Inheritance

 Although all humans are similar to each other, we are also different in many ways  The nucleus of a cell contains a chemical called DNA – deoxyribose nucleic acid which controls which proteins the cell makes  Nobody in the world has the same DNA as you

 DNA is coiled up into structures called chromosomes.  All of your body cells have the same number of chromosomes  Task: How many pairs does each cell have?  Where do these chromosomes come from?

 Each chromosome contains many genes  Each gene has coded information that controls a particular characteristic  Different genes code for different characteristics of the body  Task: Name three inherited characteristics

1 – chromatid 2 - centromere 3 – short arm 4 – long arm

Each chromosome is a very long molecule of tightly coiled DNA. The DNA molecule looks like a twisted ladder this spiral shape is called a DOUBLE HELIX DNA molecules carry the code that controls what cells are made of and what they do. They are found inside the nucleus of every cell in the body

 The DNA molecule looks like a twisted ladder Support Double Helix Steps Bases

The double helix ‘ladder’ of a DNA molecule is held together by ‘rungs’ made from pairs of chemicals called bases. There are four types of bases, and they are usually identified by their initials. A T C G

Base pairs hold the two strands of the DNA helix together. It is the sequence of these bases along a DNA molecule code for different proteins. These proteins control the processes within the cell AT CG CG AT

 DNA stands for Deoxyribonucleic acid. DNA molecules are coiled up into structures called Chromosomes. Chromosomes are found in the Nucleus of every cell. They contain Bases called Adenine, thymine, cytosine and guanine. The bases pair up. Adenine pairs with Thymine. Cytosine pairs with Guanine. The bases code for Proteins. The code determines the sequence of amino acids. The role of the proteins is to control processes within the cell.

 Chromosomes are found in pairs in the nucleus of each cell in the body. A small section of DNA is called a gene. Genes are sections of DNA molecules. DNA contains information which codes for proteins. DNA molecules contain pairs of chemicals called bases. The sequence of bases determines what protein the cell makes. Chromosomes are coiled up sections of DNA. Proteins determine the cells function and characteristics

 Can you name the three different fingerprint groups?  Whorl  Arch  Loop

 The analysis of DNA produces a genetic profile  Everyone's profile is slightly different  Police scientists can identify the DNA left behind at a crime scene  It can also be used to identify the Father of a child

 A sample of cells is collected from blood, hair, semen and skin. The cells are broken up and the DNA is extracted. The DNA is cut up by enzymes so that it is left in small pieces and different sizes. A technique called gel electrophoresis separates the fragments. The DNA fragments are placed on a gel bed and an Electric current is passed through the gel. The segments move across the gel and with the smallest moving furthest. A pattern then develops which is The Genetic Profile.

 DNA profiling can be used to help solve crimes  It can also identify health problems  Is this infringing on a person?  What are the problems?  What do you think? – write an argument For and Against

Advantages  Show the similarities between two people  Help to solve crimes  Determine paternity Disadvantages  Identity theft  wrong convictions  Disclosure of information  Human rights/ethical issues  Who owns the sample?  Does it get passed on?  Does it get kept or destroyed?

 During sexual reproduction, an egg fuses with a sperm. The egg and sperm are called gametes and when they fuse the form a zygote. This process is called fertilisation. When the gametes are formed, the chromosome number is halved. This means that only half of the genes come from the mother and the other half come from the father. A human has 46 chromosomes: 23 from the mother and 23 from the father. During fertilisation, the chromosome number is restored.

Sperm: Tip of Head Tail Nucleus Egg: Nucleus Jelly coat Nucleus Cytoplasm

 In human body cells, one of the pairs of chromosomes XX, XY, carries the genes which determines sex.  These separate and combine randomly at fertilisation.  What chromosomes are male?  XY  What chromosome are female?  XX

 Are used to show the inheritance of sex chromosomes  Can be used to determine features such as straight hair or curly hair

 Allele The description of the genotype eg black hair  Genotype Short for the first and second generation in a genetic cross  Phenotype Two identical alleles  Dominant A variety of a gene  Recessive The allele that shows the phenotype whenever it is present  F1/F2Two different alleles  Homozygous/Homozygote The allele that is hidden whenever a dominant allele is present  Heterozygous/Heterozygote The genetic make-up of an individual eg BB

 Draw punnet squares for the following;  Hair Colour – BB rr  Eye colour – Bb Bb  Height – Tt tt  Include the names of each stage and the ratio

 Parental Phenotype – male/female  Parental genotype – xx/xy  Gametes – x x / x y  F1 genotype – xx, xx, xy, xy  F1 phenotype – male, male, female, female

 Genes do not remain the same forever  New genes are rare but do occur by mutation  A mutation is the change in the structure of a gene  This can occur naturally or can be caused by environmental factors  Some mutations do not result in harm however some do

 One of the most famous scientists of all time  Experimented on “tall” and “dwarf” pea plants that were breeding  He crossed the plants and didn’t get the expected results  This was how he determined dominant and recessive genes  He also determined that most characteristics are controlled by more than one gene

 At the time, no one took notice of Mendels results – he did not publish them in a journal  He presented his results in his home town of Bruun which was then published in a local paper  Mendels paper was rediscovered in 1900 and his experiments replicated  The structure of DNA and genes was not understood until 1950’s.

 What is resistance?  Soya bean plants have a gene resistant to herbicides  The crops are sprayed with herbicides to kill the weeds but the plant remains unaffected  This results in an increased yield due to a competition for space and nutrients

 Plants that show resistance may be cut out and transferred into another plant  1980 – the potato was modified to show resistance to bacterium in the soil  Therefore it has its own insecticide  The gene for the poisons production was transferred to potato plants which then made the plant resistant to insect pests

 Why would it benefit plants to be resistant to herbicides?  Weeds compete with crops  Herbicides kills the weeds  Less chemicals used  What would be the problem?  Herbicides kill plants too  Resistant genes in plants may escape into the environment – if herbicides cannot kill them, what can?

For  No chemicals  Higher yield  Tailor made  More nutrition  Higher income  Save natural resources Against  Could get out of control  Reduce reliance form developing countries  Economic damage  Ethical issues