Expert answer:Need two short lab assignments done today.
Solved by verified expert:Lab 1: This lab activity will give you an introduction into karyotyping.Lab 2: This lab activity will allow us to explore the world of inheritance, including multiple alleles. (Genetics Practice Problems) **The link for activity 1 on the karyotyping lab has changed.http://learn.genetics.utah.edu/content/basics/kary…The link for activity 2. Please use the link below and select Patient Histories to complete activity 2.http://www.biology.arizona.edu/human_bio/activitie…
genetics_lab.pdf
karyotyping_lab.pdf
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Lab: Genetics
Gregor Mendel was an Austrian monk whose investigations into the mechanisms of
inheritance earned him the honor of being called the “Father of Genetics”. Reginald
Punnett developed a diagram called a punnett square used to illustrate Mendel’s laws of
genetics.
To be able to solve genetic problems, you must first be familiar with the critical terms in
order to understand the mechanisms. The first few exercises will familiarize yourself
with the following terms: homozygous/heterozygous, Phenotype/genotype,
dominant/recessive.
Dominant trait – a trait that expresses its phenotypic effect in the heterozygous
condition. (AA,Aa)
Recessive trait – a trait that can remain hidden in certain generations and is only
expressed in the homozygous recessive condition. (aa)
Activity 1:
Homozygous – organism with 2 identical alleles. (AA, aa)
Heterozygous – organism with 2 differing alleles. (Aa)
For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho)
AA _____
Ee ____
Ii _____
Mm _____
Bb _____
ff ____
Jj _____
nn _____
Cc _____
Gg ____
kk _____
oo _____
Activity 2:
Phenotype – physiological feature, bodily characteristics or behavior (example:
brown hair, diabetes, blue eyes)
Genotype – genetic makeup of an organism (AA, Aa, aa) These 2 letters
represent an allele. You get one allele from your mother and one allele from your
father.
For each of the genotypes below determine what phenotypes would be possible.
Purple flowers are dominant to white
flowers.
Brown eyes are dominant to blue eyes
BB ________________
PP __________________
Bb ________________
Pp __________________
bb ________________
pp __________________
For each phenotype below, list the genotypes (remember to use the letter of the
dominant trait)
Straight hair is dominant to curly.
Pointed heads are dominant to round heads.
____ straight
_____ pointed
____ straight
_____ pointed
____ curly
_____ round
Activity 3:
View the following video on filling out a punnett square.
We will now use this information to complete some genetic problems.
Fill out the Punnett square for the following problems below.
1. Blue eyes appear to be recessive to brown eyes. If two blue-eyed people have a
child, what are the chances that the child’s eyes will be brown?
2. In pea plants purple flowers are dominant to white flowers. If two white flowered
plants are crossed, what percentage of their offspring will be white flowered?
3. If you crossed two heterozygous plants for flower color (as given above) what
percentage of their offspring will have purple flowers?
Activity 4:
Now that you have a good understanding on how Mendelian genetics work it is time to
switch things up. Mendel’s pattern of inheritance works well for dominant and recessive
traits, however there are many traits that do not follow this pattern.
Incomplete dominance: In incomplete dominance the heterozygous condition (Aa)
expresses an intermediate of the 2 traits. For example: in snapdragon flowers the
homozygous dominant (AA) would express red flowers. In the homozygous recessive
(aa) they would express white flowers. In the heterozygous condition (Aa) the flower
petals are pink in color. (a mix of red and white).
Codominance: A situation in which neither genes dominant over another in
expression. The example here is human ABO blood groups. In blood typing a person
can either be blood type A, B, AB or O. If you take the 3 alleles: A, B, and O it is easy
to see the blood group AB is co-dominant meaning neither allele A or B is dominant
over the other. They will both be expressed.
X-linked or sex-linked traits: Each individual has a set of sex chromosomes. A male
has an X chromosome inherited from his mother and a Y chromosome inherited from
his father. (XY) Females have two X chromosomes, one from each parent. (XX).
Abnormal genes found on the female chromosome may dominant over the normal
genetic makeup of males. These abnormal traits are more expressed in males as they
only have 1 copy of the X chromosome. For females to express an X-linked trait, they
must express both mutated copies of the gene. For these crosses, you must include
the X and Y chromosomes in your Punnett squares.
Males can be:
XAY (normal)
Females can be: XAXA (normal),
or
XaY (they will have the trait)
XAXa (carrier), or XaXa (will have the trait)
View the following video to learn how to solve punnett squares for these conditions.
4.
Colorblindness is caused by an X-linked trait carried on the X chromosome. A
man with normal vision marries a woman who is a carrier for colorblindness. He
does not think much about it until their son is diagnosed as colorblind. Complete
and show the cross of the parents.
5. Two pink snapdragon flowers are crossed. Complete the cross and give the
phenotype and genotypes of the offspring.
6. A man is taken to court for child support of a baby whom the mother says is his.
The mother is blood type O (OO) and the father is blood type AB (AB). The child
is blood type AB. Is he the father of the child? Show your cross.
Lab: Karyotyping
Be sure to read and follow the directions carefully so that you have a complete lab
assignment when you submit it to the assignment link.
Activity #1:
Copy and paste the following link into your browser.
http://learn.genetics.utah.edu/content/begin/traits/karyotype/
Click on the hint button and then click it off. This will allow you to match the
chromosomes in this karyotype simulation.
Now that you have finished the activity answer the following questions:
1. What is a karyotype actually?
2. How many chromosomes do humans have?
3. What are karyotypes used for?
4. Do you think this would be a valuable tool for couples to use before they have
children?
5. What is the sex of this person in this karyotype you completed? How do you know?
Activity #2:
Copy and paste the following link into your browser.
http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/
This link will allow you to review the process of cell division and how chromosomes can
be altered in division. It will also allow you to test yourself on the different conditions.
Activity #3:
This exercise is a simulation of human karyotyping using digital images of
chromosomes from actual human genetic studies. You will be arranging chromosomes
into a completed karyotype, and interpreting your findings just as if you were working in
a genetic analysis program at a hospital or clinic. Karyotype analyses are performed
over 400,000 times per year in the U.S. and Canada. Imagine that you were performing
these analyses for real people, and that your conclusions would drastically effect their
lives.
G Banding
During mitosis, the 23 pairs of human chromosomes condense and are visible with a
light microscope. A karyotype analysis usually involves blocking cells in mitosis and
staining the condensed chromosomes with Giemsa dye. The dye stains regions of
chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a
dark band. A common misconception is that bands represent single genes, but in fact
the thinnest bands contain over a million base pairs and potentially hundreds of genes.
For example, the size of one small band is about equal to the entire genetic information
for one bacterium.
The analysis involves comparing chromosomes for their length, the placement of
centromeres (areas where the two chromatids are joined), and the location and sizes of
G-bands.
Your assignment
This exercise is designed as an introduction to genetic studies on humans. Karyotyping
is one of many techniques that allow us to look for several thousand possible genetic
diseases in humans.
You will evaluate 3 patients’ case histories, complete their karyotypes, and diagnose
any missing or extra chromosomes.
Patient Histories
Patient A
Patient A is the nearly-full-term fetus of a forty year old female. Chromosomes were
obtained from fetal epithelial cells acquired through amniocentesis.
Complete Patient A’s Karyotype. (hold your control button down and click on the
link here in blue for it to open or highlight the link and right click on it. You will
see a open hyperlink at this time. Click on it and it will open the link for you.)
Patient B
Patient B is a 28 year old male who is trying to identify a cause for his infertility.
Chromosomes were obtained from nucleated cells in the patient’s blood.
Complete Patient B’s Karyotype. (hold your control button down and click on the
link here in blue for it to open or highlight the link and right click on it. You will
see a open hyperlink at this time. Click on it and it will open the link for you.)
Patient C
Patient C died shortly after birth, with a multitude of anomalies, including polydactyly
and a cleft lip. Chromosomes were obtained from a tissue sample.
Complete Patient C’s Karyotype. (hold your control button down and click on the
link here in blue for it to open or highlight the link and right click on it. You will
see a open hyperlink at this time. Click on it and it will open the link for you.)
Making a diagnosis
The next step is to either diagnose or rule out a chromosomal abnormality. In a patient
with a normal number of chromosomes, each pair will have only two chromosomes.
Having an extra or missing chromosome usually renders a fetus inviable. In cases
where the fetus makes it to term, there are unique clinical features depending on which
chromosome is affected. Listed below are some syndromes caused by an abnormal
number of chromosomes.
Diagnosis
Chromosomal Abnormality
Normal # of chromosomes
patient’s problems are due to something other than an abnormal number
of chromosomes.
Klinefelter’s Syndrome
one or more extra sex chromosomes (i.e., XXY)
Down’s Syndrome
Trisomy 21, extra chromosome 21
Trisomy 13 Syndrome
extra chromosome 13
1. What observations can you make regarding patient A’s karyotype?
2. What diagnosis would you give patient A? Explain your answer.
3.What observations can you make regarding patient B’s karyotype?
4. What diagnosis would you give patient B? Explain your answer.
5. What observations can you make regarding patient C’s karyotype?
6. What diagnosis would you give patient C? Explain your answer.
…
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