Chromosomes. The entire genetic information of an individual is contained in the chromosomes. The nucleus of every cell in the human body contains 46 chromosomes, which can be said to represent the library of hereditary information. These 46 chromosomes consist of 23 pairs, with each set of chromosomes deriving from one parent (mother/father). Chromosomes 1 – 22 are called autosomes and the 23rd chromosome pair is called the sex chromosome (gonosome), since it determines the human sexual characteristics. In women this chromosome pair consists of two X chromosomes whereas men have one X chromosome and one Y chromosome. Apart from the cell nucleus, the mitochondria in the cytoplasm of the cell also possess an albeit negligibly small amount of hereditary information.
Genes, DNA. A single human chromosome is composed of 50 to 250 million building blocks, made of deoxyribonucleic acid (DNA). The DNA consists of two long strands, which are twisted together in a double helix like a spiral staircase. The hand rail or the banister of the staircase is formed by a framework of sugar and phosphate molecules, while the individual steps are each formed by one base pair. Only four different building blocks (nucleotide bases or nucleotides) are involved in the formation of these steps: adenine (A), guanine (G), cytosine (C) and thymine (T). Only the nucleotide bases A and T on the one hand and G and C on the other hand fit together. The bases are complementary – they fit together like a key in a lock (i.e. as base “pairs”). This allows the DNA to reproduce itself with the help of certain enzymes: it splits into two single strands with each strand acting as the template for the reassembly of the missing strand.
The sequence of the bases within the DNA molecule (DNA sequence) contains the entire genetic information or “code” used by a cell in order to perform its functions. So nature utilizes a code with only four different “letters” – A, G, C and T – in order to determine such different traits as hair colour, blood type, etc.
The sequence of nucleotides (of which the base is the key coding component) used by a cell to manufacture an individual protein is called a gene. In the entire human genome it is thought that there are 70,000 – 1000,000 different genes, which thus have the instructions for building every cell, organ and tissue of an individual. This information is contained in about 5% of the total DNA. This leaves 95% of DNA whose function is still unclear. It is believed, however, that these “extra” sections of DNA may govern how genes interact and are controlled.
Messenger ribonucleic acid. For a certain cell (e.g. heart muscle cell, pancreas cell, stem cell in the bone marrow) to perform its predetermined action (pumping action of the heart muscle, insulin secretion of the pancreas, formation of blood cells in the marrow), it must communicate its encoded information outside of the cell nucleus. This means that the information which is coded and stored in genes must be transported in a biologically active form. This process is called gene expression and takes place in several steps. In order to transmit its information out of the cell nucleus to the periphery, the gene first makes use of a messenger. This messenger reads the information from the gene in the cell nucleus, as defined by the sequence of bases. In this way, a complementary nucleic acid chain may be produced using the DNA segment as a template. This newly made chain is called a messenger ribonucleic acid (m-RNA) and this process is called transcription. By using m-RNA as an intermediary, it is ensured that DNA as the source of information is not used up or destroyed.
Transcription is followed by so-called translation. This involves the messenger RNA being transported from the cell nucleus and then serving in the cytoplasm (part of the cell that contains cytosol, but excluding the cell nucleus) as a pattern for a specific amino acid to be incorporated in the protein chain. The genetic information of the m-RNA is transformed into an amino acid in the cell periphery on so-called ribosomes. Here three m-RNA nucleotides are “translated” to produce one amino acid, the primary component of all proteins.
It is known from electron microscope images and biochemical investigations that DNA of a gene and the corresponding m-RNA do not have the same length. What happens is that the m-RNA is further processed before it leaves the cell nucleus, with the DNA sequences which are not needed for protein synthesis stripped away. The DNA sequences responsible for protein synthesis are called coding exons and the RNA sections stripped away before translation are called non-coding introns. So a gene consists not only of information which lays down the composition of proteins but also of controlling and regulating sections.
Proteins and their importance. Of all the organic compounds occurring in living forms, the carbohydrates (sugars) lipids (fats) and proteins are the most important substances. While the fats and carbohydrates mainly perform the function of energy carriers, proteins have a vast array of functions to fulfill. Proteins also form the majority of organic compounds, accounting for about 50% of these. Proteins are often called the building blocks of life since they represent the messengers and tools which are necessary for the processes of life in the organism. As enzymes, they catalyze the metabolic process; as hormones, they control and regulate these processes; as receptors and messenger substances, they transmit the important information to the inside of the cells; as antibodies, they form an essential part of the immune system; as plasma proteins, they transport important nutrients to the blood and as structural proteins, they form building blocks and mechanical supports for all cells, organs, bones and connective tissue.
Proteins consist of amino acids. Their function depends on which amino acids they are formed from and how many. In total, tens of thousands of different proteins are known in humans, with major differences in their function and size. This wide variety of proteins is produced from only 20 different amino acids, which in turn are coded by only four different nucleotides: adenine (A), guanine (G), cytosine (C) and thymine (T). Each of these 20 amino acids needs a combination of only three of the four nucleotides (codon) to determine its identity. This genetic language (genetic code) applies in an identical manner to (almost) all living forms. In this way, a specific sequence of letters in the genes is always translated into the same protein.
adenine (A) – аденин
amino acid – аминокислота
autosome – аутосома, неполовая хромосома
base – основание
cell – клетка
chromosome – хромосома
cytobiology – цитобиология, биология клетки
cytocinesis – цитокинез, клеточное деление
cytology – цитология (учение о клетке)
cytoplasm – цитоплазма
cytosine (C) – цитозин
cytosol – цитозоль
cytosome – цитосома, клеточное тело
deoxyribonucleic acid (DNA) – дезоксирибонуклеиновая кислота (ДНК)
enzyme – фермент, энзим
exon – экзон
expression – экспрессия
gene – ген
genome – геном
gonosome – гоносома, половая хромосома
helix (pl. helices, helixes) – спираль
hereditary – наследственный, передающийся по наследству
intron – интрон
karyon – клеточное ядро
messenger – посредник; информационная РНК, матричная РНК
mitochondrion (pl. mitochondria) – митохондрия
nucleotide – нуклеотид
nucleus (pl. nuclei) – ядро (клетки)
phosphate – фосфат
protein – белок, протеин
ribonucleic acid (RNA) – рибонуклеиновая кислота (РНК)
ribosome – рибосома
sequence – последовательность, порядок следования (нуклеотидов в нуклеиновых кислотах или аминокислот в белках)
strand – нить, цепь (ДНК)
template – матрица
thymine (T) – тимин
tissue – ткань
transcription – считывание биологической информации
translation – трансляция (синтез полипептидной цепи белковой молекулы)
12) deoxyribonucleic acid (DNA)
13) ribonucleic acid (RNA)
17) amino acid
7) половая хромосома
10) ядро (клетки)
12) дезоксирибонуклеиновая кислота
13) рибонуклеиновая кислота
14) считывание биологической информации
16) последовательность, порядок следования
21) нить (цепь) ДНК
1) The “control centre” of a cell surrounded by a membrane and containing the chromosomes
2) chromosomes present in the same number in men and women
3) constituents of the nucleotides
4) a substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction
5) the structures of the cell nucleus containing the hereditary material
6) sequence of three nucleotides (triplet) of DNA or RNA, which is responsible for translation into a specific amino acid
7) a double-stranded giant molecule which stores the genetic information in its nucleotide sequence
8) linear sequence of nucleotide units
9) a basis for inheritance
10) procedures for changing the genetic information
11) utilization of DNA polymorphisms for producing a genotype specific to the individual
12) the entire genetic information of a cell or a living organism
13) cell sequence from the fertilized egg cell to the germ cells (egg or sperm cells) of the new life form
14) sex chromosomes
15) non-coded section of a gene (or m-RNA)
1) tissue structure
2) genome research
3) muscle cell
4) cell differentiation
5) genome analysis
6) sperm cell
7) pancreas cell
8) bone marrow
9) base pair
10) point mutation
11) DNA strand substitution
12) messenger ribonucleic acid
13) heart muscle cell
14) bone marrow cell
15) germ line cell
16) stem cell
17) germ cell
The bases for hereditary diseases are changes in the hereditary substances which are passed on from one generation to the next via the germ line cells. The change in the hereditary substance may take place at chromosome level or in the DNA itself. A distinction is made between monogenic and polygenic diseases. However, it is becoming increasingly apparent that the distinction between monogenic and polygenic diseases is an artificial one. Many of the so-called monogenic diseases are not determined by a single gene but depend in their manifestation on the controlling and regulating influences of other genes. The term multifactorial illnesses refers to disorders which arise as a result of an interaction between heredity and environment that is not fully understood in the majority of cases.
MELBOURNE scientists have broken new ground in supporting the case that genetics more than individual choice play a key role in determining our sense of gender.
A transsexual gene, believed to be responsible for people feeling they were born the wrong sex, has been discovered by the Melbourne team.
The breakthrough supports the view that there is a biological basis to the gender confusion faced by transsexuals, rather than the social stigma attached with theories that gender reassignment is a lifestyle choice.
In the largest genetic study of its kind, 112 male-to-female transsexuals took part in a study involving several Melbourne research bodies and the University of California, Los Angeles.
After studying the DNA of the male-to-female transsexuals, genetic experts from Prince Henry's Institute at the Monash Medical Centre found they were more likely to have a longer version of a gene known to modify the action of sex hormone testosterone.
The genetic abnormality on the androgen receptor gene is believed to lower testosterone action during fetal development, and "under-masculinise" the person's brain, leading them to feel like a female trapped in a male body.
Lead researcher Associate Prof Vincent Harley, head of molecular genetics at Prince Henry's, said the findings dismissed decades of debate that physiological factors such as childhood trauma were responsible for people's belief they should be the opposite sex.
"There is a social stigma that transsexualism is simply a lifestyle choice. However, our findings support a biological basis of how gender identity develops," he said.
Other recent studies have indicated family history and genetics are involved in gender identity, a view supported by Monash Gender Dysphoria Clinic director Dr Trudy Kennedy.
"People who come to our clinic describe how they knew they were different at a very early age; just three or four years old when they were at kindergarten," Dr Kennedy said.
"This is something that people are born with, and it's certainly not a lifestyle choice, as some have suggested."
Publishing their results today in the Biological Psychiatry journal, the researchers call for expanded genetic studies to investigate a wider range of genes, which may also play a part in gender identity.
"It is possible that a decrease in testosterone levels in the brain during development might result in incomplete masculinisation of the brain in male-to-female transsexuals, resulting in a more feminised brain and a female gender identity," they wrote.
Julie Peters, a transgender person, said she knew from as young as three that she did not fit into being a boy.
"I have always had the personality of a girl. I suppose is the way I perceive it, and even from a very young age, three or four, I was really mad at people for making me a boy," she said.
"I personally think it (gender) is a combination of both (nature and nurture). You are born with a predisposition to have a certain personality, and then depending on the culture you are brought up in your personal situation."
The study research was jointly funded by the National Health and Medical Research Council and the US National Institutes of Health.
Reproduction of DNA (replication). Most cells have to divide all the time. They have a limited lifespan. In order to maintain their function, they must pass on the hereditary information stored in their nuclei to daughter cells. The DNA strands therefore have to be copied. For this, the DNA double strands have to divide into single strands and a complementary strand is then produced (DNA replication). In this way the genome duplicates itself. Then the sets of chromosomes move to opposite cell poles and the cell divides. In this way, the sell has propagated itself. This process happens a million times every second in the human organism and ensures that the human body renews (regenerates) itself. In old age, the production rate of new cells no longer keeps up with the dying rate of old cells. This leads to atrophy and dying processes.
Importance of mutations. For perfect functioning of the human organism, stability and constancy of the genetic information is essential. On the other hand, such a complex process as the transfer of genetic information is very susceptible to error. If the hereditary information is altered in any way, this can have far-reaching consequences. Such alterations are called mutations. A mutation can occur spontaneously during the coping of the DNA (faulty replication) or through the external influence damaging the cell. Examples of external influences (mutagens) which can damage the hereditary information are chemicals, radiation and viruses. Sometimes mutations lead to an exchange of only a single DNA base (nucleotide). Such a mutation is called a point mutation. Other kinds of mutation are the deletion and the addition of several nucleotide sequences. These lead to a change in the original nucleotide sequence with the likelihood that proteins will be improperly produced either quantitatively or qualitatively. This in its turn may have consequences with regard to the functions of the cell and the organism. Of course, mutations can affect the chromosomes as a whole, so that, for example, the number of chromosomes is increased or chromosome sections are deleted.
Mutations can occur in all types of cell; in a muscle cell, an intestinal cell or in a bone cell. Such mutations (somatic mutations; mutations of body cells) remain restricted to the corresponding body tissue of the individual and are not passed on to future progeny. On the other hand, if mutations occur in the germ line cells, these changes may be passed on to the next generation.
This distinction shows that genetic changes do not always have to be inherited. It is much more likely that during the innumerable cell divisions which take place in the organism during the course of human life, somatic mutations will occur time and time again which may cause or contribute to an illness. This is the case, for example, in the majority of cancers. A genetic disease is, therefore, not necessarily an inherited disease. On the other hand, mutations in the germ line cells can cause inherited genetic illnesses to develop. Such a mutation may have happened several thousands of years ago and has since then been passed down from one generation to the next within certain families according to certain rules of inheritance.
Not every nucleotide sequence departing from the norm within a gene (mutation) leads to illness. Our genes with their innumerable mutations, exhibit a broad span of variation which gives every individual life form its own unique identity. In medicine this fact is used not only to provide evidence of current or future diseases. Genome analysis can also be used to identify persons (e.g. as part of a paternity test) by means of a process called genetic fingerprinting (DNA fingerprinting). DNA can also be recovered from the remains of the deceased even after long periods of time. For example, after a plane crash, DNA analysis enables casualties to be identified. Historical research also makes use of genome analysis.
Active and inactive genes. Human life starts when an egg cell is fertilized by a sperm cell. Each cell contributes half a set of its hereditary material. So 23 maternal chromosomes and 23 paternal chromosomes meet in a fertilized cell. This fertilized cell (zygote) doubles its set of chromosomes before its division and so then passes on the genetic information (the genome) to two daughter cells, which in their turn divide into four cells and so on until after 9 months a child is born with all its organs fully developed. Continuous cell division associated with DNA replication guarantees that the original genetic information in the starting cell is passed on to all other cells. And yet during the embryo phase, cells emerge which have to perform very different tasks and also “know” that they have to carry out different functions (cell differentiations). But why does a muscle cell look quite different and have a function different from say an intestinal cell although they both have the same hereditary material in their nucleus? In every cell only a fraction of the entire genome is active. A large number of regulatory and control sections determine what part of the cell genome is inactivated at what time and what part actively synthesizes proteins and so also forms certain tissue structures. This is a highly complex process which is only beginning to be understood in the still relatively young branch of genome research.
allele – аллель
atrophy – атрофия, ослабление (органа, ткани), истощение
chromatin – хроматин
diploid – диплоид ( с двойным числом хромосом)
DNA fingerprinting – анализ ДНК
dying rate – скорость отмирания
egg cell – яйцеклетка
gamete – гамета, половая клетка
genome analysis – исследование генома
haploid – гаплоид
histone – гистон (низкомолекулярный белок, связанный с ДНК)
inherited disease – наследственная болезнь
life form – форма жизни, живой организм
mutagen, mutagene – мутаген
mutation – мутация
onset – вспышка, проявление (болезни), начало, наступление
ovum (pl. ova) – яйцо, женская зародышевая клетка
paternity test – тест на установление отцовства
point mutation – точечная мутация
progeny – потомство
propagate – размножаться, репродуцировать
replication – репликация, ауторепродукция
somatic mutation – соматическая мутация
sperm cell – сперматозоид
zygote – зигота, оплодотворенная яйцеклетка
4) dying rate
8) inherited disease
9) life form
10) paternity test
11) genome analysis
12) egg cell
1) воспроизведение, репродукция
3) размножаться, репродуцировать
4) скорость отмирания
5) атрофия, ослабление (органа, ткани), истощение
9) форма жизни, живой организм
10) тест на установление отцовства
11) исследование генома
13) нить (цепь) ДНК
16) репликация, ауторепродукция
20) наследственная болезнь
1) chromosomes present in the same number in men and women
2) constituents of the nucleotides
3) material from which the chromosomes are made: DNA, proteins (histones and non-histone proteins)
4) different alternative forms of the same gene
5) procedures for changing the genetic information
6) utilization of DNA polymorphisms for producing a genotype specific to the individual
7) the changing of the structure or a gene, resulting in a variant form that may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes
8) the process by which genetic material gives rise to a copy of itself
9) a fertilized ovum
10) a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote
1) production rate
2) point mutation
3) DNA double strand
4) DNA replication
5) opposite cell poles
6) nucleotide sequence
7) body tissue
8) germ cell
9) cell division
10) genome analysis (research)
11) cell differentiation
12) tissue structure
13) sickle cell
14) sickle cell disease
15) sperm cell
16) nucleotide base
17) germ line cell
18) template strand
Многие факторы (от солнечного излучения до экологической обстановки и нормальных метаболических процессов, протекающих в клетке) могут повреждать ДНК изо дня в день. В результате возникновения данных повреждений могут образовываться атипичные белковые молекулы, которые способны резко повышать вероятность возникновения новообразований.
Для того чтобы защититься от развития новообразований, поврежденная ДНК запускает в клетке сложную последовательность цепных реакций. В результате протекания данных реакций происходит замедление различных процессов или их остановка. Таким образом, клетка как бы начинает ждать, когда великое множество молекул начнет работать над поврежденной ДНК.
Идентификация белков, имеющих ключевое значение для восстановления поврежденной ДНК, может помочь в поиске новых лекарственных мишеней. И путем использования препаратов, работающих через такие мишени, возможно, получится минимизировать побочные эффекты, которые имеют место в тех случаях, когда лекарственное соединение обладает слишком широким спектром действия в организме.
It is thought that about 5% of all newborn babies come into the world with an inherited disorder. About 0.5% have a clinically relevant chromosome anomaly and about 1% have a monogenic inherited disorder. The remainder of disorders are multifactorial or due to external factors. Among those who die before their 65th year, inherited disorders are still the fifth most frequent cause of death. Most death result from inherited heart disorders followed by anomalies of the central nervous system (brain, spinal cord) as well as urogenital anomalies (urinary and reproductive organs) and gastrointestinal anomalies (digestive organs).