Genetics Unit
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Transcript of Genetics Unit
Genetics UnitGenetics Unit
Genetics = the field of biology Genetics = the field of biology devoted to understanding how devoted to understanding how characteristics are characteristics are transmitted from parents to transmitted from parents to offspringoffspringHeredity = the transmission of Heredity = the transmission of characteristics from parents characteristics from parents to offspringto offspring
MendelMendel- “father” of modern genetics - “father” of modern genetics
= laid the groundwork= laid the groundwork- experimented with garden - experimented with garden
peaspeas- looked for traits = - looked for traits =
specific specific characteristicscharacteristics
MendelMendel (cont) (cont)- P- P11 generation = parental generation = parental
generationgeneration- F- F11 generation = offspring of generation = offspring of
the parental generationthe parental generation- F- F22 generation = offspring of generation = offspring of
the Fthe F11 generation generation
MendelMendel (cont) (cont)Mendel’s 1st Law = Law of Mendel’s 1st Law = Law of
SegregationSegregation1) Organisms inherit two copies 1) Organisms inherit two copies
of each gene, one from each of each gene, one from each parentparent
2) Organisms donate one copy of 2) Organisms donate one copy of each gene in their gametes.each gene in their gametes.
MendelMendel (cont) (cont)Mendel’s 2nd Law = Law of Mendel’s 2nd Law = Law of
Independent AssortmentIndependent Assortment1) The presence of one trait does 1) The presence of one trait does
not affect the appearance of not affect the appearance of another trait another trait
Basics of GeneticsBasics of Genetics- Gene = a segment of DNA on a - Gene = a segment of DNA on a
chromosome that controls a chromosome that controls a specific traitspecific trait- because chromosomes come - because chromosomes come in pairs, genes come in pairsin pairs, genes come in pairs
Basics of GeneticsBasics of Genetics (cont) (cont)- Allele = each of several forms - Allele = each of several forms
of a gene of a gene - aka: letters- aka: letters
- each allele has a specific - each allele has a specific location on a chromosome (= location on a chromosome (= locus)locus)- capital letters = dominant - capital letters = dominant alleles - lowercase letters = alleles - lowercase letters = recessive allelesrecessive alleles
Basics of GeneticsBasics of Genetics (cont) (cont)- Homozygous = both alleles are - Homozygous = both alleles are
alikealike- homozygous dominant = both - homozygous dominant = both capital letters = BBcapital letters = BB- homozygous recessive = both - homozygous recessive = both lowercase letters = bblowercase letters = bb
- Heterozygous = alleles are - Heterozygous = alleles are different = Bbdifferent = Bb
PolydactylPolydactylyy
Polydactyly is Polydactyly is the condition of the condition of having more having more than the typical than the typical number of number of fingers or toes. fingers or toes. The allele for The allele for polydactyly is polydactyly is dominant.dominant.
Basics of GeneticsBasics of Genetics (cont) (cont)- Genotype = genetic makeup of - Genotype = genetic makeup of
an organisman organism- consists of alleles (letters)- consists of alleles (letters)
- Phenotype = the appearance of - Phenotype = the appearance of an organism as a result of its an organism as a result of its genotypegenotype- aka: what does it look like- aka: what does it look like- human phenotype can be - human phenotype can be altered by behavioraltered by behavior
Monohybrid Crosses
= a cross between individuals that involves one pair of traits
- Example: Black hair (B) in guinea pigs is dominant to brown hair (b)
Example 1:Homozygous Dominant X Homozygous Dominant
Genotypic Ratio
Phenotypic Ratio
Example 2:Homozygous Recessive X Homozygous Recessive
Genotypic Ratio
Phenotypic Ratio
Example 3:Homozygous Dominant X Heterozygous
Genotypic Ratio
Phenotypic Ratio
Example 4:Homozygous Recessive X Heterozygous
Genotypic Ratio
Phenotypic Ratio
Example 5:Heterozygous X Heterozygous
Genotypic Ratio
Phenotypic Ratio
Testcross
= an individual of unknown genotype is crossed with a homozygous recessive individual
- can be used to determine the genotype of any phenotype that is dominant
Example 6: Testcross
Genotypic Ratio
Phenotypic Ratio
Example 6: Testcross
Genotypic Ratio
Phenotypic Ratio
Example 6: Testcross
Genotypic Ratio
Phenotypic Ratio
Incomplete Dominance
= the F1 Generation will have a phenotype in between that of the parents
- Example: Red flowers (R) and White flowers (r) can make Pink flowers (Rr)
Example 7: Incomplete Dominance Pink Flower X Pink Flower
Genotypic Ratio
Phenotypic Ratio
Example 7: Incomplete Dominance Pink Flower X Red Flower
Genotypic Ratio
Phenotypic Ratio
Example 7: Incomplete Dominance White Flower X Red Flower
Genotypic Ratio
Phenotypic Ratio
Example 7: Incomplete Dominance Pink Flower X White Flower
Genotypic Ratio
Phenotypic Ratio
Codominance= when both alleles for a gene
are expressed in a heterozygous offspring
- Example: Red coat color (R) in horses is codominant with white coat color (R’) to make a horse with a mix of red and white coat color (RR’)
Example 8: Codominance Red Coat X White Coat
Genotypic Ratio
Phenotypic Ratio
Example 8: Codominance Red/White Coat X White Coat
Genotypic Ratio
Phenotypic Ratio
Example 8: Codominance Red/White Coat X Red Coat
Genotypic Ratio
Phenotypic Ratio
Dihybrid Cross
= a cross between individuals that involves two pairs of traits
- Example: Black hair (B) in guinea pigs is dominant to brown hair (b) and rough coat (R) is dominant to smooth coat (r)
Example 1:
Homozygous Dominant X
Homozygous Recessive
Example 1: Homozygous Dominant X Homozygous Recessive
Example 2:
Heterozygous X
Heterozygous
Example 2: Heterozygous X Heterozygous