mastering biology 12

enzyme:

-ase

to love:

-phil

In Mendel's experiments, if the gene for tall (T1) plants was incompletely dominant over the gene for short (T2) plants, what would be the result of crossing two T1T2 plants?

25% tall 50% intermediate 25% short

A type of muscular dystrophy shows sex-linked recessive inheritance. Affected persons usually die by the age of 20. Suppose that a boy with the disease lives long enough to marry a woman heterozygous for the trait. If they have a son, what is the probability that he will have the disease?

50%

What is the ratio of phenotypes in the offspring produced by the cross Aa x Aa? Assume complete dominance for the trait.

75% dominant: 25% recessive

What kind of mutation would have the most dramatic effect on the protein coded for by that gene?

A base insertion near the beginning of the coding sequence

What is an exon?

A segment of DNA in a eukaryotic cell that codes for a protein

When do the small and large subunits of ribosomes join together?

At the end of the initiation step of translation

Gene expression in eukaryotic cells can be regulated by controlling the rate of all of the following except __________.

DNA replication

A purple-flowered pea plant self-fertilizes and produces both purple and white offspring. What is its genotype?

Pp

Which of the following is an accurate statement concerning the differences between DNA and RNA?

RNA contains the base uracil and DNA contains the base thymine.

What is the advantage of the operon mechanism for bacteria?

They can turn the expression of genes on and off.

Imagine that a codon in the template strand of a gene has the DNA sequence TAC. What sequence of the anticodon would decode this codon? Explain your answer.

UAC, because the anticodon has the same sequence as the template strand (but it has U instead of T)

Which of the following is most likely to be passed on to the next generation?

a mutation in the DNA in cells in the ovaries

Some people have eyes of two different colors. What is a possible explanation for this trait?

a mutation occurred in the embryo in the cell that developed into one of the eyes. the other cells in the embryo were not mutated

to:

ad-

During which phase of meiosis does the law of segregation of alleles occur?

anaphase I

During which phase of the cell cycle does the law of independent assortment occur?

anaphase I

against:

anti-

an ____________ is any chromosome other than a sex chromosome

autosome

The next base to be added to the RNA strand during transcription is determined by __________.

base pairing between the template strand and the RNA nucleotides.

Which of the following occurs first in the process of translation?

bases of the tRNA anticodon bind with the bases of the mRNA codon.

In the absence of lactose, repressor proteins __________ the __________ of the lactose operon.

bind to; operator

Imagine that a newly discovered species of fish normally has three eyes (E), but the rare mutation (e) causes "diopthalmic" fish with two eyes to be born. In addition, eye color in these fish is inherited similarly to humans, with black eyes (B) being dominant to blue (b). Assuming these two genes are carried on separate chromosomes, what must the genotypes of two black-eyed, three-eyed parents be if they have a blue-eyed, diopthalmic son?

both EeBb

A mutation has occurred in the DNA coding for Leucine changing the codon from CUU to CUG, but no change occurs in the protein. Why?

both are codons for leucine

Codominance occurs when

both of the alleles in a heteroxygote are expressed phenotypically in an individual

If you were to create a drug that recognized and bound irreversibly to the promoter region of a specific gene, thereby blocking it, what effect would you expect that drug to have?

both transcription and, eventually, translation of the gene would halt

After translation is completed, the ribosome __________.

breaks into small and large ribosomal subunits

A female who is heterozygous for a recessive, sex-linked trait is a(n) ________ for that trait.

carrier

The capacity for forming the peptide bond between two amino acids resides in the __________.

catalytic site of the large subunit

with or together with:

co-

The blood types of humans are an example of ________.

codominance

_________ is a pattern of inheritance in which heterozygotes express phenotypes of both of the homozygotes

codominance

A sex-linked recessive condition that causes abnormal color vision is called

color deficiency

When genes are linked, a few of the recombinant genotypes still occur in the offspring because of

crossing over

Considering the information you have read about cystic fibrosis, which of the following descriptions of the disease best applies?

cystic fibrosis is a recessive disease with pleiotropic effects

from, out of, remove"

de-

What is found in DNA that is not in RNA?

deoxyribose

Autosomal nondisjunction can result in

down syndrome

Which disorder is more common among the babies of older mothers?

down syndrome

difficult, painful:

dys-

Which genes are expressed in a cell depends on the cell's __________.

environment, history, and function

A(n) ________ is a portion of DNA that resides at a particular locus or site on a chromosome and encodes a particular function.

gene

The genetic makeup of an individual is the

genotype

an organism's genetic makeup--its actual combination of alleles---is known as its ___________.

genotype

blood:

hem-

____________ is a recessive sex-linked disorder in which the blood fails to clot normally.

hemophilia

different, other:

hetero-

an organism that has two different alleles of a gene for a given character is said to be ___________ for that character.

heterozygous

The results of a test cross reveal that all the offspring resemble the parent being tested. This parent must be

homozygous

an organism that has two identical alleles of a gene for a given character is said to be ________ for that character.

homozygous

The flow of genetic information in cells depends on specific base-pairing between nucleotides. Which of the following correctly matches the type of base pairing with the process of translation?

in translation, tRNA base-pair with mRNA

Why are there normally no male calico cats?

inactivation of different X chromosomes in a female creates a calico appearance

A pure-breeding plant with red flowers is crossed with a pure-breeding plant with white flowers. The offspring all have pink flowers. What pattern of inheritance does this involve?

incomplete dominance

_____________________ is a pattern of inheritance in which the hererozygous phenotype is intermediate between either of the homozygous phenotypes.

incomplete dominance

What does mRNA carry from the nucleus?

information

After an RNA polymerase has completed transcription, the enzyme __________.

is free to bind to another promoter and begins transcription.

All of the following are steps in transcription except __________.

joining of short fragments of RNA by ligase steps are: elongation, recognition of the promoter by RNA polymerase, initiation, and terminiation

milk:

lact-

The information to synthesize proteins is carried to the ribosome by __________.

mRNA

Why do males suffer from sex-linked disorders more often than females?

males can express single recessive alleles from their single X chromosome

How many proteins can be made at the same time by ribosomes on a single mRNA strand?

many

What amino acid do all proteins initially begin with?

methionine

Which of the following chemical, functional groups are involved in the control of gene transcription?

methyl groups

How can a cell regulate protein activity through epigenetics?

modifications of DNA, chromosomal proteins, or use of noncoding RNA

Considering all the genetic diseases covered in this chapter, what general conclusion can you draw about genetic diseases?

most genetic diseases are pleiotropic

when three or more alleles of the same gene exist in a population, they are known as _______________.

multiple alleles

of neither gender or type:

neutr-

not:

non-

___________ is a failure of homologous chromosomes or sister chromatids to seperate during cell division.

nondisjunction

Genes are composed of __________.

nucleotides

Where is an anticodon found?

on transfer RNA

In mammals, males have one X chromosome and one Y chromosome, and females have two X chromosomes. How is the expression of genes on the X chromosome regulated so that there is equal expression of genes on the X chromosome in males and females?

one x chromosome in females is inactivated so that females have only a single X chromosome capable or transcription

The information to synthesize all of the following except __________ is directly coded by the DNA.

organelles

a __________ is a diagram showing genetic relationships among a group of individuals, usually with respect to a specific genetic trait

pedigree

The physical manifestation of an organism's genes is its

phenotype

an organism's traits--- including its outward appearance, behavior, and other observable or measurable features---- is known as its

phenotype

What is the difference between phenotype and genotype?

phenotype is the physical expression of a trait and genotype is the combination of alleles carried by the organism.

During DNA replication, a mistake was made in which an A was changed to a G. This kind of mutation is called a(n) __________.

point mutation

many:

poly-

Human skin color is the result of

polygenic inheritance

______________________ is a form of inheritance in which the interaction of multiple genes contributes to a single phenotype, such as skin color.

polygenic inheritance

The cells in your skin have a different shape and different function than the cells in your liver because the two types of cells have different __________.

proteins

How does a DNA control cell function if it just codes for proteins?

proteins are the "molecular workers" that form cell structures and functions as enzymes

Which of the following statements about the functions of RNA is correct?

rRNA is an important component of ribosomes

In the 1800s, it was commonly believed that the traits of both parents for any feature blended to create the offspring and that the blended trait was passed on. Which of the following observations was most important to Mendel's understanding of genes as unchanged units of information?

recessive traits can reappear in later generations

crossing over results in _______-- the formation of new combinations of different alleles on a chromosome.

recombination

Certain genes, sometimes called housekeeping genes, are expressed in all cells in your body. Other genes are expressed only in certain specialized cells. Genes for which of the following proteins are likely to be housekeeping genes?

ribosomal proteins

one-half:

semi-

Imagine that a probe sent to Mars brings back a sample that contains a very primitive life-form, which appears similar to bacteria. Scientists are able to revive it and begin to grow it in culture. Much to their amazement, they discover that the organism has DNA and that the DNA encodes proteins. However, the DNA of these Martian microbes contains only two nucleotides. If the Martian microbe uses triplet codons, what is the maximum number of different amino acids that it can have in its proteins? Explain.

seven because 2^3= 2x2x2=8 but at least one of the codons must be a stop

What is microRNA?

small molecules of RNA that interefere with translation

Which portion of a ribosome binds to messenger RNA?

small subunite

The molecule responsible for bringing the correct amino acid to the ribosome at the correct time is __________.

tRNA

The template strand of nucleic acids is __________.

the DNA strand used by RNA polymerase

Image that you self-pollinate heterozygous purple-flowered, long-pollened pea plants and get mostly purple-flowered, long-pollened plants and white-flowered, short-pollened plants, with a few purple-flowered, short-pollened or white-flowered, long-pollened plants. What is the most likely explanation?

the genes are linked

Traits controlled by sex-linked recessive genes are expressed more often in males because

the male has only one gene for the trait

What determines which of the two DNA strands will serve as the template during transcription?

the orientation of the promoter and other regulatory sequences determines which strand is copied.

What would be the effect of a substitution mutation resulting in a change from glutamic acid to valine when glutamic acid is hydrophilic and valine is hydrophobic?

the protein would be less soluble in water.

What is the relationship between codons and amino acids?

there are more codons than amino acids.

Three codons out of sixty-four do not code for an amino acid. What do they code for?

they are stop codons

A person is heterozygous for hair texture. Which of these statements is correct about this person's DNA?

this person has two different alleles at the locus for hair texture

across:

trans-

RNA complementary to DNA is produced via __________.

transcription

Unripe black walnuts contain a compound, juglone, that inhibits RNA polymerase. With which process would juglone directly interfere?

transcription

One way transcription differs from DNA replication is that __________.

transcription enzymes read only one strand of DNA and replication enzymes read both strands of DNA

Gene expression in prokaryotic organisms is primarily regulated at the __________ level.

transcriptional

The process that uses the genetic information carried by mRNA to specify the sequence of amino acids in a protein is called __________.

translation

three:

tri-

down syndrome is also called __________ 21 because the cells if affected individuals contain three copies of chromosome 21.

trisomy

change, turn, move:

trop-