GENETICS My scientific studies have afforded me great gratification; and I am convinced that it will not be long before the whole world acknowledges the results of my work.

THE STRUCTURE OF DNA DNA (deoxyribonucleic acid) is found in the nucleus of living cells Its structure is described as a double helix

NUCLEOTIDE BASES There are four bases Adenine (A) always bonds with Thymine (T) Cytosine (C) always bonds with Guanine (G) The bases determine your genetic code.

CHROMOSOMES DNA is divided into “chunks” called Chromosomes In humans most cells contain 46 chromosomes arranged into 23 homologous pairs. XX pair is a female XY pair is a male

GENES Each chromosome is divided up into genes. Genes code for traits (characteristics), such as fixed or free earlobes. The human genome contains more than genes Alleles are alternative forms of the same gene Sometimes the appearance can be enhanced by other means…

A LLELES Every somatic (body) cell has 23 homologous pairs of chromosomes. So each cell has a pair of genes, called alleles, coding for every trait. They may be homozygous (the same) AA or aa Or heterozygous (different) Aa or aA

S EX D ETERMINATION Gametes (sex cells) only have 23 single chromosomes. Why? During fertilisation the egg and sperm come together to give a new cell with 23 pairs of chromosomes.

COLOUR BLINDNESS What do you see here? DO NOT CALL OUT!

SEX DETERMINATION The female donates one of her two X chromosomes The male either an X or a Y Offspring are 50% male, 50% female

CELL DIVISION 2 types Mitosis Occurs in body cells Exact copy Growth/repair of organism Meiosis Occurs in GAMETES Results in half the chromosomes Produces variation

This single cell is copied repeatedly to form an adult with approximately 10,000,000,000,000 cells – all with exactly the same information. How does this copying take place? 1.Each chromosome copies its information and is now called a chromatid. 2. The chromatids line up in the middle of the cell. 3. Half of each chromatid goes to each end of the cell. 4. Two new cells are formed. MITOSIS

MEIOSIS Meiosis is the special type of cell division that creates gametes. Why is it necessary to half the amount of information passed on? Two gametes (one from each parent) fuse to form a zygote. How does meiosis happen? 1. Chromosomes double, just like in Mitosis. 2. The chromatids pair up and “cross over’ information. Half go one way and half the other. 3. Two new cells are made. 4. The chromatids line up and divide again to form four cells. Each with one set of information. Haploid = 1 set of chromosomes Diploid = 2 sets of chromosomes Mitosis /meiosis test

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ALLELES – ALTERNATIVE FORMS OF THE SAME GENE Alleles are assigned letters to distinguish one from another e.g. Tongue roll alleles T or t. Alleles may be dominant or recessive depending on whether the trait is seen. Recessive blue eyes Small letter Dominant hitchhikers thumb, tongue roll Capital letter The characteristics displayed are known as phenotype.

ALLELES Genotytpe is the genetic make up of an individual E.g. Tongue roll alleles are represented by T or t What are the 3 possible genotypes? TT, Tt, tt What is the genotype and phenotype of the children ? Genotype Tt, phenotype can roll FatherMother GenotypeTTtt PhenotypeCan rollCan’t roll

THE MONK Who is this dude? How about this one? Gregor Mendel. He is the father of genetics – he is the reason that we can clone sheep, cure diseases and why CSI is on telly. Sort of. Mendel’s work: He spent many years studying pea plants, among other things. He found that they had a large amount of variation in their appearance, and sought to find out why.

MENDEL AND PEAS In one of his experiments he took the anthers off a purple flower. Why? To stop it self fertilizing! He then took pollen from a white flower and fertilized the purple flower. He found that 100% of the offspring were purple. He then took two of the purple offspring and crossed them. What do you think he found?

THE PEA EXPERIMENT Mendel had no answer for this. No one had studied inheritance this closely before. He deduced that: Each parent contributes a piece of information to the offspring. Some information was “dominant” to the other. Which bits of information the offspring got from it’s parent was controlled by random chance.

PUNNET SQUARE This is a monohybrid cross All possible combinations of gametes can be shown (father can roll TT, mother can’t tt) The genotype of all offspring can be worked out Can work out the chances or ratio of any combination occurring in this case: Genotype 100% Tt Phenotype 100% Can roll Mothers eggMothers egg Fathers sperm TT t t Tt

PUNNET SQUARE What are the Genotypes of children? What are the phenotypes? Roller, non roller What is the ratio of phenotypes? 3:1 How can we tell if the genotype of a tongue roller is TT or Tt? Mothers eggMothers egg Fathers sperm Tt T t ttTt TTTt

GENETICS PROBLEMS In humans, blue eyes are recessive to brown: Dad (Blue eyes)Mum (Brown eyes)Baby (Blue eyes) Is Mum homozygous for brown eyes?________ How do you know? (complete the Punnett square)

MICE In mice, albino is a recessive trait Big Momma mousePoppa mouse Stuart Little Complete the Punnett square to show how Stuart ended up an albino If there were 8 babies in the litter, how many would we expect to have normal colouring? _________

In Labs, black is the dominant trait The pups are all black What is the genotype of the pups? _____________ The pups grow up and 2 are mated LABRADORS These 2 are mated Here are their kids… Show how this came about (draw the Punnett square) What percentage would we expect to have golden colouring? ____________

TEST / BACK CROSS Shows the genotype of an unknown Eg. Dominant phenotype - Purple flower Genotype could be Pp or PP Cross with homozygous recessive (Pure Breeding) e.g. pp phenotype white 2 results All purple so genotype is PP Half purple so genotype is Pp

PEDIGREE DIAGRAMS Method for studying the inheritance of genes Male Female Affected male Mating

PEDIGREE DIAGRAMS Genotype inside, Phenotype under rr Rr rr Rr Curly Straight

PEDIGREE CHART 1. Is this trait recessive or dominant? Explain. 2. Explain why generation IV has two affected members, while generation II has only one.

APPLICATION OF GENETICS Animal/ plant breeding Genetic engineering Cloning

ANIMAL/PLANT SELECTIVE BREEDING Humans select desired traits Over generations all offspring show traits Selective breeding Inbreeding leads to recessive traits showing

ANIMAL / PLANT BREEDING Hybridisation Crossing different strains New breeds Eg Zonkey or Liger

GENETIC ENGINEERING Transfer of genes from one organism to another Good – crop yield, resistance Bad – food chain, crosses species

GENETIC ENGINEERING The human gene for the production of insulin (medicine for diabetics) has been inserted into cows so that insulin comes out with their milk. This has been done with bacteria too. The genes for human ear growth can be inserted on the back of a mouse… Spare parts! The genes for “roundup” resistance has been put into sweet corn, so we can spray around them easily and not harm the crop. This tobacco plant has had firefly genes inserted…

CLONING Production of genetically identical individuals Plants from cuttings Mammals from single cell Good - high yield, disease resistant, stem cell harvest, transplant tissue, save endangered species! Bad – inefficient (10% success), no variation, die young, super race?

1. Compare and contrast the processes of Mitosis and Meiosis. Include the purposes and end products of these. 2. Explain how sex is determined in humans, and why different families have different numbers of male and female offspring. 3. Define the following terms: ZygotePure breedingGamete haploidAlleleDiploid HomologousHeterozygousRecessive 4. Explain how 2 brown haired parents can have a blonde child. 5. How many chromosomes are in human cells? 6. Explain the connection between DNA, genes, alleles and chromosomes. RANDOM GENETICS QUESTIONS

MITOSIS

MEIOSIS