Review Flashcards
Why study genetics?
Critical role in understanding disease, improving agricultural practices, and biotechnology industry.
What is a gene?
Fundamental unit of heredity
What is an allele?
Multiple forms of genes
Where is genetic information carried?
DNA
Where are genes located?
On chromosomes
How is genetic information transferred?
From DNA to RNA to protein
What is a locus?
A specific place on a chromosome occupied by an allele
What is a genotype?
Set of alleles possessed by an individual organism
What is a heterozygote?
An individual organism possessing two different alleles at a locus
What is a homozygote?
An individual organism possessing two of the same alleles at a locus
What is a phenotype or trait?
The appearance or manifestation of a character
Who discovered the basic principles of heredity?
Gregor Johann Mendel
What is a monohybrid cross?
Cross of a single gene (ex. round x wrinkled)
What is Mendel’s law of segregation?
3:1 ratio of dominant:recessive
If an F1 plant (heterozygous) is backcrossed to the parent with round (dominant) seeds, what proportion of the progeny will have wrinkled seeds?
0
What are dihybrid crosses? What is the approximate ratio of phenotypes?
Cross of 2 genes. Approximately 9:3:3:1 (DD:Dr:rD:rr)
How is an affected person represented in a pedigree?
Shaded
How is a male represented in a pedigree?
Square
How is a female represented in a pedigree?
Circle
What is the shape on a pedigree when the gender is unknown?
Diamond
What is a generation line on a pedigree?
A vertical line = offspring.
What is a sibship line on a pedigree?
Horizontal line (above) = siblings
What do we assume for a pedigree?
If the trait is rare and autosomal recessive, then individuals who marry/mate into the pedigree are not carriers, but are homozygous for the normal allele unless there is evidence to the contrary.
What are null/amorphic alleles?
- A nonfunctional protein is produced
OR - No protein is produced
What are hypomorphic alleles?
- A poorly functioning protein is produced
OR - Reduced amounts of a normally functioning protein is produced
If the probability of being blood-type A is 1/8 and the probability of blood-type O is 1/2, what is the probability of being either blood-type A or O?
5/8
What type of alleles usually result in loss of function?
Recessive
What type of allele often involve gain/change of gene function?
Dominant
What are dominant hypermorphic alleles?
- Negative phenotypic consequences due to the overproduction of a normal protein
OR - Negative phenotypic consequences due to the production of a protein with increased activity levels
What are neomorphic alleles?
- Negative phenotypic consequences due to the presence of an altered protein that has a new function
OR - Negative phenotypic consequences when the altered protein interferes with the wildtype protein
(Dominant-negative allele)
For traits that are rare and dominant, affected individuals are most likely to be ____________. Why?
- Heterozygous
- If the trait is rare, then matings between heterozygous individuals would be infrequent
(you will see Bb x bb)
Albinism is a recessive condition. A couple with normal skin want to have 2 children. The man has one albino parent; the woman has parents with normal skin, but an albino brother.
What is the probability that their first child will be albino?
2/3 x 1 x 1/4 = 2/12 = 1/6
