Reproduction Year 10 What is the purpose of reproduction? To pass on genetic material which will ensure the survival of the species To make babies To have fun! 2 types: Asexual Reproduction Budding Binary Fission (split in two as in bacteria) Use of a host cell (as in viruses) Spores Vegetative (cutting, rhizomes) Sexual Reproduction Seed Formation by way of Pollen and Egg fusion Reproduction Puffball Asexual Reproduction All offspring are identical (clones) Advantage Quick population growth No partner needed Logging trunks straight, bananas no seeds Disadvantage Kill one, kill all Human intervention cuttings, genetic engineering Strawberry runners Potato tubers Cooch grass rhizome Aphids Sexual Reproduction Offspring are different from parents (variation) Advantage Survival of the fittest (finches)finches If environmental change occurs, increased chance of species survival. Disadvantage Need a partner!? Energy wastage The Structure of DNA DNA (deoxyribonucleic acid) is the genetic material found in the nucleus of living cells Its structure is described as a double helix Animation of DNA in the body Chromosomes DNA is divided into chunks called Chromosomes Humans have 23 pairs of chromosomes Why? 1 from Mum, 1 from Dad XX pair is a female XY pair is a male Karyotype diagram Genes Each chromosome is divided up into genes. Genes are a sequence of DNA that codes for a trait, such as fixed or free earlobes. Alleles are alternative forms of the same gene Sometimes the appearance can be enhanced by other means Gametes 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. Gametes A gamete is a single cell, one from each parent, that creates a new individual Female gamete is known as an ovum or egg Male gamete is known as a sperm Each human gamete has 23 chromosomes All other cells in your body have 46 chromosomes. When the egg and sperm fuse, a new life is produced, having all 46 chromosomes Fertilisation This is the process when the chromosomes of the egg and sperm combine, creating a new individual Fertilisation may occur inside the animal or in the environment (water) The single cell organism (zygote) starts to divide into an embryo then a foetus Nine months is required for the foetus to develop into a fully developed newborn baby Male reproductive Organs Penis Insertion of semen Urethra Tube expelling sperm and urine Scrotum Temp. regulation Testes Make sperm and testosterone Vas deferens Transports sperm Seminal vesicle Produce fluid to help motility of sperm Female reproductive organs Vagina Birth canal Cervix Allows passage of sperm and menstrual blood Uterus Egg implantation site Expands to hold baby Ovary Produces eggs and hormones Fallopian tube Allows passage of egg Site of conception Menstrual Cycle Once a month an egg leaves the ovaries (ovulation) travels down the fallopian tubes towards the uterus Before ovulation Oestrogen stimulates the uterus lining to build up in preparation for pregnancy If the egg is fertilized by a sperm it attaches to the wall of the uterus and develops into a baby. If the egg isn't fertilized it doesn't attach to the wall so the uterus sheds the extra lining. The blood and unfertilized egg leave the uterus through the vagina. This is a menstrual period. Menstrual Cycle Hormones are the chemical messengers which co-ordinate the 28 day cycle Changes during puberty Hormonal changes cause: Growth spurt Hair growth Body shape changes Voice changes Menstruation begins Body odour Emotions fluctuate Amphibian life cycle Create a poster which explains the life cycle of a frog. Groups of 4 (think about the make up of your team not just friends!) Marked on teamwork Informative resources Presentation Timescale? amphibian Alleles Every body cell has 23 pairs of chromosomes. WHY? During fertilisation one came from Mums egg and one from Dads sperm So each cell must have a pair of genes, called alleles, coding for every trait. They may be the same e.g AA Or different e.g. Aa 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 rollCant roll Punnet Square All possible combinations of gametes can be shown (father can roll TT, mother cant 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? ____________ Eye colour In eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b: bbBBBb Homozygous brown-eyed parent Heterozygous brown-eyed parent Blue-eyed parent What would the offspring have? This is an example of monohybrid inheritance Eye colour Example 1: A homozygous brown-eyed parent and a blue-eyed parent: Example 2: 2 heterozygous brown-eyed parents BBbb X Bb X Parents: Gametes: Offspring: Bb BBBbbbbB BBbbBbBb All offspring have brown eyes25% chance of blue eyes Eye colour Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Bb bb bbBb Equal (50%) chance of being either brown eyed or blue eyed. Example questions 1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram. 2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kittens genotype first). Trait Gene Location Dominant Phenotype Possible Dominant Genotypes Recessive Phenotype Recessive Genotype color of iris2not blueEE or Eeblueee widow's peak4peakPP or Ppno peakpp cheek dimples5dimplesDD or Ddnot dimplesdd face freckles9frecklesFF or Ffno frecklesff mid-digital hair10hairHH or Hhno hairhh Hitchhiker's thumb 17straightTT or Ttcurvedtt Hallux length (toes) 20long 2nd toeBB or Bb long big toe or = to 2nd toe bb ear lobes21freeLL or Llattachedll tongue rolling22abilityRR or Rrno abilityrr cleft chin16cleftYY or Yyno cleftyy DISCRETE HUMAN CHARACTERISTICS Discrete is not continuous it must be one of a few possibilities. 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 Blue rose 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? Clone a mouse! MORE ON CLONING Why NOT clone? Do we understand all the issues? Inefficient less than 10% of all cloning attempts work. Lack of variation. Ethical issues -Can you produce a human foetus just to use as spare parts? Celebrity Sheep Has Died at Age 6 Dolly, the first mammal to be cloned from adult DNA, was put down by lethal injection Feb. 14, Prior to her death, Dolly had been suffering from lung cancer and crippling arthritis. Although most Finn Dorset sheep live to be 11 to 12 years of age, postmortem examination of Dolly seemed to indicate that, other than her cancer and arthritis, she appeared to be quite normal. The unnamed sheep from which Dolly was cloned had died several years prior to her creation. Dolly was a mother to six lambs, bred the old-fashioned way. Something to think about Plants are cloned all the time. NZ has forests made up entirely of clones. All bananas are cloned (they dont have seeds do they?) and so are lots of other plants. No one is worried about that. Whats the difference? RANDOM GENETICS QUESTIONS 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. biology/variationandinheritance/index.shtm lhttp://www.bbc.co.uk/schools/gcsebitesize/ biology/variationandinheritance/index.shtm l Mitosis Meiosis