Topic 1 Flashcards
Why did Mendel get it right but not others?
He took the time to properly understand the variables of the experiment
How do some peas stay green and others yellow?
Mutation in Sgr prevents chlorophyll degradation
Why did Mendel choose the garden pea?
Easy to grow, short life cycle, mating could be controlled
7 characters Mendel studied
Round or wrinkled seeds
Yellow or green seeds
Yellow or green pods
Purple or white petals
Inflated or pinched pods
Axial or terminal flowers
Long or short stems
Why were the traits that Mendel chose lucky?
They were not linked and controlled by single genes
How did Mendel keep records of his experiments?
Counted # of offspring that had desired trait and kept track of generations
Controlled crosses
A way to track down the segregation and inheritance of traits down generations, and has predictable frequencies
First hybrid generation
F1
2 hybrid generation
F2
Mendelian laws apply to _______________
Any genetic cross/pedigree
What control step explains Mendel’s success?
Created true breeding lines (homozygous) for his desired traits
Monohybrid crosses
Crosses of 2 varities of true-breeding plants that differed in only one characteristic
What was Mendel’s 1st experiment?
Crossed a smooth pea and a wrinkled pea. F1 produced all smooth seeds. Then crossed F1pea and got mixture of smooth and wrinkled in a ratio 3:1
Homozygous recessive
1 phenotype, 1 possible genotype
Homozygous/heterozygous dominant
1 phenotype, 2 possible genotypes
Test cross
F1 hybrid is crossed with a recessive individual called the tester
If the info for a trait can be silenced, __________ cannot apply
Genetic blending
What is responsible for the distribution of dominant and recessive info?
Randomness
Law of segregation
Alleles of a gene separate independently from each other during transmission from parent to offspring
The dominat phenotype appears 100% in F! and follow the 3:1 ratio in F2
The principle of dominance
In a heterozygote, 1 allele may hide another
The principle of segregation
In a heterozygote, 2 different alleles segregate from each other during the formation of gametes
Probability of occurence of2 independent events =
probability of 1st event x probability of 2nd event
Probability of a particular genotype =
probability of obtaining a particular allele in the male gamete x the probability of obtaining a particular allele in the female gamete
What are the frquencies in a test cross?
1:1
Which generation directly shows evidence for dominance?
F1
Which generation directly provides evidence for the independent segregation of alleles?
F2
The multiplication rule (probability)
P(A&B) = P(A) X P(B)
The additive rule - only 1 event occurs(probability)
P(A) + P(B) - [P(A) x P(B)]
The additive rule - mutually exclusive (probabiliy)
P(A or B) = P(A) + P(B)
Dihybrid crosses
Crosses of varieties of true-breeding plants that differ in 2 characters
What dihybrid cross did Mendel analysis?
Seed color (yellow and green) and seed shape (round and wrinkled)
Dominance relationships are ______ altered by the presence of a second pair of factors
Not
In dihybrid crosses, how many gamete combinations are possible?
4
Parental phenotypes
Look same as parents
Recombinant phenotype
Looks different than parents
Dihybrid cross frequencies
9:3:3:1
Law of independent assortment
Alleles of 2 genes segregate independently during transmission from parent to offspring
In order for 2 gene pairs to assort independently, they must be on __________ pairs of chromosomes
Different
First mendelian law
Equal segregation of alleles
2nd mendelian law
Independent assortment of alleles
Will the phenotypic frequencies change if u switch the order of a recessive gamete and a dominant gamete?
No, the recessive and dominant traits will remain the same, even if the gametes switch places
Degrees of freedom
of phenotypic classes - 1
Monohybrid
3:1
Dihybrid
9:3:3:1
Trihybrid
27:9:9:9:3:3:3:1
Test cross frequency
1:1:1:1
Human genome
23 pairs of chromosomes
22 pairs of autosomes
I pair of sex chromosomes
Obstacles to human genetic analysis
Incomplete family records
Small # of progeny
Uncontrolled environment
Pedigree
Diagrams that show the relationships among the members of a family and the inheritance pattern of a specific character/condition
Haplosufficency
A heterozygote will make enough of the normal product encoded by the 1 wildtype allele and have a normal phenotype
If no other info is given, what can u assume outsiders married to the family are?
Homozygous dominant
Albinism
Deficient pigmentation due to inability to produce melanin (recessive)
Example of haplosufficent gene
Albinism
Cystic fibrosis
Serious disease caused by non-functional CFTR gene causes thick mucus to build upon lungs
Autosomal dominant
Caused by a mutant allele that is dominant over the normal allele
Causes of autosomal dominance
Production of too much of a normal protein
Haplo-insufficiency
Production of an abnormal varient of a protein
Production of protein with some entirely new function
Achondroplasia
A dominant form of dwarfism where homozygous dominant is lethal
