Chapter 17: Inheritance Flashcards
What are chromosomes made of?
DNA, which contains genetic information in the form of genes
Define ‘gene’
A length of DNA that codes for a protein
Define ‘allele’
An alternative form of a gene
How is sex determined?
By an entire chromosome pair, females have sex chromosomes XX and males have sex chromosomes XY; the sex of the child depends on whether the sperm that fertilises the egg carries his X or his Y chromosome
How are specific proteins made?
The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein; different sequences give different shapes to protein molecules
How does DNA control cell function?
By controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters
How are proteins made?
The gene coding for the protein remains in the nucleus, and messenger RNA (mRNA) is a copy of a gene. The mRNA passes through ribosomes, and the ribosome assembles amino acids into protein molecules. The specific sequence of amino acids is determined by the sequence of bases in the mRNA
Do all body cells in an organism contain the same genes?
Yes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
Define ‘haploid nucleus’
A nucleus containing a single set of chromosomes
Define ‘diploid nucleus’
A nucleus containing two sets of chromosomes
What is in a diploid cell?
There is a pair of each type of chromosome, and in a human diploid cell, there are 23 pairs
Define ‘mitosis’
Nuclear division giving rise to genetically identical cells
What are the roles of mitosis?
Growth: in animals, each tissue provides its own new cells when needed
Repairing damaged tissues: e.g, when you cut your skin, mitosis provides new cells to cover up cuts
Replacement of worn-out cells
Asexual reproduction in plants
What happens during mitosis?
Before mitosis, the exact replication of chromosomes occurs. The copies of chromosomes then separate, maintaining the chromosome number in each daughter cell
Define ‘stem cells’
Unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
Define meiosis
A reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells
What is meiosis involved in?
The production of gametes
Define ‘inheritance’
The transmission of genetic information from generation to generation
Define ‘genotype’
The genetic make-up of an organism in terms of the alleles present (e.g. Tt or Gg)
Define ‘phenotype’
The observable features of an organism (e.g. tall plant or green seed)
Define ‘homozygous’
Having two identical alleles of a particular gene (e.g. TT or gg), two identical homozygous individuals that breed together will be pure-breeding
Define ‘heterozygous’
Having two different alleles of a particular gene (e.g. Tt or Gg), a heterozygous individual will not be pure-breeding
Define ‘dominant allele’
An allele that is expressed if it is present in the genotype
Define ‘recessive allele’
An allele that is only expressed when there is no dominant allele of the gene present in the genotype
