achilles - mendelian genetics Flashcards
(25 cards)
Who is considered the father of classical genetics?
Gregor Mendel
What is continuous variation?
Inheritance involving blending of parental traits to produce an intermediate phenotype.
What is discontinuous variation?
Inherited traits retain their distinctiveness; no blending.
What is a model organism?
An organism representative of a variety of systems and biological processes.
Practical considerations when choosing a model organism?
Predictability, low cost, easy maintenance, short life cycle, availability.
What is the principle of segregation?
Individuals have two copies of each trait; each parent transmits one copy to offspring.
What is the principle of dominance?
In heterozygotes, only the dominant phenotype is expressed.
What is the principle of independent assortment?
Genes sort independently into gametes; all allele combinations are equally likely.
What are alleles?
Gene variants located at the same genetic locus.
What is a locus?
The specific position of a gene on a chromosome.
What is a mutation?
A change in a DNA sequence from what is considered “normal.”
What is polymorphism?
Common DNA sequence variation; no single allele is seen as the standard.
Define homozygous.
Two copies of the same allele (e.g., YY or yy).
Define heterozygous.
Two different alleles (e.g., Yy).
In a Punnett square, what does ‘y’ and ‘Y’ represent?
‘y’ is recessive; ‘Y’ is dominant.
What is a test cross?
A cross used to determine the genotype of an individual with a dominant phenotype.
What is a dihybrid cross?
A cross that looks at how two different traits are passed on, showing that the genes for each trait are inherited separately.
What is the phenotypic ratio for YYRr x YyRr?
3:1 (arises from a 9:3 underlying genotypic pattern).
What are sex-linked traits?
Traits linked to genes located on sex chromosomes (commonly the X chromosome).
Gene for eye color in Drosophila is located on which chromosome?
X chromosome; W = red eyes (dominant), w = white eyes (recessive).
Name common X-linked disorders.
Red-green color blindness, muscular dystrophy, haemophilia.
What are lethal alleles?
Alleles (usually recessive) where homozygotes do not survive.
How do lethal alleles affect genotypic ratios?
Heterozygous parents yield a 2:1 ratio instead of 1:2:1.
Give an example of a dominant lethal allele.
Huntington’s disease; symptoms appear at age 35–40.
