Chapter 7 CMB Mendel's Law Flashcards
What are the 3 Mendel’s Laws?
- the Law of Dominance
- the Law of Segregation
- the Law of Independent Assortment
What is the genotype for TT?
Homozygous DOMINANT
What is the genotype for Tt?
Heterozygous dominant
What is the genotype for tt?
Homozygous RECESSIVE
What is a phenotype?
Physical appearance of a trait
What is the Law of Dominance?
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.
What is the genotype vocab and phenotype for the genotype symbol TT?
T- Tall
t- Short
Genotype symbol: Homozygous DOMINANT or pure tall
Phenotype: Tall
What is the genotype vocab and phenotype for the genotype symbol Tt?
Genotype symbol: Heterozygous or hybrid
Phenotype: Tall
What is the genotype vocab and phenotype for the genotype symbol tt?
Genotype symbol: Homozygous RECESSIVE or pure short
Phenotype: Short
What is the Law of Segregation
During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then “recombined” at fertilization, producing the genotype for the traits of the offspring.
What is the Law of Independent Assortment?
Alleles for different traits (alleles) are distributed to gametes or sex cells (& offspring) independently of one another.
What do homologous chromosomes contain?
Homologous chromosomes contain DNA that codes for the same genes.
Difference between sister chromatids and homologous chromosomes?
Sister chromatids are exact replica, but homologous chromosomes are not
What is the ratio of a dihybrid cross?
9:3:3:1
What is test cross used for?
Determine unknown genotypes
What is polygenic?
Human traits that are complexed and are affected by several genes
How can an unknown genotype be revealed?
By mating between an unknown genotype and a homozygous recessive
State examples of polygenic inheritance
Hair and eye color, intelligence and musical ability
What are the 4 patterns of inheritance?
- Recessive: trait can skip one generation
- Recall short phenotype in F1 generation - Dominant: trait appears in all generations
- Autosomal: trait is carried on autosomes
- Huntington disease is an autosomal dominant trait
- Cystic fibrosis is an autosomal recessive trait - Sex-linked: trait is carried on X chromosomes
What is the purpose of a family pedigree?
Family pedigrees are used to determine patterns of inheritance and individual genotypes
What happens to those traits exhibiting recessive gene action? (Recessive Pedigree)
- Unaffected parents can have affected offspring
- Affected progeny are both male and female
What are recessive disorders caused by?
They are caused by autosomal recessive alleles
What happens to those traits exhibiting dominant gene action? (Dominant Pedigree)
- Affected individuals have at least one affected parent
- The phenotype generally appears every generation
- Two unaffected parents only have unaffected offspring
What type of chromosomes do mammals have?
In mammals, a male has one X chromosome and one Y chromosome (XY) and a female has two X chromosomes (XX)
What gene does the Y chromosome contain?
Has genes for the development of testes
Absence of Y chromosome allows ________?
Allows ovaries to develop
What are sex-linked human disorders caused by?
- Are due to recessive alleles
- Genetic mutation on the X-chromosomes
Why are sex-linked human disorders mostly seen in males and provide examples.
It is because a male receives only a single X-linked allele from his mother hence will have the disorder while a female has to receive the allele from both parents to be affected
Examples: Hemophilia, red-green color blindness
What are some examples of autosomal RECESSIVE disorders? (6 examples)
- Cystic Fibrosis*
- Albinism*
- Sickle-cell disease*
- Tay-Sachs disease
- Phenylketonuria
- Hemochromatosis
What are some examples of autosomal DOMINANT disorders? (3 examples)
- Huntington disease*
- Polycystic kidney disease*
- Neurofibromatosis*
What is the offspring and law for this parent cross? (TT x tt)
Offspring: 100% Tt and Tall
Law of Dominance
What is the offspring and law for this parent cross? (Tt x Tt)
Offspring: 75% tall and 25% short
Law of Segregation
What is the offspring and law for this parent cross? (RrGg x RrGg)
Offspring: 9 RG, 3 Rg, 3, rG, 1rg (9:3:3:1)
Law of Independent Assortment
(where RG is round green, Rg is round yellow, rG is wrinkled green, rg is wrinkled yellow)