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Exam 2 questions

Describe pleiotropy

Pleiotropy occurs when one gene influences multiple phenotypic traits or functions. This means a single genetic mutation can have various effects on an organism.

You discover a genetic disease caused by a mutant gene in the mitochondrial genome. Which of the following would be the most reasonable assumption?

inherited from the mother WITH pleiotropic effects

A man and a woman both have normal vision, although both of their fathers are red-green color-blind (RCB). RCB s an X-linked recessive condition. What is the probability that the couple’s first child will be a color-blind son?

¼ = 25%

A man and a woman both have normal vision, although both of their fathers are red-green color-blind (RCB). RCB s an X-linked recessive condition. She gives birth to a color-blind daughter. From this we can conclude…

the man is probably NOT the father of the daughter

The following cross involving true-breeding parental (P1) cattle was made and carried out to the F2 generation

P1: horned females x hornless males

F1: all females horned & all males horned

F2: produced from F1 x F1 crosses: 25% hornless males, 25% horned males, and 50% horned females

The most likely explanation for the inheritance and expression of this trait is:

hornless is X-linked recessive

The following cross involving true-breeding parental (P1) cattle was made and carried out to the F2 generation

P1: hornless females x horned males

F1: all females horned & all males hornless

F2: produced from F1 x F1 crosses: 3/8 hornless males, 1/8 horned females, 1/8 horned females, 3/8 horned females

What is the most likely explanation for the inheritance of this trait with this data?

sex-influenced

Pattern baldness is a six-influenced trait, with heterozygous males exhibiting the trait. A woman WITH pattern baldness and a male WITHOUT pattern baldness are going to have children. Which of the following matches the expected probability for their children to have pattern baldness?

daughters 0% and sons 100%

After a genetic screening, your doctor tells you that you have the genotype for a disease that causes you to drop dead at 24. You leave crying hysterically because you are 22. You quickly google the disease and find out that it has a 1% penetrance. This information would result in you:

becoming much calmer because you only have a 1% hence of dropping dead in 2 years

Through genetic screening, a couple finds out that despite normal phenotypes, they are both carriers (heterozygous) for the allele causing holoprosencephaly (a brain malformation). The allele causing the disorder is dominant with 25% penetrance. What is the probability that their first child will have the brain malformation phenotype?

3/16

Define autosomes

Autosomes are chromosomes that are not directly involved in determining the sex of an organism; humans have 22 pairs of autosomes.

Besides on the sex chromosomes, where can genes for sex-limited traits also be located?

Genes for sex-limited traits can also be located on autosomes.

Genes for six-limited traits are always located on the sex chromosomes. True or false?

False

You are studying a know single-gene trait. You notice that when you perform a heterozygote x heterozygote cross, offspring are always produced in a 2/3 : 1/3 phenotypic ratio. What is the best explanation for this?

one of the homozygotes is lethal

The phenotype of an individual is never influenced by environment, only their genotype. True or false?

False

Autosomal traits where the dominant and recessive interaction between alleles differs between sexes are:

sex-influenced traits

Mitochondrial diseases often don’t develop until after 20 years of age. In addition, a female who does not have a mitochondrial disease can have a child WITH a mitochondrial disease. These patterns happen because (bubble in all that apply):

• The ratio of disease-mutant and wild-type mitochondria can change over the lifespan

• The ratio of diseases-mutant to wild-type mitochondria can change during meiosis

Tail length in pigs is inherited in a polygenic additive manner. When true breeding pigs with 6 cm long tails are crossed with true breeding pigs with 30 cm tails, the F1 piglet offspring all grew tails that were 18 cm. When the F1s were crossed, an F2 generation resulted in many piglets with tails ranging from 6 to 30 cm. the F2 offspring had a variety of tail lengths, and 1/1024 had 6-cm tails and 1/1024 had 30-cm tails. Given this information, how many genes (gene pairs contribute to this trait?

5

A Dihybrid cross for two different traits (AaBb x AaBb) is made in which the gene loci are autosomal, independently assorting, and incomplete dominant mode of inheritance. How many different phenotypes are expected in the offspring?

9

Bell-shaped or continuous distributions produced by plotting results of F2 offspring in hybrid cross experiments are typical of which type of inheritance?

Quantitive polygenic inheritance

The probability of non-disjunction in unmans increases with female age of reproduction but not male age of reproduction. The cause is of this is thought to be:

the amount of time chromosomes are synapses during meiosis is longer in females

In a species of horse, coat color is a single gene trait where one homozygote is black, the other homozygote is white, and the heterozygote expresses an equal number of black and white hairs. In a species of dog, coat color is inherited in the same manner, except that the heterozygote expresses all gray hairs. You can conclude from this that coat color alleles:

show co-dominance in the horse and incomplete dominance in the dog

Which gametes will be produced if nondisjunction occurs during the first meiotic division

Two diploid gametes and two gametes missing copies of the chromosomes

If a species as a diploid number of 10, what term would we use to described an individual with 9 chromosomes?

monosomy

Cri-du-syndrome is due to a _______________ in the short arm of chromosome 5

Deletion

Which of the following is the most accepted explanation as to why nondisjunction is more common during oogenesis (creation of eggs) than spermatogenesis (creation of sperm) in humans?

meiosis in oocytes involves serval prolonged pauses in the process

A female is heterozygous (Aa) and a male homozygous recessive (aa). Which of the following genotype IS possible upon fertilization if, during egg formation, nondisjunction occurred in meiosis I?

• Aaa

• a

A chromosome is produced with two centromeres, gene duplications, and gene deletions when crossing over happens in an individual that is heterozygous for which type of chromosomal rearrangement?

Inversion

Trisomy X (47, X+) and Klinefelter Syndrome (47, XXY) often go undiagnosed suggesting sex chromosome aneuploidy has less severe consequences than autosomal aneuploidy. True or False?

True; sex chromosome aneuploidies often have milder phenotypic effects than autosomal aneuploidies.

A genetic counselor is looking at two clients that are both inversion heterozygote for chromosome 2. Client A has an inverted region that is 5x smaller than client B. Which of the following would be true for these clients?

Client A would have about a 5x higher fertility rate than Client B

Down Syndrome (trisomy 21) in humans can be more common in some families (i.e. heritable) if it is a result of?

Robertsonian translocation

Why do translocation hetero zygotes produce a low percentage of viable gametes (i.e. have reduced fertility)?

Independent assortment results in gametes with large duplicated and deleted segments

Someone tells you they have a living 10-year-old child with monosomy. What is the best assumption you can make about this child from this information alone?

female with sex chromosome monosomy

Palau Syndrome (chromosome 13) and Down Syndrome (chromosome 21) are both aneuploidy conditions. Palau Syndrome is estimated at 1/8000 live births and Down Syndrome at 1/500 live births. What correct interpretation of these numbers?

the probability of nondisjunction is equal for both chromosomes, but chromosome 13 results in more miscarriages

A couple finds out that one of them has Robertsonian translocation at chromosome 21 and 14. They want to have children. Which of the following is the most accurate information you can give them?

Every conception has a 25% chance of miscarriage, and if miscarriage does not occur there is a 33% chance the child will have down syndrome

In a species of flower, additive alleles add one petal to the total number of petals in the flower, and non-additive alleles do not add to or subtract to the petal number phenotype. A true-breeding six-petal strain and a true-breeding twelve petal strain of flowers are crossed and produce an intermediate, nine-petal F1. When the F1 plants are interbred, an F2 generation is produced in the phenotypic ratio of:

1 six-petal

6 seven-petal

15 eight-petal

20 nine-petal

15 ten-petal

6 eleven-petal

1 twelve-petal

Based on the ratios in the F2 population, how many genes (gene pairs) are involved in the production of color?

3 genes (gene pairs)

In a species of flower, additive alleles add one petal to the total number of petals in the flower, and non-additive alleles do not add to or subtract to the petal number phenotype. A true-breeding six-petal strain and a true-breeding twelve petal strain of flowers are crossed and produce an intermediate, nine-petal F1. When the F1 plants are interbred, an F2 generation is produced in the phenotypic ratio of:

1 six-petal

6 seven-petal

15 eight-petal

20 nine-petal

15 ten-petal

6 eleven-petal

1 twelve-petal

How many additive alleles does the genotype of a ten-petal individual contain?

4

In a species of flower, additive alleles add one petal to the total number of petals in the flower, and non-additive alleles do not add to or subtract to the petal number phenotype. A true-breeding six-petal strain and a true-breeding twelve petal strain of flowers are crossed and produce an intermediate, nine-petal F1. When the F1 plants are interbred, an F2 generation is produced in the phenotypic ratio of:

1 six-petal

6 seven-petal

15 eight-petal

20 nine-petal

15 ten-petal

6 eleven-petal

1 twelve-petal

Given this mode of inheritance, if you produced 640 F2 offspring from a hybrid cross, how many would you expect to have twelve petals?

Approximately 10

A geneticist working at a zoo has spent several years studying coat color in foxes. She found that when two platinum-colored foxes are crossed, litters with both platinum and silver-colored offspring are always produced. Over the years, she collected the following data.

Platinum x platinum → 199 platinum foxes and 101 silver foxes

Which of the following is the most likely explanation for platinum and silver coat color in foxes?

Silver is homozygous, platinum is heterozygous, and the platinum allele is lethal when homozygous

A geneticist working at a zoo has spent several years studying coat color in foxes. She found that when two platinum-colored foxes are crossed, litters with both platinum and silver-colored offspring are always produced. Over the years, she collected the following data.

Platinum x platinum → 199 platinum foxes and 101 silver foxes

if a platinum foxes is crossed with a silver fox, what phenotypic frequency is expected among their progeny?

½ platinum, ½ silver

The what you know about multiple alleles, the mode of inheritance of the ABO blood type gene/alleles in humans, and the following information of parental blood types to answer the questions.

Male parent: Blood type B; his mother is type O

Female parent: Blood type A; her father is type O

What will be the possible phenotypes for blood type of the children of this couple?

A, B, AB, and O

The what you know about multiple alleles, the mode of inheritance of the ABO blood type gene/alleles in humans, and the following information of parental blood types to answer the questions.

Male parent: Blood type B; his mother is type O

Female parent: Blood type A; her father is type O

What is the probability that their first child will have an AB blood type?

1/4

The following diagrams represent two normal chromosomes and five aberrant forms (choices A - E) of these chromosomes. Circles represent centromeres and letters represent different loci/genes. For the following questions, match the appropriate diagram to the correct term.

Non-reciprocal translocation:

A

The following diagrams represent two normal chromosomes and five aberrant forms (choices A - E) of these chromosomes. Circles represent centromeres and letters represent different loci/genes. For the following questions, match the appropriate diagram to the correct term.

Inversion:

B

The following diagrams represent two normal chromosomes and five aberrant forms (choices A - E) of these chromosomes. Circles represent centromeres and letters represent different loci/genes. For the following questions, match the appropriate diagram to the correct term.

Duplication:

C

The following diagrams represent two normal chromosomes and five aberrant forms (choices A - E) of these chromosomes. Circles represent centromeres and letters represent different loci/genes. For the following questions, match the appropriate diagram to the correct term.

Deletion:

D

The following diagrams represent two normal chromosomes and five aberrant forms (choices A - E) of these chromosomes. Circles represent centromeres and letters represent different loci/genes. For the following questions, match the appropriate diagram to the correct term.

Reciprocal translocation:

E

What are the additive quantitative Trait equations?

• 2n+1

• (1/4)ⁿ