Genes & DNA
What molecule carries an organism's genetic code?
DNA
A dominant trait is expressed when --
1. two recessive genes are present
2. at least one dominant gene is present
3. there are no chromosomes
4. both parents have the trait
2. at least one dominant gene is present
A Punnett square predicts—
A. the exact traits of one offspring
B. the probability of inherited traits
C. mutations
D. DNA sequences
B. the probability of inherited traits
In a pedigree, a square represents a—
Male
What is heredity?
The passing of traits from parents to offspring.
What structure inside a cell contains DNA?
Chromosomes
A recessive trait appears only when --
1. one dominant gene is present
2. both parents are carriers
3. two recessive genes are inherited
4. one recessive gene is inherited
3. two recessive genes are inherited
Cross: RR × rr
What percentage of offspring will show the dominant trait?
100%
In a pedigree, a circle represents a—
female
Who is known as the "Father of Genetics"?
A. Charles Darwin
B. Albert Einstein
C. Louis Pasteur
D. Gregor Mendel
D. Gregor Mendel
A gene is best described as...
1. a type of cell
2. a section of DNA that carries information
3. a chromosome
4. a protein
2. a section of DNA that carries information
In pea plants, yellow seeds are dominant over green seeds. Which genotype produces green seeds?
A. YY
B. Yy
C. yy
D. YYY
C. yy
Cross: Yy × Yy
What percentage of offspring will have the recessive trait?
25%
What is a carrier?
A person who has one dominant gene and one recessive gene but does not show the recessive trait.
True or False:
Traits can be determined by more than one gene.
True
How many copies of each gene does a person usually inherit?
Two copies -- one from the mother and one from the father.
A plant has genotype Yy. What color will its seeds most likely be?
Yellow
Cross: DD × Dd
What percentage of offspring will have dimples if D is dominant?
100%
A fully shaded symbol represents—
A. a carrier
B. someone without the trait
C. someone with the trait
D. an unknown person
C. someone with the trait
Which cell part would a scientist study to learn about inherited traits?
A. Cell membrane
B. Cell wall
C. Chloroplast
D. Chromosomes
D. Chromosomes
Explain the relationship between DNA, chromosomes, and genes.
Genes are sections of DNA, and DNA is organized into chromosomes.
Why can two parents without a recessive trait have a child with the recessive trait?
Both parents can be carriers (Yy or Ff) and each pass the recessive gene to the child.
Why can't a Punnett square predict the exact traits of one specific child?
It only predicts probabilities, not exactly which genes an individual offspring will inherit.
Two individuals with the recessive trait have children together. What will all of their children inherit?
All will have the recessive trait because each parent passes on a recessive gene.
A pea plant with genotype Yy is crossed with another Yy plant.
Fill in the Punnett square and answer: