Mendelian Genetics Flashcards
What was the correct hypothesis of inheritance of traits? (Genes)
Individual units of inheritance deliver specific traits that are maintained in offspring
Who discovered the basic principles of heredity by breeding garden peas?
Gregor Mendel
We didn’t know about genes being encoded by ____ until ____ and ____ until _____
DNA
1944 (Griffith)
DNA structure
1953 (Watson and Crick…and Franklin)
Traits that are controlled by many genes
Polygenic
Crossing two contrasting ‘true-breeding varieties’ (PPxpp) is called?
Hybridization
The result of Mendel’s experiments came the two fundamental principles of genetics, which are…
- The Law of Segregation
- The Law of Independent Assortment
What were Mendel’s conclusions?
- There are “heritable units” that can be passed on to progeny called alleles
- For each character, an organism receives two copies of any given gene, one from each parent
- If alleles differ at a locus, then one must be dominant
- The Law of segregation: The two alleles separate from each other during gamete formation and end up in different gametes
What is a phenotype?
An observed trait of a characteristic (what you can see)
What is a genotype?
The genetic makeup that produces the phenotype
What is a test cross?
Breeding the individual with the dominant phenotype, with a true-breeding parent that displays the recessive phenotype to determine the genotype of the dominant phenotype
Law of Independent Assortment
Two or more genes will assort independently into gametes
If genes are really close on a chromosome, they are ____?
Linked
How do you determine the probability that two or more independent events will occur together in some specific combination?
The multiplication rule
Ex. Rr x Rr. 50% chance of getting R or r from each parent. 1/2 x 1/2 = 1/4
If genes are really far apart on the same chromosome, the odds of them crossing over is very likely, so they are _____ ?
Not linked, assort independently
How do you determine the probability that two or more mutually exclusive events will occur together in some specific combinations?
The addition rule
ex. The probability of Rr, with the R coming from the sperm is 1/4. The probability of Rr, with the R coming from the egg is 1/4. 1/4+1/4 = 1/2
What is complete dominance?
Phenotype is dominant in heterozygotes
Incomplete dominance
The phenotype is a blend of both in heterozygotes
Co-dominance
Both alleles are expressed
Pleiotropy
One gene affects multiple phenotypes
If a homozygous genotype doesn’t always produce a specific phenotype in all members of the group, it is known as?
Penetrance
Even if you have the genotype, you may not get the phenotype
When in a group of individuals with the genotype for a specific gene, a range of traits is displayed it is called?
Expressivity
The amount of the phenotype produced
Epistasis
The phenotypic expression of a gene at one locus affects the phenotypic expression at a second locus
ex. Labs. If they have the ee gene, no matter what the other gene codes for, the dog will be yellow
Multifactorial
The phenotype depends on the genotype and the environment
Polygenic inheritance
Many genes contribute to a single phenotype
What are polygenic traits affected by?
The environment
Ex. Human skin can be affected by exposure to sunlight
Pedigree analysis
Traces a character through family generations
If a trait is dominant it will:
- Appear more often in the progeny
- An offspring displaying that trait will always have a parent with the trait
If a trait is recessive, it will:
- Appear less often in the progeny
- An offspring displaying that trait can have parents that do not display that trait (can skip generations)
A recessive allele usually results in?
A protein malfunction or lack of protein altogether
Carriers are what genotype?
Heterozygote
Which allele is usually the harmful one?
Recessive
Some recessive alleles are ____ if an individual is homozygous recessive
Lethal
Some alleles are lethal when in the _____ state
Homozygous
Dominant lethal alleles are much more rare than recessive lethal alleles
