CB3 - Genetics

• What is the human genome?

  The complete set of genetic information in a human - our DNA
• What does DNA stand for?

  Deoxyribonucleic Acid
• Where is the human genome found?

  The human genome is found on 46 long molecules of DNA called chromosomes. Along the length of a DNA molecule, there are sections that each contain a code for making a protein, called genes.
• What is meiosis?

  Type of cell division which produces gametes.
• What is the product of meiosis?

  Meiosis produces four haploid daughter cells, each one being a gamete.
• Describe the meiosis process:

  Each chromosome replicates, remaining attached, making each chromosome look like a X. The two sets of chromosomes 'pair up', forming 23 pairs, and the pairs then separate into two new cells. Next, the two copies of a chromosome in each X-shape split into two more new cells.
• Why is each gamete produced genetically different?

  Each chromosome in a pair contains different versions of the same genes, meaning they are genetically different. Gametes are all different because they contain genetically different chromosomes.
• What are the four bases of DNA?

  Adenine, Thymine, Guanine, Cytosine.
• Describe the structure of DNA.

  The molecule of DNA contains two strands, which when joined together by bases, form a double helix.
• What are the complementary base pairs and how are they bonded?

  The complementary base pairs join the molecules to form a double helix: adenine-thymine & cytosine-guanine. They are joined by weak hydrogen bonds.
• What do the nucleotides consist of?

  Each base is attached to a sugar and each sugar is attached to a phosphate group, forming the backbone of DNA strands.
• What are Alleles?

  Different forms of the same gene
• What is the effect of alleles on inherited characteristics?

  Genetic variation - the different combination of alleles in each person gives us a slightly different characteristics.
• What does a homozygous organism mean?

  Identical alleles.
• What does a heterozygous organism mean?

  Different alleles
• What is the difference between homozygous and heterozygous organisms?

  An organism that is homozygous has alleles which are both the same while an organism that is heterozygous means the alleles are different.
• What is the difference between a dominant and recessive allele?

  In an offspring, a recessive allele would not occur if a dominant allele is there. A recessive allele will be hidden in the presence of a dominant allele, and will not appear in the phenotype.
• What does phenotype mean?

  How an organism looks like - their physical characteristics.
• What does genotype mean?

  The alleles in an organism make up their genotype.
• Which sex chromosomes do females have?

  XX
• Which sex chromosomes do males have?

  XY
• What is the difference between genetic variation and environmental variation and how do they affect the phenotype?

  Genetic variation leads to different characteristics as a result of mutation and sexual reproduction whilst environmental variation is cause by an organism's environment and their evolution and adaptation to such environment, leading to acquired characteritics.
• What is the Human Genome Project?

  The Human Genome Project aimed to map all of the genes in the human genome, showing us that although there are variations between people, over 99% of the DNA bases in different people are the same.
• How did the Human Genome Project help with medicine?

  Mapping the human genome can indicate their risk of developing diseases that are caused by different alleles of genes. It can also help to identify which medicines might be best to treat a person's illness, since the alleles in our body can affect how we interact with medicines.
• What is Genetic Variation caused by?

  It is caused by different alleles inherited during sexual reproduction - different alleles are produced by mutations, causing changes in the phenotype.
• What is Environmental Variation caused by?

  External factors or an organism's surroundings.
• What are acquired characteristics?

  Characteristics which are acquired during an organism's lifetime, due to change in their environment or conditions.
• What is the difference between continuous and discontinuous variation?

  Continuous variation refers to data that can be any value in a range, whilst discontinuous variation is where the data can only take a limited set of values. In short terms, discontinuous are only integer values whilst continuous are decimals.
• Most genetic mutations have no effect on the phenotype, some mutations have a small effect on the phenotype, and, rarely, a single mutation will significantly affect the phenotype.