Inheritance - Biology

• What are chromosomes?


  Thread-like structures which are made of DNA, and contain genetic information in the form of genes.
• What are genes?


  A length of DNA which codes for a protein.
• What is an allele?


  An allele is an alternative form of a gene.
• What chromosomes do males have?


  XY
• What chromosomes do females have?

  XX
• What determines the synthesising of specific protiens?

  Sequences of bases in a gene determine the sequence of amino acids used to make a specific protein.
• Different sequences of amino acids give different shaped to protein molecules
• What does DNA do?

  Controls the cells function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters.
• What is the first stage in making a protein?

  1 - The gene coding for the protein remians in the nucleus
• Second stage in protein synthesis?

  Messanger RNA (mRNA) is a copy of a gene
• Stage three in protein synthesis?

  3 - mRNA molecules are made in the nucleus, and move to the cytoplasm.
• Srage four in protein synthesis?

  The mRNA pass through ribosomes.
• Fifth stage in protein synthesis?

  5 - The ribosomes assemble amino acids into protein molecules.
• The sixth and final stage of protein synthesis?

  6 - The specific sequence of amino acids is detmermined by the sequence of bases in the mRNA.
• Are all genes in all cells expressed?

  No - Most body cells contain the same genes, but many genes in a particular cell ar enot expressed because the cell only makes the specific proteins it needs - gene expression (switched 'on and off')
• What is a haploid nucleus?

  Nucleus containing only half of the gentic information, so half the chromosomes.
• What is a diploid nucleus?


  Nucleus containing two sets of chromosomes.
• What is a diploid cell?


  A cell where there is a pair of each type of chromsome (in a human diploid cell there are 23 pairs).
• What is mitosis?


  Mitosis is nuclear division which produces two gentically identical daughter cells.
• When would mitosis occur?

  In growth, reapir of damaged tissues, replacement of cells and asexual reproduction.
• What happens before mitosis?

  Exact replication of chromosomes in parent cells.
• In terms of chromosomes, what happens during mitosis?

  The copies of chromosomes seperate, maintaining the chromosome number in each daughter cell.
• What are stem cells?

  Stem cells are unsepcialised cells which can divide by mitosis in order to produce daughter cells that are able to become speiclaised for specific functions.
• What is meiosis?


  Meisosis is a reduction division in which the chromosome number is halved from diploid, to haploid - this results in genetically DIFFERENT cells.
• When would meiosis occur?

  Involved in the production of gametes (e.g. sperm and egg cells).
• Define the term inherticance?

  Inhertiance is the trasnmission of genetic information from generation to generation.
• What is a genotype?


  The genetic make-up of an organism and depends on the alleles present.
• What are phenotypes?


  Observable characteristics or traits of an organism resulting from the interaction between its genes and the environment.
• What does homozygous mean?

  Having two dientical alleles of a particular gene.
• What is the result when two homozygous indivuduals breed?

  Pure-breeding.
• What does the term heterozygous refer to?

  Having two different alleles of a particular gene.
• Will breeding between two heterozygous indiviudals result in pure-breeding?

  No - only between two homozygous indivudals.
• What is a dominant allele?

  A dominant allele is an allele that will ALWAYS be expressed if present in the genotype.
• What is a recessive allele?

  A recessive allele is an allele which is only expressed IF there is NO dominant allele of the gene in the genotype.
• What is codminance?


  A situation in which both alleles in a heterozygous organism contriubte to the phentotype.
• What are the blood groups?

  A, B, AB and O.
• What are the alleles for the blood groups?

  I,^A, I^B, and I^O
• What is a sex linked characteristic?


  A feature in which the gene repsonsible is lovated on a sex chromosome, and this makes the charcateristic more common in one sex than the other.
• What is an example of a sec linkage?


  Red-green colourblindess