Transcript Mendel's genetics - Klahowya Secondary School

February 10, 2011
Make Sure you have
your Notebook
Checked for 9
Grades Posted
Read and Define 10.1
Vocabulary
Notes 10.1
1
Mendelelian
Genetics
http://sps.k12.ar.us/massengale/pwpt_biology.htm
2
Gregor Mendel
(1822-1884)
Responsible
for the Laws
governing
Inheritance of
Traits
3
Gregor Johann Mendel
Austrian monk
Studied the
inheritance of
traits in pea plants
Developed the laws
of inheritance
Mendel's work was
not recognized until
the turn of the
20th century
4
Gregor Johann Mendel
Between 1856 and
1863, Mendel
cultivated and
tested some 28,000
pea plants
He found that the
plants' offspring
retained traits of
the parents
Called the “Father
of Genetics"
5
Site of
Gregor
Mendel’s
experimental
garden in the
Czech
Republic
6
Particulate Inheritance
Mendel stated that
physical traits are
inherited as “particles”
Mendel did not know
that the “particles”
were actually
Chromosomes & DNA
7
Genetic Terminology
 Trait - any characteristic that
can be passed from parent to
offspring
 Heredity - passing of traits
from parent to offspring
 Genetics - study of heredity
8
Types of Genetic Crosses
 Monohybrid cross - cross
involving a single trait
e.g. flower color
 Dihybrid cross - cross involving
two traits
e.g. flower color & plant height
9
Punnett Square
Used to help
solve genetics
problems
10
11
Designer “Genes”
 Alleles - two forms of a gene
(dominant & recessive)
 Dominant - stronger of two genes
expressed in the hybrid;
represented by a capital letter (R)
 Recessive - gene that shows up less
often in a cross; represented by a
lowercase letter (r)
12
More Terminology
 Genotype - gene combination
for a trait (e.g. RR, Rr, rr)
 Phenotype - the physical
feature resulting from a
genotype (e.g. red, white)
13
Genotype & Phenotype in Flowers
Genotype of alleles:
R = red flower
r = yellow flower
All genes occur in pairs, so 2
alleles affect a characteristic
Possible combinations are:
Genotypes
RR
Rr
rr
Phenotypes
RED
RED
YELLOW
14
Genotypes
 Homozygous genotype - gene
combination involving 2 dominant
or 2 recessive genes (e.g. RR or
rr); also called pure
 Heterozygous genotype - gene
combination of one dominant &
one recessive allele
(e.g. Rr);
also called hybrid
15
Genes and Environment
Determine Characteristics
16
February 22, 2011
Vocab #3 pre-test…
Check off on Monohybrid Principles of
Genetics
Notes 10.1
Monohybrid Worksheet
Make sure to read chapter and understand
Monohybrid concepts and vocabulary
17
Mendel’s Pea Plant
Experiments
18
Why peas, Pisum sativum?
Can be grown in a
small area
Produce lots of
offspring
Produce pure plants
when allowed to
self-pollinate
several generations
Can be artificially
cross-pollinated
19
Reproduction in Flowering Plants
Pollen contains sperm
Produced by the
stamen
Ovary contains eggs
Found inside the
flower
Pollen carries sperm to the
eggs for fertilization
Self-fertilization can
occur in the same flower
Cross-fertilization can
occur between flowers
20
Mendel’s Experimental
Methods
Mendel hand-pollinated
flowers using a
paintbrush
He could snip the
stamens to prevent
self-pollination
He traced traits
through the several
generations
21
How Mendel Began
Mendel
produced
pure
strains by
allowing the
plants to
selfpollinate
for several
generations
22
Eight Pea Plant Traits
Seed shape --- Round (R) or Wrinkled (r)
Seed Color ---- Yellow (Y) or Green (y)
Pod Shape --- Smooth (S) or wrinkled (s)
Pod Color --- Green (G) or Yellow (g)
Seed Coat Color ---Gray (G) or White (g)
Flower position---Axial (A) or Terminal (a)
Plant Height --- Tall (T) or Short (t)
Flower color --- Purple (P) or white (p)
23
24
25
Mendel’s Experimental Results
26
Did the observed ratio match
the theoretical ratio?
The theoretical or expected ratio of
plants producing round or wrinkled seeds
is 3 round :1 wrinkled
Mendel’s observed ratio was 2.96:1
The discrepancy is due to statistical
error
The larger the sample the more nearly
the results approximate to the
theoretical ratio
27
Generation “Gap”
Parental P1 Generation = the parental
generation in a breeding experiment.
F1 generation = the first-generation
offspring in a breeding experiment. (1st
filial generation)
From breeding individuals from the P1
generation
F2 generation = the second-generation
offspring in a breeding experiment.
(2nd filial generation)
From breeding individuals from the F1
generation
28
Following the Generations
Cross 2
Pure
Plants
TT x tt
Results
in all
Hybrids
Tt
Cross 2 Hybrids
get
3 Tall & 1 Short
TT, Tt, tt
29
Monohybrid
Crosses
30
Mendel’s Law of Genetics
Reproduction produces
different combinations
of genes
Many variations within
each kind of life
Great variations possible
in skin, hair, eye color,
facial structure, body
size
P1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Round seeds
x Wrinkled seeds
RR
x
rr
r
r
R
Rr
Rr
R
Rr
Rr
Genotype: Rr
Phenotype: Round
Genotypic
Ratio: All alike
Phenotypic
Ratio: All alike
32
P1 Monohybrid Cross Review
 Homozygous dominant x Homozygous
recessive
 Offspring all Heterozygous
(hybrids)
 Offspring called F1 generation
 Genotypic & Phenotypic ratio is ALL
ALIKE
33
F1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Round seeds
x Round seeds
Rr
x
Rr
R
r
R
RR
Rr
r
Rr
rr
Genotype: RR, Rr, rr
Phenotype: Round &
wrinkled
G.Ratio: 1:2:1
P.Ratio: 3:1
34
F1 Monohybrid Cross Review
 Heterozygous x heterozygous
 Offspring:
25% Homozygous dominant RR
50% Heterozygous Rr
25% Homozygous Recessive rr
 Offspring called F2 generation
 Genotypic ratio is 1:2:1
 Phenotypic Ratio is 3:1
35
What Do the Peas Look Like?
36
…And Now the Test Cross
Mendel then crossed a pure & a
hybrid from his F2 generation
This is known as an F2 or test
cross
There are two possible
testcrosses:
Homozygous dominant x Hybrid
Homozygous recessive x Hybrid
37
F2 Monohybrid Cross
st
(1 )
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Round seeds
x Round seeds
RR
x
Rr
R
r
R
RR
Rr
R
RR
Rr
Genotype: RR, Rr
Phenotype: Round
Genotypic
Ratio: 1:1
Phenotypic
Ratio: All alike
38
F2 Monohybrid Cross (2nd)
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Wrinkled seeds x Round seeds
rr
x
Rr
R
r
r
Rr
Rr
r
rr
rr
Genotype: Rr, rr
Phenotype: Round &
Wrinkled
G. Ratio: 1:1
P.Ratio: 1:1
39
F2 Monohybrid Cross Review
 Homozygous x heterozygous(hybrid)
 Offspring:
50% Homozygous RR or rr
50% Heterozygous Rr
 Phenotypic Ratio is 1:1
 Called Test Cross because the
offspring have SAME genotype as
parents
40
Practice Your Crosses
Work the P1, F1, and both
F2 Crosses for each of the
other Seven Pea Plant
Traits
41
February 23, 2011
?? Of day – Left side
Differentiated
between the P 1, F1
and F 2 cross.
Review Monohybrid
crosses
Monohybrid Worksheet
HOMEWORK: PSLab 10.1
Read Chapter 10!!
42
February 24, 2011
Correct Mono
Hybrid
Worksheet
Notes Dihybrid
Principles of
Genetics
Flipping…
43
Mendel’s Laws
44
Results of Monohybrid Crosses
Inheritable factors or genes are
responsible for all heritable
characteristics
Phenotype is based on Genotype
Each trait is based on two genes,
one from the mother and the
other from the father
True-breeding individuals are
homozygous ( both alleles) are the
same
45
Law of Dominance
In a cross of parents that are
pure for contrasting traits, only
one form of the trait will appear in
the next generation.
All the offspring will be
heterozygous and express only the
dominant trait.
RR x rr yields all Rr (round seeds)
46
Law of Dominance
47
Law of Segregation
During the formation of gametes
(eggs or sperm), the two alleles
responsible for a trait separate
from each other.
Alleles for a trait are then
"recombined" at fertilization,
producing the genotype for the
traits of the offspring.
48
Applying the Law of Segregation
49
Law of Independent
Assortment
Alleles for different traits are
distributed to sex cells (&
offspring) independently of one
another.
This law can be illustrated using
dihybrid crosses.
50
Dihybrid Cross
A breeding experiment that tracks
the inheritance of two traits.
Mendel’s “Law of Independent
Assortment”
a. Each pair of alleles segregates
independently during gamete formation
b. Formula: 2n (n = # of heterozygotes)
51
Question:
How many gametes will be produced
for the following allele arrangements?
Remember: 2n (n = # of heterozygotes)
1. RrYy
2. AaBbCCDd
3. MmNnOoPPQQRrssTtQq
52
Answer:
1. RrYy: 2n = 22 = 4 gametes
RY
Ry
rY ry
2. AaBbCCDd: 2n = 23 = 8 gametes
ABCD ABCd AbCD AbCd
aBCD aBCd abCD abCD
3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64
gametes
53
Dihybrid Cross
Traits: Seed shape & Seed color
Alleles: R round
r wrinkled
Y yellow
y green
RrYy
RY Ry rY ry
x
RrYy
RY Ry rY ry
All possible gamete combinations
54
Dihybrid Cross
RY
Ry
rY
ry
RY
Ry
rY
ry
55
Dihybrid Cross
RY
RY RRYY
Ry RRYy
rY RrYY
ry
RrYy
Ry
rY
ry
RRYy
RrYY
RrYy
RRyy
RrYy
Rryy
RrYy
rrYY
rrYy
Rryy
rrYy
rryy
Round/Yellow:
Round/green:
9
3
wrinkled/Yellow: 3
wrinkled/green:
1
9:3:3:1 phenotypic
ratio
56
Dihybrid Cross
Round/Yellow: 9
Round/green:
3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1
57
Test Cross
A mating between an individual of unknown
genotype and a homozygous recessive
individual.
Example: bbC__ x bbcc
BB = brown eyes
Bb = brown eyes
bb = blue eyes
CC = curly hair
Cc = curly hair
cc = straight hair
bC
b___
bc
58
Test Cross
Possible results:
bc
bC
b___
C
bbCc
bbCc
or
bc
bC
b___
c
bbCc
bbcc
59
Biology 3/4/11
Pass Out Papers.
Science Vocab #4
Notes on 10.2
Vocab and PS Lab 10.2
Make sure I have Mono,
Di hybrid and
Principles of Genetics
worksheet
60
Summary of Mendel’s laws
LAW
DOMINANCE
SEGREGATION
INDEPENDENT
ASSORTMENT
PARENT
CROSS
OFFSPRING
TT x tt
tall x short
100% Tt
tall
Tt x Tt
tall x tall
75% tall
25% short
RrGg x RrGg
round & green
x
round & green
9/16 round seeds & green
pods
3/16 round seeds & yellow
pods
3/16 wrinkled seeds & green
pods
1/16 wrinkled seeds & yellow
pods
61
10.2 Meiosis
Chromosomesthousand or more
genes located on a
chromosome
Diploid Cell 2ncontains a pair of
chromosomes one
from the male and
one from the female
Haploid Cell n-cell
with one of each
kind of chromosome
62
Homologous
chromosomes
contain
genes for
the same
trait, in the
same order
63
Zygote – fertilized egg
which has a 2n diploid
number of chromosomes
Sexual reproduction –
figure 10.11 , doubling
of chromosomes and
then halving the
DNA is located on
chromosomes, these
chromosomes are made up
of 2 halves called sister
chromatids and are exact
copies held together by a
centromere
64
March 7, 2011
?? Of the Day:
Differentiate between a diploid
and haploid cell.
STAMP ON VOCAB 10.2
Vocab Pretest #5
Notes on Meiosis
PS Lab 10.2
65
Meiosis is divided into
2 separate divisions:
Meiosis I – begins with
one 2n diploid cell
Meiosis II – ends with 4
n haploid cells, called
sex cells or gametes
Sperm – male gametes
Egg – female gametes
66
Meiosis – cell division allows for
offspring to have the same
number of chromosomes as
their parents (Mitosis would
be double)
Meiosis/Mitosis Animation
67
March 9, 2011
Finish Meiosis Notes
Meiosis Stages - Draw out all stages
and describe each stage
Meiosis Activity
All Learning Targets due and finish up
summaries of notebooks
Add 2 level questions to notes
Test Thursday!!
68
Phases of Meiosis
Interphase –cell is reproducing its
chromosomes and has 2 identical sister
chromatids held together by a centromere
Prophase I – each pair of homologous
chromosomes ( 2 sister chromatids) come
together, matched gene by gene to form a 4
part structure called a tetrad
Crossing Over – exchange of genetic
material between homologous
chromosomes, this results in new
combinations of alleles on a chromosome
69
Metaphase I
Centromere of each chromosome becomes
attached to a spindle fiber
Spindle fibers pull the tetrads into the middle
of the equator of the spindle
Homologous chromosome line up side by side as
tetrads (in mitosis they line up independently)
Anaphase I
Homologous chromosomes each with its 2
chromatids separate move to opposite ends of
the cell
Centromeres holding the sister chromatids do
not split (as in mitosis)
70
This ensures that each new cell will receive
only one chromosome from each homologous
pair
Telophase I
Spindle is broken down, chromosomes uncoil
Cytoplasm divides to yield 2 new cells
Each cell has only half the genetic info of the
original cell but it is in only 1 chromosome so
we still need another cell division
Meiosis II – identical to mitosis
Prophase II
Spindle forms in each of the 2 new cells & the
spindle fibers attach to the chromosomes
71
Metaphase II
Chromosomes (still made up of sister
chromatids), are pulled to the center of the
cell and line up randomly at the equator
Anaphase II
Centromere of each chromosome splits
Sister chromatids split and move to opposite
poles
Telophase II
Nuclei reform
Spindles break down
Cytoplasm divides
72
73
Genetic Recombination-
Allows for variation in organisms
Each of the pairs of
chromosomes can line up at the
cells equator 2 different ways
Humans
23 chromosomes 223
Times this by 2 parents 223X223
74
Mistakes in
Meiosis –
Nondisjunction
when the
chromosomes
don’t separate
properly
NonDisjunction
75
Trisomy
extra
chromosome
Downs
syndrome
http://www.ds-health.com/images/trisomy.gif
76
Triploidy – complete extra
“set” of homologous
chromosomes can be
beneficial in agriculture
http://://www.tokyo-med.ac.jp/genet/cki-e.htm&h=28
77
Monosomy
one less chromosome
Turners syndrome (X)
http://://www.tokyo-med.ac.jp/genet/cki-e.htm&h=28
78