

49
How Many Chromosomes?
Interest Grabber
Section 11-4

• Normal human body cells each contain 46
  chromosomes. The cell division process that body
  cells undergo is called mitosis and produces
  daughter cells that are virtually identical to
  the parent cell. Working with a partner, discuss
  and answer the questions that follow.

50
Interest Grabber continued
Section 11-4

• 1. How many chromosomes would a sperm or an egg
  contain if either one resulted from the process
  of mitosis?
• 2. If a sperm containing 46 chromosomes fused
  with an egg containing 46 chromosomes, how many
  chromosomes would the resulting fertilized egg
  contain? Do you think this would create any
  problems in the developing embryo?
• 3. In order to produce a fertilized egg with the
  appropriate number of chromosomes (46), how many
  chromosomes should each sperm and egg have?

51
Crossing-Over
Section 11-4
52
Crossing-Over
Section 11-4
53
Crossing-Over
Section 11-4
54
Figure 11-15 Meiosis
Section 11-4
Meiosis I
55
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Meiosis I
56
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Meiosis I
57
Figure 11-15 Meiosis
Section 11-4
Meiosis I
58
Figure 11-15 Meiosis
Section 11-4
Meiosis I
59
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
60
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
61
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
62
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
63
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
64
Forever Linked?
Interest Grabber
Section 11-5

• Some genes appear to be inherited together, or
  linked. If two genes
• are found on the same chromosome, does it mean
  they are linked forever?
• Study the diagram, which shows four genes labeled
  AE and ae, and then answer the questions on the
  next slide.

65
Interest Grabber continued
Section 11-5

• 1. In how many places can crossing over result in
  genes A and b being on the same chromosome?
• 2. In how many places can crossing over result in
  genes A and c being on the same chromosome? Genes
  A and e?
• 3. How does the distance between two genes on a
  chromosome affect the chances that crossing over
  will recombine those genes?

66
Section Outline
Section 11-5

• 115 Linkage and Gene Maps
• A. Gene Linkage
• B. Gene Maps

67
Comparative Scale of a Gene Map
Section 11-5
Mapping of Earths Features
Mapping of Cells, Chromosomes, and Genes
Cell
Earth
Chromosome
Country
Chromosome fragment
State
Gene
City
People
Nucleotide base pairs
68
Figure 11-19 Gene Map of the Fruit Fly
Section 11-5
Exact location on chromosomes
Chromosome 2
69
Video Contents
Videos

• Click a hyperlink to choose a video.
• Meiosis Overview
• Animal Cell Meiosis, Part 1
• Animal Cell Meiosis, Part 2
• Segregation of Chromosomes
• Crossing Over

70
Video 1
Video 1
Meiosis Overview

• Click the image to play the video segment.

71
Video 2
Video 2
Animal Cell Meiosis, Part 1

• Click the image to play the video segment.

72
Video 3
Video 3
Animal Cell Meiosis, Part 2

• Click the image to play the video segment.

73
Video 4
Video 4
Segregation of Chromosomes

• Click the image to play the video segment.

74
Video 5
Video 5
Crossing Over

• Click the image to play the video segment.

75
Internet
Go Online

• The latest discoveries in genetics
• Interactive test
• Articles on genetics
• For links on Punnett squares, go to
  www.SciLinks.org and enter the Web Code as
  follows cbn-4112.
• For links on Mendelian genetics, go to
  www.SciLinks.org and enter the Web Code as
  follows cbn-4113.
• For links on meiosis, go to www.SciLinks.org and
  enter the Web Code as follows cbn-4114.

76
Section 1 Answers
Interest Grabber Answers

• 1. In the first generation of each experiment,
  how do the characteristics of the offspring
  compare to the parents characteristics?
• All offspring had the same characteristic, which
  was like one of the parents. The other
  characteristic seemed to have disappeared.
• 2. How do the characteristics of the second
  generation compare to the characteristics of the
  first generation?
• Both characteristics appeared in this
  generation. The characteristic that had
  disappeared in the first generation did not
  appear as often as the other characteristic. (It
  appears about 25 percent of the time.)

77
Section 2 Answers
Interest Grabber Answers
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 partners
tosses? How close was each set of results to what
was expected? Results will vary, but should be
close to 5 heads and 5 tails. 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? The results
for 20 tosses may be closer to the predicted 10
heads and 10 tails. 3. If you compiled the
results for the whole class, what results would
you expect? The results for the entire class
should be even closer to the number predicted by
the rules of probability. 4. How do the expected
results differ from the observed results? The
observed results are usually slightly different
from the expected results.
78
Section 3 Answers
Interest Grabber Answers

• 1. Make a list of 10 adults whom you know. Next
  to the name of each adult, write his or her
  approximate height in feet and inches.
• Check students answers to make sure they are
  realistic.
• 2. What can you observe about the heights of the
  ten people?
• Students should notice that there is a range of
  heights in humans.
• 3. Do you think height in humans is controlled
  by 2 alleles, as it is in pea plants? Explain
  your answer.
• No, height does not seem to be controlled by two
  alleles, as it is in pea plants. Height in humans
  can vary greatly and is not just found in tall
  and short phenotypes.

79
Section 4 Answers
Interest Grabber Answers

• 1. How many chromosomes would a sperm or an egg
  contain if either one resulted from the process
  of mitosis?
• 46 chromosomes
• 2. If a sperm containing 46 chromosomes fused
  with an egg containing 46 chromosomes, how many
  chromosomes would the resulting fertilized egg
  contain? Do you think this would create any
  problems in the developing embryo?
• 46 46 92 a developing embryo would not
  survive if it contained 92 chromosomes.
• 3. In order to produce a fertilized egg with the
  appropriate number of chromosomes (46), how many
  chromosomes should each sperm and egg have?
• Sperm and egg should each have 23 chromosomes.

80
Section 5 Answers
Interest Grabber Answers

• 1. In how many places can crossing over result in
  genes A and b being on the same chromosome?
• One (between A and B)
• 2. In how many places can crossing over result in
  genes A and c being on the same chromosome? Genes
  A and e?
• Two (between A and B and A and C) Four (between
  A and B, A and C, A and D, and A and E)
• 3. How does the distance between two genes on a
  chromosome affect the chances that crossing over
  will recombine those genes?
• The farther apart the genes are, the more likely
  they are to be recombined through crossing over.

81
End of Custom Shows

• This slide is intentionally blank.