Key Words

DNA – contains deoxyribonucleic acid a chemical that all of the genetic material in a cell is made up from. It is also a polymer.

Chromosomes – really long molecules of DNA. Chromosomes come in pairs.

Gene – a small section of DNA found on a chromosome.

Genome – the entire set of genetic material in an organism.

Nucleotides – repeating units that make up the DNA strands.

mRNA – a molecule which acts as a messenger between the DNA and the ribosome.

Enzymes – biological catalysts that speed up chemical reactions in the body.

Hormones – carry messages around the body.

Mutations – random changes in an organism’s DNA. These can sometimes be inherited. Three types of mutation are:

  • Insertions – a new base is inserted into the DNA base sequence.
  • Deletions – a random base is deleted from the DNA base sequence.
  • Substitutions – a random base is changed in the DNA base sequence.

Sexual reproduction – genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to the parent.

Asexual reproduction – carried out by mitosis. There is only one parent so the offspring are genetically identical to that parent.

Gametes – contain 23 chromosomes. Instead of having two of each chromosome, a gamete has just one.

Meiosis – produces cells which have half the normal number of chromosomes.

X and Y chromosomes – males have an X and a Y choromosome (XY), females have two X chromosomes (XX).

Alleles – different versions of genes.

Homozygous – when an organism has two alleles for a particular gene that are the same.

Heterozygous – when an organism has two alleles for a particular gene that are different.

Dominant allele – the allele for the characteristic that’s shown when two alleles are different.

Recessive – the allele for the characteristic that is not shown when two alleles are differnet.

Genotype – combinations of alleles you have.

Phenotype – the characteristics you have.

Recessive allele – people with one copy of the allele (a carrier) won’t have the disorder. However for a child to have the disorder both parents will have to be carriers.

Cystic Fibrosis – genetic disorder caused by a recessive allele. The body produces a lot of thick sticky mucus in the air passages and int the pancreas.

Dominant allele – only one parent needs to be a carrier in order for the child to be able to inherit the condition.

Polydactyly – genetic disorder caused by a dominant allele. A baby is born with extra fingers or toes.

IVF┬á– fertilising and egg with sperm in a lab.

Embryonic screening – a embryo cell is analysed for it’s genes before the embryo is implanted after IVF.

Gregor Mendel – an Austrain monk who noted how characteristics in plants where passed on from one generation to the next.


Also see Hormonal coordination, Genetics & Evolution,

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