Download Slide 1

Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
MT
FT
Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
MT
FT
Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
MT
FT
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
Arisaema triphyllum
“Jack-in-the-Pulpit”
Small plants - male
Large plants - female
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
Benefit of being male – quantity of offspring
Benefit of being female – regulate quality of offspring
Cervus elaphus
Red deer
Starving pregnant females
selectively abort male
embryos. Small daughters
may still mate; small sons will
not acquire a harem and will
not mate. Selection has
favored females who save
their energy, abort male
embryos when starving, and
maybe live to reproduce next
year.
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Sexually mature female
(Inhibits development of males)
Sexually mature male
Immature males
Wouldn’t the species do better if there were more females/group?
Yes, but selection favors individual reproductive success.
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Brood
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Add Larger juveniles
Brood
female
A. Sex Determination
1. Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Add smaller juveniles
Brood
male
A. Sex Determination
1. Environmental Sex Determination
2. Chromosomal Sex Determination
a. Protenor sex determination
The presence of 1 or 2 sex chromosomes determines sex
Order: Hemiptera “True Bugs”
Family Alydidae – Broad-headed bugs
A. Sex Determination
1. Environmental Sex Determination
2. Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
The type of sex chromosomes determines sex
Order: Hemiptera
Family: Lygaeidae “Chinch/Seed Bugs”
A. Sex Determination
1. Environmental Sex Determination
2. Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
Which sex is the ‘heterogametic’ sex varies
XX female, XY – male
ZZ male, ZW female
Most mammals, including
humans
Some insects
Some plants
Birds
Some fish
Some reptiles
Some insects (Butterflies/Moths)
Some plants
A. Sex Determination
B. Gender
‘Gender’ is a role or behavior that a human society correlates with a sex
Behavior: wear make-up and a skirt
Modern USA Society:
Gender = woman
Medieval Scotland, modern Wodaabe:
Gender = man
A. Sex Determination
B. Gender
‘Gender’ is a role or behavior that a human society correlates with a sex
Sexual Behavior: like most behaviors, a given sexual
behavior is not necessarily restricted to one sex or another.
And sex is used for more than procreation; it is used for
communication, conflict resolution, deception, and
establishing dominance within and between sexes.
Female Bonobo chimps (Pan paniscus)
‘sneaker’ male
A. Sex Determination
B. Gender
C. Sex Linkage
A. Sex Determination
B. Gender
C. Sex Linkage
1. For Comparison –heredity for sex (as a trait) and an autosomal dominant trait.
MALE: AAXY
AX
FEMALE:
aa XX
MALE: aa XY
AY
aX
AaXX AaXY
aX
AaXX AaXY
aX
FEMALE:
AA XX
aY
AX
Aa XX Aa XY
AX
Aa XX Aa XY
All offspring, regardless of sex, express the A trait in both reciprocal crosses
A. Sex Determination
B. Gender
C. Sex Linkage
1. For Comparison –heredity for sex (as a trait) and an autosomal dominant trait.
2. Sex Linkage example: red-green coloblindness in humans
MALE
FEMALE
Xg
Y
XG
XGXg
XGY
XG
XGXg
XGY
100% G, for all offspring
MALE
FEMALE
XG
Y
Xg
XGXg
XgY
Xg
XGXg
XgY
50% G daughters, 50% g sons
Now, the sex of the parent that expresses the G trait matters; the transmission of
this gene correlates with the sex of the offspring, because this trait and ‘sex’ are
influenced by the same chromosome.
Queen Victoria of England
Her
daughter
Alice
X-linked recessive traits are expressed in
males more than females, because females
get a second X that may carry the dominant
allele.
Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
V. Linkage
A. Overview
Independent Assortment
A
a
AB
A
ab
B
b
a
Ab
aB
b
B
Independent Assortment
V. Linkage
A
a
A
A. Overview
AB
ab
B
Ab
b
aB
b
Linkage
A
a
AB
ab
B
a
b
B
V. Linkage
Linkage
A. Overview
A
a
AB
ab
B
b
In Prophase I of Meiosis – Crossing-over
A
A a
a
AB
ab
B
b B
Ab
aB
b
V. Linkage
A.Overview
B.Complete Linkage
Test Cross
AABB
aabb
AB
X
AB
ab
ab
V. Linkage
A.Overview
B.Complete Linkage
- if genes are immediate neighbors, they are almost never separated by
crossing over and are ‘always’ inherited together. The pattern mimics that of a single
gene.
AABB
aabb
AB
ab
X
ab
AB
Gametes
AB
ab
ab
F1
AB
V. Linkage
A.Overview
B.Complete Linkage
- if genes are immediate neighbors, they are almost never separated by
crossing over and are ‘always’ inherited together. The pattern mimics that of a single
gene.
ab
ab
F1 x F1
X
ab
AB
Gametes
ab
AB
ab
V. Linkage
A.Overview
B.Complete Linkage
- if genes are immediate neighbors, they are almost never separated by
crossing over and are ‘always’ inherited together. The pattern mimics that of a single
gene.
ab
ab
1:1 ratio A:a
F1 x F1
X
AB
ab
1:1 ratio B:b
1:1 ratio AB:ab
NOT 1:1:1:1
Gametes
ab
AB
ab
Phenotypes
AaBb
AB
aabb
ab
aB ?
Ab ?
C. Incomplete Linkage
a
A
b
B
a
a
b
b
C. Incomplete Linkage
- So, since crossing-over is
rare (in a particular region),
most of the time it WON’T
occur and the homologous
chromosomes will be
passed to gametes with
these genes in their original
combination…these
gametes are the ‘parental
types’ and they should be
the most common types of
gametes produced.
a
A
b
a
B
a
b
A
B
a
b
b
C. Incomplete Linkage
- But during Prophase I,
homologous chromosomes
can exchange pieces of
DNA.
- This “Crossing over”
creates new combinations
of genes…
These are the ‘recombinant
types’
a
A
b
a
B
a
b
A
B
a
B
A
b
a
b
b
C. Incomplete Linkage
As the other parent only
contributed recessive
alleles, the phenotype of the
offspring is determined by
the gamete received from
the heterozygote…
a
A
b
a
a
B
a
b
A
B
b
b
gamete
genotype
phenotype
ab
aabb
ab
ab
AaBb
AB
LOTS of these
a
B
ab
aaBb
aB
A
b
ab
Aabb
Ab
FEW of these
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked,
or are assorting independently:
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
Number
43
Ab
12
aB
8
ab
37
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
- determine expectations under the
hypothesis of independent assortment
Number
43
Ab
12
aB
8
ab
37
The frequency of ‘AB’ should = f(A) x f(B) x N = 55/100 x 51/100 x 100 = 28
The frequency of ‘Ab’ should = f(A) x f(B) x N = 55/100 x 49/100 x 100 = 27
The frequency of ‘aB’ should = f(a) x f(B) x N = 45/100 x 51/100 x 100 = 23
The frequency of ‘ab’ should = f(a) x f(b) x N = 45/100 x 49/100 x 100 = 22
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
- determine expectations under the
hypothesis of independent assortment
Number
43
Ab
12
aB
8
ab
37
B
b
A
43
12
a
8
37
Easy with a 2 x 2
contingency table
Col.
Total
Row
Total
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
- determine expectations under the
hypothesis of independent assortment
Easy with a 2 x 2
contingency table
Compute Row, Columns,
and Grand Totals
Number
43
Ab
12
aB
8
ab
37
B
b
Row
Total
A
43
12
55
a
8
37
45
Col.
Total
51
49
100
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
- determine expectations under the
hypothesis of independent assortment
Easy with a 2 x 2
contingency table
Compute Row, Column,
and Grand Totals
E = (RT x CT)/GT
Number
43
Ab
12
aB
8
ab
37
B
Exp.
b
Row
Total
A
43
28
12
55
a
8
37
45
Col.
Total
51
49
100
V. Linkage
AaBb x aabb
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are linked, Offspring
or are assorting independently:
AB
- test cross
- determine expectations under the
hypothesis of independent assortment
Easy with a 2 x 2
contingency table
Compute Row, Column,
and Grand Totals
E = (RT x CT)/GT
Number
43
Ab
12
aB
8
ab
37
B
Exp.
b
Exp.
Row
Total
A
43
28
12
27
55
a
8
23
37
22
45
Col.
Total
51
49
100
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are
linked, or are assorting independently:
B
Exp.
b
Exp.
Row
Total
A
43
28
12
27
55
a
8
23
37
22
45
Col.
Total
51
49
- Chi-Square Test of Independence
Obs
Exp
(o-e)
(o-e)2/e
AB
43
28
15
8.04
Ab
12
27
-15
8.33
aB
8
23
-15
9.78
ab
37
22
15
10.23
X2 =
36.38
Phenotype
100
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are
linked, or are assorting independently:
2. Detemining the arrangement of
alleles in the F1 individual; which alleles are
paired on each homolog?
AaBb x aabb
Offspring
Number
AB
43
Ab
12
aB
8
ab
37
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are
linked, or are assorting independently:
2. Detemining the arrangement of
alleles in the F1 individual; which alleles are
paired on each homolog?
AaBb x aabb
Offspring
Number
AB
43
Ab
12
aB
8
ab
37
- most abundant types are ‘parental types’
A
B
a
b
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are
linked, or are assorting independently:
A
B
a
b
2. Detemining the arrangement of
alleles in the F1 individual; which alleles are
paired on each homolog?
- most abundant types are ‘parental types’
- least abundant are products of crossing-over:
‘recombinant types’
a
B
A
b
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
1. Determining if the genes are
linked, or are assorting independently:
2. Detemining the arrangement of
alleles in the F1 individual; which alleles are
paired on each homolog?
AaBb x aabb
Offspring
Number
AB
43
Ab
12
aB
8
ab
37
3. Determining the distance between loci:
Add the recombinant types and divide by total
offspring; this is the percentage of recombinant
types. Multiply by 100 (to clear the decimal) and
this is the index of distance, in ‘map units’ or
centiMorgans.
A
B
a
b
20/100 = 0.20 x100 = 20.0 centiMorgans
20 map units
V. Linkage
A.Overview
B.Complete Linkage
C.Incomplete Linkage
D.Summary
- by studying the combined patterns of heredity among linked genes, linkage
maps can be created that show the relative positions of genes on chromosomes.
Heredity, Gene Regulation, and Development
I. Mendel's Contributions
II. Meiosis and the Chromosomal Theory
III. Allelic, Genic, and Environmental Interactions
IV. Sex Determination and Sex Linkage
V. Linkage
VI. Mutation
A. Overview
DON’T WORRY!! Just a photoshop award winner…
VI. Mutation
A. Overview
A change in the genome
Occurs at four scales of genetic organization:
1: Change in the number of sets of chromosomes ( change in ‘ploidy’)
2: Change in the number of chromosomes in a set (‘aneuploidy’)
3: Change in the number and arrangement of genes on a chromosome
4: Change in the nitrogenous base sequence within a gene
VI. Mutation
A. Overview
B. Changes in Ploidy
- These are the most dramatic changes, adding a whole SET of chromosomes
Triploidy occurs in 2-3% of all
human pregnancies, but almost
always results in spontaneous
abortion of the embryo.
Some triploid babies are born
alive, but die shortly after.
Syndactyly (fused fingers),
cardiac, digestive tract, and
genital abnormalities occur.
VI. Mutation
A. Overview
B. Changes in Ploidy
- These are the most dramatic changes, adding a whole SET of chromosomes
1. Mechanism #1: Complete failure of Meiosis
- if meiosis fails, reduction does not occur and a diploid gamete is produced. This can occur
because of failure of homologs OR sister chromatids to separate in Meiosis I or II, respectively.
Failure of Meiosis I
2n = 4
Gametes:
2n = 4
VI. Mutation
A. Overview
B. Changes in Ploidy
- These are the most dramatic changes, adding a whole SET of chromosomes
1. Mechanism #1: Complete failure of Meiosis
- if meiosis fails, reduction does not occur and a diploid gamete is produced. This can occur
because of failure of homologs OR sister chromatids to separate in Meiosis I or II, respectively.
Failure of Meiosis II
2n = 4
Normal gamete formation is on the bottom, with 1n=2 gametes. The error occurred
up top, with both sister chromatids of both chromosomes going to one pole,
creating a gametes that is 2n = 4.
VI. Mutation
A. Overview
B. Changes in Ploidy
- These are the most dramatic changes, adding a whole SET of chromosomes
1. Mechanism #1: Complete failure of Meiosis
- if meiosis fails, reduction does not occur and a diploid gamete is produced. This can occur
because of failure of homologs OR sister chromatids to separate in Meiosis I or II, respectively.
- this results in a single diploid gamete, which will probably fertilize a normal haploid gamete,
resulting in a triploid offspring.
-
negative consequences of Triploidy:
1) quantitative changes in protein production and regulation.
2) can’t reproduce sexually; can’t produce gametes if you are 3n.
VI. Mutation
A. Overview
B. Changes in Ploidy
- These are the most dramatic changes, adding a whole SET of chromosomes
1. Mechanism #1: Complete failure of Meiosis
- negative consequences of Triploidy:
1) quantitative changes in protein production and regulation.
2) can’t reproduce sexually; can’t produce gametes if you are 3n.
3) but, some organisms can survive, and reproduce parthenogenetically (mitosis)
Like this Blue-spotted Salamander A. laterale,
which has a triploid sister species, A. tremblayi
A. tremblayi is a species that consists of
3n females that reproduce clonally –
laying 3n eggs that divide without
fertilization.