Exam 1-Genetics Flashcards
What is genetics?
The study of heredity - how traits are passed from parent to offspring.
What are traits?
Anything that you inherit from your parents, e.g., hair color, freckles, dimples.
Who is considered the Father of Genetics?
Gregor Mendel.
What did Gregor Mendel study to discover the laws of heredity?
Pea plants.
When was Mendel’s work rediscovered?
In 1900.
What is a trait?
A genetically determined variant of a characteristic, e.g., white flowers vs purple flowers.
What does P1 generation refer to?
The parent generation.
What does F1 generation refer to?
The first filial generation, the offspring from the P1 generation.
What does F2 generation refer to?
The second filial generation, the offspring from the F1 generation.
Define a dominant trait.
The trait that is expressed more often.
Define a recessive trait.
The trait that is expressed less often because it is covered up by the dominant trait.
What is a gene?
The segment of DNA on a chromosome that controls a particular trait.
What is an allele?
The different forms of a gene, represented by letters (lower case and capital).
What is the probability of an event?
The likelihood that a specific event will occur.
What is a genotype?
The set of alleles that an organism has, represented by a combination of letters.
What is a phenotype?
An organism’s physical appearance.
What does homozygous mean?
When the two alleles for a particular gene are the same.
What does heterozygous mean?
When the two alleles for a particular gene are different.
What is a Punnett Square?
A diagram that predicts the expected outcome of a genetic cross by considering all possible combinations of gametes.
What is a monohybrid cross?
A cross involving a single trait.
In a Punnett Square, what is represented by ‘R’ and ‘r’ in seed shape?
R represents round seeds and r represents wrinkled seeds.
What is incomplete dominance?
When the phenotype of the offspring is in-between that of the parents.
Give an example of incomplete dominance.
Four O’Clock flowers: Red flower + White flower = Pink flower.
What is codominance?
When both alleles for a gene are expressed in a heterozygous offspring.
In codominance, how are the alleles typically represented?
Both alleles are usually written as capital letters.
What is the phenotype of a horse with genotype RW?
Roan coat color (mix of red and white).
What are the genotypes of a black cat and a tan cat in codominance?
Black cat = BB, Tan cat = TT, Checkered cat = BT.
What is the result of crossing a checkered hen with a checkered rooster?
Genotype: BB = 1/4, BW = 2/4, WW = 1/4; Phenotype: Black = 1/4, Checkered = 2/4, White = 1/4.
Fill in the blank: A dominant allele is written with a _______.
capital letter.
Fill in the blank: A recessive allele is written with a _______.
lowercase letter.
What are multiple alleles?
More than two alleles for a given gene
Can an individual have more than two alleles?
No, any given individual can have no more than two alleles: one from the mother and one from the father
Provide an example of multiple alleles in humans.
Human blood type
What are the possible genotypes for blood type A?
AA, AO
What blood types can a person with type A receive?
A or O
What are the possible genotypes for blood type B?
BB, BO
What blood types can a person with type B receive?
B or O
What is the genotype for blood type AB?
AB
What blood types can a person with type AB receive?
A, B, AB or O
What is the genotype for blood type O?
OO
What blood type can a person with type O receive?
O
In Labrador Retrievers, what determines coat color?
One gene with four different alleles
What are the three most common coat colors in Labrador Retrievers?
- Yellow
- Black
- Chocolate
What are polygenic traits?
Traits that are controlled by 2 or more genes
How does each allele affect the phenotype in polygenic traits?
Each allele intensifies or diminishes the phenotype
What is the nature of variation in polygenic traits?
Continuous or quantitative
What is an example of a polygenic trait in humans?
Skin color
How many genes influence human skin color?
3-6 genes
What is another example of a polygenic trait in humans?
Height
How many genes influence height in humans?
Over 400 genes
What factors can influence gene expression?
- Temperature
- Water
- Acid levels
- Food sources
What happens to hydrangea flowers in acidic soil?
The flower will be blue
What happens to hydrangea flowers in basic soil?
The flower will be pink
How do environmental factors affect the Arctic fox’s coat color?
Changes from summer to winter
What is unique about the pigmentation of Siamese cats?
Darker pigmentation develops in cooler body parts
What are the sex chromosomes in humans?
X and Y
What is the genotype of a human female?
XX
What is the genotype of a human male?
XY
What are sex-linked traits?
Traits located on the sex chromosomes
Which sex chromosome carries most sex-linked traits?
X chromosome
Why are males more likely to express sex-linked traits?
Males have only one X chromosome
What is an example of a sex-linked trait in fruit flies?
Eye color
What is the phenotype ratio from a cross of a red-eyed male and a white-eyed female fruit fly?
1:1
What are common examples of sex-linked traits in humans?
- Colorblindness
- Hemophilia
- Male pattern baldness
- Duchenne Muscular Dystrophy
Why can’t males be carriers of sex-linked traits?
They only have one X chromosome
Fill in the blank: Females are carriers of sex-linked traits if they have the _______ genotype.
heterozygous
