Begegnungen mit der Natur 8, Arbeitsheft

In the nuclei of body cells there are long threads made of __________ and protein, called chromosomes. The chromosomes contain _______________ , units which determine all sorts of things about us – the colour of our hair or eyes, our height or whether we have a genetic disease for example. Humans have got 23 pairs of _________________________ inside each cell. The two chromosomes of a pair are the same size and shape. They are called ______________________________________ . They have genes for the same characteristic in the same position. So we have two copies from each gene, one from the mother, the other from the father. There are different varieties of DNA codes of a gene, called ___________________. If  the  two  alleles (from father and mother) are identical, we call this______________________. If the alleles are different, we call this __________________________. The genes that we have are our ___________________ , the features we have are called _______________________ . Alleles can be dominant, recessive or codominant. If you have got one allele for brown eyes and one allele for blue eyes, the colour of your eyes will be brown, because the allele for brown eyes is __________________ while the allele for blue eyes is ___________________. Is neither of the alleles dominant or recessive, both alleles have an effect on the phenotype. We call this ___________________________ . The last pair of our chromosomes makes us male or female. They are called _____________________ . In the picture you can see that the man’s sex chromosomes are not alike. The bigger one is the __________________ , the smaller one, the _____________________ . Men have the genotype XY while women have the genotype XX. Eggs and sperm are made by ______________. Therefore there are only 23 chromosomes in the nuclei of ________________________ – one allele for any characteristic. 1 2 3 4 5 1 2 3 4 5 6 7 8 9 10 11 12 6 7 8 9 10 11 12 13 14 15 16 17 18 13 14 15 16 17 18 19 20 21 22 X 19 20 21 22 X Y Because the sex chromosomes in the body cells of a woman are both X, all her eggs have ________________________________. In the body cells of a man there are X- and Y-chromosomes. Therefore one half of a man’s sperm contain ___________________________ , the other half _________________________ . If an X-sperm fertilises an egg, the baby will be a ____________ . In the other case, when a ______________ fertilises an egg, the baby will be a boy. Grundlagen der Genetik alleles, chromosomes, codominance, DNA, dominant, gametes, genes, genotype, girl, heterozygous, homologous chromosomes, homozygous, meiosis, phenotype, recessive, sex chromosomes, X-chromosome, X-chromosomes, X-chromosomes, Y-chromosome, Y-chromosomes, Y-sperm 9 How about using English – The units of heredity Fill in the correct words: Schulbuch Seiten 4–17 O Nur zu Prüfzwecken – Eigentum des Verlags öbv