First, the basic law of heredity
Isolation of (1) gene
① Advantages of peas as raw materials:
(1) Pea can be strictly self-pollinated and can remain pure under natural conditions.
(2) There are easily distinguishable characters among varieties.
② Experimental process of artificial hybridization: castration (keeping pistil) → bagging (anti-interference) → artificial pollination.
③ Genetic phenomenon of a pair of relative traits: when a pair of homozygous parents cross, the offspring show phenotype, F 1 generation self-crossing, and F2 generation segregation, with segregation ratio of 3: 1.
④ The essence of gene segregation: In heterozygote cells, alleles located on a pair of homologous chromosomes have certain independence. When an organism undergoes meiosis, alleles will separate with the separation of homologous chromosomes, enter two gametes respectively, and be passed on to offspring independently with the gametes.
(2) the law of gene free combination
① Genetic phenomenon that two pairs of relative traits are controlled by two pairs of alleles: after two pairs of parents with homozygous relative traits cross, F 1 selfs, and four phenotypes appear in the offspring, with the ratio of 9: 3: 3: 1. Each of the four phenotypes has a homozygote, the second generation accounts for116, and * * * accounts for 4/16; The proportion of double dominant individuals is 9/16; The proportion of double recessive individuals is116; Single heterozygote accounts for 2/16× 4 = 8/16; Double heterozygotes accounted for 4/16; The proportions of parental types were 9/ 16 and116, respectively. The proportion of recombination types is 3/ 16 and 3/ 16 respectively.
② The essence of the law of free combination of genes: the separation or combination of non-allelic genes on non-homologous chromosomes does not interfere with each other. In the process of meiosis to form gametes, alleles on homologous chromosomes are separated from each other, and non-alleles on non-homologous chromosomes are freely combined.
(3) the method of cultivating new varieties by using the principle of free combination of genes: among different varieties, the desired ones are selected first, and then homozygous excellent varieties are obtained through continuous self-crossing.
Memory point:
1. gene segregation phenomenon: when two organisms with a pair of relative traits are hybridized, the first generation only shows dominant traits; In the second generation, the phenomenon of character separation appeared, and the quantitative ratio of dominant characters to recessive characters was close to 3: 1.
2. The essence of gene segregation is that it is located on a pair of homologous chromosomes in heterozygote cells and has certain independence. When an organism undergoes meiosis to form a gamete, the alleles will separate with the separation, enter two gametes respectively, and be passed on to the offspring independently with the gametes.
3. Genotype is the memory factor of trait expression, while phenotype is the expression form of genotype. Phenotype = genotype+environmental conditions.
4. The essence of the law of free combination of genes is that the separation or combination of non-allelic genes located on non-homologous chromosomes does not interfere with each other. In the process of meiosis to form gametes, alleles on homologous chromosomes are separated from each other, and non-alleles on non-homologous chromosomes are freely combined. Within the scope of the law of free combination of genes, individuals with n pairs of alleles can produce 2n gametes at most.
Second, cell proliferation.
(1) Cell cycle: refers to the continuous division of cells, from the completion of one division to the completion of the next division.
(2) Mitosis:
The biggest feature of interphase is to complete the replication of DNA molecules and the synthesis of protein.
The main changes of chromosomes during mitosis are: prophase appearance; Clear and arrange in the medium term; Late division; Finally disappear. Pay special attention to the temporary doubling of chromosome number due to centromere division in the later stage.
The differences of mitosis between animal cells and plant cells are as follows: a. The early spindle formation mode is different; B. the way of cytoplasmic division at the end stage is different.
(3) Meiosis:
Object: Sexually reproducing organisms.
Stage: Primitive germ cells form mature germ cells.
Features: Chromosomes are copied only once, and cells divide twice continuously.
Results: The chromosome number of the newly produced germ cells was reduced by half compared with that of the original germ cells.
The main changes of chromosomes in the process of sperm and egg cell formation are as follows: during the first meiotic interval, homologous chromosomes in the early stage form tetrads (cross-exchange often occurs between non-sister chromosomes), homologous chromosomes in the middle stage are arranged on the equatorial plate, homologous chromosomes are separated in the later stage, and non-homologous chromosomes are freely combined; Chromosomes in the prophase of the second meiosis are scattered in cells, centromeres in the metaphase are arranged on the equatorial plate, and centromeres in the anaphase are separated.
Identification of mitotic and meiotic patterns: (taking diploid organisms as an example)
1. There is no homologous chromosome in the cell ... the second meiosis.
2. Homologous chromosomes unite, form tetrads, arrange on the equatorial plate or separate from each other ... the first meiosis.
3. Homologous chromosomes do not have the above special behavior ... mitosis.
Memory point:
1. As a result of meiosis, the number of chromosomes in new germ cells is reduced by half compared with the original germ cells.
2. Synaptic homologous chromosomes are separated from each other during meiosis, which shows that chromosomes have certain independence; When two homologous chromosomes randomly move to which pole, different pairs of chromosomes (non-homologous chromosomes) can be freely combined.
3. In the process of meiosis, the number of chromosomes is halved in the first meiosis.
4. One spermatogonia undergoes meiosis to form four sperm cells, and the sperm cells undergo complex changes to form sperm.
5. Oocytes undergo meiosis, and only one egg cell is formed.
6. For sexually reproducing organisms, meiosis and fertilization are very important for maintaining the constant number of chromosomes in somatic cells of each offspring, as well as for the inheritance and variation of organisms.
Third, sex determination and sex-linked inheritance
Sex determination of (1)XY type: females have a pair of homozygous chromosomes (XX) and males have a pair of heterozygous chromosomes (XY). When meiosis forms sperm, sperm containing X chromosome and sperm containing Y chromosome are produced. Women only produce one kind of egg cell with X chromosome. At the time of fertilization, X sperm and Y sperm have equal opportunities to combine with egg cells, so the offspring have equal opportunities to have children, and the ratio is 1: 1.
(2) It has the characteristics of X recessive inheritance (such as color blindness, hemophilia, Drosophila expression, leaf shape, etc.)
① Male patients are more than female patients.
② It belongs to cross inheritance (atavism), that is, grandfather → daughter → grandson.
③ Female patients, whose father and son are both patients; If a man is sick, his mother and daughter are at least carriers.
(3) recessive inheritance on X chromosome (such as VD rickets and pendulum nystagmus)
① There are more female patients than male patients.
(2) It has the phenomenon of generational continuity.
③ Male patients, whose mothers and daughters must be patients.
(4) Inheritance on Y chromosome (such as hirsutism of external auditory canal)
Pathogenic genes are passed on from generation to generation and from son to grandson, which is also called limited male inheritance.
(5) The relationship between sex-linked inheritance and segregation of genes: Sex-linked genes are on sex chromosomes, and sex chromosomes are also a pair of homologous chromosomes. Sex-linked inheritance is essentially consistent with the phenomenon of gene separation.
Memory point:
1. Chromosomes in cells of organisms can be divided into two categories: autosomes and sex chromosomes.
There are two main methods to determine biological sex: one is XY type, and the other is ZW type.
2. The characteristics of sex-linked inheritance:
It has the characteristics of (1) recessive inheritance of X chromosome: there are more male patients than female patients; There is atavism (because the pathogenic gene is on the X chromosome, it is generally passed from male to grandson through daughter); The father and son of female patients must be patients, on the contrary, male patients must have inherited the pathogenic genes from their mothers.
(2) It has the characteristics of dominant inheritance of X chromosome: there are more female patients than male patients, and most of them have intergenerational continuity, that is, there are patients from generation to generation, and the mother and daughter of male patients must be patients.
(3) Genetic characteristics of Y chromosome: All patients are male; Pathogenic genes are passed down from generation to generation, and passed from son to grandson (male only).
Fourth, the nature of genes.
(1)DNA is the main genetic material.
① Biological genetic material: In the whole biological world, most organisms take DNA as their genetic material. For organisms with DNA (organisms with cellular structure and DNA viruses), DNA is genetic material; Only a few viruses (such as AIDS virus, SARS virus, avian influenza virus, etc.). ) there is no DNA, only RNA is genetic material.
② Experimental design idea to prove that DNA is genetic material: Try to separate DNA from protein and observe the function of DNA directly.
(2) the structure and replication of 2)DNA molecules
① ① The structure of ①①DNA molecule
A basic unit: deoxynucleotide (composed of phosphoric acid, deoxyribose and bases).
B deoxynucleotide long chain: formed by polymerization of deoxynucleotides in a certain order.
C. plane structure:
D. Spatial structure: regular double helix structure.
E. structural characteristics: diversity, specificity and stability.
②DNA replication
A. Time: the interval between mitosis or first meiosis.
B. features: unwinding and copying; Semi-conservative replication.
C conditions: template (double strand of DNA molecule), raw material (four kinds of free deoxynucleotides), enzyme (helicase, DNA polymerase, DNA ligase, etc. ), energy (ATP)
D. results: the same DNA molecule as the template DNA was produced by replication.
E. Significance: Genetic information is transmitted to future generations through replication, thus maintaining the continuity of genetic information.
(3) the structure and expression of the gene
① The concept of genes: genes are DNA molecular fragments with genetic effects, and genes are arranged linearly on chromosomes.
② Gene controls the process of protein synthesis:
Transcription: the process of forming messenger RNA using a strand of DNA as a template and the principle of base complementary pairing.
Translation: protein molecules with certain amino acid sequences were synthesized in ribosomes using messenger RNA as template and transport RNA as carrier.
Memory point:
1.DNA is a substance that causes stable genetic changes of R-type bacteria, and various characteristics of phage are also passed on to future generations through DNA. These two experiments proved that DNA is a kind of genetic material.
2. The genetic material of all living things is nucleic acid. The biological genetic material that contains both DNA and RNA in cells and only DNA is DNA, and the genetic material of a few viruses is RNA. Because the genetic material of most organisms is DNA, DNA is the main genetic material.
3. The ever-changing base pair sequence constitutes the diversity of DNA molecules, and the specific base pair sequence constitutes the specificity of each DNA molecule. This explains why organisms have diversity and specificity at the molecular level.
4. The transmission of genetic information is accomplished by the replication of DNA molecules. Gene expression is achieved by DNA controlling the synthesis of protein.
5.5 Unique double helix structure. DNA molecules provide accurate templates for replication; Through base complementary pairing, replication can be accurately guaranteed. The proportions in the two complementary chains are mutual. In the whole DNA molecule, the sum of purine bases = the sum of pyrimidine bases. In the whole DNA molecule, the ratio is the same as that on each chain in the molecule.
6. The offspring are similar to their parents in character, because they got a copy of DNA copied by their parents.
7. Genes are DNA fragments with genetic effects. Genes are arranged in a straight line on chromosomes, which are the carriers of genes.
8. Because different genes have different sequences of deoxynucleotides (base sequences), different genes contain different genetic information. (that is, the deoxynucleotide sequence of a gene represents genetic information).
Sequence of deoxynucleotides in 9.9. DNA molecule determines the arrangement order of ribonucleotides in messenger RNA, and then determines the arrangement order of amino acids, and finally determines the specificity of protein's structure and function, thus making organisms show various genetic characteristics. When protein synthesis is controlled by gene, the number of bases in the gene: the number of bases on mRNA: the number of amino acids = 6: 3: 1. The codons of amino acids are three adjacent bases on messenger RNA, not bases on transport RNA. In the process of transcription and translation, the principle of base complementary pairing is strictly followed. Note: When pairing, A corresponds to U on RNA.
10. All genetic traits of organisms are controlled by genes. Some genes control the metabolic process by controlling the synthesis of enzymes; Another situation in which genes control traits is to directly affect traits by controlling the structure of protein molecules.
Biological variation of verb (abbreviation of verb)
(1) gene mutation
① The concept of gene mutation: the change of gene structure caused by the addition, deletion or change of base pairs in DNA molecules.
② Characteristics of gene mutation: A. Gene mutation is ubiquitous in biology. B. gene mutation occurs randomly. C. the frequency of gene mutation is very low. D. most gene mutations are harmful to organisms. E. gene mutation has no directionality.
③ The significance of gene mutation: the fundamental source of biological variation, which provides raw materials for biological evolution.
④ Types of gene mutation: natural mutation and induced mutation.
⑤ Application of artificial mutation in breeding: Artificial mutation can increase the frequency of mutation and greatly improve biological characteristics.
(2) Chromosome variation
① Variation of chromosome structure: deletion, addition, inversion and translocation. Such as: meow syndrome.
(2) Variation of chromosome number: including the increase or decrease of individual chromosomes in the cell and the increase or decrease of index in the form of genome.
(3) Genome characteristics: A. A genome does not contain homologous chromosome B, the chromosomes contained in a genome are different in morphology, size and function, and a genome contains a set of genes that control biological characteristics.
(4) Diploid or polyploid: an individual developed from a fertilized egg, and how many chromosomes are contained in a somatic cell is polyploid; Individuals developed from unfertilized germ cells (sperm or egg cells) are haploid (there may be 1 or more chromosomes).
⑤ Method of artificially inducing polyploid: Treating germinated seeds and seedlings with colchicine. Principle: When colchicine acts on dividing cells, it can inhibit the formation of spindle in the prophase of cell division, resulting in chromosome non-separation, thus doubling the number of chromosomes in cells.
⑥ Characteristics of polyploid plants: stout stems, relatively large leaves, fruits and seeds, and increased contents of nutrients such as sugar and protein.
⑦ haploid plant characteristics: the plant is weak and highly sterile. Haploid plants were obtained by retired anther culture. Significance of haploid breeding: obviously shorten the breeding cycle (only two years).
Memory point:
1. Genome is a set of non-homologous chromosomes in cells, which are different in morphology and function, but the vector controls all the information of organism growth, development, heredity and variation. Such a set of chromosomes is called genome.
2. Genetic variation refers to the change of genetic material, including gene mutation, gene recombination and chromosome variation. The biggest feature of gene mutation is the production of new genes. It is a genetic change at a certain point on the chromosome. Gene mutation is ubiquitous, random, low mutation rate, mostly harmful to organisms, and mutation is not directional. Gene mutation is the fundamental source of biological variation and provides the initial raw materials for biological evolution. Gene recombination is the recombination of the original genes of an organism, which does not produce new genes, but recombines genes that are not in the same individual into an individual through hybridization. Gene recombination through sexual reproduction provides an extremely rich source of biological variation. This is one of the important reasons for the formation of biodiversity and is of great significance to biological evolution. The above two kinds of variation are invisible to the microscope, while chromosome variation is the change of chromosome structure and quantity, which can be seen clearly by the microscope. This is the most important difference from the first two. Its changes involve changes in chromosomes. Such as structural change, individual number and ploidy change, among which ploidy change is of great significance in real life, from which a series of concepts and types such as genome, diploid, polyploid, haploid and polyploid breeding are derived.
Six, human genetic diseases and eugenics
(1) eugenic measures: forbidding consanguineous marriage, conducting genetic counseling, advocating childbearing at appropriate age and prenatal diagnosis.
(2) Reasons for forbidding consanguineous marriage: Couples who are married by consanguineous relatives are much more likely to inherit the same pathogenic gene from their ancestors, and the probability of their children suffering from recessive genetic diseases is also greatly increased.
Memory point:
1. Polydactyly, syndactyly and achondroplasia are single-gene autosomal dominant genetic diseases; Vitamin D-resistant rickets is a single-gene X-chromosome dominant genetic disease. Albinism, phenylketonuria and congenital deafness are single-gene autosomal recessive genetic diseases; Progressive muscular dystrophy, red-green color blindness and hemophilia are recessive genetic diseases of single gene X chromosome. Cleft lip, anencephaly, essential hypertension and juvenile diabetes are hereditary diseases; In addition, autosomal diseases also include 2 1 trisomy syndrome and meow syndrome. Sex chromosome diseases include gonadal dysplasia.
Seven, cytoplasmic inheritance
① Characteristics of cytoplasmic inheritance: maternal inheritance (reason: almost all cytoplasm in fertilized eggs comes from mother cells); There is no certain segregation ratio in offspring (reason: during meiosis of germ cells, the genetic material in cytoplasm is randomly and unequally distributed to daughter cells).
② Material basis of cytoplasmic inheritance: There are DNA molecules in cytoplasm, mainly located in mitochondria and chloroplasts, which can control some characters.
Memory point:
1. Eggs contain a lot of cytoplasm, while sperm only contains a very small amount of cytoplasm, which means that almost all cytoplasm in fertilized eggs comes from eggs. In this way, the traits controlled by genetic material in cytoplasm are actually passed from eggs to offspring, so offspring always show the characteristics of female parents.
2. The main characteristics of cytoplasmic inheritance are: maternal inheritance; There is no certain separation ratio in offspring. Reasons for the formation of cytoplasmic genetic characteristics: almost all cytoplasm in fertilized eggs comes from egg cells; In the process of meiosis, the genetic material in cytoplasm is randomly and unevenly distributed to egg cells. The material basis of cytoplasmic inheritance is DNA in cytoplasmic structures such as chloroplasts and mitochondria.
3. Nuclear inheritance and cytoplasmic inheritance are relatively independent. This is because, although there is no chromosome-like structure in cytoplasm, cytoplasmic genes, like nuclear genes, can replicate themselves, and the synthesis of protein can be controlled by transcription and translation, that is, they all have stability, continuity, variability and independence. However, nuclear inheritance and cytoplasmic inheritance are interactive, and many cases are the result of nuclear-cytoplasmic interaction.
Eight. Introduction to genetic engineering
The concept of (1) genetic engineering
Standard concept: in vitro, DNA molecules are artificially "cut" and "spliced" to transform recombinant biological genes, and then introduced into recipient cells for asexual reproduction, so that the recombinant cells can be expressed in recipient cells to produce gene products needed by human beings.
Popular concept: according to people's wishes, the individual genes of one organism are copied, transformed and transformed, and then put into the cells of another organism to directionally transform the genetic traits of that organism.
(2) Genetic manipulation tools
A. scissors of gene-restriction endonuclease (restriction endonuclease for short).
① Distribution: Mainly in microorganisms.
② Functional features: specificity, that is, recognizing specific nucleotide sequences and cutting specific tangents.
Results: sticky end (base complementary pairing) was produced.
B. gene needle and line -DNA ligase.
① Connection site: phosphodiester bond, not hydrogen bond.
Results: Two identical sticky ends were connected.
C. transport vehicles with poor foundation-transport vehicles
① Function: Send foreign genes into recipient cells.
② Conditions: A. It can be replicated in the host cell and stably preserved. B, with multiple restriction enzyme cut points.
C, there are some marker genes
③ Species: plasmid, phage and animal and plant viruses.
④ Characteristics of Plasmids: Plasmids are the most commonly used vectors in genetic engineering.
(3) Basic steps of gene manipulation
A. extracting a target gene
Objective Gene concept: People need specific genes, such as human insulin gene, insect-resistant gene, disease-resistant gene and interferon gene.
Select route:
B, combining the target gene with the vector
Using the same restriction endonuclease to cut the target gene and plasmid DNA (vector) respectively to make them produce the same sticky end, mixing the cut target gene with the cut plasmid, and adding an appropriate amount of DNA ligase to form a recombinant DNA molecule (recombinant plasmid).
C. introducing the target gene into the recipient cell.
Commonly used recipient cells: Escherichia coli, Bacillus subtilis, Agrobacterium tumefaciens, yeast, animal and plant cells.
D. detection and expression of target gene
The detection method is as follows: put the Escherichia coli cells with antibiotic resistance genes in the plasmid into the corresponding antibiotics. If the cells grow normally, it means that the cells contain recombinant plasmids.
Expression: The recipient cells showed specific characteristics, indicating that the target gene completed the expression process. For example, after the insect-resistant cotton gene is introduced into cotton cells, the cotton bollworm is killed when it eats cotton leaves; Insulin can be synthesized by introducing insulin gene into Escherichia coli.
(4) Achievements and development prospects of genetic engineering A. Genetic engineering and medical health B. Genetic engineering and agriculture, animal husbandry and food industry.
C. genetic engineering and environmental protection
Memory point:
1. As a vector, it must have the following characteristics: it can be replicated in host cells and stored stably; Having a plurality of restriction enzyme cutting points for connecting foreign genes; With some marker genes, it is easy to screen. Plasmids are the most commonly used vectors in genetic engineering. It exists in bacteria, yeast and other organisms, and it is a small circular DNA molecule that can replicate independently.
2. The general steps of genetic engineering include: ① extracting the target gene; (2) combining the target gene with the vector; ③ Introducing the target gene into the recipient cell; ④ Detection and expression of the target gene.
3. After the recombinant DNA molecule enters the recipient cell, the recipient cell must show specific characters, which can indicate that the expression process of the target gene has been completed.
4. Distinguish and understand commonly used vectors and commonly used receptor cells. At present, the commonly used vectors are plasmids, bacteriophages, animal and plant viruses, and the commonly used recipient cells are Escherichia coli, Bacillus subtilis, Agrobacterium tumefaciens, yeast and animal and plant cells.
5. Gene diagnosis uses DNA molecules labeled with radioisotopes and fluorescent molecules as probes, and uses the principle of DNA molecular hybridization to identify the genetic information of the detected samples, so as to achieve the purpose of detecting diseases.
6. Gene therapy is to introduce healthy foreign genes into gene-deficient cells to achieve the purpose of treating diseases.
Nine, biological evolution
(1) The content of natural selection theory is: over-reproduction, survival competition, gene variation and survival of the fittest.
(2) Species: refers to a group of individuals who are distributed in a certain natural area, have certain morphological structure and physiological functions, can mate and reproduce with each other in the natural state, and can produce fertile offspring.
Population refers to a group of individuals of the same species living in the same place.
Population gene bank: All genes contained by all individuals in a population.
(3) The basic viewpoint of modern biological evolution theory: population is the basic unit of biological evolution, and the essence of biological evolution lies in the change of gene frequency of population. Mutation and gene recombination, natural selection and isolation are three basic links in the process of species formation. Through their comprehensive action, the population differentiates and eventually leads to the formation of new species.
(4) Mutation and gene recombination are raw materials for biological evolution. Natural selection changes the gene frequency orientation of population and determines the direction of biological evolution. Isolation is a necessary condition for the formation of new species (the formation of reproductive isolation marks the formation of new species).
The basis of modern biological evolution theory: natural selection theory.
Memory point:
1. The process of biological evolution is essentially the process of population gene frequency change.
2. The basic view of modern biological evolution theory with natural selection as the core is that population is the basic unit of biological evolution, and the essence of biological evolution lies in the change of gene frequency of population. Mutation and gene recombination, natural selection and isolation are three basic links in the process of species formation. Through their comprehensive action, the population differentiates and eventually leads to the formation of new species.
3. Isolation refers to the phenomenon that individuals of the same species and different populations cannot communicate freely under natural conditions. Include geographical segregation and reproductive segregation. Its function is to block the gene communication between populations and make the gene frequency of populations develop in different directions in natural selection, which is a necessary condition and an important link for species formation.
4. The difference between speciation and biological evolution: biological evolution refers to the development and change of the same species, which can be long or short, with different degrees of character change. Any change in gene frequency, regardless of size, belongs to the scope of evolution. Only when the change of gene frequency breaks through the boundaries of species and forms reproductive isolation can the formation of species be established.
5. Every cell of an organism contains a whole set of genetic material of the species, and all the genes necessary to develop into a complete individual.
6. In organisms, cells do not show totipotency, but differentiate into different tissues and organs, which is the result of gene selective expression under specific time and space conditions.