Year 12 Biology: Genetic Variation

Who can roll their tongue?

Who has blue eyes?

Who has a hitchhikers thumb?

Create a mind map….

DNA Contains genetic information Double stranded 5' 3' 3' 5' DNA Contains genetic information Double stranded DNA is 'read' in the 5' to 3' direction Complementary strand 3' to 5' How would you describe the structure of DNA?

DNA – what is it? DNA is a polymer – it is made up of many repeating monomers called nucleotides Nucleotides = phosphate, sugar and base

DNA Structure All of the genetic information a cell requires is coded within the cell’s DNA Four different bases: Thymine (T) Adenine (A) Cytosine (C) Guanine (G) It is the SEQUENCE of bases along the DNA that code for this information

DNA replication overview

What is a chromosome? Tightly wound and packaged DNA is called chromatin Chromosomes are made up of chromatin

Homologous Chromosomes Matching chromosome pairs One from each parent Same size and same shape

There are 46 human chromosomes in a diploid cell Watch Down’s video Autosomes = chromosomes 1 to 22 Sex determining chromosomes = X and Y Karyotype = entire chromosome complement

What is a gene??? A section of DNA that codes for a particular protein The instruction for a characteristic One gene = one characteristic (e.g. eye colour, hair colour) Look back at your picture from last lesson and see if you drew the relationship correctly  can you now write the relationship

So one gene in a chromosome might be written like this…. ATGCAGTACAGTACTGACTACATCGATCGATCGATCGATCGATCGATCGATCGATCGATCATCGATCGATCGATCGATCGATCGATCGATGCATCGATCGATCGATCGATCGATCGATCGATCGATCGGGGGGGGGCGACGACCCCCCCCCCCCAAAAAAAAAAATCGATCGATCGATCGATCTAGTCGATCGATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTAAAAAAAAAATTTTAAAAAAAATATAATATATTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGGATCGGGGGGGGGCGACGACCCCCCCCCCCCAAAAAAAAAAATCGATCGATCGATCGATCTAGTCGATCGATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTGATACTACGACACTATATATTATCATCGATCATCGAGCTATCATCATCATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAATTTTAAAAAAAATATAATATATTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGGATCGGGGGGGGGCGACGACCCCCCCCCCCCAAAAAAAAAAATCGATCGATCGATCGATCTAGTCGATCGATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTGATACTACGACACTATATATTATCATCGATCATCGAGCTATCATCATCATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTGATACTACGACACTATATATTATCATCGATCATCGAGCTATCATCATCATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAATTTTAAAAAAAATATAATATATTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGACAGTACAGTACTGACTACATCGATCGATCGATCGATCGATCGATCGATCGATCGATCATCGATCGATCGATCGATCGATCGATCGATGCATCGATCGATCGATCGATCGATCGATCGATCGATCGGGGGGGGGCGACGACCCCCCCCCCCCAAAAAAAAAAATCGATCGATCGATCGATCTAGTCGATCGATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTGATACTACGACACTATATATTATCATCGATCATCGAGCTATCATCATCATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAATTTTAAAAAAAATATAATATATTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGGATCGGGGGGGGGCGACGACCCCCCCCCCCCAAAAAAAAAAATCGATCGATCGATCGATCTAGTCGATCGATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCCCCCCCCCCCAAAAAAAAAAAAAGTACGATCGACGATCACTAGCATCGATCGATCGATTTTTTTTTTAAAAAAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTACTGATACTACGACACTATATATTATCATCGATCATCGAGCTATCATCATCATGCACGACTACTACATCAGCTAGCTAGCTAGCATCGATGCATCGATCATCGACGATTATTTTTTTTTTTTTCCCCCCCGACCACACACGGGGGGGGCCCCAAATATAATATATTTTTTTTTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCTTCGGGGGGGGGGATCAGCTACGATCGATCGATCGGGGGGGGGGGGGGGGGCTACGATCGATCGATCATCGTAGCTAGCTAGCTAGCTATCATCGATCGATCGATCGATCGATCGATCGACACGAGTCAGTGCAGGCTGTGTCGTGTGTTGTACCACACCACATCTGCAGTA So one gene in a chromosome might be written like this….

WHAT the heck is the difference between a gene and an allele????!!!

Alternative forms of a gene Alleles Alternative forms of a gene Alleles are different forms of a gene e.g. if the gene is hair colour then the alleles are brown, black, blonde, etc) HOWEVER Alleles have a slightly different order of bases so they cause different traits (e.g. brown hair, blonde hair) Alleles therefore produce variation in the population

Dominant vs. Recessive Alleles Dominant Alleles – always expressed in the individual even if only one dominant allele is present  Shown as a capital letter (e.g. B for brown eyes) Recessive Alleles – only expressed if TWO recessive alleles are present in the genotype  Shown as a lower case letter (e.g. b for blue eyes)

Phenotype = the physical appearance of a gene Genotype = an individuals genetic makeup Brown hair Bb Curly hair CC

Genetic Variation A difference in genetic sequence (A, T, C, G's) The difference in alleles (genes) between individuals in a population Genetic variation is required for change in a population Over time, genetic change = evolution

There are two types of variation….. Continuous eg, skin colour height Discontinuous eg, blood groups

Acquired (non-inherited) Variation Variation we gain during our lifetime from the environment Not in our genes – e.g. my scar from falling up the stairs

Sources of genetic variation The ultimate source of variation is… Mutation, a change in the DNA sequence Other sources of variation are: Sexual reproduction (the process of meiosis) Random fertilisation Continuous – there is a range of measurements e.g. height, weight, foot length, etc Discontinuous – characteristics fall into distinct categories e.g. eye colour, hair colour, tongue rolling etc

Examples For example, if you eat too much you will become heavier, and if you eat too little you will become lighter. A plant in the shade of a big tree will will grow taller as it tries to reach more light. If you lie in the sun a lot you will get browner. Flower colour in hydrangeas - these plants produce blue flowers in acidic soil and pink flowers in alkaline soil.

What causes variation Some variation within a species is inherited, and some variation is due to the environment/acquired. Drill into the students that variation is differences in a population

Examples of inherited variation eye colour hair colour skin colour lobed or lobeless ears. Gender is inherited variation too, because whether you are male or female is a result of the genes you inherited from your parents.

Just basics: Each egg cell and each sperm cell contains half of the genetic information needed for an individual. When these join at fertilisation a new cell is formed with all the genetic information needed for an individual.

Enzyme that is responsible for producing melanin is heat sensitive – it is denatured at body temperature. Only works at the extremeties of the rabbit as this is cold enough for the enzyme not to be denatured

Task In your books copy the table and give 3 examples of each inherited variation and acquired variation Inherited Variation Acquired Variation

What are some examples of variation that are truly inherited and not affected by the environment at all? Natural eye colour, blood type, some diseases, natural hair colour Then get the students to make a table – sexual vs asexual  Come up with advantages and disadvantages of these two methods of reproduction

Activity You each have 12 cards showing different characteristics. In pairs, decide how much of the variation in each characteristic is due to genes (inherited variation) and how much is due the environment Put the cards on a line like this: You have 8 minutes to sort all the cards Be ready to share your reasons! completely genetic completely environmental

How do we know what causes variation? Same genes Different environment Same environment Different genes Identical twins, separated at birth Identical twins Non - identical twins

Use the reading to write definitions for the following: DNA Chromosome Gene Allele Can you DRAW the relationship between these 4???

Karyotype activity – go through the key words like – chromosome, karyotype, autosomes, sex chromosomes, homologous chromosomes

Alleles Alleles of a gene are shown by letters (upper case and lower case letters) There are two chromosomes in a pair of chromosomes – therefore alleles are in pairs too! e.g. Eye colour – B, b  brown eyes, blue eyes

Mitosis vs. Meiosis Using the information from the video and the picture given to you, write as many similarities and differences between these two processes

Mitosis You started life as just one cell – a fertilised egg cell. Very soon one cell became two, two cells became four, four cells became eight… and five thousand cells became ten thousand. By the time you were born your body was made of some 20 billion cells. In this lesson you will investigate how more cells are made through a process called mitosis.

Meiosis Production of sex cells/gametes – sperm and egg Processes that occur during meiosis results in gametes that are genetically different to each other and to the parent cell  Contributes to VARIATION!

Random Fertilisation It is random as to which sperm will fertilise the egg  even more variation possible

Genotype + Environment  Phenotype The environment can contribute to the phenotype WITHOUT altering the genotype Genotype + Environment  Phenotype E.g. Skin Colour, Hair colour, etc

Environment Mutagens are environmental factors that increase the rate of mutation Mutagens will alter the DNA and therefore the genotype E.g. UV light, X-ray, Radiation

Mutations and alleles A mutation is a random change to the base sequence of DNA  If this mutation occurs in the DNA sequence of a gene this can produce a new allele  NEW ALLELE = VARIATION

Punnett Squares The Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment. Using Punnett squares you can determine the probability of an offspring having a particular genotype. The Punnett square is a summary of possible combinations of mum allele's with dad’s alleles.

Problem: If 2 parents are both heterozygous for the tongue rolling gene, predict their chances of getting the different kinds of offspring STEPS Write down the phenotype and genotype of each parent Father: roller Rr Mother: roller Rr Identify the gametes that will be produced by each parent: R r x R r Gametes = R r R r

Punnet Squares R r R RR Rr r Rr rr Draw the following grid: GAMETES FROM THE EGG Draw the following grid: R r GAMETES FROM SPERM R RR Rr r Rr rr In the left column of the square write the alleles of sperm R and r Above the square write down the alleles of eggs In each box record the genotype of the zygote formed if the sperm on the left met the egg from above R sperm and R egg gives RR zygote etc.

Identify the distinct genotypes and the chances of getting each: RR = 25% (1/4) Rr = 50% (2/4) rr = 25% (1/4) R r RR Rr rr

R r RR Rr rr Decide on the expected ratio of the 2 phenotypes Rollers (RR and Rr) = 75% chance (3/4) Non-rollers (rr) = 25% chance (1/4) R r RR Rr rr

R r RR Rr rr PUNNET SQUARE: GAMETES FROM THE EGG R r RR Rr rr GAMETES FROM SPERM PUNNET SQUARE: Genotype chances: RR = 25%, Rr = 50%, rr = 25% Phenotype chances: roller = 75%, non-roller = 25% Harry Potter Genetics