Lecture 24 → Exam 4 Lecture Notes
What is Genetics
- genetics: study of hereditability
- the study of how genes and how traits are passed down from one generation to the next
Gregor Mendel
- worked with pea plants
- observed characteristics
- phenotype: all traits together
Mendels Rediscovery
- blending inheritance: the expression in offspring of phenotypic characters (as pink
flower color from red and white parental plants) intermediate between those of the
parents
- children are an average of both parents
- particulate inheritance: genetic information is transmitted from one generation to the
next in discrete units (particles) so that the character of the offspring is not a smooth
blend of essences from the parents
Mendel's Experiments
- self-pollination: when gametes come from the same individual
- ex: plants
- cross-pollination: when gametes come from different individuals
- true breeding: only one allele is present
- ex: color of flowers
Do Traits Really Blend
- crosses: the purposeful mating of two individuals resulting in the combination of genetic
material in the offspring
- white x purple
- Parent generation
- produce offspring
- F₁ = first offspring
- F₂ = offspring of the F₁
- phenotypic ratio: #:#
- 1:0 → 1 purple flower, 0 white flowers
Mendel's Experiments
- every individual has two alleles
- purple and purple → homozygous
- purple and white → heterozygous
- white and white → homozygous
- dominant allele: effectively overrules the other (recessive) allele
- written with an uppercase letter
- recessive allele: is overruled by the other (dominant) allele
- written with a lowercase letter
- heterozygous: having inherited different versions (alleles) of a genomic marker from
each biological parent
- homozygous: the presence of two identical alleles at a particular gene locus
, Dominant vs Recessive
- broken vs functional hypothesis
- broken = recessive
- functional = dominant
- smooth vs wrinkled pea pods
- smooth = dominant
- wrinkled = smooth
- due to starch
- if it can build starch = dominant
- if it cannot build starch = recessive
- Y = yellow
- y = green
- Y+Y = yellow
- Y+y = yellow
- y+y = green
Mendel’s Law #1
- The Law of Segregation
1. every adult has two alleles of a gene
2. a gamete has one allele
3. two gametes create a two allele offspring
The Punnett Square
- R = purple
- r = white
- P = RR x rr
- homozygous
R R
r Rr Rr
r Rr Rr
4:0 (F₁)
R r
R RR Rr
r Rr rr
3:1 (F₂)
Phenotype vs Genotype
- genotype: a scoring of the type of variant present at a given location (i.e., a locus) in the
genome
- represented by symbols
What is Genetics
- genetics: study of hereditability
- the study of how genes and how traits are passed down from one generation to the next
Gregor Mendel
- worked with pea plants
- observed characteristics
- phenotype: all traits together
Mendels Rediscovery
- blending inheritance: the expression in offspring of phenotypic characters (as pink
flower color from red and white parental plants) intermediate between those of the
parents
- children are an average of both parents
- particulate inheritance: genetic information is transmitted from one generation to the
next in discrete units (particles) so that the character of the offspring is not a smooth
blend of essences from the parents
Mendel's Experiments
- self-pollination: when gametes come from the same individual
- ex: plants
- cross-pollination: when gametes come from different individuals
- true breeding: only one allele is present
- ex: color of flowers
Do Traits Really Blend
- crosses: the purposeful mating of two individuals resulting in the combination of genetic
material in the offspring
- white x purple
- Parent generation
- produce offspring
- F₁ = first offspring
- F₂ = offspring of the F₁
- phenotypic ratio: #:#
- 1:0 → 1 purple flower, 0 white flowers
Mendel's Experiments
- every individual has two alleles
- purple and purple → homozygous
- purple and white → heterozygous
- white and white → homozygous
- dominant allele: effectively overrules the other (recessive) allele
- written with an uppercase letter
- recessive allele: is overruled by the other (dominant) allele
- written with a lowercase letter
- heterozygous: having inherited different versions (alleles) of a genomic marker from
each biological parent
- homozygous: the presence of two identical alleles at a particular gene locus
, Dominant vs Recessive
- broken vs functional hypothesis
- broken = recessive
- functional = dominant
- smooth vs wrinkled pea pods
- smooth = dominant
- wrinkled = smooth
- due to starch
- if it can build starch = dominant
- if it cannot build starch = recessive
- Y = yellow
- y = green
- Y+Y = yellow
- Y+y = yellow
- y+y = green
Mendel’s Law #1
- The Law of Segregation
1. every adult has two alleles of a gene
2. a gamete has one allele
3. two gametes create a two allele offspring
The Punnett Square
- R = purple
- r = white
- P = RR x rr
- homozygous
R R
r Rr Rr
r Rr Rr
4:0 (F₁)
R r
R RR Rr
r Rr rr
3:1 (F₂)
Phenotype vs Genotype
- genotype: a scoring of the type of variant present at a given location (i.e., a locus) in the
genome
- represented by symbols
