Genetics Notes – Pt 1

Gregor Mendel “father” of genetics Austrian Monk Watched how traits passed from parent generation to offspring in plants.

His Studies 7 traits; each had 2 possibilities (ex: yellow or green seed color) Crossed plants with opposite traits Parent plants called the P generation (parental) 1 st generation of offspring called F 1 generation (F = Filial)

What he found… P generation yellow X green All offspring = yellow Green seemed to disappear

Mendel’s Theory 1. We have 2 copies of each trait 2. Different “versions” of these traits are called alleles 3. Some alleles are dominant over others 4. Sperm & Egg will only form with one copy of those alleles

Segregation Separation of chromosomes into different gametes (sperm & egg)

Dominant Vs Recessive Genes When 2 different genes come together, one will be dominant over the other = that will be the one we see recessive gene is masked Ex: Rr (roll = dom)

Writing out Genes Dominant = upper case letter Recessive = lower case letter Ex: Dimples = Dominant = D No dimples = Recessive = d

Homozygous and Heterozygous Homozygous = same 2 alleles (DD or dd) Homozygous Dominant = DD Homozygous Recessive = dd Heterozygous = alleles are different (Dd)

Genotype vs Phenotype Genotype – the gene combination an organism has Pp Phenotype – the physical trait exhibited b/c of the genes

Punnett Squares A diagram that allows you to predict the possibility that a trait will be seen

If curly hair is dominant over straight… What percentage of offspring will have curly hair? ________ %

What percentage will have straight hair? _______ %

RATIOS The genotypic ratios are: ____ : ____ : ____ The phenotypic ratios are: ______ : _____

Genetics – Pt 2

1. Incomplete dominance No allele is completely dominant. Heterozygous (Rr) offspring end up with a blended phenotype. RR rr Rr

RR (red) X rr (white) _____ % Red _____ % Pink _____ % White

Codominance more than one dominant allele. Ex: sickle cell anemia

N1N1N1N1 N2N2N2N2 N1N2N1N2 Healthy Sickle Cell Anemia

Multiple Alleles When more than 2 possible alleles (ex: blood types (A,B,O) I A (A protein) I B (B protein) i (no protein)

Polygenic Traits Traits produced by the interaction of several genes Ex: skin, eye, & hair color

Sex-linked Traits Traits controlled by genes found only on the X or Y chromosomes (sex chromosomes ) ALD (Lorenzo) was sex-linked Male Pattern Baldness

Gender Determination A baby’s gender is determined by the father.

Pedigrees A family history that shows how a trait passes down through several generations Males = squares Females = circles

Nn X Nn (both are carriers, but do not have disease) ______ % Normal ______ % Carriers ______ % Sickle Cell Anemia