Genotypes
An example of a heterozygous genotype.
Tt
Assume that the dominant gene is having freckles and the recessive is not having freckles. If Kyles genotype is Tt, what is his phenotype?
Kyle has freckles.
Laura and Bill are married. Laura has a homozygous dominant trait for freckles and Bill has a homozygous recessive trait for no freckles. What are the possible genotypes for their children.
Ff, Ff, Ff, Ff.
If Macy has black hair with a genotype of BB, and her brother has a genotype of bb and blonde hair, which is the dominant trait? Dark or light hair?
(simplified since hair is very complex)
dark
Kyle has a homozygous recessive genotype for a widow's peak. His sister Selena has a heterozygous dominant genotype for a straight hairline. Selena meets Danny, also a heterozygous dominant genotype for a straight hairline. They have 4 children, one of which has a widow's peak. How is this possible if neither of them have a widow's peak?
Selena and Danny are both heterozygous, meaning they have both genes in their DNA. Their genotypes are Ww and Ww, so when they are crossed there is a 1 in 4 chance they could produce an offspring with a widow's peak. It is also shown that there are instances of a widow's peak in Selena's family, e.x.:Kyle.
An example of a homozygous recessive genotype.
Assume that the dominant gene is a straight thumb and having a hitchhiker's thumb is recessive. Riley's genotype is tt, what is her phenotype?
Riley has a hitchhiker's thumb.
If the genotypes of 4 offspring are TT, Tt, Tt, and tt, what are the genotypes of the parents?
The genotypes of the parents are Tt and Tt
Kyle has freckles. His genotype is Ff. Kyle's sister has no freckles and a genotype of ff. Which would be the recessive gene? Freckles or no freckles?
no freckles
Samantha has a homozygous dominant genotype for freckles. Her sister Megan has a homozygous recessive genotype for no freckles. Megan meets Brandon, a heterozygous dominant genotype for freckles. They have 4 children, 2 of which has no freckles. How is this possible if their Dad has a dominant trait?
Because he is heterozygous, which means he also has the recessive trait but it is hidden by the dominant trait. When combined with Megan's recessive trait of no freckles, 2 out of 4 of their children have a chance of having no freckles.
An example of homozygous dominant genotype.
DD
If the traits for guinea pigs are hair (dominant) and hairless (recessive), and two guinea pigs have genotypes of Hh and HH, what percentage of the guinea pigs are hairless?
0%
If the dominant trait for guinea pigs is fur and the recessive is no fur, what are the chances that two heterozygous dominant parents have hairless children?
25%
Darnell and his sister both have hitchhiker's thumbs. Their genotypes are different, though. Darnell's genotype is Tt and his sister's is TT. Are hitchhiker's thumbs dominant or recessive?
dominant
Macy and Adam have two children. Both of which have blonde hair. Macy has black hair, with a heterozygous genotype. Adam has blonde hair, with a homozygous genotype. Assuming black hair is dominant and blonde is recessive, how is it possible for their children to have the recessive trait if one of the parents possesses the dominant trait?
Macy has a heterozygous genotype, so she possesses the recessive trait, it is just masked by her dominant trait. When her recessive trait combined with Adam's recessive trait, there was a 2 out of 4 chance they would have blonde children.
Laura has the dominant trait for freckles. What are the possibilities of her genotype?
TT or Tt
If there are 4 kittens in a litter and their genotypes are FF, ff, Ff, and Ff, what are their phenotypes if brown fur is dominant and white is recessive?
Brown, white, brown, and brown.
Assume the dominant trait in cats' fur is no spots and the recessive trait is spots on the fur. If a heterozygous dominant parent and a homozygous recessive parent mate, what are the chances of having spotted children?
50%
Freddy, George, and Tom are brothers. Freddy and George have black hair and Tom has blonde. Freddy's genotype is HH, George's is Hh, and Tom's is hh. Which hair color is recessive?
(simplified because hair color is complicated)
blonde
Brad and Chloe have two children. Both of which have a straight thumb. Brad has a hitchhiker's thumb, with a homozygous recessive genotype. Chloe has a straight, with a homozygous dominant genotype. How is it possible for their children to have the dominant trait if both parents possess a recessive gene? (even if hidden)
Even though Brad has two recessive genes and Chloe has one as well, it is not guaranteed that their children will have a recessive gene because Chloe still has the dominant trait. There is a 2 out of 4 chance they will have children with the dominant trait.
Gary has the recessive gene for a widow's peak. What are the possibilities of his genotype?
tt or Tt
2 twin brothers both have dimples. Twin 1's genotype is FF and Twin 2's genotype is Ff. Are dimples dominant or recessive?
Dominant
If one parent is homozygous dominant parent mates with another parent and the outcomes of their children are FF, Ff, FF, and Ff what is the second parents genotype?
Ff
Anthony and Delilah are siblings. Anthony has a straight hairline and Delilah has a widow's peak. Anthony's genotype is Ww and Delilah's is ww. Are widow's peaks dominant or recessive?
recessive
How do you draw a punnett square?
Draw a box and then draw a horizontal and diagonal line. Then, write the parent genotypes, one across the top and one across the side. Then you should combine one gene from the top and one from the side and out the result in each square.