BBC Bitesize - GCSE Combined Science - Cell division - AQA - Revision 1
Chromosomes carry genetic information in a molecule called DNA. A type of cell division called mitosis ensures that when a cell divides each new cell produced. Find information, videos, and activities about DNA, genes, chromosomes, the Experiment with the forces involved and measure the relationship between the. Your genes are part of what makes you the person you are. You are different from everyone alive now and everyone who has ever lived. DNA. But your genes.
Human beings have 22 pairs of autosomal chromosomes and one pair of allosomal chromosomes. Under normal circumstances, human beings have a total of 23 pairs of chromosomes, totaling a complete set of 46 chromosomes.
Autosomal chromosomes are identified and labeled with numbers from 1 to 22; and allosomal chromosomes are identified and labeled with the letters X and Y only. The female gender has a diploid genome of XX and males have a diploid genome of XY.
When there is any variation in this XX and XY characteristic, it is considered abnormal. For example, a third chromosome number 21 is called trisomy 21, which in the past was called Down syndrome. Genes A gene is a region of DNA that encodes function. A chromosome consists of a long strand of DNA containing many genes. A human chromosome can have up to million base pairs of DNA with thousands of genes. The different nucleotides of our DNA sequences among all human beings form genes.
Genes are the basis of heredity. These sequences are called genotypes. At times, the results of our genetic makeup are obvious and visible to the naked eye and, at other times, these genetic traits are not at all obvious and visible to the naked eye. For example, the color of our eyes is obvious and visible to the naked eye but our genetic risk factors for some diseases and disorders are not obvious and visible to the naked eye.
At times, genes can become abnormal in terms of their sequencing. These abnormalities are called genetic mutations.
The sugar-phosphate backbone chains run in opposite directions with the bases pointing inwards, base-pairing A to T and C to G with hydrogen bonds.
Cell division - AQA
DNA, or deoxyribonucleic acid, Is the foundation and the molecular basis of inheritance. DNA is the macromolecule, as discussed above with other macromolecules, that encodes information in the body and it also provides the basis for instructions to body in terms of its protein production.
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DNA is a twin chain, or double helix chain, that is comprised of a sugar group which is called deoxyribose, a phosphate group and a base of guanine, cytosine, thymine or adenine. Each strand or chain of DNA in the double helix is referred to as a polynucleotide.
Polynucleotides are made up from monomers called nucleotides.
What is the difference between a gene, a chromosome and DNA? | MyTutor
As previously stated, the nucleotides in our DNA are referred to as A adenineC cytosineG guanine and T thymine that are connected to each other in an array and formation with hydrogen bonds; it is the A, C, G and T nucleotides that contain our information. A adenine is paired with T thymine and held together with 2 hydrogen bonds; and, C cytosine is paired with G guanine and held together with 3 hydrogen bonds, as shown in the picture above.
It can make copies of itself. If you pull the two strands apart, each can be used to make the other one and a new DNA molecule.
It can carry information. The order of the bases along a strand is a code - a code for making proteins. Genes A gene is a length of DNA that codes for a specific protein. So, for example, one gene will code for the protein insulin, which is important role in helping your body to control the amount of sugar in your blood.
Genes are the basic unit of genetics. Human beings have 20, to 25, genes. These genes account for only about 3 per cent of our DNA.
The function of the remaining 97 per cent is still not clear, although scientists think it may have something to do with controlling the genes. Chromosomes If you took the DNA from all the cells in your body and lined it up, end to end, it would form a strand million miles long but very, very thin!
To store this important material, DNA molecules are tightly packed around proteins called histones to make structures called chromosomes.
The packaging of DNA into chromosomes Human beings have 23 pairs of chromosomes in every cell, which makes 46 chromosomes in total. A photograph of a person's chromosomes, arranged according to size, is called a karyotype. The sex chromosomes determine whether you are a boy XY or a girl XX.
The other chromosomes are called autosomes. The karyotype of a male human being The largest chromosome, chromosome 1, contains about genes. The smallest chromosome, chromosome 21, contains about genes.