1. Mendelian Genetics
Study Guide

2. Explain each of Mendel’s law. How is each law used in Punnett Squares?
Law of….
1.Independent Assortment: alleles sort randomly and independently of each other (seen in dihybrid Punnett squares)
2.Segregation: paired alleles for a trait separate when gametes are formed (why sperm and egg only carry one allele for a trait, not a pair)
3.Unit Characters: units in a cell are responsible for traits (genes), and these units come in pairs otherwise known as alleles (an early explanation of genes)

3. Compare and contrast mitosis and meiosis.
2 identical diploid daughter cells produced
4 haploid daughter cells produced
one duplication of DNA, one cell division
one duplication of DNA, two cell divisions
a form a asexual reproduction
1st stage in sexual reproduction

4. How are human egg cells similar to human sperm cells?
both are haploid

5. combinations different from those of either parent
How many chromosomes does a cell have after meiosis (as compared to a parent cell)?
½ the number with gene
combinations different from
those of either parent

6. What is the F1 and F2 generation?
F1 generation is the offspring of
the P generation (true-breeding)
F2 generation is a result of the
crossing of two F1 hybrids

7. Describe and give an example of polygenic traits.
traits controlled by multiple genes; ex> skin color

8. What happens during oogenesis in humans?
Meiosis in females that produces 3 inactive polar bodies and one egg cell

9. Define and give an example of incomplete dominance and codominance.
Incomplete dominance: one allele not completely dominant over another; heterozygous phenotype lies between the two homozygous phenotypes; 2 alleles produce 3 phenotypes; Example: red, white, and pink or straight, curly, and wavy hair
Co-dominance: both phenotypes produced by different alleles are expressed; ex> the allele for black feathers is codominant with the allele for white feathers; heterozygous chickens are speckled with black and white feathers.

10. Define phenotype and genotype.
Genotype: allele combination for a particular trait in an organism Phenotype: The physical appearance for a particular trait in an organism

11. What is the diploid number of chromosomes in a human cell?46

12. A sex cell (sperm cell or egg cell)
Define gamete.
A sex cell (sperm cell or egg cell)

13. Define zygote.
Single cell formed when the egg and sperm cell unite during fertilization

14. If an organism has 20 chromosomes for his normal diploid number, then how many chromosomes will it have after meiosis? 10

15. Describe the process of fertilization.
Sperm cell and egg cell unite to form a zygote

16. How are identical twins formed?
One sperm cell fertilizes one egg cell and the zygote then splits in half.

17. What alleles represent homozygous dominant tall. Heterozygous tall
What alleles represent homozygous dominant tall? Heterozygous tall? Homozygous recessive short? TT Tt tt

18. What happens in the process of “crossing over?”
chromatids of the homologous chromosomes cross over one another and the crossed sections of the chromatids exchange

19. Define Heredity:
A set of characteristics passed from parent to offspring

20. What did Mendel work when studying heredity? Why did he use these?
mathematical analysis of the offspring of pea plants; small, could produce large amounts of offspring in short amount of time

21. What did Mendel discover from his test crosses?
Mendel was able to develop his laws that described inheritance: law of independent assortment, law of segregation, and the law of unit characters

22. What is the difference between self-pollination and cross pollination?
Self-pollination: Pollen from a flower fertilizes an egg cell on the same flower; offspring have a single parent.
Cross-pollination: Pollen from one plant fertilizes eggs from another plant; offspring have 2 different parents

23. Complete a monohybrid cross for the following examples
Complete a monohybrid cross for the following examples. Give the phenotype and genotype.
In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). Cross a heterozygous squirrel with a black fur squirrel . What percentage of the off-spring will have black fur? %
G g g gg

24. In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). Cross a heterozygous squirrel with a heterozygous squirrel . What percentage of the off-spring will have gray fur? 75%
G g G g GG Gg

25. In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). Cross a homozygous dominant squirrel with a black fur squirrel . What percentage of the off-spring will have black fur? 0%
G G g Gg

26. Genotype: 4SSRR, 4SsRR, 4 SsRR, 4 SsRr
In tomatoes, the texture and color of the skin matter a great deal. The smooth texture (S) is dominant to the peachy texture (s) and the red color (R) is dominant to yellow ( r ). Complete a dihybrid cross between two tomatoes. One tomato is SSRR. The other is SsRr. Determine the phenotype and genotype of your dihybrid cross SR Sr sR sr SR
Genotype: 4SSRR, 4SsRR, 4 SsRR, 4 SsRr
Phenotype: all smooth texture/red color
SSRR
SSRr
SsRR
SsRr

27. What happens to the diploid number of chromosomes that an organism has after it undergoes meiosis?
It is cut in half

28. What is the chromosome arrangement for the picture above?
(n + n  2n) Fertilization

29. The diploid number of chromosomes for a human cell is ­­­­­­­____?46

30. Complex organisms produce gametes (egg and sperm) that unite during fertilization, forming a single cell known as _______.
Zygote

31. Which of Mendel’s laws in shown in the picture above?
segregation

32. The picture above demonstrates what concept?
fertilization

33. The picture above demonstrates what concept?
Crossing-over

34. The picture shown above demonstrates what concept?
meiosis