Reproduction
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,
Links for Learning
Websites  Videos  Games  Quizzes
Your Genome: What is DNA?
Your Genome: What is a chromosome?
Your Genome: What is a gene?
Your Genome: What is a genome?
Bitesize: Reproduction, the genome and gene expression
Pass my exams: Alleles
Revision World: Alleles and Inheritance
Bitesize: Genetic Inheritance
Your Genome: What is inheritance?
Bitesize: Inherited disorders
Your Genome: What is a mutation?
Your Genome: What types of mutation are there?
Bitesize: Genetic diagrams
Bitesize: Reproduction, the genome and gene expression test
Bitesize: Genetic Inheritance test
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