Concatenated inheritance. Morgan's Law. Linked inheritance of traits. Thomas Morgan's Law Chained inheritance of traits presentation

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Mendel's laws on the independent nature of the inheritance of traits - universal (experimentally confirmed) But !!! 1906, W. Betson, R. Pennett (England) - - exceptions to Mendel's laws Beginning of the twentieth century - experiments of Thomas Morgan (USA) with the fruit fly Drosophila (convenient object) A little history ...

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The object of Morgan's genetic research was the fruit fly Drosophila. Advantages: Outwardly distinguishable female and male (his abdomen is smaller and darker). Unpretentious in conditions of detention. Short development cycle - after 14 days new numerous offspring are hatched. A wide range of mutations expressed in morphological features: body color, wing size, number of bristles, eye color These mutations do not affect the viability of the fly

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Analysis of exceptions to Mendel's laws. 2. Experimental and theoretical substantiation of linked inheritance of traits. 3. Creation of the chromosomal theory of inheritance. Works by Thomas Morgan

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Chromosomal theory of inheritance by T. Morgan Genes are located in chromosomes, their number is not the same. Each gene has a specific location on the chromosomes; allelic genes are located in identical loci of homologous chromosomes. Genes are located linearly on chromosomes. Genes located on the same chromosome form a linkage group and are inherited together. Number of linkage groups \u003d n (haploid set of chromosomes). Gene coupling can be disrupted as a result of crossing over. Crossover frequency is in direct proportion to the distance between genes. Each species has a set of chromosomes characteristic only of it - a karyotype.

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P: Experiments by Thomas Morgan (dihybrid crossing) Gray body Normal wings Black body Reduced wings AABB aavb F1: 100% AaBb According to Mendel's I law, uniformity of features is observed

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Experiments by Thomas Morgan (backward, analyzing crossing) F2: Expected results of crossing, if non-allelic genes are in different chromosomes:?

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Experiments of Thomas Morgan (backward, analyzing crossing) F1: Real results of crossing:

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Cytological foundations of Thomas Morgan's law of linked inheritance of traits Non-allelic traits lie in different loci of the same chromosome Inherited linked - - linkage group Conclusion: new combinations of traits P should be absent in the offspring: AaBb aavb

Morgan's law
G. Mendel traced inheritance
seven pairs of signs in peas. Many
researchers, repeating the experiments of Mendel,
confirmed the laws discovered by him. It was
recognized that these laws are universal
character.
However, in 1906 English geneticists
W. Batson and R. Pennett, carrying out crossing
sweet pea plants and analyzing
inheritance of pollen shape and coloration
flowers, found that these signs are not
give an independent distribution in
offspring. Descendants have always repeated
signs of parental forms.
It became clear that not all genes are characterized by independent
distribution in offspring and free combination.
Each organism has a huge number of signs, and the number
chromosomes are small. Therefore, each chromosome carries more than one
gene, but a whole group of genes responsible for the development of different traits.

Morgan's law
Thomas Ghent Morgan
(1886 - 1945)
Studying the inheritance of traits,
whose genes are localized in one
chromosome, engaged in outstanding
American geneticist T. Morgan
(Nobel Prize 1933). If
Mendel conducted his experiments on peas,
then for Morgan the main object was
fruit fly fruit fly. Front sight
every two weeks at a temperature of 25 ° C
gives numerous offspring. Male and
the female is outwardly well distinguishable - in
the abdomen of the male is smaller and darker.
In addition, they have only 8 chromosomes
in the diploid set and differences in
numerous signs may
multiply in test tubes on cheap
nutrient medium.

Morgan's law
Crossing the fly with Drosophila
gray body and normal
wings with a front sight
dark body coloration and rudimentary
wings, first generation
Morgan got hybrids
having a gray body and
normal wings.
When analyzing
crossing F1 female with male,
had recessive symptoms,
theoretically expected to receive
offspring with combinations of these
features in a ratio of 1: 1: 1: 1.

Morgan's law
However, the offspring was 41.5%
gray long-winged and 41.5%
black with rudimentary wings and
only a small fraction of flies
had recombined
signs (8.5% black
long-winged and 8.5% gray with
rudimentary wings).
Morgan concluded that genes,
causing the development of sulfur
body coloration and long wings,
localized on one chromosome,
and the genes that cause
the development of black body coloration and
embryonic wings - in the other.

Morgan's law

signs Morgan named
clutch. Material basis
gene linkage is a chromosome.
Genes localized in one
chromosome, are inherited together
and form one clutch group.
Since homologous chromosomes
have the same set of genes,
the number of clutch groups is
haploid set of chromosomes
The phenomenon of joint inheritance
genes localized in one
chromosome, called linked
inheritance. Chained
inheritance of genes localized
in one chromosome, called
Morgan's law.

Morgan's law
The appearance of individuals with
recombined
signs Morgan explained
crossing over during meiosis.
As a result of crossing over in
some cells occur
exchange of sections of chromosomes between
genes A and B, gametes appear
AB and AB, and, as a consequence, in
offspring are formed four
groups of phenotypes, as in
free combination of genes.
But since crossing over
does not occur in all gametes,
numerical ratio of phenotypes
does not match the ratio
1:1:1:1.

Morgan's law
Depending on the features
formation of gametes are distinguished:
non-crossover gametes - gametes
with chromosomes formed without
crossing over:
crossover gametes - gametes with
chromosomes that have undergone
crossing over:

Morgan's law
Genes localized on one chromosome are inherited together and
form one clutch group. In each pair of homologous chromosomes
there are identical groups of genes. A person has 23 clutch groups,
Drosophila - four. It has also been shown that each gene in
the chromosome has a strictly defined place - a locus.
The likelihood of crossover between genes depends on their
location in the chromosome: the farther from each other are
genes, the higher the likelihood of overlap between them.

Genetic scheme

Morgan's law
Per unit distance between genes,
located on the same chromosome,
accepted 1% crossing over. For example, in
analyzed above
crossing received 17% of individuals with
overcombined signs.
Therefore, the distance between
genes of gray body color and long
wings (as well as black body color
and rudimentary wings) is equal to 17%. IN
T. Morgan's honor unit of distance
between genes called morganida,
the distance between these genes
equal to 17 morganids. And the adhesive force
calculated by the formula: strength
adhesion \u003d 100% -% crossover
gametes. The strength of adhesion between genes
body color and wing shape is
100% - 17% = 83%.

Morgan's law
What is the genotype of a diheterozygous gray female with long wings?
AB // ab - cis phase.
Ab // aB - trans phase.

Let's summarize:
Morgan's Law:
Genes located on one chromosome are inherited predominantly
linked.
Clutch group:
Genes located on one chromosome form a linkage group.
Number of clutch groups:
The number of linkage groups is equal to the number of pairs of homologous chromosomes,
haploid set of chromosomes. A person has 23 clutch groups,
fruit flies - four.
Crossover gametes:
Gametes with chromosomes formed as a result of crossing over.
Morganida:
In honor of T. Morgan, the unit of distance between genes is named
morganida, 1 morganida \u003d 1% crossover gametes.
How is the bond strength between genes determined?
The adhesion force is calculated using the formula:
adhesion force \u003d 100% -% of crossover gametes.

Let's summarize:
When is Morgan's Law satisfied?
If genes are on the same chromosome, then they are inherited linked
and are included in one clutch group.
How many pairs of homologous chromosomes control body color and shape
of Drosophila wings?
One pair of homologous chromosomes.
How many crossover gametes (in%) are formed in a diheterozygous female?

17%.
What is the distance between genes that control body color and shape
wings of Drosophila?
17 morganid.
What is the bond strength between genes that determine body color and shape?
wings of Drosophila?
83%.
How many crossover gametes are formed in a diheterozygous male?
Drosophila with a gray body and normal wings?
The male Drosophila has a grip strength of 100%, he does not have
crossing over.

Let's summarize:
How many clutch groups does Drosophila have? A person?
Drosophila has 4 clutch groups, and humans have 23.
What is the phenomenon causing Morgan's Law violation?
Crossing over.
What determines the frequency of crossing over between genes located in
one chromosome?
From the distance between genes, the greater the distance, the greater
the probability of crossing over.
The genotype of the individual Ac // ac. What gametes will be formed if
the distance between the Ac genes is 10 morganids.
Non-crossover gametes: 45% Ac and 45% aC, 5% each crossover gametes
AC and AC.


Thomas Morgan
(1866-1945).
Modern chromosome theory
heredity created by outstanding
American geneticist Thomas Morgan
(1866-1945).
1. Genes are located on chromosomes; various
chromosomes contain an unequal number
genes, and the set of genes of each of
non-homologous chromosomes are unique;
2. Each gene has a specific location (locus)
in the chromosome; at identical loci
homologous chromosomes are allelic
genes;
3. Genes are located on chromosomes in
a certain linear sequence;
4. Genes localized on one chromosome,
inherited together, forming a group
clutch; the number of clutch groups is
haploid set of chromosomes and constantly
for each type of organism;

Chromosomal theory of heredity:
5. The linkage of genes can be disrupted in
the process of crossing over; This leads to
the formation of recombinant chromosomes;
6. The crossover frequency is
a function of the distance between genes: than
more distance, more
crossover value (straight
dependence);
7. Each species has a characteristic only
for him a set of chromosomes is a karyotype.
Crossover phenomenon helped scientists
establish the location of each gene in
chromosome, create genetic maps
chromosomes. The further apart
there are two genes on the chromosome, so
more often they will diverge into different
chromosomes in the process of crossing over.

Chromosomal theory of heredity:
Thus, the probability of divergence of two genes in different
chromosomes during crossing over depends on the distance between them in
chromosome. Therefore, having calculated the frequency of crossing over between any two genes of the same chromosome, which are responsible for different traits,
you can accurately determine the distance between these genes, which means you can start
building a genetic map, which is a diagram
the relative position of genes that make up one chromosome.

Genetic maps
1. The distance between genes A and B is 6 morganids. How many crossover and
non-crossover gametes are formed in this individual? What is the strength
linkage between genes?
Non-crossover by 47%; Crossover 3% each.
Adhesion strength: 100% - 6% \u003d 94%
1. The distance between genes C and A is 8 morganids, between A and B - 6
morganid, between B and C - 14 morganid. Where is the C gene located?

Full adhesion tasks
Objective 1.
Cataract and polydactyly (polydactyly) are caused by dominant
alleles of two genes located in one pair of autosomes. Woman
inherited cataracts from her father, and many fingers from her mother. Define
possible phenotypes of children from her marriage to a healthy man.


polydactyly. Genotype of woman Аb // aB, chromosome with cataract from
father, chromosome with polydactyly from the mother. Healthy genotype
men ab // ab. In the offspring, half of the children will be with genotypes
Ab // ab and with cataracts, half with genotype aB // ab and c
polydactyly.

Full adhesion tasks
Objective 2.
The dominant genes for cataract and elliptocytosis are located in the first
autosome. Determine the likely phenotypes and genotypes of children from marriage
a healthy woman and a diheterozygous man whose father was with
cataract and elliptocytosis. There is no crossover.
Decision. (Without recording the genetic scheme)
We determine the genotypes of the parents. Let A - cataract, B -
elliptocytosis. Genotype of a healthy woman ab // ab, genotype of a man
AB // ab, since he received cataracts and elliptocytosis from his father. IN
offspring, half of the children will be with genotypes AB // ab, c
cataract and elliptocytosis, half with genotype ab // ab -
healthy.

Full adhesion tasks
Objective 3.
Dominant genes for cataract, elliptocytosis and polydigital
located in the first autosome. Identify possible phenotypes
children from the marriage of a woman with cataracts and elliptocytosis (her mother
was healthy), with a multi-fingered man (his mother had a normal
brush).
Decision. (Without recording the genetic scheme)
We determine the genotypes of the parents. Let A - cataract, B -
elliptocytosis, C - multiple fingers. Female genotype ABc // abc,
chromosome ABc / she received from her father, the genotype of a multi-fingered man
abC // abc, he received chromosome abC / from his father as well. In offspring
expected 25% with genotype ABc // abC (cataract, elliptocytosis and
multi-finger), 25% with the ABc // abc genotype (cataract, elliptocytosis),
25% with the abc // abc genotype (multi-finger), 25% with the abc // abc genotype
- healthy.

Solve the Problem An aspiring experimenter caught a mouse with surprisingly long, curled hair. He decided to develop a line of such mice in order to sell them as pets and get rich. To do this, he crossed her with a male with short, straight hair, which he bought at a pet store. Unfortunately, among the six offspring obtained, all were short, straight hair. Knowing that in mice closely related crosses are permissible, he crossed the original mouse (long wavy hair) with one of its descendants. Among the descendants, two mice had the desired characteristics, and the remaining six were similar to their father. Help the experimenter! Explain to him the results of his experiment and advise how to achieve the task.


Solve another problem In the fruit fly Drosophila melanogaster, gray body coloration dominates over black, and the gene for normal wing development dominates over the underdeveloped wing gene. From crossing a fly with a gray body and normal wings with a fly with a dark body color and rudimentary wings, hybrids with a gray body and normal wings are obtained. The resulting hybrids are crossed with flies that have two recessive traits. Among the offspring, approximately 50% of flies were found to have two dominant traits and approximately 50% - with two recessive traits. Make a crossing scheme, explain the results obtained.


Thomas Morgan was the first to introduce the fruit fly to Drosophila as a genetic object of Drosophila melanogaster Thomas Hunt Morgan About T. Morgan's experimental works - the classic textbook "Genetics with the basics of breeding", by S.G. Inge-Vechtomov On the experimental works of T. Morgan - a classic textbook "Genetics with the basics of selection", by S.G. Inge-Vechtomov






GEN A GEN B Allelic genes are located in identical regions of homologous chromosomes Linkage group - all genes located on one chromosome Homologous chromosomes GEN a GEN b Test for self-test - Lnekrasova.ru In the section "Biology lessons" Test for self-testing - Lnekrasova.ru In the section "Biology lessons"


The main thoughts of the lesson Gene - a section of a chromosome Genes are located linearly in chromosomes, each gene in its own locus In identical loci of homologous chromosomes there are allelic genes Genes localized on one chromosome are inherited together, forming a linkage group Morgan's law Chromosomal theory of heredity:




Resources: ozof.htm - Drosophila ozof.htm dical / Thomas_Morgan / - T. Morgan, portrait dical / Thomas_Morgan / \u003d person & more \u003d morgan - T. Morgan, portrait \u003d person & more \u003d morgan - T. Morgan, quote

Linked trait inheritance Thomas Morgan's Law


Genes located on the same chromosome, during meiosis, fall into one gamete, i.e. are inherited linked.

XX X Y

T. Morgan


  • Fly every two weeks at t \u003d 25 C gives numerous offspring.
  • The male and female are outwardly well distinguishable - the male has a smaller and darker abdomen.
  • Flies can reproduce in test tubes on cheap growth media

Inheritance of wing length and color in fruit flies

The emergence of intermediate genotypes in which both alleles were involved.


Conjugation and crossing over (prophase of 1 meiotic division)

Biological significance:

  • new combinations of genes
  • the occurrence of hereditary variability
  • selection of individual genes, not their combinations

Sex chromosomes and autosomes

Whose chromosome set?

How many autosomes?

Graphical representation of chromosomes


Detailed map Human X chromosome

(370 diseases linked to the X chromosome

in men, all diseases linked to the X chromosome are manifested in the phenotype)


DALTONISM

Women get sick -0.5%

Men-8%

In table number 1, people with normal vision see the number 16.

People with acquired visual impairment have difficulty or do not at all distinguish the number 96 in Table 2.




The sex ratio in nature is 1: 1 when crossing heterozygotes (Aa) homozygous (aa)


Females - XX

Males - X0

grasshoppers, ants

sea \u200b\u200bworm - bonelia (gender depends on external conditions)


Terms to remember:

  • Linked genes -
  • Chromosome genetic map -
  • Chained inheritance -
  • Crossover -
  • Conjugation -
  • Morgan's Law -
  • Autosomes and sex chromosomes
  • Homogametic and heterogametic sex

Problem 1 Which pairs are most profitable to cross to obtain platinum foxes, if platinum dominates over silver, but in the homozygous state the platinum gene causes the death of the embryo?

Problem 2

The pink ridge is the dominant feature in chickens, the simple one is recessive. What will the offspring be if you cross heterozygous chickens with pink combs and homozygous roosters with simple ones?


Problem 3

When two white pumpkins were crossed in the first generation, ¾ of the plants were white and ¼ were yellow. What are the genotypes of the parents if white dominates over yellow?


ANSWER 1: it is most profitable to cross silver and platinum heterozygous foxes

ANSWER 2: 50% of heterozygous chickens with

simple combs and 50% homozygous

roosters with pink combs

ANSWER 3: parent plants are heterozygous


summaries of other presentations

"Interaction of non-allelic genes" - The presence of pigment. Pink comb. Split. Modifying action of genes. Recessive epistasis on the example of staining inheritance in mice. Types of non-allelic gene interaction. Complementary interaction. Dominant epistasis on the example of color inheritance in horses. Additive polymer. Interaction of non-allelic genes. Polymeric interaction of genes. Non-additive polymerization. Cleavage by phenotype.

Mendel's third law - Plant. Round fruit shape. The law of independent combination. Results. Color inheritance. Red coloration. Solving problems. Crossbreeding. Signs. The probabilities of the appearance of a particular genotype. Plants with rounded red fruits. Genotypes of parents. Organisms. Analyzed genes. Rh-positive boy. Crossbreeding of heterozygous organisms. The probability of birth. Dihybrid crossing.

"Law of Independent Inheritance" - Correct definition all possible gametes. If there is work, then there will be success. Black color. Decision. Dihybrid crossing. Results of Mendel's experiments. Justification of the third law of G. Mendel. Plants have yellow smooth seeds. Good disposition. Pennett Lattice. Theoretical foundations of the third law of G. Mendel. Independent inheritance law.

"Regularities of monohybrid crossing" - Monohybrid crossing. The dominant variant of the trait. Color inheritance of pea flowers. Inheritance of the color of strawberries. Saturating crosses. Backcrossing. Incomplete dominance. Cytological (cytogenetic) bases of the inheritance of traits. Analyzing crosses. First generation hybrids. Pea seed color inheritance.

"Genetics of Mendel" - Problem using the 3rd Mendel's law. Inferences. Gregor Mendel. Fundamentals of Genetics. Illustrations of Mendel's first and second laws. Phenotype. Mendel's third law. An atmosphere of cooperation. Dihybrid crossing. Long-haired.

"Pedigree" - Blood groups. Hair shape inheritance. Family pedigree. Hair color. Goals and objectives of the study. Hair shape. Genealogical method of human genetics. The pedigree shows an autosomal recessive type of inheritance. Inheritance of blood groups in humans. Failure to distinguish between individual colors. Pedigree analysis. Pedigree.

 

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