Trilogy – Biology – CHAPTER 6 – Genetics What is a gene? Sexual reproduction involves the joining (fusion) of male and female g__________ (sperm and egg cells in animals). In sexual reproduction there is mixing of g___________information, which leads to v__________ in the offspring. The formation of gametes involves cell division called m___________. The genetic material in the nucleus of a cell is composed of a chemical called D____contained in the c___________ Human body cells contain __________ pairs of chromosomes. DNA is made of very large molecules in long strands, twisted to form a d_______ h________. A g________ is a small section of DNA on a chromosome. All the genetic material of an individual is called its g____________ What is an allele? If an individual is heterozygous, what can you say about their two alleles? Cystic fibrosis is caused by a recessive allele. Using N to represent the normal dominant allele and n to represent the cystic fibrosis allele, answer the following questions. A Complete this diagram to show what the possible genotypes would be if two parents, both of genotype Nn, had children. X Y An embryo is formed from the two gametes above. Will it be male or female? ______________ What type of cell division produces gametes? _______________ How many daughter cells are produced by this type of cell division? ______   Male Gametes N n Female B What percentage of the children would have the disease? __________ C A ‘carrier’ is someone who does not have a genetic disease but whose cells contain one allele for the disease. What percentage of the children would be carriers? _______________ KEY WORDS: Gene allele dominant recessive chromosome DNA homozygous heterozygous Double helix ASSESSMENT:

Trilogy – Biology – CHAPTER 6 – Genetics What are clones? Advantages of sexual reproduction 1 2 Advantages of asexual reproduction What type of reproduction produces clones? Name an organism that reproduces both sexually and asexually? In this genetic diagram, the gene for a genetic condition called Huntington’s is dominant. What is the phenotype of the mother? What is the phenotype of the father? What percentage of their children are likely to inherit the condition? What is the name of this type of diagram? What is it used for? What is embryo screening? Give an example of a potential social problem associated with embryo screening.

Trilogy – Biology – CHAPTER 6 – Genetics What is a gene? Part of a chromosome that codes for a protein ( controls a characteristic) Sexual reproduction involves the joining (fusion) of male and female gametes (sperm and egg cells in animals). In sexual reproduction there is mixing of genetic_information, which leads to variation in the offspring. The formation of gametes involves cell division called meiosis. The genetic material in the nucleus of a cell is composed of a chemical called DNA_contained in the chromosomes Human body cells contain 23 pairs of chromosomes. DNA is made of very large molecules in long strands, twisted to form a double helix. A gene is a small section of DNA on a chromosome. All the genetic material of an individual is called its genome. What is an allele? One version of a gene If an individual is heterozygous, what can you say about their two alleles? They are different. Cystic fibrosis is caused by a recessive allele. Using N to represent the normal dominant allele and n to represent the cystic fibrosis allele, answer the following questions. A Complete this diagram to show what the possible genotypes would be if two parents, both of genotype Nn, had children. X Y An embryo is formed from the two gametes above. Will it be male or female? ___male_____ What type of cell division produces gametes? __meiosis___ How many daughter cells are produced by this type of cell division? __4__   Male Gametes N n Female  NN  Nn Nn   nn B What percentage of the children would have the disease? ____25%______ C A ‘carrier’ is someone who does not have a genetic disease but whose cells contain one allele for the disease. What percentage of the children would be carriers? __50%_______ KEY WORDS: Gene allele dominant recessive chromosome DNA homozygous heterozygous Double helix ASSESSMENT:

Trilogy – Biology – CHAPTER 6 – Genetics What are clones? Genetically identical copies Advantages of sexual reproduction 1 Produces variation in the offspring. 2 Offspring can survive a wider range of environmental conditions/ diseases. Advantages of asexual reproduction 1 Produces large numbers very quickly. 2 Can take advantage of good conditions or food sources. What type of reproduction produces clones? Asexual reproduction Name an organism that reproduces both sexually and asexually? A flowering plant like a strawberry. Aphids. In this genetic diagram, the gene for a genetic condition called Huntington’s is dominant. What is the phenotype of the mother? Suffers from the disease What is the phenotype of the father? Does not have the disease. What percentage of their children are likely to inherit the condition? 50% What is the name of this type of diagram? Family tree for pedigree analysis What is it used for? Working out the chance of inheriting a condition What is embryo screening? Testing embryos for genetic diseases Give an example of a potential social problem associated with embryo screening. People could choose the sex of their babies and lead to an imbalance in numbers.