genetics study guide key to success on the test. 1. what scientist experimented with pea plants to...

Genetics Study Guide

Key to Success on the Test

1. What scientist experimented with pea plants to establish

modern genetics?

• Gregor Mendel

2. What is the difference between a monohybrid and a dihybrid cross

• Monohybrid examines 1 trait, Dihybrid examines 2 traits

3. What is the difference between a gene and an allele?

• Genes are a segment of DNA that code for a trait. Alleles are alternate forms of that gene.

• Gene: Pea Pod Color

• Alleles: Yellow pod color or Green pod color

4. What is the difference between genotype and phenotype?

• Genotype is the code or letter that represent a trait

• Phenotype is the physical way that the trait is expressed

• Genotype: YY

• Phenotype: Yellow

5. What is the difference between homozygous and heterozygous?

• Homozygous means that you have 2 same alleles for a trait (YY or yy)

• Heterozygous means that you have 2 different alleles for a trait (Yy)

6. What is the difference between a hybrid and a purebred?

• Hybrids have 2 different alleles from the parent(s) Yy

• Purebreds have two same alleles from the parent(s) YY or yy

7. What is the difference between dominant and recessive?

• Dominant alleles have the ability to mask a recessive allele.

• With the genotypes YY and Yy the dominant trait will be expressed

• With the genotype yy, the recessive trait will be expressed

8. What are Punnett Squares used for?

• To find out the possible outcomes for a genetic cross

9. Create a Punnett Square for a monohybrid cross for two

individuals that are heterozygous for brown eyes

(Bb). Brown eyes are dominate to blue eyes.

10. Give 3 reasons that Mendel used pea plants for his studies.

• Short growing period/Easy to Grow

• 7 traits in 2 distinct forms

• Produces many offspring

11. Mendel’s Laws

– The Law of Segregation-During Meiosis each pair of alleles separate

– The Law of Independent Assortment-gene pairs separate randomly and independently of each other

– The Law of Dominance-dominant allele masks recessive allele

12. What are 3 ways you can show probability?

• Ratio

• Percent

• Fraction

13. Define trait.

• Anything that can be passed down from parent to offspring

14. What are carriers?

• Individuals who are heterozygous for a recessive trait. They carry the trait, but they are not affected by it.

15. What is a pedigree used for?

• To examine inheritance patterns in families.

• Circles are females

• Square are males

• Individuals that exhibit the trait are shaded in

• Individuals that carry the trait are partially shaded in

16. What is the difference between sex chromosomes and

autosomes?

• Sex chromosomes determine the sex of the offspring and X-linked traits. Autosomes carry the genes that affect the rest of the individual.

17. What is the genotype for a female and what is the genotype for

a male

• FEMALE: XX

• MALE: XY

18. What is one difference between X and Y chromosomes?

• Size. The X chromosome is significantly larger than the Y chromosome

19. When babies are made, which gamete controls the sex of the

offspring?

• Male gamete - Sperm

20. What are sex-linked traits?

• Sex-linked traits are from genes located on the X chromosome of the sex chromosome.

21. Create a Punnett Square to show the recessive sex-linked trait “male pattern

baldness” Cross a carrier female with a normal male.

Give Ratios.

22. What are karyotypes?

• Diagram that shows the cell’s chromosomes organized from smallest to largest.

• It allows people to determine gender and find out if the individual has any chromosomal disorders.

23. How many chromosomes do people with Down Syndrome

have?

• 47. They have 3 chromosomes located on chromosome 21

24. What do you observe about this karyotype? Is it going to

produce a “normal” offspring?