Genetics Notes – Pt 1

Gregor Mendel “father” of geneticsAustrian MonkWatched how traits passed from parent generation to offspring in plants.

His Studies7 traits; each had 2 possibilities (ex: yellow or green seed color)

Crossed plants with opposite traits

Parent plants called the P generation (parental)

1st generation of offspring called F1 generation (F = Filial)

What he found…P generation yellow X green

All offspring = yellow Green seemed to disappear

Mendel’s Theory1. We have 2 copies of each trait2. Different “versions” of these

traits are called alleles3. Some alleles are dominant

over others4. Sperm & Egg will only form

with one copy of those alleles

SegregationSeparation 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 maskedEx: 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

N1N1N2N2N1N2

Healthy Healthy Sickle Cell Anemia

Multiple Alleles When more than 2 possible

alleles (ex: blood types (A,B,O) IA (A protein) IB (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