B3

Mitosis Meiosis - Forms 2 cells - Forms 4 cells - Forms genetically identical cells - Forms genetically different cells - Forms diploid cells - Forms haploid cells - Forms body cells for growth and repair - Forms gametes for sexual reproduction

Advantages: - Genetically different offspring ( variation in the population), If selection pressure there is increased chance for survival Disadvantages: - Takes a longer time and more energy - Requires the need to find a mate

Advantages: - Produces lots of offspring quickly (only offspring with desired characteristics), could increase yield and lead to more profit Disadvantages: - All offspring are genetically identical (No genetic variation), More likely to be affected by a selection pressure/Natural selection cannot happen

• Polymer of nucleotides ( base, phosphate, sugar ) • 2 strands of complimentary base pairs ( A & T ), ( C & G ) • Forms a double helix shape • Held together by weak hydrogen bonds • Phosphate and sugar are the backbone • Genome is the entire DNA of an organism • Gene is a section of a DNA molecule that codes for a specific protein • The order of bases in a section of DNA decides the order of the amino acids in the protein and then fold to produce specifically shaped proteins such as enzymes • 3 bases / triplet= 1 amino acid

1 - RNA polymerase binds to the non-coding region ( the area just before a gene starts ) 2 - RNA polymerase unwinds the DNA helix at the gene that is being transcribed 3 - RNA polymerase makes a strand of DNA that is complimentary to the main strand called mRNA 4 - Nucleotides are joined together to form mRNA ( short single strand of DNA with U not T ) 5 - mRNA leaves the nucleus through a nuclear pore and travels to the ribosome

1 - mRNA attaches onto the ribosome 2 - Every 3 bases on the mRNA is known as a codon 3 - tRNA (from the cytoplasm) attaches to the codon using its own anti-codon ( complementary bases ) 4 - tRNA molecules bring a specific amino acid to the ribosome 5 - when two tRNA molecules are bound to an mRNA, a peptide bond forms between the two amino acids 6 - Amino acids are joint to make a polypeptide chain 7 - This then folds into a specific shape to form a specific protein ( hormones, antibodies, enzymes )

• A mutation is a change in genes and also leads to variation • Genetic variation ( different versions of genes caused by mutations ) can be produced if a mutation occurs in the non-coding DNA of a gene • Most genetic mutations have no effect on the phenotype (characteristics), Some mutations have a small effect on the phenotype, Rarely, a single mutation has a significant effect on the phenotype. • Genetic variants can affect the phenotype by influencing the binding of RNA polymerase and altering the quantity and activity of protein produced • Most phenotypic features are the result of multiple genes rather than a single gene inheritance

• Mash the sample of fruit using a pestle and mortar • Mix with detergent/soap to break down the cell membranes • Mix with protease enzyme to break down the nuclear membrane and any proteins • Filter to remove insoluble material and heat in a water bath • Add ice-cold ethanol to precipitate the DNA ( Forms white strands ) and make it visible ( DNA is not soluble in ethanol )

Genotype - The alleles are organism has for a gene (genetics) Phenotype - The characteristics an organism shows because of its genotype (physical) Allele - different forms of the same gene Dominant - Always expressed in the phenotype if present Recessive - Only expressed in phenotype if two copies are present Homozygous - Both alleles of the gene are the same ( BB ) Heterozygous - Both alleles of the gene are different ( Bb )

In the mid 19th century, Mendel carried out breeding experiments on plants He studied how characteristics were passed on between generations of plants Characteristics are determined by hereditary units passed on from parent to offspring unchanged The offspring receives one hereditary unit from each parent Hereditary units can be dominant or recessive

The fusion of the nuclei of male and female gametes which both contain only 50% DNA/ genetic material, form a zygote with 100% DNA / genetic material

A grid that shows how alleles combine in offspring Male gametes _____________|____A____|____b____| Female gametes|_____A______|___AA____|___AB___| |_____a______|___Aa____|____ab___| 25% = AA ( homozygous dominant ) 25% = AB ( homozygous dominant ) 25% = Aa ( heterozygous dominant ) 25% = ab ( homozygous recessive )

A genome is all genetic material of an organism The human genome project mapped and sequenced the entire human genome This has allowed us to identify faulty/ mutated genes associated with diseases and make personalised medicine Uses: - Find specific mutations that are causing a disease - Allows for personalised medicine - Gives a better understanding of genetic disease And inherited disorders

Antigens are found on the surface of red blood cells and determine a person’s blood type Codominance - When both alleles in the genotype are expressed in the phenotype of an individual If you get “A” and “B” which are both dominant, the phenotype “AB” blood type is made which is an example of codominance

|A |A OR |A |O = A |B |B OR |B |O = B |A |B = AB |O |O = O

The X chromosome is much larger than the Y chromosome This means as males only have one X chromosome they are much more likely to show sex-linked genetic disorders such as red-green colour blindness or haemophilia Females have 2 X chromosomes and are more likely to inherit the dominant allele that masks the effect of the recessive allele Female can not have the disease but will be a carrier of the disease, if offspring is a male then the male will have the disease

A mutation in the non-coding region may stop/ reduce RNA polymerase binding to the non-coding region, preventing/reducing mRNA and protein being made. OR A mutation in the non-coding DNA may also make it easier for RNA polymerase to bind, meaning more mRNA and protein will be made

• If there is a change in DNA, mRNA will be different • When mRNA goes to the ribosome the codons will be different so different amino acids may be brought to the ribosomes by tRNA • The sequence of amino acids may be changed • When the chain of amino acids is released, the chain may unfold into a different shaped enzyme/hormone and alter its function

Substitution / addition + deletion There is a change in the DNA base sequence ( 2 bases are swapped ) ( a base is added ) ( a base is deleted ) There is a change in the mRNA base sequence There is a change in the mRNA triplet ( no triplet Is formed - deletion ) There is a change in the amino acid and polypeptide sequence There is a change in the function of the protein ( functioning protein not formed - deletion )