If you are a sophomore, you must learn more, and the more the better.

(1) 1. Meiosis is a kind of cell division. When sexual reproductive organisms produce mature germ cells, the number of chromosomes is halved. In the process of meiosis, chromosomes are copied only once and cells divide twice.

Due to meiosis, the number of chromosomes in cells has been reduced by half.

Oocytes undergo meiosis to form only one egg cell; However, one spermatogonia can form four sperms through meiosis.

2. Homologous chromosomes: Two pairs of chromosomes are generally the same in shape and size, one from the father and the other from the mother.

Non-homologous chromosomes: chromosomes that cannot be paired are called non-homologous chromosomes.

Synapsis: the appearance of homologous chromosomes in pairs in the early stage of meiosis.

Tetrad: Each pair of homologous chromosomes contains four chromatids. 1 tetrad has 1 pair of homologous chromosomes, 2 chromosomes, 4 chromatids and 4 molecules of DNA.

(2) Sperm formation process:

1. location: in the sexual reproductive organs.

2. Intermittent period (preparation period): DNA replication and protein synthesis;

3. Features: The prophase of the first meiosis: synapse, forming tetrads, and each chromatid contains two sister chromatids; Meiosis metaphase: homologous chromosomes are arranged on the equatorial plate, and each chromosome contains two sister monomers; In the late stage of the first meiosis, homologous chromosomes are separated and non-homologous chromosomes are freely combined, and each chromosome contains two sister monomers; At the end of the first meiosis: a primary spermatocyte divides into two secondary spermatocytes, with half chromosomes and DNA, and each chromosome contains two sister monomers;

3. The prophase of the second meiosis: (generally considered to be the same as the anaphase of the first meiosis); Meiosis metaphase: Centromeres are arranged on the equatorial plate; Late meiosis: centromere divides, sister chromatids separate into chromosomes, the number of chromosomes doubles, and there is no homologous chromosome in each polar cell; At the end of the second meiosis, two secondary spermatocytes split into four spermatocytes. Sperm cells become sperm.

(3) Similarities and differences between egg cells and sperm formation:

Similarities: they are all carried out in reproductive organs; Related to the formation of germ cells, the changes of chromosomes and DNA molecules are completely consistent with the results.

Differences: ① interphase spermatogonia → primary spermatocytes only increased slightly. Oocytes → primary oocytes store a lot of yolk, and the volume has increased many times. ② In the process of sperm formation, the two divisions are equal, resulting in four sperm cells. When an egg cell is formed, it divides unevenly twice, producing only one egg cell and three polar bodies. ③ Sperm cells must be deformed to become fertile sperm, while eggs can be fertilized without deformation. ④ Sperm is formed in testis, and egg cells are formed in ovary.

(4) Compare the similarities and differences between mitosis and meiosis:

Mitosis: once the cell divides, the chromosomes of daughter cells are the same as those of somatic cells, forming somatic cells without synapses and tetrads, and cross-exchange;

Meiosis: the cell divides twice continuously, and the number of chromosomes in the daughter cell is halved, forming a sexual germ cell with synapses and tetrads, with cross-exchange behavior.

Similarity: Chromosomes are copied once.

In the sperm (egg) nest of animals, spermatogonia can divide in two ways. If mitosis is carried out, spermatogonia will still be formed, and if meiosis is carried out, mature germ cell sperm (egg cell) will be produced.

The characteristics of fertilization: the nucleus of sperm and the nucleus of egg fuse to make each other's chromosomes meet.

Significance of meiosis and fertilization: For sexually reproductive organisms, meiosis and fertilization are very important for maintaining the chromosome number of the first and second generation somatic cells of each organism, as well as the inheritance and variation of organisms.

Second, the molecular basis of heredity.

1. There are two experiments to prove that DNA is genetic material, namely, the transformation experiment of pneumococcus and the phage infection of bacteria test. Experimental process of bacteriophage infecting bacteria: Because bacteriophage is a virus parasitic in bacteria, its head and tail have _ protein _ shell, and its head contains _DNA_. ① Radioisotope 35S labeled phage protein and radioisotope 32P labeled phage DNA. ② The experimental results show that DNA is genetic material, and DNA can control the synthesis of protein.

2. In nature, some microorganisms only contain ribonucleic acid, but not deoxyribonucleic acid. In this case, RNA is genetic material. The genetic material of organisms with DNA (prokaryotes, eukaryotes and DNA viruses) is DNA, so the genetic material of most organisms is DNA, so DNA is the main genetic material.

3. The main features of the three-dimensional structure of 3.DNA molecules are as follows: ① Two long chains spiral into a _ reverse _ _ parallel structure.

② _ deoxyribose _ and _ phosphate _ are alternately connected and arranged on the outside of DNA molecules to form the basic skeleton, and _ bases _ are arranged on the inside.

③ The bases on the two strands of ③DNA molecules are connected into base pairs by hydrogen bonds, and the pairing has certain rules, namely, A and T pairing, G and C pairing.

4. The genetic information of 4.DNA molecules is stored in deoxynucleotide sequences (base pairs).

5. The characteristics of 5.DNA: _ diversity _ and _ specificity.

6. The process of 6.DNA replication: unwinding and replication. (1) Under the action of _ATP_ energy and _DNA melting _ enzyme, the base pairs of two deoxynucleotide chains of DNA molecules are disconnected from _ hydrogen bonds, and the double-stranded DNA molecules are melted. This process is called unwinding. ② Synthesis of complementary sub-chains: Using two mother chains of DNA as templates and four deoxynucleotides in the surrounding environment as raw materials, a sub-chain complementary to the mother chain is synthesized under the action of related enzymes (DNA polymerase and DNA ligase) according to the principle of base complementary pairing. ③ Subchains and parent chains are combined and curled to form a new DNA molecule: under the action of DNA polymerase, with the unwinding process, the newly synthesized subchains are continuously extended, and each subchain and its corresponding parent chain are curled into a double helix structure, thus forming a new DNA molecule.

Characteristics of DNA replication: the new DNA molecule is a semi-conservative replication, which consists of a chain of the parent DNA molecule and a newly synthesized sub-chain.

Biological significance of DNA replication: DNA replication enables genetic information to be transmitted from parents to offspring, thus maintaining the continuity of genetic information.

7. Genes are DNA fragments with genetic effects. Genes are on chromosomes. DNA is the main genetic material. Chromosome is the main carrier of DNA and consists of DNA and protein.

8. Genetic control of traits: ① Directly control the molecular structure of protein; ② The metabolic process is controlled by controlling the synthesis of enzymes, so as to control biological characters.

9. The synthesis of protein includes two processes: transcription and translation.

Concept: the process of synthesizing _RNA_ using a DNA as a template and the principle of _ base complementary pairing.

Transcription refers to DNA _ deoxynucleotide _ sequence →→→ mRNA _ ribonucleotide _ sequence.

Location: _ nucleus _.

Concept: The process of synthesizing protein with a certain amino acid sequence using _ mRNA _ template.

Translation is the _ nucleotide sequence of mRNA → _ amino acid sequence of protein.

Location: _ cytoplasmic ribosome _.

Types of RNA: mRNA (messenger RNA), tRNA (transporter RNA) and r RNA (ribosomal RNA).

Codon: Three adjacent bases on messenger RNA determine an amino acid.

There are 64 codons * * *, of which 6 1 determines the amino acid and 3 are stop codons.

Each tRNA can only recognize and transport 1 amino acid, so the type of tRNA is 6 1.

Comparison of DNA Replication, Transcription and Translation

Transfer genetic information

(Replication) Expression of Genetic Information

Transcription translation

Time interval (silk, minus one) interval (silk, minus one) interval (silk, minus one)

This site is mainly in the nucleus, mainly in the ribosome of the cytoplasm of the nucleus.

Raw material free deoxynucleotide free ribonucleotide amino acid

Two template DNAs, one DNA mRNA.

Product deoxyribonucleic acid protein

get in touch with

(Central Rule) DNA → RNA → protein

Third, the gene separation phenomenon.

(1) Common symbols in genetic map: p- parent ♀ a female parent ♂-male parent×-cross selfing (self-pollination, homozygous hybridization) f1-f1-F2. In somatic cells, genes controlling traits exist in pairs, while in germ cells, genes controlling traits exist alone.

(2) Genetic experiment of a pair of relative characters:

① Experimental phenomenon: p: tall stem× short stem →F 1: tall stem (dominant character) →F2: tall stem ∶ short stem =3∶ 1 (character separation).

② Explanation: Two male gametes, D and D; The female gametes D and D are fertilized in four ways, so the genetic composition of F2 is DD∶Dd∶dd= 1∶2∶ 1, and the characters are: tall stem ∶ short stem =3∶ 1.

Test cross: cross the first hybrid with recessive type to determine the genotype of F 1. F 1 was identified as heterozygote. The correctness of allele segregation in gametophyte formation.

Note: Crossing and self-crossing can judge the dominant and recessive relationship in a pair of relative traits, and test crossing can verify whether dominant individuals are homozygous or heterozygous.

(3) Genotype and phenotype: the phenotype is the same, but the genotype is not necessarily the same; The genotype is the same, the environment is the same and the phenotype is the same. Phenotypes are not necessarily the same in different environments. Homozygotes can only produce one kind of gamete, and selfing will not cause character separation. The gamete type produced by heterozygote is 2n (n is the logarithm of allele), and the self-bred offspring of heterozygote will have character separation.

(d) Mendel's hypothesis about the cause of separation.

Biological characteristics are determined by genetic factors; Genetic factors in somatic cells exist in pairs; When germ cells are formed, the paired genetic factors are separated from each other and enter different gametes; In the process of fertilization, the combination of male and female gametes is random.

(5) Segregation phenomenon: In the somatic cells of organisms, genetic factors controlling the same trait exist in pairs and do not fuse; In the process of gametophyte formation, pairs of genetic factors are separated, and the separated genetic factors enter different gametes and are passed on to future generations with the gametes.

(VI) The essence of segregation phenomenon: alleles on homologous chromosomes are separated.

Fourth, the law of gene free combination.

Genetic detection of (1) two pairs of related traits;

① P: yellow round grain × green wrinkle grain →F 1: yellow round grain → F2: 9 yellow round: 3 green round: 3 yellow wrinkle: 1 green wrinkle.

② Species and proportion of gametes formed by F1(YYRR): Alleles are separated, and non-alleles are freely combined. The number of four gametes YR, Yr, Yr and yr is the same.

(2) Verification of free combination-test crossing phenomenon: F 1(YyRr)× recessive (yyrr)→( 1Yr, 1YR, 1YR )× yr →

(3) The reason for Mendel's success: 1) The experimental materials were selected correctly. 2) In the analysis of biological characters, the method of starting with a pair of relative characters and then proceeding step by step (from single factor to multi-factor research method) is adopted. 3) The experimental results are processed by statistical methods. 4) Scientifically design the experimental program (hypothesis-deduction method).

(5) the law of gene free combination: the separation and combination of genetic factors controlling different traits do not interfere with each other; During gamete formation, the paired genetic factors that determine the same trait are separated from each other, and the genetic factors that determine different traits are freely combined.

(6) The essence of the law of free combination: the separation and combination of alleles located on homologous chromosomes do not interfere with each other. During meiosis, alleles on homologous chromosomes are separated, but non-alleles on non-homologous chromosomes are free to combine.

Verb (abbreviation of verb) sex determination and sex-linked inheritance

1, sex determination: generally refers to the biological sex determination of hermaphroditism.

Sex chromosome: Sex-determining chromosome. Autochromosome: A chromosome that has nothing to do with sex determination. Sex-linked inheritance: a gene on a sex chromosome. Its genetic mode is related to sex. This mode of inheritance is called sex-linked inheritance.

2.XY sex determination model: (1): Male individuals have two heterozygous chromosomes (XY) in their somatic cells, while female individuals have two homozygous chromosomes (XX).

3. Common recessive genetic disease of X chromosome-red-green color blindness: When writing color vision genotype, in order to distinguish it from autosomal gene, we must first write the sex chromosome, and then indicate the genotype in the upper right corner. ) color-blind women (xbxbxbxb), normal (carrier) women (xbxbxb), normal women (xbxbxb), color-blind men (XBY), normal men (XbY).

4. Types, characteristics and examples of common genetic diseases

(1) autosomal recessive genetic diseases, such as albinism, are judged on the basis that they are out of thin air and recessive, and women's diseases are often recessive. The ratio of male to female patients is close to 1: 1.

(2) Autosomal dominant genetic diseases, such as syndactyly and polydactyly, are judged on the basis of the dominance of inaction in middle age, and normal delivery is common. The ratio of male to female patients is close to 1: 1.

(3) X chromosome recessive inheritance, such as color blindness and hemophilia. , is based on the mother will get sick, female father will get sick, male patients more than female patients to judge. Generally speaking, color blindness is a disease that men pass on to their grandchildren through their daughters (carriers) (atavism, cross inheritance). Color blindness genes cannot be passed from male to male.

(4) The dominant inheritance of X chromosome, such as vitamin D-resistant rickets, is judged on the basis that the sick mother will get sick, the sick father will get sick, and women are more miserable than men.

Six, biological variation

1, the difference between genetic variation and non-genetic variation, and whether the genetic material has changed.

2. Gene mutation refers to the change of gene structure, including the addition, deletion or change of DNA base pairs. Gene mutation can occur in both lower organisms and higher organisms, which shows the universality of gene mutation. Gene mutation can occur at any stage of individual development, and it can also occur in any cell of an organism, which shows that gene mutation is random. A gene can mutate in different directions, producing more than one allele, indicating that gene mutation has no directionality; The result of gene mutation often makes the body unable to adapt to the environment, which shows the harm of gene mutation.

3. Significance of gene mutation: Gene mutation is the way to produce new genes, the fundamental source of biological variation and the original material of biological evolution.

Factors causing gene mutation: A. Physical factors: mainly X-rays, γ-rays, ultraviolet rays and laser lamps. Chemical factors: nitrite, base analogues. C. Biological factors: mainly some viruses and some bacteria parasitic in living cells.

4. Gene recombination refers to the recombination of genes that control different traits during sexual reproduction.

There are two kinds: ① when gametes are produced by biological meiosis, non-alleles on non-homologous chromosomes are freely combined;

② When meiosis forms tetrads, non-sister chromatids of homologous chromosomes cross-exchange.

5. The significance of gene recombination

Gene recombination is also one of the sources of biological variation, which is also of great significance to the evolution of organisms.

6. Gene mutation is different from gene recombination. Gene recombination is the recombination of genes to produce new genotypes. Gene mutation is the change of gene structure, resulting in new genes.

7. Chromosome variation refers to the variation of chromosome structure and chromosome number visible under optical microscope. Gene mutation and gene recombination are invisible under the optical microscope.

8. Chromosome structural variation: ① a fragment in the chromosome is missing; (2) adding a fragment to the chromosome; ③ One chromosome fragment is transferred to another non-homologous chromosome; ④ The position of a fragment in the chromosome is reversed.

Variation of chromosome number: ① increase or decrease of individual chromosomes in cells; ② The number of chromosomes in cells increases or decreases exponentially in the form of genome.

Genome: A group of non-homologous chromosomes in a cell, with different shapes and functions, carrying all the genes that control the growth and development of an organism.

Part of genetic information, such a set of chromosomes is called genome.

Remarks: the number of chromosomes is judged (according to the number of chromosomes with the same morphology or the number of genes controlling the same trait)

9. Diploid: an individual developed from a fertilized egg, with two chromosomes in the somatic cell.

Polyploid: an individual developed from a fertilized egg, whose somatic cells have three or more chromosomes.

Remarks: Banana is triploid, potato is tetraploid and common wheat is hexaploid.

Haploid: an individual developed from gametes, whose somatic cells contain the chromosome number of gametes of this species. Its plants are characterized by weakness and high sterility.

Remarks: (1) Haploid chromosome number is greater than or equal to 1.

(2) The plants formed by anther culture in vitro of octoploid wheat are haploid.

(3) The reason why haploid plants are highly sterile _ chromosomes can't combine normally and produce normal gametes during meiosis, so they are highly sterile.

(4) Judgment: Haploid contains only one chromosome set (×), and the one containing one chromosome set must be haploid (√).

10. Reasons for polyploid formation in nature: _ Somatic cells have completed chromosome replication during mitosis, but the cells are disturbed by external environmental conditions (such as temperature mutation) or internal factors of organisms, and the formation of spindles is destroyed, so that chromosomes cannot be pulled to two poles, and cells cannot be divided into two daughter cells, so the number of chromosomes formed is doubled.

Application of biological variation in breeding.

Principles, methods and characteristics of (1) polyploid breeding

Principle: Chromosome variation

Methods: The germinated seeds or seedlings were treated with colchicine (colchicine can inhibit the formation of spindle, and the action period is in the prophase of mitosis).

Characteristics: The produced polyploid has thick stems, large leaves, large fruits and seeds, and the contents of nutrients such as sugar and protein are increased.

(2) Application of mutation breeding in production.

Principle: gene mutation

Physical mutagenesis: X-ray, ultraviolet ray, laser, etc.

Methods Chemical mutagenesis: nitrous acid, diethyl sulfate, etc.

Biological mutation: virus, etc.

Features: Increase the mutation frequency and get more excellent mutation types in a short time.

(3) The principles, methods and characteristics of haploid breeding.

Principle: Chromosome variation

Methods: Anthers were cultured in vitro and treated with colchicine.

Characteristics: Shorten the breeding years, and the offspring can be inherited stably.

Seven, genetic engineering

Genetic engineering: also called gene splicing technology or DNA recombination technology. In layman's terms, it is to extract a gene of an organism, transform it, and then put it into the cells of another organism to directionally transform the genetic traits of that organism.

1, gene manipulation tools and tool enzymes

① Scissors of genes: restriction endonuclease (the role is to cut DNA molecules)

② Needle and thread of gene: DNA ligase (the function is to connect the chemical bond between phosphate and deoxyribose in DNA skeleton).

③ Means of gene transportation: vectors (commonly used vectors include plasmids, bacteriophages and animal and plant viruses).

2, the basic steps of gene manipulation:

① extracting the target gene

② The target gene is combined with the vector.

③ Introduce the target gene into the recipient cell.

④ Detection and expression of the target gene.

3. Safety of genetically modified food

Safety point of view: Genetically modified food, like non-genetically modified food, is composed of amino acids, protein and carbohydrates, which is theoretically safe.

Unsafe point of view: HIV and cold virus can be assembled in a simple laboratory, so that HIV can spread on a large scale like a cold, so the insecurity of genetically modified organisms and genetically modified foods should be strictly controlled.

Eight, human genetic diseases

1. Etiology: Diseases caused by changes in genetic material are called genetic diseases.

2. Types: monogenic genetic diseases (genetic diseases controlled by one pair of alleles), polygenic genetic diseases (genetic diseases controlled by two or more pairs of alleles) and chromosomal abnormal genetic diseases.

3. Characteristics: The characteristics of monogenic genetic diseases: the incidence of siblings is higher, and the incidence of population is lower.

Characteristics of polygenic genetic diseases: high incidence rate in the population.

4. Inheritance of common monogenic diseases

Autosomal dominant genetic diseases: polydactyly, syndactyly and achondroplasia.

Autosomal recessive genetic diseases: albinism, congenital deafness, phenylketonuria.

Dominant genetic disease on X chromosome: vitamin D-resistant rickets

Genetic diseases invisible on X chromosome: color blindness and hemophilia.

5. Detection and prevention of human genetic diseases

Relationship between prenatal diagnosis of genetic diseases and eugenics (1)

Prenatal diagnosis: amniotic fluid examination, B-ultrasound examination, maternal blood cell examination and gene diagnosis.

(2) the relationship between genetic counseling and eugenics

Doctors examine clients, understand their family history, diagnose whether they have a certain disease, calculate the recurrence risk rate of future generations by analyzing the genetic mode of genetic diseases, and put forward prevention and control policies and suggestions.

It is forbidden to marry close relatives: direct and collateral blood relatives within three generations. Reason: There is a high probability that close relatives carry the same recessive pathogenic gene.

6. The human genome project and its significance

Determine the whole DNA (22+X+Y) sequence of human genome and explain the genetic information contained in it. The base composition of 24 human chromosomes was determined.

Significance: Through the human genome project, we can understand the related genes of cancer, diabetes, Alzheimer's disease, hypertension and other diseases, and make timely and effective gene diagnosis and treatment for these diseases that are difficult to cure at present.

Nine, biological evolution

(A) the main content of modern biological evolution theory

1, Lamarckian evolution theory-school dropout theory.

Darwin's Theory of Biological Evolution —— Natural Selection Theory

Darwin's theory of natural selection has four aspects: excessive reproduction; Struggle for survival; Genetic variation; survival of the fittest

2. The main content of modern biological evolution theory.

(1) population is the basic unit of biological evolution.

Population: all individuals of the same species living in a certain area are the basic units of biological reproduction.

Gene bank: All genes contained in all individuals of a population are called the gene bank of this population, and the genes contained in each individual are only a part of the gene bank.

Gene frequency: the ratio of one gene to all alleles;

(2) Mutation and gene recombination provide raw materials for biological evolution.

Genetic variation: mutation and gene recombination;

Non-genetic variation: caused by environmental factors.

(3) Natural selection determines the direction of biological evolution.

Under the action of natural selection, the gene frequency of population will change directionally, which will lead to the continuous evolution of organisms in a certain direction.

Note: Mutation and gene recombination are not directional, but natural selection is directional. The essence of biological evolution is the directional change of population gene frequency.

(4) Isolation leads to speciation: Isolation is a necessary condition for speciation.

Species: refers to a group of biological individuals that are distributed in a certain natural area, have certain morphological structure and physiological functions, and can mate with each other in a natural state to produce fertile offspring.

Isolation: refers to the phenomenon that individuals of the same species and different populations cannot communicate freely under natural conditions.

Including: a, geographical isolation: due to geographical obstacles such as mountains, rivers and deserts, it is impossible to meet and mate. (e.g. Northeast Tiger, South China Tiger) B. Reproductive isolation: individuals between populations cannot mate freely or cannot produce fertile offspring after mating.

Judging whether there is reproductive isolation: whether mating can produce fertile offspring, such as the offspring of horses and donkeys, mules are highly sterile, and there is reproductive isolation between horses and donkeys, which are two different species.

Remarks: Three basic links of speciation ① Mutation and gene recombination; ② Natural selection; ③ Isolation

Speciation: Reproductive isolation is a common way of speciation after long-term geographical isolation.

2. The relationship between biological evolution and biodiversity

* * * Co-evolution: Different species, organisms and inorganic environments constantly evolve and develop under the influence of each other, which is * * * Co-evolution.

Biodiversity: genetic diversity; Species diversity; Ecosystem diversity.