BBC - GCSE Bitesize: DNA, genes and chromosomes
Learn about and revise genetic inheritance, the genome, mutation, sexual and DNA determines the characteristics of a living organism. The diagram shows the relationship between the cell, its nucleus, chromosomes in the nucleus, and genes. Sample exam questions - Genes, inheritance & selection - OCR Gateway. A chromosome is a division of that genome, just like a chapter is a division of a book. So each chromosome is a chunk of DNA. In humans you have Genes and Chromosomes and Fundamentals - Learn about from the Merck Self-Assessment Tools · Tables · Common Medical Tests · Medical Terms Genes are segments of deoxyribonucleic acid (DNA) that contain the code The genotype (or genome) is a person's unique combination of genes or genetic makeup.
Info DNA, genes and chromosomes 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 also mean that you probably look a bit like other members of your family.
For example, have you been told that you have 'your mother's eyes' or 'your grandmother's nose'? Genes influence what we look like on the outside and how we work on the inside. They contain the information our bodies need to make chemicals called proteins. Proteins form the structure of our bodies, as well playing an important role in the processes that keep us alive. Genes are made of a chemical called DNA, which is short for 'deoxyribonucleic acid'. The DNA molecule is a double helix: The DNA double helix showing base pairs The sides are sugar and phosphate molecules.
Genes and Chromosomes - Fundamentals - Merck Manuals Consumer Version
The rungs are pairs of chemicals called 'nitrogenous bases', or 'bases' for short. There are four types of base: Most significant of these new discoveries was in when the haplogroup A00 was discovered, which required theories about Y-chromosomal Adam to be significantly revised.
SNP testing confirmed that he does not descend patrilineally from the "old" Y-chromosomal Adam and so a much older man became Y-Chromosomal Adam. Using DNA test results[ edit ] Ethnicity estimates[ edit ] Many companies offer a percentage breakdown by ethnicity or region.
Generally the world is specified into about 20—25 regions, and the approximate percentage of DNA inherited from each is stated. This is usually done by comparing the frequency of each Autosomal DNA marker tested to many population groups.
DNA, genes and chromosomes
Earlier ethnicity estimates were often wildly inaccurate, but their accuracies have since improved greatly. For example, Europeans often receive an exaggerated proportion of Scandinavian. Audience[ edit ] The interest in genealogical DNA tests has been linked to both an increase in curiosity about traditional genealogy and to more general personal origins. Those who test for traditional genealogy often utilize a combination of autosomal, mitochondrial, and Y-Chromosome tests.
Those with an interest in personal ethnic origins are more likely to use an autosomal test. However, answering specific questions about the ethnic origins of a particular lineage may be best suited to an mtDNA test or a Y-DNA test. Maternal origin tests[ edit ] For recent genealogy, exact matching on the mtDNA full sequence is used to confirm a common ancestor on the direct maternal line between two suspected relatives.
Because mtDNA mutations are very rare, a nearly perfect match is not usually considered relevant to the most recent 1 to 16 generations. Tests for ethnicity and membership of other groups[ edit ] European genetic structure based on Autosomal SNPs by PCA As discussed above, autosomal tests usually report the ethnic proportions of the individual.
Cell division - AQA
These attempt to measure an individual's mixed geographic heritage by identifying particular markers, called ancestry informative markers or AIM, that are associated with populations of specific geographical areas. They show with whom you have common ancestry today. Many direct-to-consumer DNA tests described this association to infer the test-taker's ancestral homeland.
By the early 19th century, substantial families of Free Persons of Color had been established in the Chesapeake Bay area who were descended from free people during the colonial period; most of those have been documented as descended from white men and African women servant, slave or free. Double strand of polynucleotides The double helix of the complete DNA molecule resembles a spiral staircase, with two sugar phosphate backbones and the paired bases in the centre of the helix. This structure explains two of the most important properties of the molecule.
First, it can be copied or 'replicated', as each strand can act as a template for the generation of the complementary strand. Second, it can store information in the linear sequence of the nucleotides along each strand. DNA helix showing nitrogenous bases It is the order of the bases along a single strand that constitutes the genetic code.Genes, DNA and Chromosomes explained
The four-letter 'alphabet' of A, T, G and C forms 'words' of three letters called codons. Individual codons code for specific amino acids. A gene is a sequence of nucleotides along a DNA strand - with 'start' and 'stop' codons and other regulatory elements - that specifies a sequence of amino acids that are linked together to form a protein.
There are a two points to note about the genetic code: All life on Earth uses the same code with a few minor exceptions.
DNA, Genes and Chromosomes — University of Leicester
Each amino acid can be coded for by more than one codon. A codon table sets out how the triplet codons code for specific amino acids. DNA replication The enzyme helicase breaks the hydrogen bonds holding the two strands together, and both strands can then act as templates for the production of the opposite strand. The process is catalysed by the enzyme DNA polymerase, and includes a proofreading mechanism.
Genes The gene is the basic physical and functional unit of heredity.