Biology Mrs Edwards
- Created by: Alice Buzzard
- Created on: 20-04-12 18:14
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Chromosomes and Genes
- most cells contain nucleus
- nucleus contain chromosomes
- 46 chromosomes (23 pairs) made of long strands of DNA
- small selection of DNA is called a gene
- each chromosome has lots of genes
genes control inherited characteristics e.g. eye colour, natural hair colour
passed on from parent to young in sex cells called gametes (sperm/egg cells)
- egg contains X (female **)
- sperm contains X or Y (male XY)
genes, like chromosomes are found in pairs - 2 genes for each characteristic
genotype: what gene you have // phenotype: what you look like
- e.g. genotype = brown gene and blue gene, phenotype = brown eyes
different forms of the same genes are called ALLELES e.g. brown eyes, blue eyes
- alleles may be dominant (stronger) - only one allele needed e.g. brown eyes
- alleles may be recessive (weaker) - two alleles would be needed e.g. blue eyes
if alleles are the same it is homozygous e.g. brown brown
if alleles are different it is heterozygous e.g. brown blue
CELLS -> NUCLEUS -> CHROMOSOMES (made of DNA) -> GENE is…
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