Genetics Test Review Mrs. Callan Biology 2017

Vocabulary to Know… Punnett Square – chart used to determine the probable outcome of genetic crosses Heredity – The passing of traits from parent to offspring Gregor Mendel – “The Father of Genetics” Alleles – Different forms of a single trait Dominant - a genetic trait that appears in every generation of offspring and that masks/covers the other trait

Vocabulary to Know… 6) Recessive - the allele only expressed in a homozygous state 7) Genotype – the genetic makeup of an organism 8) Phenotype – the physical appearance of an organism 9) Heterozygous – an organism that has inherited two different alleles of a gene from its parents

Vocabulary to Know… 10) Incomplete Dominance - A trait in an individual that is intermediate (a blend) between the phenotype of the individual’s two parents because the dominant allele is unable to express itself fully 11) Codominance - A condition in which both alleles for a gene are fully expressed 12) Genetics – a branch of biology that studies heredity 13) Polygenic Traits – traits controlled by multiple genes. Example: SKIN COLOR

Can a mother and father with brown eyes have a child with blue eyes? Yes! If both parents are heterozygous for the brown eyed trait. This means that they have brown eyes, but carry the blue eyed trait. There is a 25% chance of them having a child with blue eyes.

Explain the difference between homozygous dominant, homozygous recessive and heterozygous. Give an example of each. Homozygous Dominant – having two dominant alleles. EX: BB Homozygous Recessive – having two recessive alleles. EX: bb Heterozygous – having a dominant and recessive allele. EX: Bb

Explain the difference between chromosome and gene mutations Explain the difference between chromosome and gene mutations. Give an example of each. Chromosome Mutations – changes to the structure of a chromosome. Examples: Deletion, Inversion, Translocation, Nondisjuction Gene Mutations – changes to the DNA sequence Examples: Point mutation, frameshift mutation, insertion, substitution

In humans, having freckles (F) is dominant over not having freckles (f). Cross a girl and boy who are both heterozygous for freckles. List the genotype and phenotype percentages. F f Genotypes: ¼ 25% FF 2/4 50% Ff ¼ 25% ff Phenotypes: ¾ 75% Freckles ¼ 25% No freckles Ff F FF f Ff ff

From the previous question, what is the probability their children would have freckles? Would not have freckles? There would be a 75% chance of having children with freckles. There would be a 25% chance of having children without freckles. See punnett square on previous slide.

Cross a homozygous recessive individual with a heterozygous individual using the letter B. List the genotype percentages from the cross. b b Genotypes: 2/4 50% Bb 2/4 50% bb Bb Bb B b bb bb

Tallness (T) is dominant over shortness (t) in pea plants Tallness (T) is dominant over shortness (t) in pea plants. How would you write the genotype of a plant that is heterozygous for tallness? Tt

Genotypes: 4/4 100% Bb Phenotypes: 4/4 100% Black Fur In rabbits, black fur (B) is dominant over brown fur (b). Cross a homozygous dominant rabbit with a homozygous recessive rabbit. List the genotype and phenotype percentages. Genotypes: 4/4 100% Bb Phenotypes: 4/4 100% Black Fur B B Bb Bb b b Bb Bb

Key: B = Black Fur b = Brown Fur What fur color would a homozygous dominant rabbit have? … A homozygous dominant rabbit would have BLACK FUR. Key: B = Black Fur b = Brown Fur B B Bb Bb b b Bb Bb

Key: B = Black Fur b = Brown Fur What fur color would a homozygous recessive rabbit have? … A homozygous recessive rabbit would have BROWN FUR. Key: B = Black Fur b = Brown Fur B B Bb Bb b b Bb Bb

The offspring would be ROAN (BOTH Red & White) If the trait for coat color in cows is codominant, what color would offspring cows be if their parents are a red cow and a white cow? The offspring would be ROAN (BOTH Red & White)

What kind of traits determine skin color? Polygenic Traits When you see a range of phenotypes (such as skin color), those traits are polygenic which means they are controlled by multiple genes

There is a 25% chance of them having a child with Blood Type O. A mother is heterozygous for blood type A and the father is heterozygous for blood type B. What is the probability that their child will be blood type O? Show the cross. A O There is a 25% chance of them having a child with Blood Type O. AB BO B O AO OO

Within the skin cells of a child, a mutation occurs that causes skin cancer. Who will this mutation effect? The mutation will affect this child only because somatic cell (body cell) mutations CANNOT be passed onto offspring. The only way to pass mutations onto offspring is for the mutation to be in a germ cell (gamete/sex cell).

If a red flower and white flower are crossed to make pink flowers, what is this an example of? Incomplete Dominance

Using the letter B, write the genotype for a heterozygous organism. Bb