Unit 13 Inheritance And Selection

Science Interactive LTD Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk Science Interactive LTD Copyright 2005 Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150 PowerPoint slides . Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images , graphics , challenging exercises and questions . Units can be used in the classroom via an interactive whiteboard , data projector or used during individual study via a PC or school network . Unit 19: The Transitional Metals Unit 18: Metals and their Properties Unit 17: The Alkali Metals Unit 16: The Periodic Table and its Elements Unit 15: Genetic Engineering Unit 14: Evolution and Human Impact Unit 13: Inheritance and Selection Unit 12: Mitosis and Meiosis Unit 11: Flow of Energy and Elements through the Environment Unit 10: Water Transport in Plants Unit 9: Photosynthesis in Green Plants Unit 8: Drugs and Bad Body Maintenance Unit 7: Hormones and the Endocrine System Unit 6: Human Homeostasis Unit 5: Nervous System and the Senses Unit 4: The Respiratory System Unit 3: Healthy Body and Immunity Unit 2: The Circulatory System Unit 1: The Digestive System Unit 38: Cells, Tissue, Organs and Organs systems Unit 37: Natural Forces Unit 36: Sound and Hearing Unit 35: The Alkaline Earth Metals Unit 34: The Earth and Plate Tectonics Unit 33: Earth and Space Unit 32: Newton's Forces and the Effects of Forces Unit 31: Radioactivity Unit 30: Light and the Electromagnetic Spectrum Unit 29: Electricity Unit 28: Generating Electricity and its Domestic Use Unit 27: Energy Unit 26: Rates of Reaction Unit 25: The Noble Gases, their Properties and Uses Unit 24: The Halogens, their Uses and Compounds Unit 23: Ionic and Covalent Compounds Unit 22: Elements, Molecules and Compounds Unit 21: Rock Cycle Unit 20: Crude Oil and its Products

Unit 13

Inheritance and Selection

What is the material of inheritance in organisms.

That the material of inheritance is the gene and that human DNA contains just over 31,000 different genes.

How we inherit these different genes from our father and mother.

That meiosis in humans leads to the production of the sperm and egg cells.

That during meiosis, the number of chromosomes in both the sperm and the egg cells are halved.

That we inherit certain characteristics including eye colour and blood group.

That a mutation is a change in a gene or chromosome causing a change in a characteristic, for example sickle cell anaemia.

How to predict the genotype and phenotype of offspring using monohybrid crosses.

The evolution of humans from our ancestors.

How to use pedigree analysis to trace inherited diseases like haemophilia.

Inheritance, Genes, Chromosomes, Allele, Mitosis, Meiosis, Cell, Division, Clones, Reductive, Sperm, Ovum, Traits, Gametes, Characteristics, Pedigree, Recessive, Dominant, Genetic, Crosses, Diploid, Haploid Mutations, Monohybrid & Sickle cell. Unit 13: Inheritance and Selection web: www.science-interactive.co.uk email: sales@science-interactive.co.uk Science Interactive LTD PO BOX 50764 LONDON NW6 9AT Click mouse to begin Science Interactive LTD Copyright 2005 Understand: Keywords:

Material of inheritance: Genes and chromosomes Inheritance is the method by which parents pass on their traits or characteristics to their offspring. During fertilization, where the sperm and egg fuse, genes from the father and mother join and code for a new unique individual. Inside nearly all cells, there is a nucleus containing thread like c___________ which contain many thousands of g_______ that control all your characteristics. Each chromosome contains hundreds of genes. Each gene codes for a c___________, for example eye or hair colour. Genes and chromosomes are made from DNA. Genes and chromosomes: Science Interactive LTD Copyright 2005 Word bank: chromosomes genes characteristic Each gene codes for a particular characteristic or trait, for example eye colour, blood type or skin colour. There are dominant and recessive genes for these traits. Gene and alleles Notes Diagram In humans, most cells have a nucleus containing chromosomes, half inherited from the mother (contained in the egg) and half from the father (in the sperm.) Human skin cell In humans there are 23 pairs of genes. A single chromosome may contain hundreds of separate genes. Humans have over 31,000 genes coding for life. Human chromosomes

DNA and genes Each gene codes for a c___________ for example eye or hair colour. One gene is made from a short length of D eoxyribo N ucleic A cid. DNA is like a list of instructions made from 4 different bases located on a sugar-phosphate chain. Every 3 bases codes for a particular amino acid which are the building blocks of p_______ which help build cells and enzymes. These enzymes control your metabolism. The DNA molecule: Science Interactive LTD Copyright 2005 Word bank: characteristic protein The DNA molecule contains thousand of genes coded from 4 bases: Adenine, Guanine, Thymine & Cytosine. These bases are read like a code of instructions building proteins and enzymes. Humans have 23 pairs of chromosomes containing just over 31,000 genes. Each base pairs with another base on the opposite strand. Remember, one strand is inherited from your mother, the other from your father. DNA is found in the nucleus of all cells. It is a double stranded helix, one strand inherited from your mother, the other from your father. Notes A = T T = A C = G G = C A Adenine G Guanine T Thymine C Cytosine S Sugar P Phosphate Diagram Key DNA double helix and DNA base pairs DNA molecule

Genes in different species Each chromosome is made from hundreds of genes made from deoxyribonucleic acid ( DNA ). These genes carry the i___________ that codes for how we grow and what we look like. Each trait or characteristic is coded for by a pair of genes located on the same part of a chromosome pair. One g_____ is inherited from your father the other from your mother. So two genes code for every characteristic that you have like eye or skin colour. Genes in different species: Science Interactive LTD Copyright 2005 Word bank: information gene In red clover there are only six pairs of chromosomes. Most plants have less chromosomes than animals. Red clover In chickens there are actually 39 pairs of chromosomes, with over 50,000 pairs of genes, 19,000 more than humans ! Chicken Notes Diagram In humans there are 23 pairs of chromosomes in every cell nucleus apart from red blood cells. Human In cats there are 19 pairs of chromo-somes. The cat has around 20,000 pairs of genes, some 11,000 less than humans. Cat

Meiosis gametes in humans Meiosis leads to the formation of only two types of cells. Meiosis in males forms the s______ and in females the o______ or egg cells. Meiosis halves the number of chromosomes, so that when the sperm and egg fuse, the fertilised zygote will have the correct number of chromosomes ( 23 chromosomal pairs). Meiosis also produces random gene mixing leading to variation of human traits in new individuals. Gamete production in the male and female: sperm egg Science Interactive LTD Copyright 2005 Word bank: sperm ovum All of these 31,000 genes code for all the traits and characteristics that make human life unique. Cells now divide by mitosis. After fertilisation, all cells of the developing embryo now contain 23 pairs of chromosomes with over 31,000 genes. Sperm and egg cells are haploid with only 23 single chromosomes, only half the normal number Gametes cells (sperm and egg) are produced by the testis and ovaries in the male and female. Pregnancy Embryo Fertilisation Gametes

Meiosis Reductive cell division During meiosis, the number of chromosomes are halved so that the s______ and egg carries 23 single chromosomes. During meiosis, paternal genes that code for your characteristics randomly mix, so that we are all not the same. Name the cells in plants that are produced by the process of meiosis ? Stages in meiosis: Science Interactive LTD Copyright 2005 Word bank: sperm Meiosis Stage one Stage four Stage two Stage three 2n n 4n 2n Parent cell & replicates 2 daughter cells 4 daughter cells DNA mixes Sperm production Notes Diagram Stage 1: Chromosomes double and randomly mix inside the nucleus. The cell now contains 46 pairs of chromosomes. Stage 2: The chromosomes move to the centre and line up before separation. Stage 3: The cell divides, producing two new cells each containing 23 pairs of chromosomes. Stage 4: The two daughter cells divide again halving the number of chromosomes. Each gamete now contains only 23 single chromosomes. A sperm cell carries 23 single chromosomes and fuses with an egg cell which also carries 23 single chromosomes to form a zygote, which now carries the normal diploid number of chromosomes. Meiosis (reductive cell division)

Meiosis Variation in humans one Humans have many of their genes which are common to us all. Over 99% of our genes in all the races are shared. Only 1% of human genes are unique and different. These genes code for differences in the c_______ of skin, eyes and hair and other features like the shape of our faces. Unless you’re an identical twin, your genes, your traits and you are u_________ amongst the other 5.5 billion human beings found on this planet. What are the advantages of variation in a species like humans? Variation in humans: Science Interactive LTD Copyright 2005 Word bank: colour unique Variation in humans (traits such as skin and eye colour) occur due to the random mixing of DNA during meiosis ensuring that no egg or sperm carry exactly the same genes or DNA and of course during fertilisation, when the genes from your mother and father mix to form you. Notes Japanese Maori Arab Diagram Masai warrior Aborigine

Meiosis Variation in humans two Variation in the human race is caused by d___________ in your genes, caused by the random mixing of DNA during the production of sperm and egg and of course when the genes from your f______ and mother join during fertilisation. Your mother and father both share exactly 50% of your DNA and are your closest biological relatives. Brothers and sisters can share up to 50% of their DNA, but the figure is usually only around 25%. Why do brothers and sisters look very similar to one another ? Variation in humans: Science Interactive LTD Copyright 2005 Word bank: differences father Look around you in class, we all have certain similarities, but we are all unique. We belong to the same species, can reproduce with one another but are all different. Some people are taller or heavier or have different colour hair, skin or eyes. This is called variation. This is because we all have different genes in our cells from our parents. Notes South American Europe (south) Asian Diagram African Europe (north)

Characteristics in humans one You carry two genes for each characteristic. These two genes are found opposite each other in identical chromosome pairs. One gene is inherited from your f________, the other from your m________. During fertilisation, single chromosomes from your parents pair and determine all your characteristics, including e____ colour, blood group, height and skin colour. Why is variation in individuals beneficial to a species’ survival ? Characteristics in humans... discontinuous: Science Interactive LTD Copyright 2005 Word bank: father mother eye Discontinuous variation : Some people have blue eyes, some have brown. This is an example of discontinuous variation. Here there is no range or in between, you are either blue eyed or brown eyed. Blood group in humans is another example of this type of variation. Humans have four distinct blood groups: A, B, AB and O. Notes Double jointed Blood group Eye colour Diagram Freckles

Characteristics in humans two Even humans are adapted to where they live through evolution and survival of offspring that carry the right genes for the right characteristics that make us suited to our e___________. An example of adaptation in humans is skin colour and nose size. In humans, skin colour is caused by melanin, a pigment which protects us from UV radiation. Skin colour darkens as we travel further s_______ from northern Europe to central Africa. Our nose warms and moistens the air we breathe. In this example, as you travel away from the equator, noses become bigger and more prominent because of the colder air. Why do Eskimos have no facial hair ? Characteristics in humans... continuous: Science Interactive LTD Copyright 2005 Word bank: environment south Continuous variation : If you measure the height of one hundred people, you would obtain a whole range of heights from the very tall to the very small. Most people would be of average height. This is an example of continuous variation. Skin colour, hand span and shoe size are other good examples of continuous variation. Make a survey of height and hand span. Plot your results and determine whether these traits are linked to one another ? Notes Hand span Height Skin colour Diagram Hair colour

Phenotype and genotype Every human has a unique DNA or gene code contained in the 23 chromosome pairs found in all cells. This is called their genotype and cannot be changed. A humans’ phenotype is what they look like and is the result of a person’s genotype and their environment. For example, a human cannot change their b_______ group, it is either A, B, AB or O, but they can change their hair colour by simply dying it. Other traits that can be changed include w_______, eye colour and skin colour. List other ways in which you can change your appearance or phenotype ? Phenotype and genotype: Blood group Male Female Skin colour Hair colour Science Interactive LTD Copyright 2005 Word bank: blood weight Changing your phenotype : You can easily change the way you look by tanning your skin, dying your hair, overeating or even by wearing coloured contact lenses. Some even have cosmetic surgery to change the way they look. What you can’t change are traits like your blood group. Make a survey of those in your class who have changed the way they look by dying their hair or perhaps by wearing coloured contact lenses ? Notes Phenotype one Genotype two Phenotype two Diagram Genotype one

Genes and alleles Different forms of the same gene are called alleles . You have two alleles which control your eye colour: one from your father (sperm) and one from your mother (egg). There are 4 different alleles in the human race for e_____ colour: Blue allele, Green allele, Brown allele and Hazel allele. There are many more for s______ colour which explains why humans have many different flesh tones from the very dark to the very light. Make a survey in your class of which is the most common allele for eye and hair colour...are they linked ? Alleles in humans: Blue Green Brown Hazel AB group A group B group O group or or Black Red Brown Blonde Science Interactive LTD Copyright 2005 Word bank: eye skin Hair colour Blood group Eye colour Trait Diagram

Dominant and recessive genes Different forms of the same gene are called alleles. Humans carry different alleles for one particular t______, for example eye colour. When there are two different alleles for one characteristic, one is usually stronger or d_________ to the other. For example, eye colour in humans is controlled by a blue and a brown allele. The brown allele is dominant and the blue allele is recessive, which means that a person with blue eyes must have both blue alleles, whereas a person with brown eyes can either have one or two brown alleles. In the table below are some examples of dominant and recessive characteristics (B = allele for brown eyes, b = allele for blue eyes; H = Brunette, h = Blonde; F = Plain skin, f = freckles; S =Normal blood, s = Sickle cell) Dominant and recessive traits in humans: BB or Bb HH or Hh bb FF or Ff SS or Ss hh ff ss Science Interactive LTD Copyright 2005 Word bank: trait dominant Genotype Recessive genotype Blood type Freckles in humans Dominant genotype Genotype Eye colour Hair colour

Meiosis Determining sex by chromosomes Your chromosomes also determine what sex you are at b_______. In humans there are 23 pairs of chromosomes found in every cell. 22 pairs are identical, but pair 23 do not match. Pair 23 are called the sex chromosomes. All eggs from the female contain the X chromosome, all sperm from the male contain either the X or Y chromosome. At fertilisation, the egg may join with either an X or Y sperm producing equal numbers of males ( XY ) or females ( XX ). What are the gametes cells called in plants ? Inheritance of the sex chromosomes: Science Interactive LTD Copyright 2005 Word bank: birth During fertilisation, the number of chromosomes are restored to their normal diploid number (23 pairs) The embryo now grows by normal cell division called mitosis. The gamete cells (sperm and egg) carry only 23 single chromosomes. They are haploid cells. Your sex is determined at the moment of fertilisation by the male sperm. An X carrying sperm produces a girl, and a Y carrying sperm produces a boy. There is a 50: 50 chance of either sex. Sex inheritance Gamete cells Female Male

Studying genetics using pea plants Geneticists use pea plants to determine how genes interact with one another to produce different phenotypes in individuals because: They can use pure breeds with known genotypes; They can control which plant p________ another plant; They are easy to grow and have a very short life cycle. Mendel, with knowledge of the genotype of both parents ( P 1 ), used peas to work out the inheritance of characteristics in the offspring ( f 1 ), showing their phenotypes and genotypes. He also worked out which characteristics were dominant and recessive in pea plants by the ratio of these traits in the offspring. Mendel's work in peas: Pink White Science Interactive LTD Copyright 2005 Word bank: pollinates Plant seeds from pod are allowed to germinate producing the f 1 offspring . The pollinated carpel (egg) is allowed to mature producing seeds in a pod. Transfer pollen from stamen of white flowers to the carpel of pink flowers. Select pure breeds of pink and white flower pea plants. These are the P 1 parents . Notes Seed pods Controlled cross f 1 Offspring Diagram P 1 Parents

Working with genetic crosses in pea plants Using genetic crosses, with knowledge of the genotype of both parents ( P 1 ), you can work out the inheritance of characteristics in the offspring ( f 1 ), showing their phenotypes and genotypes using the dominant-recessive rule. Genetic crosses in peas: (Pea plants can either have green or yellow seed pods.) Green Yellow Genetic cross: A heterozygous smooth seed plant ( Gg ) is crossed with a homozygous wrinkled seed plant ( gg ) Complete the table Science Interactive LTD Copyright 2005 Offspring ratios: Cross Gametes Female ( gg ) Male ( Gg ) Genotype S S g g G g g g Sperm Egg Pollen We can show the recessive wrinkled allele as g Recessive We can show the dominant smooth allele as G Dominant Strength Character

More genetic crosses in peas one Work out the following offspring ratios ( f 1 generation ) Genetic crosses in peas: (Pea plants can also have either pink or white flowers) Genetic cross: A homozygous pink flower plant ( PP ) is crossed with a homozygous white flower plant ( pp ) Pink White Complete the table Science Interactive LTD Copyright 2005 We can show the recessive white allele as p Recessive We can show the dominant pink allele as P Dominant Strength Character Offspring ratios: Cross Gametes Female ( pp ) Male ( PP ) Genotype P P p p P P p p Sperm Egg Pollen

More genetic crosses in peas two Work out the following offspring ratios ( f 1 generation ) Crosses in peas: (Pea plants can also have either smooth or wrinkled seed pods) Genetic cross: A heterozygous smooth seed plant ( Ss ) is crossed with a heterozygous smooth seed plant ( Ss ) Smooth Wrinkled Complete the table Science Interactive LTD Copyright 2005 We can show the recessive white allele as s Recessive We can show the dominant pink allele as S Dominant Strength Character Offspring ratios: Cross Gametes Female ( Ss ) Male ( Ss ) Genotype S s s S S s s S Sperm Egg Pollen

Mutations in humans A mutation is a change in a single g_____ or allele, which can cause a change in a trait or characteristic. In humans, these m_________ are sometimes very trivial (e.g. hairy ears) to life changing and sometimes fatal (e.g. sickle cell anaemia.) These mutations are passed from parents to offspring like any other traits during fertilisation. Why do families who have a high risk from having offspring with a inherited disease screen embryos for the disease ? Mutations in humans: Science Interactive LTD Copyright 2005 Word bank: gene mutations Down’s syndrome is caused by an extra chromosome inherited from the mother. The egg contains 24 single chromosomes, not 23 . Down’s syndrome An extra copy of the gene that codes for fingers has been somehow inherited from either parent. Explain why this is not fatal ? Extra finger Notes Diagram Sickle cell anaemia is an inherited disease of the blood. Sickle cells carry less oxygen to tissues and cells. This disease is fatal. Sickle cell anaemia In Albinos, the gene that controls skin pigment does not work. Albinos need to avoid UV light. Why do all albinos need to avoid UV light ? Albino humans

Sickle cell anaemia Sickle cell anaemia is a genetic disease of the blood that affects African populations. The disease is passed through faulty genes carried by the paternal s_____ or maternal eggs. Red blood cells are sickle shaped with a reduced s_________ area, which reduces the amount of o________ carried to the cells and tissues. This disease is normally fatal. How can genetic counselling help parents and families who carry the faulty gene for sickle cell anaemia make choices when having children ? Sick cell anaemia: Science Interactive LTD Copyright 2005 Word bank: sperm surface oxygen O 2 O 2 O 2 O 2 O 2 O 2 O 2 O 2 O 2 O 2 O 2 Oxygen O 2 O 2 O 2 O 2 O 2 Oxygen Oxygen Oxygen Normal cell Sickle cell Faulty genes inherited from one or both parents cause sickle cell disease. The surface area of the sickle cell is reduced. Sickle cell Less oxygen than normal reaches the tissues and cells. The sickle shaped red blood cells are not able to carry sufficient oxygen because of their reduced surface area. Oxygen transport Normal red blood cells have no nucleus and are biconcave in shape to help transport oxygen around the body. Notes Diagram Normal blood

Sickle cell anaemia: Case study Sickle cell humans have malformed red b_______ cells (sickle shaped.) These cells have abnormal haemoglobin, which makes it difficult for the blood cells to carry sufficient oxygen. This disease is common in West Africa. Although the homozygous (ss) condition is fatal, the heterozygous (Ss) individual is resistant to malaria, a fatal microbe carried by m__________. So the gene survives in the population in heterozygous carriers. Example: ( What’s the ratio of normal: sickle cell offspring ?) A heterozygous carrier male ( S s ) is crossed with a heterozygous carrier female ( S s ) Normal Sickle Science Interactive LTD Copyright 2005 Word bank: blood mosquitoes Offspring ratios: Cross Gametes Female ( Ss ) Male ( Ss ) Genotype S s s S S s s S Sperm Egg We can show the dominant normal red blood cell as S We can show the recessive sickle cells as s Recessive Dominant Strength Character

Pedigree and the Royal Family Genetic counselling provides information and advise to couples who wish to have children but are worried that they might pass on a genetic disease to their c_________. Scientists often make use of a diagram known as a pedigree, which is a tool for tracing a disease or its carriers through generations in a family. A famous example of using a pedigree is haemophilia in the the royal family. Queen Victoria was a carrier for haemophilia, a blood c__________ disorder. In boys, only one copy is required to produce the disease, in girls both recessive copies are required. This is because the haemophilia allele is carried on the XY sex chromosomes. Look at the pedigree of the royal family and trace how the gene for haemophilia has moved through the generations ? Tsar Romanov Rasputin Royal family pedigree Science Interactive LTD Copyright 2005 Word bank: children clotting Victoria carried the haemophilia gene, but did not suffer any illness. Boys who inherit one copy, suffer the full effects of haemophilia. See how the gene affected the Romanov family, with Tsarina Nikolas passing the gene to her son Alexis. In 1918, the Bolsheviks executed the Tsar and his children including Alexis the haemophiliac partly because of Rasputin’s influence over the Tsar ! Tsar Nicholas Romanov had a haemophilic son who constantly bled. Rasputin, a priest claimed to be able to cure his son. Rasputin, because of his ‘healing powers’ had great influence with Tsar Nicholas. This lead to suspicion and the revolution by the Bolsheviks in 1918. Tsar Nicholas, his wife and five children were executed by soldiers.

Evolution is about a gradual change in the features or c_____________ of a species over time that help it to survive in their environment. These changes in characteristics are brought about by random changes in the g______ of an individual. This happens during meiosis when the gametes are produced . Offspring with inherited adaptations that give them a unique advantage over others, are more likely to survive, compete for resources and breed. These adaptations are then passed on to the next generation. Visit google.co.uk and type in key word ‘Lucy’ and ‘Ethiopia’.... Why is the Lucy skull a very significant scientific find ? Human evolution: 4.0 million years BC 2005 AD New species Old species 3,000,000BC 2,000,000 B.C 1,000,000 B.C 500,000 B.C Human evolution Science Interactive LTD Copyright 2005 Word bank: evolution gene Homo sapiens Homo neandertalensis Homo erectus Homo habilis Australopithecus africanus Australopithecus afarensis We know from fossil evidence and DNA comparisons that are nearest primates are the chimpanzees. Over the last 3 to 4 million years, humans have formed a new species distinct and different from one common ancestor like ‘LUCY.’ A new species is so different that neither can mate with one another. Notes Diagram

Human progress one From ‘Lucy’ the first human like ape who walked the Earth around four million years ago to now, we as a race have evolved like no other species. We have the ability to communicate, learn, solve complex tasks, record all our achievements through l__________, change our own environment and even fight d_________ with medicines. We also care for our less able through the community. The sense of community and sharing in all our achievements is perhaps our biggest evolutionary adaptation. In Europe for the young and old, there is little ‘struggle for existence.’ Do any other species live in large communities cooperating with one another ? Human progress: Science Interactive LTD Copyright 2005 Word bank: language disease Stonehenge Lascaux caves Communities Using tools Beginning of humans Stonehenge was built around 6000 years ago. This monument marks the Sun’s position during the summer and winter solstice. These painting were drawn on the walls of the Lascaux caves in France around 15,000 B.C. Earliest cave paintings are 50,000 old. Humans lived in large social groups, able to share every day tasks including hunting, building shelter and raising their young. Humans began to use tools, live in groups and use basic languages to enable them to communicate. Hunting for food became common. Lucy's fossil remains were discovered in 1974 in Ethiopia. She is the oldest recorded human like primate. Her age is about 3.2 million years.

Human progress two Successful civilisations rise and f_____ with time, but progress for the entire human race continues. One of our great strengths is our ability to record using the written word , all the previous innovations and discoveries of our forefathers. In addition, it is the continued curiosity of the human r_____ that leads us to make new and exciting discoveries. Furthermore, we educate and care for our young for many years. What lies next for our species is our responsibility. How we treat our environment, our home and other minorities is a major issue for our continued success. The only question is what part will you play ? Human progress: Science Interactive LTD Copyright 2005 Word bank: fall race Electronic age Industrialisation Iron age Romans Pyramids The silicon chip used in circuits has revolutionised how we work and live. Modern life is based upon this technology. The 18 th century industrial revolution began the biggest increase in our quality of life and life expectancy. The iron age led to the discovery of how to extract iron from its ore. Iron is used for many structures and for making steel. Romans perhaps the most successful empire saw its lands stretch from Britain to the shores of North Africa. The pyramids built by the Egyptians around the same time as Stonehenge shows great differences in a nations progress.

1: Define the following terms: Chromosome, Gene, Allele, Characteristic, Diploid, Haploid, Trait, Genotype, Phenotype, Mutation, Recessive and Dominant. 2: Look at the two pictures below. Complete the table. 3: Answer the following: a) Give 3 examples of human traits or characteristics. b) Give 3 examples of traits or characteristics in plants. c) Name two cells that have a diploid number of chromosomes and two cells that have a haploid number of chromosomes. Do any cells in humans have no chromosomes. d) From the following, decide whether each cell is the result of mitotic or meiotic cell division. Extension questions and homework Science Interactive LTD Copyright 2005 Brief description Meiosis Mitosis Example of cell produced Cell division Bacteria Sperm Muscle cell Pollen Plant ovum Sperm cell Skin cell Blood cell

4: Decide which are dominant or recessive forms of the following alleles (Clue: Make a survey of the class, recessive traits should be low in numbers) 5: (i) Chromosomes occur in pairs in all cells except gametes. (a) What are alleles (b) Why are there two alleles for each characteristic (c) Explain what is meant by dominant and recessive alleles. (ii) In flies there are two alleles for wing size; normal wing and short wing. Using the symbol W = normal wing (dominant) and w = short wing (recessive) write down the following; (a) The genotype of a fly which is heterozygous for this character (b) The possible genotypes for its gametes (c) Work out what kind of offspring would be produced ( f 1 ) if a heterozygous fly mated with one which was homozygous for normal wing. 6: (i) A couple decided to have a child. The father and mother are both heterozygous for the gene for cystic fibrosis: (a) Show the genotypes for both parents, their possible gametes and the possible genotypes and phenotypes for their children. Construct a monohybrid cross and use the symbol C for the normal allele and c for the cystic fibrosis allele. (ii) The characteristics of humans are either inherited, or are caused by environmental influences. [Blood group, Weight, Eye-colour, Gender and Accidental loss of arm] (a) Which features are controlled by environmental influences (b) Name one that is controlled by inheritance only (c) One that is controlled by both. Internet: Go to google.co.uk and find about how haemophilia affects blood clotting in males and how the Russian Romanovs (Tsar Nicholas II) were affected by this disease. See also the pedigree of our own Royal Family. Furthermore find out about genetic counselling and how is it offered to those who are at risk of inheriting or passing on genetic diseases like sickle cell anaemia. Science Interactive LTD Copyright 2005 Six fingers: Five fingers Normal skin colour: Albino Tongue rollers: Non tongue rollers Free ear lobe: Ear lobe attached Hairy ears: Hairless ears Blue eyes: Brown eyes Dark hair: Light hair Freckles: No freckles