B5: Introduction to Genetics 1 + 2​

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key words Cell Nucleus Chromosome DNA 10000 Section of DNA is a gene Task: Add descriptions to the key structures in your diagram The cell is the basic functional unit of all known living organisms. A cell is the smallest unit of life. The central part of eukaryotic cells that contains genetic material and is enclosed in a membrane. Cell Nucleus Chromosome DNA 10000 Chromosomes are tightly packaged DNA molecules. GENES - code for proteins which determine our characteristics What is DNA? • Double helix structure ● • Bases: A TCG ● Sugar-phosphate backbone A and T match • C and G match ● ● Complementary base pairs! The genome is the genetic material of an organism Base pairs Adenine Thymine. Guanine Sugar phosphate backbone Cytosine What are chromosomes? Chromosomes are long strands of genetic information located in the nuclei of cells. 0 Chromosomes are most visible during cell division when they replicate and look like this... X You will see chromosomes represented both ways. RECAP from B2: What is mitosis? gene A gene is a sequence of DNA or RNA that codes for a molecule that has a function. chromosome DNA helix * backbone base pairs bases Homologous chromosomes In most cells chromosomes are matched in pairs based on their size and shape. chromosome from female parent chromosome from male parent homologous chromosomes Matching pairs of chromosomes are called homologous chromosomes. Where do homologous chromosomes come from? Each pair of homologous chromosomes contains one chromosome that has been inherited from each parent. Human chromosomes In human body cells there are a total of 46 chromosomes. How many pairs of homologous chromosomes are there in human body cells? 23 pairs of chromosomes So... 46 chromosomes in TOTAL You inherit half your chromosomes from your mother and half from your father. How many chromosomes do you inherit from each parent? 23 unpaired chromosomes Summary so far... K 6 13 19 14 20 8 18 15 21 || 3 9 16 22 11 if 5 10 al 11 17 12 18 Y Chromosomes are made up of DNA 23 pairs of chromosomes They are paired up - homologous pairs • Total of 46 chromosomes in human body cells. Genes and Alleles EXIT DE chromosomes of the same type are the same size and have the same genes in the same order - different genes different alleles of the same gene E Chromosomes contain different genes, which exist as different alleles. Alleles: • A different form of the same gene • Same gene with slightly different instructions to create variation (blue eyes; brown eyes) • There are many alleles of the same gene in the population • Two copies of every chromosome; two copies of every gene; each copy of a gene may be a different allele variation!!!! D 1 1 2 2 3 4 3 4 5 5 6 Allele = 2 versions of the book! You can think of chromosomes 1 1 1 1 1 12 13 14 15 as a set of books. Each book (chromosome) contains a set of 8 9 10 11 12 2014 1 16 2 sentences giving instructions (genes). All of the books together contain all of the instructions needed to produce a certain organism. TACCGCG This book Chromosomes contains = books! for ye eight ht and G nose shape ACCTTATA Genes = instructions! Alleles An allele is a different form of the same gene. • 2 alleles the SAME = homozygous • 2 alleles DIFFERENT = heterozygous If someone is heterozygous - one brown and one blue - which eye colour will they have?! Individual A: heterozygous Individual B: homozygous Da Individual C: homozygous recessive Progress check: glossary ● Gene: DNA: Chromosome: Homologous chromosome: Heterozygous Homozygous Allele Define the following: 1. Allele a particular form of a gene 2. Gene section of DNA that contains the instructions for a particular characteristic W 3. DNA found as chromosomes in the nucleus Chromosome – thread like structures of DNA in the cell nucleus 4. 5. Heterozygous - 2 different alleles for a characteristic 6. Homozygous - 2 alleles that code for the same characteristic 7. Homologous - pairs of chromosomes, 1 from mother, 1 from father 8. Genome the entire genetic material of the organism Genotype vs phenotype The alleles present for a particular gene make up the genotype. ● How the gene is expressed (the appearance of the characteristics of an organism) is the phenotype. Genotype Phenotype Info on genes hair typely *00 (h)straight Physical appearance due to traits which are actually expressed...... Genotype codes for phenotype For example, I have a blue eye allele (genotype) which codes for the blue eyes (phenotype) Recessive vs dominant ALLELES Recessive allele - NEED 2 ALLELES TO BE ABLE TO SHOW THE PHENOTYPE (represented by small letters) DOMINANT allele - ONLY NEED 1 ALLELE TO BE ABLE TO SHOW THE PHENOTYPE (represented by capital letters) B (brown) is DOMINANT over the blue! This person is A CARRIER for blue! Bb BB Allele for blue eyes (recessive) Allele for brown eyes (dominant) Individual A: heterozygous H Individual B: homozygous bb Individual C: homozygous recessive