BIOL 1410 - Ch.29: Inheritance

Inheritance

The transfer of genetically determined characteristics form one generation to the next

Genetics

Study of inheritance

Chromosomes

Coiled up DNA held by histone proteins

Genes

Segments of DNA on the chromosome used to direct protein synthesis

Somatic cell chromosome pairs type

22 pairs are autosomal

1 pair are sex chromosomes

Autosomal homologous chromosomes

Chromosomes 1-22; paired chromosomes - one chromosome from mother and one form father

Alleles

Variant forms of genes located at the same site (locus) on homologous chromosomes

Homozygous alleles

Both gene copies encode the same version of the gene

Heterozygous alleles

Each gene copy encode different versions of the gene

Dominant alleles

Alleles that are fully expressed

Recessive alleles

Alleles that can be hidden by a dominant allele; only expressed if individual is homozygous recessive

Genotype

The genetic makeup of a person based on their homologous pairs

Phenotype

The way the genotype is expressed physically

Sex chromosomes

23rd chromosome pair

Female sex chromosomes

Homologous pair: XX

- Allele combinations be either be homozygous or heterozygous

- Both X chromosomes carry the same genes at the same loci

Male sex chromosomes

Non-homologous: XY

- Allele combination can NOT be homozygous

- Only have one allele for genes (carried on X chromosome) received from the mother and will be the genotype

Predicting inheritance using

Punnet squares

Punnet square

A method used to predict characteristics of the offspring from a given mating event or probability of inheritance

2 types of inheritance

Autosomal inheritance

Sex-linked inheritance

Autosomal inheritance

Genes located on chromosomes 1-22

Sex-linked inheritance

Genes located on the X chromosomes (e.g. XC Xc)