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Biology topic 3 - Genetics - Coggle Diagram
Biology topic 3 - Genetics
Mitosis - results in the formation of two genetically identical daughter cells
meiosis - used in sxual reproduction , results in formation of two genetically non identical daughter cells
meiosis
cells split - each cell has a pair of each chromosome. During meiosis each pair of chromosomes replicates and the cell splits into two
There are now two identical cells, the diploid cell divides again
This creates four genetically different gametes that each have half the number of chromosomes of the parent cell These are haploid
during sexual reproduction the male gamete fertilises the female gamete and the cell now has the normal number of chromosomes
The genome
How could the completion of the Human Genome Project, and subsequent research on the human genome, be beneficial in tackling Cystic Fibrosis?
The knowledge we have gained from the Human Genome Project and subsequent research can help us in identifying Cystic Fibrosis genes, allowing those carrying it to be made aware.
It could also further our understanding of the disorder and how we should be treating it, and whether treatment should be different for people with key genome differences.
It could lead to a treatment involving gene therapy.
Dna extraction
genome sequencing
human genome project - research on human genome , since then our understanding has improved alot
benefits of this understanding
gene therapy - The human genome project has been useful for gene therapy - inserting new or modified genes into a cells genome to treat a disease
Gene identification - identifying genes linked to certain different disorders, this would allow those at risk to make informed lifestyle decisions based on the risk factors
Improving Our understanding of inherited diseases and how we should treat them
Knowing the details of a patients genome cna help doctors choose medication whichll help them the most
dna can easily be extracted from fruit
grind a sample of fruit in soapy water, This breaks the cell open releasing dna from within the cells.
very slowly pour ice cold ethanol into the filtrate , The dna moves into ethanol by percipitation, and can then be removed with a wire loop
filter the sample to produce a filtrate
chromosomes - long strands of dna are coiled to give chromosomes
chromosomes contain many genes
Human body cells contain 23 chromosomes
Each gene tells how a specific protein should be made.
Each chromosome contains a large number of genes.
The nucleus of eukaryotic cells contains chromosomes made of DNA molecules.
Genes - a gene is a small section of DNA , genes code for a sequence of amino acids which combine to give a specific protein
DNA - double helix polymer -(large molecule made up of many sub units ) made up of two strands forming a twisted ladder shape
the genome is all the genetic material within an organism . Lots of layers of organisation
DNA structure
Dna is a polymer made up of two long strands of small units that repeat throughout the structure called nucleotides
Each of these is made up of a sugar, a phosphate and a base attached to the sugar.
nucleotides
sugar ,phosphate , base
base
attached to sugar
4 forms of base - A C G and T
each base has a specific other base it pairs with
AT, GC
The two long strands in each dna molecule are held together by weak hydrogen bonds between opposite bases
Describe the structure of DNA.
answer
DNA is a polymer consisting of two long strands of small units that repeat throughout the structure, called nucleotides.
A nucleotide is made up of a phosphate and a base attached to the sugar.
The sugar and phosphates of nucleotides form the long strands.
Weak hydrogen bonds between opposite bases holds the two strands together.
Mutation
permanent change in nucleotide sequence of dna
XY male characteristics
How can mutations lead to human evolution?
Most mutations (permanent changes in nucleotide sequences of DNA) do not affect the phenotype.
But if a mutation creates a new phenotype that is better adapted to environmental changes (than the rest of the population), the mutation is likely to spread throughout the population over a small number of generations.
For example, over time the size of the human brain has increased, as those born with a bigger brain were found to be at a survival advantage.
Variation and inheritance
variation describes the different characteristics of individuals, variation may result in differences in
genetics, environment
genetic variation is the result of mutation, some of which are inherited and passed onto next generation
inheritance
alleles- different forms of the same gene , humans have pairs of every gene , in one gene each half of the pair may have different alleles - peoples alleles can determine the characteristics that they have
Alleles can either be dominant or recessive
dominant allele - always expressed regardless of identity of the other allele, only needs one copy to be expressed
Represented by a capital letter
when a person has a copy of the B allele , theyll have brown eyes no matter what other allele is presented
recessive allele
Only expressed if other allele is also recessive
represented by lower case letter ie (b) needs two copies to be expressed (bb)
if b is the allele for blue eyes a person can only have blue eyes if their alleles are both B
mutation
a mutation is a change in the nucleotide sequence of dna, Mutations happen continuously and normally only slightly affect proteins or don't affect them at all, occasionally, a mutation may change the structure or shape of a protein
outcome of mutation almost always detrimental to protein function. Can rarely give survival advantage , such as resistence to antibiotic in bacteria
Genotype vs phenotype
when talking about the inheritance of characteristics, we use the words genotype and phenotype
Phenotype
observed characteristic of an individual
Determined by the interaction of a genotype and the environment
earlobes being attached or free is an example of a phenotype, where the alleles present will determine a characteristic, unless the environment interferes.
Genotype
The combination of alleles an organism has
if two alleles are different - (Bb) we say the organism is heterozygous
if two alleles are the same we say the person of homozygous (BB) or (bb)
monohybrid inheritence
monohybrid inheritance refers to the inheritance of traits referred to by a single gene
Punnet squares - diagrams that help us visualise the outcome of a monohybrid cross.
in these diagrams a capital letter shows the dominant allele
allele of the parent drawn along the top and side of grid, pairs of alleles offspring could have then filled in on grid
females are XX and males are XY
inherited disorders
people can develop disorders if they inherit certain alleles
eg cystic fybrosis which is caused by recessive allele
It causes thick, sticky mucus to build-up in the lungs and digestive system.
How can a mutation in a gene result in a protein not carrying out its role correctly?
If the mutation is in a coding region of DNA, the mutation may code for a different amino acid.
2
Different amino acids could alter the structure of a protein.
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The altered structure means that the protein is the wrong shape to transport water.
