Biology - Genetics Flashcards
What is DNA? Describe it’s structure.
Deoxyribonucleic acid is the chemical molecule in the nucleus that carries our genetic code. It codes for our characteristics. It is arranged into long, coiled molecules called chromosomes.
Normal human body cells (e.g skin cells) have 46 chromosomes (23 pairs)
Human sex cells (sperm and egg) have half this number (23)
Where is DNA found in the cell?
In the nucleus
What is a gene?
A gene is a section of a chromosome that codes for a particular characteristic.
What is an allele?
For each gene we inherit two forms of the gene (one from our mother and one from our father). Each form of the gene is called an allele. A different form of a gene.
What is variation?
The difference between individuals of the same species. Their are two types of variation:
genetic (inherited) variation
Environmental variation
What is the difference between dominant and recessive alleles?
• Dominant alleles are always expressed even if only one of the alleles is dominant. e.g. BB or Bb
• Recessive alleles are only expressed if there are 2 recessive alleles. e.g. bb
What are homozygous alleles?
Two identical alleles for a characteristic. (e.g. BB, tt)
What are heterozygous alleles?
Different alleles for a characteristic. (e.g. Bb, Tt)
What is genetic variation?
The variation has been inherited genetically.
What is environmental variation?
The variation hasn’t been passed down through genetics and it is based on your lifestyle.
Cat fur:
Parents phenotype: Black, Black
Parents genotype: Bb, Bb
Work out what the possible phenotype and genotypes are for the child.
BB, Bb, Bb, bb
Black, Black, Black, White
75% Black 25% White
Eye Colour:
Parents phenotype: Brown, Brown
Parents genotype: Bb, Bb
Work out what the possible phenotype and genotypes are for the child.
BB, Bb, Bb, bb
Brown, Brown, Brown, Blue
75% Brown, 25% Blue
Hair Colour:
Parents phenotype: Black, Blonde
Parents genotype: Bb, bb
Work out what the possible phenotype and genotypes are for the child.
Bb, Bb, bb, bb
Black, Black, Blonde, Blonde
50% Black, 50% Blonde
What is a genetically inherited disorder?
A genetic disorder is a disease caused by a faulty gene or chromosome.
What is a recessive genetic disorder?
This is a genetic disorder where the individual has inherited 2 faulty alleles, one from Mum and one from Dad.