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inheritance - Coggle Diagram
inheritance
definitions
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codominance
when neither allele is dominant over the other, so both contribute to the phenotype
DNA
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it is a polymer, meaning that it is made of many different molecules that join up that make a long strand. these molecules are called nucleotides
Each nucleotide is made from one sugar molecule, one phosphate group and one of the four different organic bases
bases
Adenine, Cytosine ,Guanine, Thymine
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mitosis
used for growth, repair of damaged tissues, replacement of cells and asexual reproduction
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process
Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x-shaped chromosomes)
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importance
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Mitosis is important for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo)
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variation
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divided into 2 types
Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale
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genetic variation
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This random fusion of gametes at fertilization creates genetic variation between zygotes as each will have a unique combination of alleles
environmental variation
Characteristics of all species can be affected by environmental factors such as climate, diet, accidents, culture and lifestyle
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antibiotic resistance
Antibiotics are chemical substances made by certain fungi or bacteria that affect the working of bacterial cells, either by disrupting their structure or function or by preventing them from reproducing
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Antibiotics target processes and structures that are specific to bacterial (prokaryotic) cells; as such they do not generally harm animal cells
However, since their discovery and widespread use, antibiotics have been overused and antibiotic resistance has developed in many different types of bacterial species
Bacteria, like all organisms, have random mutations in their DNA
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If an organism is infected with bacteria and some of them have resistance, they are likely to survive treatment with antibiotics
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A strain of Staphylococcus aureus has developed resistance to a powerful antibiotic methicillin, this is known as MRSA
meiosis
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process
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First division: chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair
Second division: chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)
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importance
Production of gametes e.g. sperm cells and egg cells, pollen grains and ovum
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Meiosis produces variation by forming new combinations of maternal and paternal chromosomes every time a gamete is made, meaning that when gametes fuse randomly at fertilisation, each offspring will be different from any others
Darwin
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Evolution can be defined as the change in the frequency of a phenotype in a population over many generations
theory
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Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce
Therefore these characteristics are passed to their offspring at a higher rate than those with characteristics less suited to survival
Over many generations, these beneficial characteristics become more common in the population and the species changes (the species evolves)
genetic diagrams
family pedigrees
Family pedigree diagrams are usually used to trace the pattern of inheritance of a specific characteristic (usually a disease) through generations of a family
This can be used to work out the probability that someone in the family will inherit the genetic disorder
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polygenic inheritance
Most characteristics are a result of multiple genes interacting, rather than a single gene
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Polygenic inheritance is difficult to show using genetic diagrams because of the wide range of combinations
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protein synthesis
DNA is too large to leave the nucleus in order to make the proteins and therefore a series of steps must be taken to copy and transport the genetic information
steps
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the mRNA nucleotides themselves are then joined together, creating a new strand called a template strand of the original DNA (transcription)
the template strand of mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes
at the ribosomes, the bases on the mRNA are read in threes to code for an amino acid (translation)
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mutations
rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome
how they occur
insertions
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An insertion mutation changes the amino acid that would have been coded for by the group of three bases in which the mutation occurs
An insertion mutation also has a knock-on effect by changing the groups of three bases further on in the DNA sequence
deletions
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Like an insertion mutation, a deletion mutation changes the amino acid that would have been coded for by the group of three bases in which the mutation occurs
Like an insertion mutation, a deletion mutation also has a knock-on effect by changing the groups of three bases further on in the DNA sequence
substitutions
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Unlike an insertion or deletion mutation, a substitution mutation will only change the amino acid for the group of three bases in which the mutation occurs; it will not have a knock-on effect
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