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
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