Question 1

How many Barr bodies are present in an individual with Klinefelter syndrome XXYY)?

Accepted Answer

1

Question 2

Which statement is true of sperm?

Accepted Answer

The sp erm w ill contai n either an X or a Y chromosome .

Question 3

Assume that you are looking at a case of lethal alleles.Crossing two green corn plants results in 2/3 green progeny and 1/3 white progeny.If you crossed two white progeny with each other,how many of the progeny would you predict to be white?

Accepted Answer

100%

Question 4

The difference between dominance and epistasis is that

Accepted Answer

e pistasis masks genes at diff erent loci .

Question 5

In the ABO blood-type phenotype,which gene is the most epistatic?

Accepted Answer

H

Question 6

Assume that connected earlobes are a recessive trait with 73% penetrance.The parents are heterozygous and homozygous recessive for the attached earlobe gene.What is the probability that their first child will have attached earlobes?

Accepted Answer

The probability of the child inheriting the recessive allele from both parents is 50%. With 73% penetrance, the probability of expressing the trait is 50% * 73% = 36.5%.

Question 7

What kind of dominance does the following example demonstrate? Individuals with the genotype HH have healthy levels of cholesterol,those with Hh have higher levels of cholesterol,and those with hh have dangerous levels that often lead to heart attacks during childhood.

Accepted Answer

i ncomplete dominance

Question 8

What is the sexual phenotype of Drosophila that has XXXY sex chromosomes and two sets of autosomes?

Accepted Answer

m etafemale

Question 9

Drosophila melanogaster has been used in genetic studies for over 100 years because of its many useful characteristics.Which of the following is NOT one of these characteristics?

Accepted Answer

h as a generation time similar to that of humans

Question 10

A child who is blood type A has a mother who is blood type B.In a paternity suit a man is accused of being the father.He has blood type AB.Is he the father?

Accepted Answer

He cannot be excluded as the father.

Question 11

Sex-influenced traits are encoded by ________ genes and sex-linked traits are encoded by _______ genes.

Accepted Answer

autosomal; sex - chromosome

Question 12

When studying Arabidopsis a researcher isolates a gene mutation that produces a shorter stem-height phenotype.Interestingly,when this gene is present wild-type plantand the seedling is germinated at the lower temperature of 12$\degree$C,the same short-stem phenotype is replicated.This phenomenon is known as

Accepted Answer

phenocopy

Question 13

While studying a new human disease you discover that the disease is linked to a mitochondrial gene.You can be reasonably sure that the disease is inherited _____________________.

Accepted Answer

f rom mother to child

Question 14

When Morgan crossed a red-eyed female with a white-eyed male,which results made Morgan think that the locus affecting eye color was on the X chromosome?

Accepted Answer

In the F2,all females had red eyes,and half of the males had red eyes and the other half had white eyes.

Question 15

In various crosses examining three different Drosophila traits,you find the following ratios: 9:3:4,9:7,and 12:3:1.What kind of epistasis is each?

Accepted Answer

recessive epistasis, duplicate recessive epistasis,dominant epistasis

Question 16

Males and females express the same amount of X-chromosome genes despite the fact that females have more X chromosomes.Animals approach this problem in different ways.Which of the following is an example?

Accepted Answer

Female humans inactivate one of their X chromoso mes.

Question 17

What is true about sexual reproduction?

Accepted Answer

Each parent contributes a haploid gene set to offspring .

Question 18

A human with an XY chromosome pair appears female.What might explain this person's condition?

Accepted Answer

This person has a mutated SRY g ene.

Question 19

If a color-blind female has children,what do we know about all of her sons?

Accepted Answer

All sons will be color - blind .

Question 20

Yeast mitochondria have a tubular morphology.In a mutagenic screen,two mutants are isolated that have fragmented mitochondria instead of tubular mitochondria.To determine if these two mutations are at the same or different loci,the two mutants are crossed.The progeny all have tubular mitochondria.What do you conclude?

Accepted Answer

The m utations are at different loci .

Quiz 4: Extensions and Modifications of Basic Principles

How many Barr bodies are present in an individual with Klinefelter syndrome XXYY) ?