The nucleus is a small egg-shaped structure inside the cell which acts like the brain of the cell. It tells every part of the cell what to do. But, how does the nucleus know so much? It contains our chromosomes and genes. As tiny as it is, the nucleus has more information in it than the biggest dictionary you've ever seen. In humans, a cell nucleus contains 46 individual chromosomes or 23 pairs of chromosomes chromosomes come in pairs, remember?
Half of these chromosomes come from one parent and half come from the other parent. Under the microscope, we can see that chromosomes come in different lengths and striping patterns. When they are lined up by size and similar striping pattern, the first twenty two of the pairs these are called autosomes; the final pair of chromosomes are called sex chromosomes, X and Y.
The sex chromosomes determine whether you're a boy or a girl: females have two X chromosomes while males have one X and one Y. But not every living thing has 46 chromosomes inside of its cells. For instance, a fruit fly cell only has four chromosomes! Each gene has a special job to do. The DNA in a gene spells out specific instructions—much like in a cookbook recipe — for making proteins say: PRO-teens in the cell. Proteins are the building blocks for everything in your body.
Bones and teeth, hair and earlobes, muscles and blood, are all made up of proteins. Those proteins help our bodies grow, work properly, and stay healthy. Scientists today estimate that each gene in the body may make as many as 10 different proteins.
That's more than , proteins! Like chromosomes, genes also come in pairs. Each of your parents has two copies of each of their genes, and each parent passes along just one copy to make up the genes you have. Genes that are passed on to you determine many of your traits, such as your hair color and skin color. Maybe Emma's mother has one gene for brown hair and one for red hair, and she passed the red hair gene on to Emma. If her father has two genes for red hair, that could explain her red hair.
For example if your mum has brown-eye and blue-eye genes she could pass the blue ones on to you and the brown ones on to your sibling. How do genes affect your health? Your genes are the instruction manual that makes your body work. Sometimes, one or a few bases of the DNA in a gene can vary between people. This is called a variant. A variant means the gene has slightly different instructions to the usual version. Occasionally, this may causes the gene to give cells different instructions for making a protein, so the protein works differently.
Luckily most gene variants have no effect on health. But a few variants do affects proteins that do really important things in your body, and then you can become ill. Play our Gene Finder game to see if you can spot the variant genes. Geneti c conditions: Genetic conditions are diseases you develop when you inherit a variant in a gene from your parents. As a result genetic conditions usually run in families. Scientists have identified over 10, genetic conditions. One genetic condition is called sickle cell anemia.
People with this illness have a variant in the genes that contain instructions to make haemolglobin proteins. Hemoglobin helps your red blood cells carry oxygen around your body. These sickle cell haemoglobin genes cause red blood cells to be the wrong shape, making it hard for them to carry oxygen around the body. Not all gene variants cause a genetic condition.
Many variants seem to have no effects at all, others may increase your risk of developing a disease. Rarely, there are women who are particularly at risk of developing breast cancer, because they carry some gene variants.
This can save lives. How does your environment affect you? Your characteristics are affected by your environment as well as your genes. For example you may inherit genes from your parents that should make you tall, but if you have a poor diet growing up your growth could be stunted. To try and understand how much effect your environment can have on you, scientists study identical twins.
Identical twins have the same genes, so any differences in personality, health and ability are caused by differences in their environment.
Play Troublesome Twin to discover just how much how much your environment can affect you. Why do scientists study genes? Scientists have made huge breakthroughs in genetic research over the last few years, learning more and more about our genes and how they make our bodies work.
Scientists examine our genes to work out family relationships, trace our ancestors, and find genes involved in illnesses. This gives them the tools to come up with better ways to keep us healthy. A big breakthrough in genetic research came in , with the results of the Human Genome Project. What was the Human Genome Project? The Human Genome Project was an international research study to try and understand our entire genetic code — the complete instruction manual for how our bodies work.
Thousands of scientists all over the world worked for over ten years to read every instruction inside every gene of a group of volunteers and put together a picture of the average human genome. Natural selection refers to the concept that mutations that impair survival in a given environment are less likely to be passed on to offspring and thus become less common in the population , whereas mutations that improve survival progressively become more common.
Thus, beneficial mutations, although initially rare, eventually become common. The slow changes that occur over time caused by mutations and natural selection in an interbreeding population collectively are called evolution. Not all gene abnormalities are harmful. For example, the gene that causes sickle cell disease also provides protection against malaria. A chromosome is made of a very long strand of DNA and contains many genes Genes Genes are segments of deoxyribonucleic acid DNA that contain the code for a specific protein that functions in one or more types of cells in the body.
The genes on each chromosome are arranged in a particular sequence, and each gene has a particular location on the chromosome called its locus. In addition to DNA, chromosomes contain other chemical components that influence gene function. Except for certain cells for example, sperm and egg cells or red blood cells , the nucleus of every normal human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes.
Normally, each pair consists of one chromosome from the mother and one from the father. There are 22 pairs of nonsex autosomal chromosomes and one pair of sex chromosomes. Paired nonsex chromosomes are, for practical purposes, identical in size, shape, and position and number of genes. Because each member of a pair of nonsex chromosomes contains one of each corresponding gene, there is in a sense a backup for the genes on those chromosomes.
The pair of sex chromosomes determines whether a fetus becomes male or female. Males have one X and one Y chromosome. Females have two X chromosomes, one from the mother and one from the father. In certain ways, sex chromosomes function differently than nonsex chromosomes. The smaller Y chromosome carries the genes that determine male sex as well as a few other genes. The X chromosome contains many more genes than the Y chromosome, many of which have functions besides determining sex and have no counterpart on the Y chromosome.
In males, because there is no second X chromosome, these extra genes on the X chromosome are not paired and virtually all of them are expressed. Genes on the X chromosome are referred to as sex-linked, or X-linked, genes.
Normally, in the nonsex chromosomes, the genes on both of the pairs of chromosomes are capable of being fully expressed. However, in females, most of the genes on one of the two X chromosomes are turned off through a process called X inactivation except in the eggs in the ovaries. X inactivation occurs early in the life of the fetus.
In some cells, the X from the father becomes inactive, and in other cells, the X from the mother becomes inactive. Because of X inactivation, the absence of one X chromosome usually results in relatively minor abnormalities such as Turner syndrome Turner Syndrome Turner syndrome is a sex chromosome abnormality in which girls are born with one of their two X chromosomes partially or completely missing.
Turner syndrome is caused by the deletion of part Thus, missing an X chromosome is far less harmful than missing a nonsex chromosome see Overview of Sex Chromosome Abnormalities Overview of Sex Chromosome Abnormalities Sex chromosome abnormalities may be caused by full or partial deletions or duplications of sex chromosomes. Chromosomes are structures within cells that contain DNA and many genes. A gene is If a female has a disorder in which she has more than two X chromosomes, the extra chromosomes tend to be inactive.
Thus, having one or more extra X chromosomes causes far fewer developmental abnormalities than having one or more extra nonsex chromosomes. Genes contain Males who have more than one Y chromosome Home. There are several types of chromosome abnormalities Overview of Chromosome and Gene Disorders Chromosomes are structures within cells that contain a person's genes.
A gene is a segment of deoxyribonucleic acid DNA and contains the code for a specific protein that functions in one or A person may have an abnormal number of chromosomes or have abnormal areas on one or more chromosomes.
Many such abnormalities can be diagnosed before birth see Testing for chromosome and gene abnormalities Testing for chromosome and gene abnormalities Chromosomes are structures within cells that contain a person's genes.
Abnormal numbers of nonsex chromosomes usually result in severe abnormalities. For example, receiving an extra nonsex chromosome may be fatal to a fetus or lead to abnormalities such as Down syndrome Down Syndrome Trisomy 21 Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities.
Down syndrome is caused by an extra chromosome Absence of a nonsex chromosome is fatal to the fetus. Large areas on a chromosome may be abnormal, usually because a whole section was left out called a deletion or mistakenly placed in another chromosome called translocation. For example, chronic myelogenous leukemia Chronic Myeloid Leukemia CML Chronic myeloid leukemia is a slowly progressing disease in which cells that normally would develop into neutrophils, basophils, eosinophils, and monocytes become cancerous see also Overview This abnormality can be inherited or be the result of a new mutation Mutation Genes are segments of deoxyribonucleic acid DNA that contain the code for a specific protein that functions in one or more types of cells in the body.
Mitochondria Cells Often thought of as the smallest unit of a living organism, a cell is made up of many even smaller parts, each with its own function. Unlike other structures inside cells, each mitochondrion contains its own circular chromosome. This chromosome contains DNA mitochondrial DNA that codes for some, but not all, of the proteins that make up that mitochondrion.
Mitochondria from the sperm usually do not become part of the developing embryo. A trait is any gene-determined characteristic. Many traits are determined by the function of more than one gene. For example, a person's height is likely to be determined by many genes, including those affecting growth, appetite, muscle mass, and activity level.
However, some traits are determined by the function of a single gene. Variation in some traits, such as eye color or blood type, is considered normal. Other variations, such as albinism Albinism Albinism is a rare hereditary disorder in which little or none of the skin pigment melanin is formed.
The skin, hair, and eyes, or sometimes just the eyes, are affected. Typically, the hair This syndrome is caused However, not all such gene abnormalities are uniformly harmful.
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