Download Honors Bio Genetics Exam Retake Study Guide

More Practice Problems for the Genetics Retake Exam NAME _______________
Show Crosses on a separate page. Turn this in the day of your retake exam!
Objective #1-Terms
1. Using letters show what homozygous refers to _________ heterozygous __________.
2. If the haploid number of chromosomes is 5, the diploid number is ______.
3. Using the letter “A” what would be 2 possible combinations for a dominant phenotype? ___ or ___.
4. Using the letter “A” what would the genotype be for an organism that is showing the recessive
phenotype? ___.
5. The location of a gene on a chromosome is referred to as the ________ of the gene.
Objective #2-Laws
6. This law is used during a dihybrid cross and refers to when one gene goes into a gamete cell it does
not influence how another gene will move into the same cell. For a parent that is RrYy we therefore
say there are 4 possibilities: RY, Ry, rY, ry. The Law of _________________ ________________.
7. This law says that when a gamete is made the gene pairs separate and each gamete gets one gene for
each trait. This law is demonstrated by a monohybrid cross. For a parent that is Tt we therefore say
that 50% of gametes get the T gene and 50% get the t gene. The Law of __________________.
Objective #3-Monohybrid and Dyhbrid Crosses
8. If T = tall and t = short show the cross of two heterozygous parent plants and the phenotype ratios for
the F1.
9. If R = round seed and r = wrinkled seed and P = purple flower and p = white flower show the cross of
one plant heterozygous for both traits with a plant heterozygous for seed shape but has white flowers.
Show the phenotype ratios (fractions fine) for the F1.
Objective #4-“special cases”
10. Pleiotropy—when a gene can have multiple effects. See my web site for the case of a gene that is
Lethal when the genotype is YY. Cross a mouse heterozygous for this gene with one homozygous
recessive. Give the ratios for the phenotypes in the F1.
11. Epistasis-One gene is masking the effect of another gene. Black mice is dominant to brown mice but
the mice have no color unless the other gene for color ( C ) is dominant.
Perform these 2 crosses and determine the fractions or percentages of the phenotypes in the
offspring:
Bbcc x BbCc and BbCc x bbCc
12. Codominance-both alleles are expressed in the heterozygote. A = alpha protein expressed on cell
membrane and B = Beta protein expressed on cell membrane. Cross: AB x BB and show the ratios for
the phenotypes in the offspring-% ____ express alpha % ____ express beta % ____ alpha + beta
13. X-linked (sex-linked)-gene for a trait is on the X chromosome but not the Y chromosome. Often these
are recessive genes. If B = normal color vision and b = colorblind then perform the following crosses
using the proper notation (XBXb etc.)
A. Cross a man who is colorblind with a female who is heterozygous. What fraction of males are
colorblind?
B. Cross a man who has normal vision with a female who is heterozygous. What fraction of the
offspring are colorblind?
C. A carrier is said to have this genotype ______.
14. Blood Type-an example of multiple alleles.
A. Name the three types of alleles for blood type:
___, ___, ___. One can be + for the Rh factor or – for the Rh factor.
B. What is the genotype of a type O person____.
C. Perform the following two crosses and show the fractions for the phenotypes in the F1.
IAi x IAIB and IAi +- x IBi –
15. Polygenic Inheritance—when multiple genes are responsible for a phenotype (ex. AA, Bb, Cc, DD, EE)
Polygenic traits are when can give you a wide range of phenotypes. List 2 examples:
16. Incomplete Dominance—when you see a blending in the heterozygote. What is the genotype of a
pink flower produced from a red flower parent and a white flower parent?
Objective #5 Pedigrees
17. The symbol for a man is __________, woman ________, woman with the disease ________.
18. Find the genotypes of all the individuals. The condition is testitis panicis—panicking during exam
taking. Is it recessive or dominant?
Objective # 6 Karyotype—taking a picture of chromosomes and matching them up to determine if there is a
full set.
19. List the types of information that can be determined from a karyotype. Can one determine gender?
Objective #7 Meiosis
20.
A. How many divisions are there in meiosis?
B. If you start with 1 cell how many are at the end of meiosis?
C. If the cell you start with has 10 chromosomes how many chromosomes are in each cell at the end?
D. Explain the process of crossing over and why it is important?
E. When are the cells haploid?
F. When do the sister chromatids separate: Meiosis I or Meiosis II?
G. When do the homologous chromosomes separate: Meiosis I or Meiosis II
H. Be prepared to possibly sketch the processes like we did in class.