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Leaving Cert Biology Section 2.5 Genetics Genetics Leaving Cert Biology Section 2.5 Genetics Diversity of living things Leaving Cert Biology Section 2.5 Genetics Species A species is a group of similar organisms that are capable of naturally interbreeding with each other to produce fertile offspring. Leaving Cert Biology Section 2.5 Genetics There can be individuality within species – differences between members of a species which does not affect their ability to interbreed. Leaving Cert Biology Section 2.5 Genetics Heredity • The passing on of traits from parents to offspring by means of genes Example eye colour! Leaving Cert Biology Section 2.5 Genetics Are you able to… • Define species? • Explain what heredity is? Leaving Cert Biology Section 2.5 Genetics Chromosomes Nuclear membrane Chromatin Nuclear pore Leaving Cert Biology Section 2.5 Genetics Chromosomes • Chromosomes are long strands of DNA coiled up with protein Leaving Cert Biology Section 2.5 Genetics Gene A gene is a section of DNA that causes the production of a protein. Strand of DNA Leaving Cert Biology Section 2.5 Genetics Gene expression • Gene expression is the way in which genetic information in a gene is decoded in the cell and used to make a protein •Every protein made has an effect on the organism Leaving Cert Biology Section 2.5 Genetics Gene expression Gene Expression produces characteristics or traits that are inherited Example: Gene for Tallness Organism is small – Why? Maybe due to poor nutrition Characteristics = heredity + environment Leaving Cert Biology Section 2.5 Genetics Check your learning… • State the location of chromosomes • Tell about the structure of a chromosome • Tell what genes are and where they are found • Give examples of some traits controlled by genes Leaving Cert Biology Section 2.5 Genetics 2.5.4 DNA structure Leaving Cert Biology Section 2.5 Genetics DNA structure DNA =Deoxyribonucleic Acid •DNA is a very long molecule •It is made up of two parallel strands •The strands are linked together by paired bases. The DNA Spiral Ladder Leaving Cert Biology Section 2.5 Genetics DNA structure • There are four different bases that are found in DNA Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Leaving Cert Biology Section 2.5 Genetics The Base Pair Rule • AT – Adenine only joins to Thymine • GC – Guanine only joins to Cytosine Leaving Cert Biology Section 2.5 Genetics Triplet base code Coding DNA contains information to make proteins.. The sequence of the bases on a DNA strand directs what protein our body will make. DNA codes for each amino acid by using a sequence of three consequtive bases. The amino acids are joined together to make a protein Leaving Cert Biology Section 2.5 Genetics Coding DNA • Def Coding DNA is the DNA that contains information to make proteins Strand of DNA Leaving Cert Biology Section 2.5 Genetics Non Coding DNA Non coding DNA is the DNA that does not contain information for the production of protein Also called “Junk DNA” Strand of DNA Non coding DNA Leaving Cert Biology Section 2.5 Genetics Can you.. • Describe the structure of a chromosome • Tell what genes are and where they are found • Tell what DNA stands for • Name the four bases found in DNA • Know how base pairing happens in DNA • Distinguish between coding and non coding DNA Leaving Cert Biology Section 2.5 Genetics Nucleic acid structure – HL • Deoxyribonucleic Acid (DNA) is a nucleic acid • It is made up of nucleotide units • Its shape is called the double helix Leaving Cert Biology Section 2.5 Genetics • Nucleotide structure Each nucleotide unit has: 1. A phosphate 2. A deoxyribose sugar 3. one of four nitrogenous bases adenine, ( a purine) guanine ( a purine) cytosine, ( a pyrimidine) or thymine( a pyrimidine) Leaving Cert Biology Section 2.5 Genetics Purine and pyrimidine couples! Adenine (purine) bonds to thymine (pyrimidine) Guanine (purine) bonds to cytosine (pyrimidine) Bases pairs bond to each other by Hydrogen bonding Leaving Cert Biology Section 2.5 Genetics Leaving Cert Biology Section 2.5 Genetics • HL 2011 q9A, Try now.. Leaving Cert Biology Section 2.5 Genetics To isolate DNA from a plant tissue Leaving Cert Biology Section 2.5 Genetics Step 1 Add 10 ml washing-up liquid and 3 g salt to a graduated cylinder. Make up to 100 ml and stir. Leaving Cert Biology Section 2.5 Genetics Step 2 Add chopped onion to a beaker. Pour in the salty washing-up liquid solution and stir. Leaving Cert Biology Section 2.5 Genetics Step 3 Stand the beaker in a water bath at 60°C for 15 minutes. Leaving Cert Biology Section 2.5 Genetics Step 4 Cool the mixture by standing the beaker in an ice bath for 5 minutes. Leaving Cert Biology Section 2.5 Genetics Step 5 Blend the mixture for no more than 3 seconds. Leaving Cert Biology Section 2.5 Genetics Step 6 Filter the blended mixture through coffee filter paper. Leaving Cert Biology Section 2.5 Genetics Step 7 Add 2-3 drops of protease enzyme to 10 ml of the onion extract. Leaving Cert Biology Section 2.5 Genetics Step 8 Very carefully, pour 10 ml of ice cold ethanol onto the surface of the onion extract. Leaving Cert Biology Section 2.5 Genetics Step 9 DNA forms at the interface of the ethanol and extract. Leaving Cert Biology Section 2.5 Genetics Step 10 Draw the DNA out of the solution by wrapping it around a glass rod. Leaving Cert Biology Section 2.5 Genetics Leaving Cert Biology Section 2.5 Genetics Leaving Cert Biology Section 2.5 Genetics 2.5.4 DNA Profiling • DNA Profiling is the method of cutting up a persons DNA into fragments that can be used to make a pattern of bands that are unique to each person. Leaving Cert Biology Section 2.5 Genetics 2.5.4 DNA Profiling 1. Cells are broken down to release DNA 2. DNA strands are cut into fragments using enzymes 4. The pattern of fragment distribution is analysed. 3. Fragments are separated on the basis of size Leaving Cert Biology Section 2.5 Genetics DNA Profiling applications • Can be used to investigate crimes! A DNA profile can be made form blood , semen, hair, saliva sample found at a crime scene. The DNA profile can then be compared to victims and suspects DNA profiles in a crime case Leaving Cert Biology Section 2.5 Genetics DNA Profiling applications • Can be used to resolve medical issues! Paternity and maternity cases resolved by comparing child's DNA profile with parent DNA profile. Each band in a child's profile must match a band form the either the mother or the father’s profile. Leaving Cert Biology Section 2.5 Genetics Check your learning.. • What DNA Profiling is • How DNA profiling is done (4 steps) • Why DNA profiling is used – 2 examples Leaving Cert Biology Section 2.5 Genetics Genetic screening Def Genetic screening is doing diagnostic tests on an organism to identify the presence or absence of changed genes. Foetal screening or Adult screening! But could It cause the potential for discrimination?? Leaving Cert Biology Section 2.5 Genetics Cystic fibrosis Leaving Cert Biology Section 2.5 Genetics Albinism Leaving Cert Biology Section 2.5 Genetics DNA Replication Leaving Cert Biology Section 2.5 Genetics Brainstorm • Why do cells need to divide? • What happens to a cell during its interphase stage? • What are the names of the 4 stages in Mitosis? Leaving Cert Biology Section 2.5 Genetics Mitosis 2.3.4 Mitosis Interphase • Def Mitosis is the division of the nucleus to produce two daughter nuclei, containing identical sets of chromosomes. Daughter nuclei with chromosomes identical to parent cell Revision of Mitosis Leaving Cert Biology Section 2.5 Genetics Mitosis: Stage 1 •The chromatin shortens, thickens and double stranded chromosomes become visible in the nucleus. •The Nuclear membrane breaks down : •Fibres are formed Cell membrane Double stranded chromosomes Fibres Nucleus Revision of Mitosis Nuclear membrane Leaving Cert Biology Section 2.5 Genetics Mitosis: Stage 2 • Fibres attach to the chromosomes. • The chromosomes line up along the centre of the cell. Revision of Mitosis Leaving Cert Biology Section 2.5 Genetics Mitosis: Stage 3 • Chromosomes are pulled apart to opposite ends of the cell Chromosomes pulled apart Revision of Mitosis Leaving Cert Biology Section 2.5 Genetics Mitosis: Stage 4 • A nuclear membrane forms around each set of new chromosomes and the cell divides in two Cell divides in two Revision of Mitosis Leaving Cert Biology Section 2.5 Genetics Leaving Cert Biology Section 2.5 Genetics Replication of DNA • During the Interphase stage of the cell cycle each chromosome in the nucleus makes a copy of itself. Leaving Cert Biology Section 2.5 Genetics Replication of DNA – stage 1 (1) The double helix unwinds and the DNA strands separate. Leaving Cert Biology Section 2.5 Genetics Replication of DNA – stage 2 • Base pairing occurs between the bases on the original strands of DNA and new free bases that enter the nucleus. • New complementary strands of DNA are formed alongside original strands. Leaving Cert Biology Section 2.5 Genetics Replication of DNA – Stage 3 • Two new double helixes of DNA are made – each identical to the original DNA double helix and each other. • Each new DNA double helix is made up of: ½ old DNA and ½ new DNA! Leaving Cert Biology Section 2.5 Genetics Check your learning.. • What happens during interphase in the cell cycle • What forces hold DNA strands together usually? • During which stage of DNA replication do the strands separate? • What does complementary mean? • Where do the extra bases come from to make the new strands? • How do new DNA strands compare to the original strand and to each other?