1 Year 10 Science Genetics

2 Genetics outcomes This unit will cover: History Chromosomes and genes Genetics problem solving Human inheritance DNA To gain a satisfactory for this unit: 1.Keep a careful record of all theory and related activities 2.Participate in practical work and complete a written record 3.Complete a research task 4.Complete a test or exam

3 What is genetics? Genetics is the study of heredity Animals, plants and micro-organisms are studied

4 History Gregor Mendel – father of genetics Monk in Austria in 1856 Studied peas in the monastery garden

5 Mendel’s results Parentround pea X wrinkled pea F 1 all round peas F 1 crossed F 1 X F 1 F 2 3 round : 1 wrinkled

6 Mendel’s conclusions Round is dominant to wrinkled in peas Yellow is dominant to green peas A dominant trait masks the effect of a recessive trait Mendel’s scientific work was ignored for about 40 years

7 Chromosomes Are long thread like structures found in the nucleus Made of a chemical called DNA Deoxyribonucleic acid DNA is coiled tightly inside a cell

8 Genes Genes are found on chromosomes Genes code for particular traits Many thousands of genes are found on each chromosome

9 Homologous chromosomes 2 copies of each chromosome in each body cell 2 copies of each gene in each cell Humans have 46 chromosomes in each body cell

10 Chromosomes, genes and alleles

11 Haploid and diploid cells Diploid cells have 2 copies of each chromosome eg body cells Haploid cells have 1 copy of each chromosome eg gametes (egg and sperm)

12 Human chromosomes Humans have 46 chromosomes in every body cell 23 chromosomes in every sperm and egg egg X sperm zygote 46 New individual 46

13 Mitosis The process of cell division to make new body cells replaces old and damaged cells 2n 46

14 Meiosis Formation of eggs in ovary and sperm in ovary and testes Forms haploid cells 2n n Human chromosomes in egg or sperm

15 Genotype and phenotype Let B = brown eyes, b = blue eyes B is dominant to b Every individual has 2 copies of each gene The genotype of an individual is its genetic makeup eg BB or Bb or bb The phenotype of an individual is its outward appearance eg blue eyes or brown eyes

16 Homozygous and heterozygous An allele is the alternative forms of a gene eg B or b Homozygous individuals have the same allele on both chromosomes eg BB or bb Heterozygous individuals have different alleles on both chromosomes eg Bb

17 Homozygous X homozygous Let B = brown eyes, b = blue eyes B is dominant to b P phenotype brown eyes X blue eyes P genotype BB X bb Gametes B b F 1 genotype Bb F 1 phenotype All brown eyes

18 Heterozygous X homozygous P phenotype brown eyes X blue eyes P genotype Bb X bb Gametes B, b b F 1 genotype ½Bb, ½bb F 1 phenotype ½brown eyes, ½blue eyes

19 Heterozygous X heterozygous P phenotype brown eyes X brown eyes P genotype Bb X Bb Gametes B, b B, b F 1 genotype ¼BB, ½Bb, ¼ bb F 1 phenotype ¾brown eyes, ¼ blue eyes gametes Bb BBBBb b bb

20 Co-dominance In co-dominance, the phenotype of the heterozygote is a combination of the homozygous individuals Roan cattle

21 Incomplete dominance The heterozygote is intermediate between the two homozygous organisms Snap dragons colours