Section 11.1 Intro to Genetics

Genetics: the study of heredity Genes are the units of heredity. They are sequences of DNA, located on chromosomes, that code for specific proteins.

Protein Synthesis DNA sequence (ATGCCT…)  amino acid sequence  protein  determines body structure and function!

The Father of Genetics Gregor Mendel (Austrian monk) = the “father of genetics”.

Mendel: The Father of Genetics Discovered basic laws of inheritance Cross-pollinated garden pea plants and observed how their traits were passed onto their offspring.

Genetic Traits Traits = characteristics that are passed from generation to generation. Examples: hair color, eye color, corn kernel color…

Genetic Traits Types of traits: Dominant = trait that hides another trait. As long as there is one dominant trait, it will be expressed (show up) in an organism. Recessive = trait that is hidden. It can be masked by a dominant trait.

Chromosomes Chromosome = large DNA molecules that carry the genetic material that is copied and passed from generation to generation of cells.

Chromosomes Humans have 46 chromosomes (23 pairs; one set of 23 from ma, one from pa) 22 pairs are called autosomes (chromosome 1, chromosome 2, etc…) 1 pair is the sex chromosomes (X and Y) XX = female XY = male

Are these chromosomes from a man or a woman?

Genes and Alleles Gene = unit of heredity Alleles = different forms of the same gene. Example: the gene for flower color may be a red allele (R) or a white allele (r)

Mendel’s Laws LAW OF SEGREGATION = one allele from each gene pair goes into each sex cell.

Mendel’s Laws LAW OF INDEPENDENT ASSORTMENT = each gene pair for a trait is inherited separately from all other gene pairs for other traits.

Genotype Genotype = genetic makeup of an organism Example: RR (what alleles are present; letters) Purebred = has genes that are alike for a trait. Homozygous for alleles (TT or tt) Hybrid = had genes that are different for a trait. Heterozygous for alleles (Tt)

Phenotype Phenotype = physical appearance of an organism Example: tall pea plants, blonde hair, cystic fibrosis…

Pea Phenotypes that Mendel Observed:

1. A person has red hair. This is their _____________. A. Genotype B. Phenotype 2. A person has two copies of a gene that causes hemophilia. This is their _____________. A. Genotype B. Phenotype 3. What is an allele? Why do people have pairs of them? Warm-Ups 12/15/009

Albinism is a recessive trait. 1. What is the genotypic ratio of children of an albino woman and a purebred normal man? 2. What is the phenotypic ratio of children of two hybrid parents? Warm-Ups 12/17/009

Sex-Linked Traits Sex-Linked = conditions carried on the sex chromosomes (X and Y)

Sex-Linked Traits Examples: Colorblindness, hemophilia… X-linked = males will NEVER be a carrier –“carrier” = has the gene, but doesn’t show the trait Colorblindness (c) is a recessive, X-linked trait XY = Normal male XX = Normal female X c X = Carrier female X c X c = colorblind female X c Y = colorblind male

Sex-Linked Traits Cross a carrier female with a colorblind male:

Incomplete Dominance Incomplete Dominance = neither allele is dominant. Hybrids show an intermediate phenotype. Example: coat color in cattle –RR = red –WW = white –RW = roan