This land is your land
and this land is my land
from California to the New York Island
from the redwood forest to the Gulf Stream waters
This land was made for you and me.
-Woody Guthrie

Genetics

Many people may think of "genetics" as one type of biotechnology. Actually, genetisists studied progeny of crosses of living organisms (fruit flies or pea plants), or, alternatively pedigrees (family trees say of humans). Also, the outcomes of the genetic crosses told us more about meiosis than anything else.

Assignment
Audesirk, Audesirk & Byers part of Chapter 12

Today's musical selection
Nervous Norvus - Transfusion

Mendel's work

Figure 12-2
1865 Mendel

Figure 12-3
pea flowers
(might seem strange to think about sexual reproduction in plants)
presumably genes are lined up along chromosomes, each at its own place
thus "locus" is a word for a gene

Figure 12-4
- purple vs. white flowers (phenotype)
P=parental, F1 first generation (filial)

Since cells are diploid, there are two copies (alleles) at each locus, and they can be the same or different.

Figure 12-6
true-breeding = homozygous PP or pp (genotype)

Figure 12-7
hybrids = heterozygous (Pp)
purple (P) is dominant, white (p) is recessive
Thus Pp genotype has purple phenotype

Figure 12-5
F2 has 3/1 ratio
units = gene separate Mendel's first law (segregation)

Figure 12-11
Punnett square
shows haploid gametes (ova and sperm) and genotypes and phenotypes

Mutations - variation and evolution (many are bad also recessive, many are neutral, some might be good under the right environmental circumstances. They can be caused by ionizing radiation or chemicals (mutagens which are also carcinogens).

Taboos against insest-
People carry several detrimental or lethal alleles (such as those discussed later in this outline). They are usually not expressed because they are recessive and heterozygous. Inbreeding is a problem because related people would have mutations in the same genes, resulting in a homozygous recessive expression. "Hybrid vigor" refers to a stronger genetic constitution in organisms with more heterozygosity (and hence more genetic variability

Mendel (knew about Darwin but Darwin did not know about Mendel)
"...this seems to be the one correct way of finally reaching the solution to a question whose significance for the evolutionary history of organic forms must not be underestimated."

Figure 12-14
Mendel's Second Law
The law of independent assortment
green-yellow, round-wrinkled
dihybrid cross (two genes each on a separate chromosome, two alleles each) fill in "Punnett square"
Independent assortment does not apply to linked genes. i.e. genes that are on the same chromosome.

A few human examples

Figure 12-24
Here is a picture showing incomplete dominance (hair texture)

Table 12-1
Blood groups
A=B (co-dominant), O is recessive -- 3 alleles

genotypes...............phenotype.........antigens..........antibodies
IA IA or IA i...........A......................A.....................anti-B
IB IB or IB i...........B......................B.....................anti-A
IA IB......................AB....................A and B..........anti neither
ii ............................O......................none................anti both

O universal donor, AB universal recipient

Question: What is unusual about this situation? Answer: There are already antibodies even though there was no previous exposure to antigens.

Genetic disorders in people

Figure 12-29
Sickle cell anemia
If homozygous, red blood cells have abnormal shape
hgb clumps in low O2, heterozygotes (trait) largely normal
2 alpha, 2 beta. Beta 146 aa, 6th valine instead of
glutamic acid, GUG instead of GAG
blacks, heterozygous gives resistance to malaria

Figure 12-31
Hemophelia
pedigree
Victoria, Nicholas II & Alexandra - Alexis, Rasputin
on X
problem with AIDS for clotting factor

Lethals detrimentals
- everyone carries several recessives, but different
become homozygous if inbreeding

Huntington's - chorea - age 40's or 50's death in 10-20 years
By that age, person has probably already reproduced
autosomal dominant - 50:50 chance to pass on mapped to chromosome #4
Woody Guthrie died of it

Figure E12-1
Cystic fibrosis
lungs fill up with thick mucus
cloned as CFTR, mutation in Cl- transport, children have salty sweat
Life is short, chest must be thumped to clear lungs

Some others we will not take the time to cover
Tay-Sachs disease
Phenylketonuria (PKU)

Mild disorders

Figure 12-30
color blindness
X-linked

Figure 12-28
Albinism
Melanin formed from polymerization of dopa quinones derived from the amino acid tyrosine

Figure 12-26
Himalayan rabbit (like Siamese cat)
"temperature sensitive" presumably missense mutation, enzyme works if cool but body heat denatures it

Questions used in 2007 and 2008 related to this outline

A dihybrid cross was presented to explain
*(a) the 9:3:3:1 ratio.
(b) genetics of blood groups.
(c) sex-linked (X-linked) diseases.
(d) the Hardy-Weinberg ratio.
(e) cephalization.

What blood type is known as the universal donor?
(a) AB
(b) A
(c) B
(d) C
*(e) O

Why is a Siamese cat's nose black?
*(a) There is a temperature sensitive missense mutation.
(b) Cats are mosaic for whether there is a mutation on of the X chromosomes.
(c) Because of convergent evolution.
(d) There was an evolutionary bottleneck.
(e) Because of homeostasis.

Why are some people from African descent resistant to malaria?
(a) They use banked umbilical blood in Africa.
(b) Hemophelia heterozygotes are immune.
(c) They have Down's syndrome.
(d) They are carriers of PTC insensitivity.
*(e) They are heterozygous for sickle cell anemia.

Why does Huntington's disease create such a dilemma?
(a) If they knew how antisocial they were expected to be, they would consider it the self-fulfilling prophesy.
(b) Much of what we know was presented by a nineteenth century British physician with an unsavory attitude toward non-European races.
*(c) Most people did not show symptoms until they already had children.
(d) Though retarded, children with Huntington's disease are pleasant and happy.
(e) Richard Speck, accused murderer of 8 student nurses in Chicago in 1966, had Huntington's disease.

In genetics, if there are two or more different copies of a gene possible, they are referred to as
(a) pedigrees.
(b) homologues.
*(c) alleles.
(d) kinetochores.
(e) filials.

A pea that is heterozygous for purple colored flowers is crossed with a plant having white flowers. What is the makeup the F1 generation?
*(a) 1/2 purple, 1/2 white
(b) 1/4 purple, 3/4 white
(c) all purple
(d) 1/2 pink, 1/2 purple
(e) 1/3 white, 2/3 purple

What genetic disorder relates the history of Europe's royal families and a unique evolutionary selection pressure in the first years of the AIDS epidemic?
(a) Down syndrome
(b) albinism
(c) Huntington's disease
*(d) hemophelia
(e) green-wrinkled syndrome

What is true about people with type AB blood?
(a) They are universal donors.
(b) On the surface of their red blood cells, they do not have A or B glycoproteins (antigens).
(c) They are homozygous dominant.
(d) They are homozygous recessive.
*(e) They don't have antibodies against A or B glycoproteins.

Which statement is false?
(a) Meiosis leads to segregation of two alleles at one locus in plants.
(b) Separate male and female structures in pea flowers allowed Mendel to cross-fertilize.
(c) Mendel knew about Darwin and thought his own genetic studies could help to explain evolution.
(d) The F2 ratio of 3:1 describes phenotypes, not genotypes.
*(e) Plants do not reproduce sexually.

Most people are not born with fatal genetic diseases. Why not?
*(a) Detrimental mutations are usually heterozygous recessive.
(b) The only mutations that can possibly be detrimental are autosomal dominant.
(c) Mutations only occur on extra chromosomes produced by nondisjunction.
(d) Mutations only occur on the Y chromosome.
(e) Most parents do not have detrimental mutations.

Cystic fibrosis
(a) causes spastic movements referred to as "chorea."
*(b) results in thick mucus in the lungs.
(c) is the cause of red-green color blindness.
(d) only begins to appear in people in their 50's.
(e) probably first appeared in Queen Victoria.

What would have happened if Mendel had done his dihybrid cross using two traits that were near each other on the same chromosome?
(a) That is what he did and how he got the 3/1 ratio.
(b) That is what he did and how he got the 9/3/3/1 ratio.
*(c) His ratio would not have been 9/3/3/1 and he might have discovered linkage.
(d) That is what he did and how he obtained the ratio of ABO blood groups.
(e) He would have discovered Klinefelter syndrome.

In the US, sickle cell anemia is most common among Afro-Americans because
(a) it is a mutation in the enzymes that form melanin.
(b) it is an example of convergent evolution.
(c) the antibodies are already present in the blood, even before exposure to the antigen.
(d) it is on the X chromosome, and Afro-Americans are mosaics for which X is active.
*(e) it confers resistance to malaria.

Cystic fibrosis is a genetic disease that leads to the production of excessive thick mucous in the respiratory tract, leading to frequent and serious respiratory infections. The defect is due to
*A) faulty transport of chloride (Cl-) ions.
B) antibodies attacking antigens on red blood cells.
C) bleeding into the mucous because of a mutation that originated in Queen Victoria.
D) a dominant gene defect that is not expressed until about age 50.
E) faulty melanin synthesis.

Which is NOT a difference between the examples of Mendel's dihybrid cross (YyRr) and the ABO blood groups?
A) There are two alleles per gene only for the Mendel example.
B) There are two alleles in one gene that are equally dominant only for the blood groups.
C) There are two genes (loci) only for the Mendel example.
D) ABO blood groups cannot be used to demonstrate independent assortment while Mendel's work on peas can.
*E) Antibodies and antigens apply only for peas.

Gregor Mendel concluded that two units determined pea flower color, and each sperm cell or egg cell contains only one unit. Each individual unit is a(n) ________.
A) chromosome.
*B) allele.
C) trait.
D) homozygote.
E) gamete.

According to the Law of Segregation, in an organism with the genotype Aa,
A) A and a will blend and never be passed on to progeny intact.
B) the organism can have a as its genotype
C) the gametes can be AA, Aa or aa.
*D) half the gametes will have A and half will have a.
E) the phenotype of the gametes can be either A or a.

Red-green colorblindness
A) explains the black extremities on the otherwise white Himalayan rabbit.
B) is dominant.
C) results from nondisjunction.
*D) is on the X chromosome.
E) would be lethal if hemizygous.

Sickle-cell anemia
A) is expressed only after the age of 50.
B) explains the appearance of the calico cat.
C) was the blood disorder in the Russian royal family.
*D) confers resistance to malaria.
E) is caused by a stop codon.

In flowering plants, meiosis
A) makes gametes just as it does in animals.
B) makes sperm and eggs.
*C) gives rise to a separate gamete-forming organism.
D) makes zygotes, in contrast with the situation for animals.
E) makes all the cells of the plants.

Which of the following statements is FALSE?
A) Individuals with the same phenotype might have different genotypes.
*B) Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes.
C) Matings between individuals with recessive phenotypes do not produce offspring with dominant phenotypes.
D) Mating between heterozygotes produce a 3:1 ratio of dominant:recessive phenotypes.
E) Mating between heterozygotes produce a 1:2:1 ratio of genotypes.

Blood typing is often used as evidence in paternity cases in court. In one case, the mother had blood type B and the child had blood type O. Which of the following blood types could the father NOT have?
A) A
B) B
*C) AB
D) O
E) Both choices C and D are correct.


Questions used in 2002 relating to this outline (and other outlines)

What is one reason that type O individuals would be especially useful in a blood drive?
*(a) They are universal donors.
(b) They are universal recipients.
(c) They have A and B antigens as well as antibodies against A and B.
(d) They are homozygous dominant.
(e) They are the only people that are not mutant.

A pea plant with purple flowers is referred to as Pp. Pp
(a) is the plant's phenotype.
(b) indicates that the plant is homozygous.
(c) are only seen in the F2 of a cross of purple- and white-flowered pea plants.
*(d) is the plant's genotype.
(e) is a gamete.

Which is a dominant lethal mutation which probably would not be expressed until after affected men and women have had children?
(a) Down's syndrome
(b) PKU
*(c) Huntington's chorea
(d) Tay Sachs disease
(e) Sickle cell anemia

What made the example of the ABO blood groups an interesting contrast with the pea crosses used to exemplify Mendel's first and second laws?
(a) There were more than two loci.
(b) There are no homozygotes.
(c) There are no genotypes, only phenotypes.
(d) The genes are sex-linked.
*(e) There were three alleles.

Mendel's second law
(a) explains how both yellow or green pea bearing plants would be seen in subsequent generations if homozygous yellow or green pea bearing plants are crossed.
*(b) applies to two alleles of two genes on two different chromosomes.
(c) is the law of segregation.
(d) was used by Darwin to explain some aspects of evolution.
(e) is how linked genes are mapped on one chromosome.

Mendel's laws of segregation and independent assortment apply to
(a) mitosis.
(b) non-disjunction.
*(c) meiosis.
(d) linkage.
(e) mapping.

Which is a mutation?
(a) Klinefelter's syndrome
*(b) Tay Sach's disease.
(c) Down's syndrome
(d) XYY
(e) Turner's syndrome

Hemophelia is a sex-linked recessive allele. If a mother and father have a daughter with hemophelia, which of the following statements is the only one which MUST be correct on the basis of this information?
*(a) The father has hemophelia.
(b) The mother has hemophelia.
(c) Both father and mother have hemophelia.
(d) The daughter inherited all hemophelia alleles from the mother.
(e) Half of the mother's sons would have hemophelia.

Most people are not born with fatal genetic diseases. Why not?
(a) Most parents do not have detrimental mutations.
(b) The only mutations that can possibly be detrimental are autosomal dominant.
(c) Mutations only occur on extra chromosomes produced by nondisjunction.
(d) Mutations only occur on the Y chromosome.
*(e) Detrimental mutations are usually heterozygous recessive.

Which statement applies to the Siamese cat having white fur with black extremities?
*(a) A mutation makes an enzyme for melanin synthesis temperature-sensitive.
(b) Black vs. white depends on which X chromosome is active.
(c) There is incomplete dominance like for snapdragon flower color.
(d) The cat is heterozygous for the body color gene.
(e) Sons of such a female cat will be either black or white.

To analyze a situation like hemophelia in Queen Victoria's family, you use
(a) a Punnett square.
(b) a dihybrid cross.
(c) a pedigree.
(d) PCR.
(e) a northern blot.

Human evolution takes place in a changing environment of medical intervention (allowing survival of some people with genetic disorders). After treatment that helped this condition were established, the early years of the AIDS pandemic created a particularly harsh selection pressure against people with
(a) Tay-Sachs disease.
(b) Turner's syndrome.
(c) anthrax.
*(d) hemophelia.
(e) PKU.

The famous American folk singer Woody Guthrie, as well as a large population from Venezuela, had this genetic disorder:
(a) Tay Sach's disease.
(b) PKU.
(c) Klinefelter's syndrome
(d) Huntington's disease.
(e) sickle cell anemia.


This page was last updated 7/9/09

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