Genetics Flashcards
What is the genetic chromosome theory?
Genes that are inherited by chromosomes.
What is a pedigree?
Family tree that shows physical/genetic trait or condition that gets passed down.
Def. of Homozygous
Identical alleles in a gene which is pure
Ex. Recessive gene rr and dominant gene RR
What is a Punnet square
Diagrams geneticists use to predict possible genetic outcomes when cross breeding.
What is the Law of Dominance?
When a dominant and recessive gene is present and usually dominant expresses itself and recessive gene is masked and recessive shows rr and dominant shows in Rr and RR.
Definition of Heterogeneous
Non-identical alleles in a gene where one is recessive and one is dominant.
What is a genotype?
How genes look like (GENo - GENe)
What is a phenotype
How physical traits look like (PHeno - PHysical)
How do you know if a gene is recessive or dominant?
Dominant trait: Shows BB or Bb
Recessive trait: Shows only bb pure recessive
What are the different generations in a pedigree?
P - Parent generation
F1-First generation
F2 - Second generation
What is a dihybrid cross?
It is a genetic cross that describes the inheritance of two traits for example: RrTtXRrTt
How do you find the possible allele combinations in the cross?
Each parent can form 4 possible allele combos, and to find them you must distribute it
Ex:RrBb-RB, Rb, rB, rb
What is the probability ratio for dihybrid combos?
9:3:3:1
How do you find the probability of traits found in the offspring?
One way is the 4x4 punnett square method and the other way is the “shortcut”.
What is the 4x4 punnett square method?
It is when you put all of the mothers possible combinations on one side and the fathers combinations on the other side and you fill in the boxes through multiplication to find the allelic combinations. Then you find the possible combinations for each of the four phenotypes out of 16.
Ex: RT- 9/16 Rt- 3/16 rT-3/16 rt-1/16
What about the “shortcut method” that sound pretty cool…
Well stupid Eli from the past, the shortcut method is the better 2nd option. The one the regents exams are likely to ask you to use. Basically you get 2 2x2 punnett squares each one will have one side for mothers traits and the other side for the fathers traits (each will have four alleles), and you do the same for the other box. Then you find the probabilty of each trait from different squares. THEN you multiply from each square and you find 4 different combinations.
What is intermediate inheritance or incomplete dominance.
It is when the offspring’s phenotype or physical looks is a blend of both parents.
What is Codominance?
Both alleles are dominant and they both show up in the phenotype
What is polygenic inheritance?
Multiple genes needed to form one trait
What are sex linked traits
Genes found on the X-chromosome that is passed from mother to son.
Why can only mothers pass on the gene to the son?
Males pass single X to all daughters and sons receive y chromosome from the dad.
Why can male exhibit sex-linked traits more often than females?
Males need only one recessive gene to have the trait since there is only one X chromosome and it is more expressed.
What are some examples of sex linked traits?
Hemophilia-Can’t form blood clots
Color blindness- Can’t see color
Duchenne Muscular dystrophy- Progressive muscle disorder.
Four types of genes that can be passed down
Autosomal Dominant and Recessive and Sex-linked dominant and recessive.
