Each protein is represented by one or more polypeptide chains. A section of DNA that carries information about one polypeptide chain is called a gene. Each DNA molecule contains many different genes. The totality of DNA molecules in a cell acts as a carrier of genetic information. Thanks to a unique property - the ability to duplicate, which no other known molecule has, DNA can be copied. When dividing, “copies” of DNA are dispersed into two daughter cells, each of which will therefore have the same information that was contained in the mother cell. Since genes are sections of DNA molecules, two cells formed during division have the same sets of genes. During sexual reproduction, each cell of a multicellular organism arises from a single fertilized egg as a result of multiple divisions. This means that a random error in the gene of one cell will be reproduced in the genes of millions of its descendants. This is why all the red blood cells of a patient with sickle cell anemia have equally degraded hemoglobin. The error occurred in the gene that carries information about the beta chain of the protein. A copy of the gene is mRNA. According to it, like a matrix, the wrong protein is “printed” thousands of times in each red blood cell. Children receive damaged genes from their parents through their reproductive cells. Genetic information is transmitted both from one cell to daughter cells and from parents to children. A gene is a unit of genetic, or hereditary, information.
Lesson on general biology.
Topic: “DNA is a carrier of hereditary information.
Genetic code".
The purpose of the lesson : consolidate knowledge about the structure of DNA and RNA, study the concept of a gene, genetic code, its properties.
Equipment: table “Structure of an animal cell”, “Proteins”, DNA model, multimedia installation,Power Point presentation.
During the classes
1. Org. moment……………………………………………………………………1-2 min.
2. Main part: …………………………………………………………….... 30 min.
2.1 Repetition of previously learned: ………………………………………….…. 12 min
2.2 Studying new material: …………………………….………………18 min
3. Fastening ……………………………………………………………………………….8 min
2.1. Repetition of previously learned
Questions for students:
- What are proteins?
- What are the monomers of all natural proteins? (20 amino acids).
- Remember what functions proteins perform? (Name the structural features of nucleic acids)
- Remember where DNA molecules are found in plant and animal cells?
- What is complementarity?
- Name the types of RNA.
2.2. Learning new material
All properties of any organism are determined by its protein composition. Moreover, the structure of each protein is determined by the sequence of amino acid residues. Consequently, as a result, hereditary information that is passed on from generation to generation must contain information about the primary structure of proteins.
Genetic information– this is information about the structure of all proteins in the body contained in DNA molecules.
Gene is a section of a DNA molecule that encodes the primary structure of one polypeptide chain. DNA contains information about the primary structure of the protein.
Genetic code– a set of combinations of three nucleotides encoding 20 types of amino acids that make up proteins.
Properties of the genetic code:
- The code is triplet. Each AK (amino acid) corresponds to a section of a DNA chain, and, accordingly, an mRNA of three adjacent nucleotides. Currently, the genetic code has been completely deciphered and a map has been drawn up, that is, it is known which triplets correspond to one or another amino acid out of the 20 that make up proteins.
- The code is clear. Each codon encrypts only one AK.
- The code is redundant (specific). This means that each AK is encrypted by more than one codon (with the exception of methionine and tryptophan). DNA consists of 4 different types nucleotides, and the smallest structural unit of a gene is a triplet of nucleotides. Therefore, the number of possible combinations is 43 = 64. There are only 20 different amino acids. Thus, there are more than enough different nucleotide triplets to encode all the amino acids.
- The code does not overlap. Any nucleotide can be part of only one triplet.
- There are “punctuation marks” between genes. Of the 64 triplets, U-A-A, U-A-G, U-G-A do not encode AK (consider the genetic code table in the textbook). These triplets are signals for the end of polypeptide chain synthesis. The need for these triplets is explained by the fact that in some cases, several polypeptide chains are synthesized on mRNA, and these triplets are used to separate them from each other.
- The code is universal. The genetic code is the same for all living organisms living on Earth.
3. Fastening:
Doing exercises in the workbook. (Workbook to the textbooks of Zakharov V.B., Sukhova T.S. and etc.)
Homework.§ 2.10 p. 73–75, textbook by V. B. Zakharova, S. G. Mamontov, N. I. Sonina, E. T. Zakharova, grade 10 “Biology. General biology", lesson notes.
Preview:
To use presentation previews, create a Google account and log in to it: https://accounts.google.com
Slide captions:
Topic: “DNA is a carrier of hereditary information. Genetic code"
Structural Catalytic (B-enzymes) Regulatory (B-hormones) Contractile Transport Protective Spare Energy F U N C C I I B E L K A
Structure of RNA RNA ________________________________ DNA Nitrogenous base (A, G, C, U) FA residue Carbohydrate - ribose Nitrogenous base (A, G, C, T) Carbohydrate - deoxyribose FA residue
In the chromosomes of the nucleus
Complementarity - spatial complementarity of molecules or their parts, leading to the formation hydrogen bonds. Complementary structures fit together like a “key and lock” (A+T)+(G+C)=100%
Genetic information is information about the structure of all proteins of the body contained in DNA molecules 1 gene = 1 protein molecule
Types of RNA There are several types of RNA in a cell. All of them are involved in protein synthesis. Transfer RNAs (tRNAs) are the smallest RNAs. They bind AAs and transport them to the site of protein synthesis. Messenger RNA (i-RNA) - they are 10 times larger than tRNA. Their function is to transfer information about the structure of the protein from DNA to the site of protein synthesis. Ribosomal RNA (r-RNA) - have the largest molecular size and are part of ribosomes.
A gene is a section of a DNA molecule that encodes the primary structure of one polypeptide chain. A genetic code is a set of combinations of three nucleotides that encode 20 types of amino acids that make up proteins.
One amino acid is encoded by three nucleotides (one codon). ACC AGC GAT Triplet, codon gene AK1 AK2 AK3 protein Properties of the genetic code: The code is triplet. Each AK corresponds to a section of a DNA chain, and, accordingly, an mRNA of three adjacent nucleotides.
The code is clear. Each codon encrypts only one AK. The code is redundant. This means that each AK is encrypted by more than one codon (with the exception of methionine and tryptophan). The code is non-overlapping. Any nucleotide can be part of only one triplet. There are “punctuation marks” (polarity) between genes. Of the 64 triplets –U-A-A, U-A-G, U-G-A do not encode AK. The code is universal. The genetic code is the same for all living organisms living on Earth.
Homework Lesson notes Prepare a message: “Genetic code.”
Problem solving 1) Using the DNA genetic code table, determine which AKs are encoded by triplets: TsAT, TTT, GAT. 2) Using the genetic code table, draw a section of DNA that encodes information about the following sequence of amino acids in a protein: - alanine - arginine - valine - glycine - lysine.
Determining the possibility of developing a particular trait
of a cell or organism is a GENE.
When genes are passed on over a series of generations,
inheritance of parental traits by offspring.
The main property of the gene as a functional unit
material of heredity and variability, is its
chemical organization.
When forming features it is required
synthesis of many substances, firstly
sequence of proteins with specific
properties.
Property
protein
molecule is determined by amino acid
sequence
her
peptide
chains,
which
is given
sequence of DNA nucleotides.
Nucleic acids - DNA and RNA
Nucleic acids DNA and RNAThere are two types of nucleic acids
Deoxyribonucleicacid (DNA), included
which contains the carbohydrate deoxyribose
Ribonucleic
acid (RNA), included
which contains the carbohydrate ribose. DNA is the largest molecule in a cell.
It is much larger than proteins and RNA
Each chromosome = one DNA molecule
23 human chromosomes = 23 DNA molecules
The longest of them are ≈ 8 cm
DNA is a text molecule. IN
its nucleotide sequences
the entire hereditary program is recorded
body
Location of DNA in a cell
CoreMitochondria
Plastids
Core
Chloroplast
Mitochondria 1 DNA molecule
gene
another gene
chromosome
chromosomes in
core
DNA
cell
Functions of DNA
Storagegenetic
information
Broadcast
genetic
information from
parents
posterity
Implementation
genetic
information in
process
vitally active
sti cells and
body
Consolidation
History of discovery
1. 1869 Friedrich Miescherdiscovered NK and gave them
name (“nucleus” core).
2. 1905 Edwin Chargaff
studied nucleotide
composition of NK.
3. 1950 Rosalind
Franklin established
double-stranded DNA.
Edwin
Chargaff
Rosalind
Franklin X-ray diffraction
DNA portrait –
famous photo 51
Rosalind Franklin
1920 - 1958http://www.bbc.co.uk/bbcfour/documentaries/features/rosalind- 1953
Open
structure
DNA
date
birth
molecular
biology
James
Watson
Francis
Scream James Dewey
Watson
Francis Harry Compton
Crick
DNA molecules can be seen through an electron microscope
DNA of bacterial plasmids Reovirus DNAscanning electric microscope DNA isolated
from one chromosome
person
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/Laemmli
DNA is a polymer molecule consisting of 2 complementary polynucleotide chains connected by hydrogen bonds, they have large
DNA molecule structureDNA is a polymer
molecule consisting of 2
complimentary
polynucleotide chains
connected
hydrogen
connections,
are large in size and
huge molecular
mass.
Structure of the DNA molecule
Nucleotide chainsform
right-handed
volumetric spirals of 10 pairs
bases in each turn
Chains are twisting around
each other and around
common axis and form
double helix
The circuits are antiparallel or
multidirectional.
Subsequence
nucleotide compounds
one circuit
opposite to that in
another
Schematic structure of DNA
Nucleotides:1. Located away from each other
friend at a distance
0.34nm
2. Mass of one
nucleotide is 345.
3. Helix width 2nm
4. These values
permanent Principles of DNA structure
5"
3"
A
G
G
T
C
A
A
C
5"
Irregularity
T
C
C
A
Double-stranded
Complementarity
Antiparallelism
G
T
T
G
3"
DNA structure
DNA is a polymer.Monomers are nucleotides.
Nucleotide - chemical compound
residues of three substances:
Nucleotide structure
Nitrogenous
grounds:
- Adenine;
- Guanine;
- Cytazine
- Timin
Carbohydrate:
- Deoxyribose
Phosphorus residue
acids (FA) Nucleotide
5’
1’
phosphate
Nitrogenous
base –
one of 4
3’
Sugar (ribose/deoxyribose)
Schemes of the structure of nitrogenous bases.
DNA containsfollowing
nitrogenous
grounds:
Purine
1. Adenine,
2. Guanine
Pyrimidine
3. Timin
4. Cytazine
Connections between nucleotides in one DNA strand
Are being carried outthrough education
phosphoester
connections between
deoxyribose one
nucleotide and residue
phosphoric acid
another nucleotide
Links between strands in a DNA molecule
Implementedwith help
hydrogen bonds,
emerging
between
nitrogenous
reasons
inbox
V
compound
different circuits
1950 Chargaff Rules
Erwin ChargaffChargaff's rules were explained by Watson and Crick
DNA is 2 strands connectedaccording to principle
complementarity
Complementarity
ComplementarityThis
principle of mutual
paired nucleotide matches or ability
nucleotides combine in pairs
Chargaff rules
[A] + [G] = [T] + [C] = 50% Principlecomplementarity:
A
-- -- --
T
G
-- -- ----
C
More durable
Weak
hydrogen
connections!
Principle of complementarity
Property of "replication"
DNA replication iscopying process
deoxyribonucleic acid
acid, which
happens in the process
cell division.
At the same time, genetic
material encrypted
in DNA, doubles and
divided between subsidiaries
cells.
DNA replication
Intime
replication
Part
molecules
"maternal" DNA unwinds into two strands with
using a special enzyme, and this
achieved by breaking hydrogen bonds between
complementary nitrogenous bases:
adenine-thymine and guanine-cytosine.
Further to each nucleotide of the diverged threads
DNA enzyme DNA polymerase adjusts
its complementary nucleotide.
Property of "replication"
Genetic code
Hereditary information is recorded inNA molecules in the form of a sequence
nucleotides.
Certain
plots
DNA and RNA molecules (in viruses and phages)
contain information about the primary structure
one protein and are called genes.
1 gene = 1 protein molecule
That's why
hereditary
information,
which
contain
DNA
called
genetic.
Properties of the genetic code:
VersatilityDiscreteness
(code
triplets
read from the entire RNA molecule)
Specificity (codon encodes only AK)
Code redundancy (somewhat)
Property of "reparation"
Reparation is the ability of a DNA moleculecorrect those occurring in its circuits
changes.
In restoring the original DNA structure
At least 20 proteins are involved:
1. Recognize altered DNA sections;
2. Remove them from the circuit;
3. Restore the correct
nucleotide sequence;
4. Sew the restored fragment with
the rest of the DNA molecule
Bibliography
Zakharov V.B. and others. “General Biology”Ruvinsky A.O. Moscow “Enlightenment”
1993 “General Biology”
“Biology in tables and diagrams”,
“Bustard” 2005
Internet: Google
1) mRNA 2) t-RNA 3) DNA 4) chromosome
A2. During their reproduction, the daughter cells of human skin receive from the mother cell:
complete genetic information
half the information
a quarter of the information
there is no right answer
A3. DNA replication is accompanied by the breaking of chemical bonds:
peptide, between amino acids
covalent, between carbohydrate and phosphate
hydrogen, between nitrogenous bases
ionic, within the structure of a molecule
A4. When a DNA molecule is replicated, it produces:
a thread that has broken up into separate fragments of daughter molecules
molecule made up of two new strands of DNA
molecule, half of which consists of a strand of mRNA
daughter molecule consisting of one old and one new strand of DNA
A5. Transcription is the process of:
1) DNA replication
2) synthesis of mRNA
3) protein synthesis
4) joining tRNA to amino acid
A6. If an amino acid is encoded by the UGG codon, then in DNA it corresponds to a triplet:
TCC 2) AGG 3) UCC 4) ACC
A7. One triplet of DNA carries information about:
Amino acid sequences in a protein molecule
The location of a specific amino acid in a protein chain
Sign of a specific organism
An amino acid included in a protein chain
A8. The number of tRNAs involved in translation is equal to the number of:
mRNA codons that encode amino acids
mRNA molecules
Genes included in a DNA molecule
Proteins synthesized on ribosomes
A9. The period of a cell's life from division to division is called:
Interphase 3) meiosis
Mitosis 4) cell cycle
A10. How many chromatids are contained in the 8 chromosomes visible in metaphase of mitosis:
1) 6 2) 8 3) 12 4) 16
A11. The number of chromosomes in human somatic cells after mitosis is:
1) 23 2) 46 3) 92 4) 44
Genetic information is encoded in DNA. The genetic code was elucidated by M. Nirenberg and H.G. the Koran, for which they were awarded the Nobel Prize in 1968.
Genetic code- a system for the arrangement of nucleotides in nucleic acid molecules that controls the sequence of amino acids in the polypeptide molecule.
Basic tenets of the code:
1) The genetic code is triplet. The mRNA triplet is called a codon. A codon encodes one amino acid.
2) The genetic code is degenerate. One amino acid is encrypted by more than one codon (from 2 to 6). The exceptions are methionine and tryptophan (AUG, GUG). In codons for one amino acid, the first two nucleotides are most often the same, but the third varies.
3) Codons do not overlap. The nucleotide sequence is read in one direction in a row, triplet by triplet.
4) The code is unambiguous. A codon codes for a specific amino acid.
5) AUG is the start codon.
6) There are no punctuation marks inside the gene - stop codons: UAG, UAA, UGA.
7) The genetic code is universal, it is the same for all organisms and viruses.
The discovery of the structure of DNA, the material carrier of heredity, contributed to the solution of many issues: gene reproduction, the nature of mutations, protein biosynthesis, etc.
The mechanism of genetic code transmission contributed to the development molecular biology, as well as genetic engineering, gene therapy.
DNA is located in the nucleus and is part of chromatin, as well as mitochondria, centrosomes, plastids, and RNA is in the nucleoli, cytoplasmic matrix, and ribosomes.
The carrier of hereditary information in the cell is DNA, and RNA serves to transmit and implement genetic information in pro- and eukaryotes. With the help of mRNA, the process of translating the sequence of DNA nucleotides into a polypeptide occurs.
In some organisms, in addition to DNA, RNA can be the carrier of hereditary information, for example, in tobacco mosaic viruses, polio, and AIDS.
The monomers of nucleic acids are nucleotides. It has been established that in the chromosomes of eukaryotes, a giant double-stranded DNA molecule is formed by 4 types of nucleotides: adenyl, guanyl, thymidyl, cytosyl. Each nucleotide consists of a nitrogenous base (purine G + A or pyrimidine C + T), deoxyribose and a phosphoric acid residue.
Analyzing DNA of different origins, Chargaff formulated patterns of the quantitative ratio of nitrogenous bases - Chargaff's rules.
a) the amount of adenine is equal to the amount of thymine (A=T);
b) the amount of guanine is equal to the amount of cytosine (G=C);
c) the number of purines is equal to the number of pyrimidines (G+A = C+T);
d) the number of bases with 6-amino groups is equal to the number of bases with 6-keto groups (A+C = G+T).
At the same time, the ratio of bases A+T\G+C is a strictly species-specific coefficient (for humans - 0.66; mice - 0.81; bacteria - 0.41).
In 1953, a biologist J.Watson and physicist F.Crick a spatial molecular model of DNA was proposed.
The main postulates of the model are as follows:
1. Each DNA molecule consists of two long antiparallel polynucleotide chains forming a double helix twisted around a central axis (right-handed - B-form, left-handed - Z-form, discovered by A. Rich in the late 70s).
2. Each nucleoside (pentose + nitrogenous base) is located in a plane perpendicular to the helix axis.
3. Two polynucleotide chains are held together by hydrogen bonds formed between nitrogenous bases.
4. Pairing of nitrogenous bases is strictly specific; purine bases combine only with pyrimidine bases: A-T, G-C.
5. The sequence of the bases of one chain can vary significantly, but the nitrogenous bases of the other chain must be strictly complementary to them.
Polynucleotide chains are formed by covalent bonds between adjacent nucleotides through a phosphoric acid residue that connects the carbon in the fifth position of the sugar to the third carbon of the adjacent nucleotide. The chains have a direction: the beginning of the chain is 3 "OH - in the third position of the deoxyribose carbon a hydroxyl group OH is attached, the end of the chain is 5" F, a phosphoric acid residue is attached to the fifth carbon of deoxyribose.
The autosynthetic function of DNA is replication - autoreproduction. Replication is based on the principles of semi-conservatism, anti-parallelism, complementarity and discontinuity. The hereditary information of DNA is realized as a result of replication according to the type of template synthesis. It occurs in stages: binding, initiation, elongation, termination. The process is confined to the S-period of interphase. The enzyme DNA polymerase uses single-stranded DNA as a template and, in the presence of 4 nucleotides, a primer (RNA) builds a second DNA strand.
DNA synthesis is carried out according to the principle of complementarity. Phosphodiester bonds are formed between the nucleotides of the DNA chain due to the connections of the 3 "OH group of the very last nucleotide with the 5 "-phosphate of the next nucleotide, which must join the chain.
There are three main types of DNA replication: conservative, semi-conservative, dispersed.
Conservative - preservation of the integrity of the original double-chain molecule and synthesis of the daughter double-chain molecule. Half of the daughter molecules are built entirely from new material, and half are built entirely from the old parent material.
Semi-conservative – DNA synthesis begins with the attachment of the helicase enzyme to the origin of replication, which unwinds sections of DNA. DNA binding protein (DBP) is attached to each of the chains, preventing their connection. The unit of replication is the replicon - this is the region between two points at which the synthesis of daughter chains begins. The interaction of enzymes with the origin of replication is called initiation. This point moves along the chain (3 "OH → 5" F) and a replication fork is formed.
The synthesis of a new chain occurs intermittently with the formation of fragments 700-800-2000 nucleotide residues long. There is a start and end point for replication. The replicon moves along the DNA molecule and its new sections unwind. Each of the mother chains is a template for the daughter chain, which is synthesized according to the principle of complementarity. As a result of successive connections of nucleotides, the DNA chain is lengthened (elongation stage) with the help of the enzyme DNA ligase. Upon reaching required length molecule synthesis stops - termination. In eukaryotes, thousands of replication forks operate at once. In prokaryotes, initiation occurs at one point in the DNA ring, with two replication forks moving in 2 directions. At the point where they meet, the two-stranded DNA molecules are separated.
Dispersed - the breakdown of DNA into nucleotide fragments, the new double-stranded DNA consists of spontaneously assembled new and parent fragments.
Eukaryotic DNA is similar in structure to prokaryotic DNA. The differences relate to: the amount of DNA by gene, the length of the DNA molecule, the order of alternation of nucleotide sequences, the shape of the fold (in eukaryotes it is linear, in prokaryotes it is circular).
Eukaryotes are characterized by DNA redundancy: the amount of DNA involved in coding is only 2%. Some of the excess DNA is represented by identical sets of nucleotides repeated many times (repeats). There are multiple and moderately repeating sequences. They form constitutive heterochromatin (structural). It is embedded between unique sequences. Redundant genes have 10 4 copies.
Metaphase chromosome (coiled chromatin) consists of two chromatids. The shape is determined by the presence of a primary constriction - the centromere. It divides the chromosome into 2 arms.
The location of the centromere determines the main shapes of chromosomes:
Metacentric,
Submetacentric,
Acrocentric,
Telocentric.
The degree of chromosome spiralization is not the same. Regions of chromosomes with weak spiralization are called euchromatic. This is an area of high metabolic activity where DNA is composed of unique sequences. Zone with strong spiralization - heterochromatic region capable of transcription. Distinguish constitutive heterochromatin - genetic inert, does not contain genes, does not transform into euchromatin, and also optional, which can transform into active euchromatin. The terminal sections of the distal sections of chromosomes are called telomeres.
Chromosomes are divided into autosomes (somatic cells) and heterochromosomes (germ cells).
At the suggestion of Levitsky (1924), the diploid set of somatic chromosomes of a cell was called karyotype. It is characterized by the number, shape, and size of chromosomes. To describe the chromosomes of the karyotype according to the proposal of S.G. Navashina they are arranged in the form idiograms - systematic karyotype. In 1960, the Denver International Chromosome Classification was proposed, where chromosomes are classified according to the size and location of the centromere. In the karyotype of a human somatic cell, there are 22 pairs of autosomes and a pair of sex chromosomes. The set of chromosomes in somatic cells is called diploid, and in germ cells - haploid (it is equal to half the set of autosomes). In the human karyotype idiogram, chromosomes are divided into 7 groups, depending on their size and shape.
1 - 1-3 large metacentric.
2 - 4-5 large submetacentric.
3 - 6-12 and X chromosome are average metacentric.
4 - 13-15 average acrocentric.
5 - 16-18 relatively small meta-submetacentric.
6 - 19-20 small metacentric.
7 - 21-22 and the Y chromosome are the smallest acrocentric.
According to Paris classification chromosomes are divided into groups according to their size and shape, as well as linear differentiation.
Chromosomes have the following properties (chromosome rules):
1. Individualities - differences between non-homologous chromosomes.
2. Pairs.
3. Constancy of number - characteristic of each type.
4. Continuity - ability to reproduce.