chromosomes structure

chromosomes structure

Genetic information is stored in the the form of DNA within the cell nucleus. Here are some key definitions that you must be aware of: 

•      Chromosome is a thread like structure of DNA 

•      A gene is a length of DNA which codes for a specific protein 

Gene expression

• chromosome exists in pairs, in males there are 22homologous and 23 pairs which Xy in females all the chromosomes are xx

• alleles are different versions of genes

• genes are sections of DNA that codes for specific amino acids

• TT Dorminant allele -are normally expressed

• recessive allele are only expressed when both are homozygous recessive

• heterozygous alleles has a dorminant and recessive alleles. only dorminant allele is expressed, recessive allele is suppressed.

genotype- is the genetic composition of the organisms.

phenotype is the physical appearance of the organisms eg skin colour,height,weight,eye colour

locus is the specific place where genes are located in the chromosome

human genome

• Human genome, all of the approximately three billion base pairs of deoxyribonucleic acid (DNA) that make up the entire set of chromosomes of the human