Download Genetics- What do you recall

This is your WHAT TO KNOW paper. It is a study guide and an intro and includes the things that you need to
know to do well on your assessments for this topic. The questions will not be the same as your assessment
questions, they will be different questions over the same topics.
1) Know all the following terms and how they relate to one another. Be able to give examples or recognize
them in a scenario:
 Codominance
 Sex linkage
 Roan
 Incomplete Dominance
 Environmental genes
 Blood Type
 Epistasis
 Pleiotropy
 Holandric
 Polygenic
 Carrier
 Sex influenced
 Gene Linkage
Be able to answer all of the questions below. Some of these things you should know already, some
you will need to fill in after the lecture. You can seek out your own answers, but this paper should but
used throughout the topic, not just once.
1) Predict what you think “non-Mendelian” inheritance is referring to.
2) Think about when Mendel did his work. Therefore what do you think is the reason that may have caused
Mendel to not be able to predict all possible inheritance patterns in nature?
3) REVIEW: What are Mendel’s 3 Laws? Explain what each law means.
4) One of Mendel’s Laws, we will never defy, which one do you think that is?
5) Read this information and as you do, highlight anything that is brand new to you! Use this information to
complete #6 below.
Complete dominance is an inheritance pattern where the dominant allele (noted as a
capital letter) always trumps the recessive allele when present. For example, if T, the dominant
allele, codes for a tall plant and t, the recessive allele codes for a short plant, than plants with
the genotypes TT or Tt will be tall. The only time the recessive phenotype is expressed is in the
homozygous recessive genotype (ex: the genotype tt codes for a short plant). In humans,
polydactyly (having extra fingers or toes) follows a simple dominance inheritance pattern.
Polydactyly is actually the dominant trait, but there is a low frequency of the dominant allele in
the population. Students may ask why polydactyly is rare if it is dominant.
Incomplete dominance inheritance occurs when the heterozygote (Tt) phenotype is a
blending of the dominant and recessive phenotypes. In the case of the homozygous dominant
(TT=tall) and homozygous recessive (tt=short) plant, the heterozygous (Tt) plant would be of
medium height. In humans, the trait for sickle cell anemia is incompletely dominant. A person
who is heterozygous for the sickle cell trait has less severe anemic symptoms than the
homozygous recessive person. Sickle cell heterozygotes are also resistant to malaria. Codominant inheritance is when the heterozygote exhibits both the dominant and the recessive
phenotype. A black chicken (BB) mated with a white chicken (bb) will produce a heterozygous
(Bb) chicken, checkered with black and white feathers. Human blood type is inherited codominantly. A mother with A type blood has blood cells with the A protein. A father with B type
blood has blood cells with the B protein. Their child with AB type blood has blood cells that
have both the A and the B protein.
Finally, sex-linked inheritance refers to the genes that are carried on the sex
chromosomes. Females are XX and males are XY. The X chromosome is much larger than the Y
chromosome, and contains more genes. For this reason, most sex-linked traits in humans affect
males more often than females. Some genes, like the recessive gene for colorblindness, are
found only on the X chromosome and not the Y. Girls who inherit the gene for colorblindness
from their mothers still have a chance to inherit the dominant, normal gene from their father.
Boys who inherit the gene for colorblindness from their mothers don’t get that second chance
because the Y chromosome they inherit from their fathers does not contain any gene for color
vision, normal or not.
6) Use the reading above and your iPad or other device to research the following inheritance patterns. (Some
do not come from the above readings) Briefly describe/define each:
A) Codominance
B)
Incomplete Dominance
C)
Epistasis
D)
Pleiotropy
E)
Environmental Genes
7) Based on what you said in #6, place the examples below under the type of inheritance pattern you
discovered or read about.
A) Blood type
B) Himalayan rabbit’s coat colors
C) Result in disorders like sickle cell anemia
D) Eye color
E) Pink flowers from red and white parents
8) Explain the difference between codominance and incomplete dominance and be able to give examples
of each.
9) What is “gene linkage”?
10) What Mendelian Law is directly defied by gene linkage?
11) Give several examples of polygenic traits.
12) Explain why sex linked traits are seen in males more often than females.
13) Explain why females can’t have holandric traits.
14) Now using what you have read about and your knowledge of basic genetics, perform the following crosses:
Red-flowering snapdragons are homozygous for allele R1. White –flowering snapdragons are homozygous
for a different allele R2. Heterozygous plants R1R2 bear pink flowers. What phenotypes should appear
among first generation offspring of the crosses listed? What are the expected proportions for each
phenotype?
A) R1R1 x R1R2
C) R1R2 x R1R2
B) R1R1 x R2R2
D) R1R2 x R2R2
15) Explain why is the above scenario considered “Non-Mendelian”?
16) Be able identify the genetic inheritance pattern based on a description given.
17) Cross a Homozygous black mouse that is a carrier for albinism and a brown mouse that is a carrier for
albinism. What percentage of the offspring will albino? What percentage of the offspring will be carriers?
What percentage of the offspring will carry the gene for brown fur and the gene for albinism?
18) If you have a woman with hemophilia, what percentage of her sons will have hemophilia?
19) If you cross a carrier for colorblindness with someone with normal vision, what fraction of their sons will be
colorblind?