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Chapters 9 and 10

A plant with yellow flowers was crossed with a plant with red flowers. All of the numerous offspring had red flowers. What does this show about the genotype of the parental plant with yellow flowers?

It is homozygous recessive

A woman who can roll her tongue (presumably dominant) is married to a man who cannot. Two of their four children can roll their tongues and two cannot. What is the genotype of the parents?

Woman Aa, man aa

Assume freckles and dimples are dominant traits. Two individuals with freckles and dimples have a child with no freckles and no dimples. What are the genotypes of the parents?

Ff Dd x Ff Dd

Both parents are heterozygous for the autosomal recessive Tay-Sachs disease. If three children in a row were born with Tay-Sachs disease, what are the chances that the next child will have Tay-Sachs disease?


If an organism shows a recessive phenotype, such as short pea plants, it can be:

Only tt

If you were studying the phenomena of one gene having more than one effect, you would be studying which of the following?


If your mother is homozygous recessive and your father is heterozygous for the autosomal dominant Huntington disease, what are your chances of escaping the disease?


In a recessive disorder, individuals who have that recessive allele but not the disorder are referred to as:


In guinea pigs, B = black, b = brown, S = short hair, s = long hair. What would be the expected results if a BbSs mated with a BbSs?

9 black short hair, 3 black long hair, 3 brown short hair, 1 brown long hair

In humans, brown eyes (B) are dominant over blue eyes (b). A brown-eyed woman who has a blue-eyed child would have the genotype:


In humans, brown eyes (B) are dominant over blue eyes (b). If a homozygous brown-eyed woman mates with a homozygous blue-eyed man, what would be the chances of producing a blue-eyed child?


Individuals who are heterozygous for the sickle-cell disease have an increased resistance to the protozoan which causes malaria.


The four o'clock flower is an example of incomplete dominance. R = red, r = white, and Rr = pink. If two hybrids are crossed, what are the chances that an offspring will have pink flowers?


This figure shows a human pedigree. Based on the information presented in this figure, what type of disorder would this be?

Autosomal recessive

This figure shows a dihybrid cross. What does "A" represent?


This figure shows a dihybrid cross. What does "E" represent?


This figure shows a dihybrid cross. What does "C" represent?

Tall plant, yellow pod

When a trait has more than two different forms, the gene has

multiple alleles

When two different dominant alleles are both fully expressed in the phenotype, it is referred to as:


When two or more sets of alleles affect the same trait, it is referred to as:

Polygenic inheritance

This figure shows DNA replication. What does "B" represent?

A new strand

This figure shows DNA replication. What does "E" represent?

The parental DNA region

A biologist is studying the process of how DNA is copied. What is she studying?

DNA replication

During DNA replication, which enzyme is responsible for unzipping and unwinding the original molecule of DNA?


If 23% of a species' DNA contains adenine, how much guanine is in this species' DNA?


In semiconservative DNA replication, each new double helix formed will have:

One new strand and one old strand in each helix

The enzyme that is used to join complementary DNA nucleotides together is:

DNA polymerase

The scientists credited with the discovery of the helix structure of DNA and later won the Nobel Prize are:

Watson and Crick

Which of the following best describes the chemical composition of a nucleotide?

A nitrogen-containing base, a phosphate, and a pentose sugar

Which of the following is NOT true about RNA?

RNA forms a helix

Which of the following is not a nucleotide found in DNA?


Which of the following is not a nucleotide found in RNA?


Which of the following is not true of DNA?

It remains constant among different species

Which of the following nitrogenous bases are correctly paired in DNA?

Adenine-thymine, guanine-cytosine

rRNA is joined with various proteins to form _____.

structures known as ribosomes needed for translation

A __________ of mRNA nucleotides is known as _________.

triplet, a codon

Each sequence of three bases on an mRNA molecule codes for_______which is brought to the mRNA by______.

a specific amino acid, a tRNA molecule carrying the exact amino acid needed

Translation occurs in the cytoplasm.


RNA allows DNA, which remains in the nucleus, to _____.

direct the production of polypeptides in the cytoplasm

Which occurs in the nucleus?



Adenine 25%


Thymine 25%


Guanine 25%


Cytosine 25%

In DNA complimentary base pairs are

A-T, G-C 25% + 25% + 25% + 25% = 100%

Who gets the credit for discovering DNA?

Watson and Crick

Nucleotide -5 Carbon Sugar(Deoxyribose), Phosphate Group(P&O), Nitrogen Base

Deoxyribose and P&O make up the backbone of DNA ladder

Base Pairs are attached by what?

Hydrogen Bonds(HB = weak associations)

A and T are attached by how many Hydrogen Bonds?


G and C are attached by how many Hydrogen Bonds?


What is a Semiconservative Molecule that can copy itself during Interphase?


DNA is a Seminconservative Molecule that can copy itself during what phase of the Cell Cycle?


DNA unwinds and seperates caused by:

DNA Helicase

Forms the replication fork:

DNA Helicase

Adds complimentary Nucleotides to the leading strand one at at time:

DNA Polymerase

Copied backwards by breaking off in fragments:

the lagging strand

Proofreads strand and breaks off new strand:

DNA Polymerase

What assists DNA in making proteins?


Double Strand, Confined in Nucleus, A-T & C-G, Deoxyribose


Single Strand, can leave Nucleus (found) floating freely in the Cytoplasm, A-U(Uracil 25%) & C-G, Ribose


Carrier of genetic info found on DNA from nucleus to ribosome

mRNA - messenger RNA

brings complimentary Nucleotides carrying Amino Acids to Ribosome

tRNA - transfer RNA

where proteins are assembled

rRNA - Ribosomal Subunit

mRNA is a/an _______ and tRNA is a/an _______.

Codon; Anticodon

Information from DNA is used to make a complementary RNA strand


where protein is made


_________ happens in the nucleus and ________ occurs in the cytoplasm at the Ribosome.

Transcription; Translation

________ codon are paired with complimentary _______ anticodon which carry _______ ________.

mRNA; tRNA; Amino Acids

Chemical bonds that join amino acids together to form polypeptide chains.

Peptide Bonds

Long chains of amino acids joined together by peptide bonds are known as:

Polypeptide Chains

DNA Helicase

an enzyme that unwinds the DNA double helix during DNA replication

DNA Polymerase

enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule.

Watson & Crick

nobel prize winners for correctly describing the structure of DNA as a double helix


The building block of a nucleic acids (DNA & RNA), consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

5 carbon sugar

DNA->deoxyribose; RNA->ribose

phosphate group

molecule in the backbone of DNA and RNA that links adjoining bases together


nitrogen base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA


nitrogen base found ONLY in DNA that pairs with adenine


nitrogen base found ONLY in DNA that pairs with adenine


Nitrogen base that pairs with guanine in DNA and RNA


Nitrogen base that pairs with cytosine in DNA and RNA

Hydrogen Bonds

The Weak bond that hold together complimentary bases in DNA


deoxyribonucleic acid; genetic formation in a double-helix; can replicate or reproduce itself; made of genes


ribonucleic acid; manufacture specific forms of proteins using DNA as a template; three forms: rRNA, mRNA, tRNA


ribosomal RNA; type of RNA that makes up part of the ribosome


Transfer RNA; type of RNA that carries amino acids to the ribosome


Messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome


three mRNA nucleotides that code for a specific amino acid


group of three bases on a tRNA molecule that are complementary to an mRNA codon.


process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA


The process of reading a strand of mRNA to synthesize protein. Protein translation takes place on a ribosome.

Gregor Mendel

studied the inheritance of certain traits in pea plants (known as the father of genetics)

True Breeding

organisms that produce offspring identical to themselves if allowed to self-pollinate

Particulate Theory of Inheritance

Traits are inherited as "particles,"(genes) offspring receive a "particle" from each parent

Monohybrid Cross

A cross in which only one characteristic is tracked.

Law of Segregation

Mendelian principle explaining that because each plant has two different alleles, it can produce two different types of gametes. During fertilization, male and female gametes randomly pair to produce four combination of alleles


different form of a gene (ex. T or t)

Gene Locus

specific location of a gene on a chromosome

Dominant Allele

An allele that is fully expressed in the phenotype of a heterozygote.

Recessive Allele

an allele that is masked when a dominant allele is present


refers to the alleles an individual receives at the time of fertilization


allele combination with both parts of genotype identical (example: TT or tt)


allele combination with two different parts of genotype (example: Tt)


Physical expression of a gene - Ex. Widow's peak. "What you see"

Genotype vs. Phenotype

Genotype refers to alleles and Phenotype refers to appearance

Law of Independent Assortment

each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random

Dihybrid Cross

cross of two different traits in which the parents are heterozygous for both traits. Results in a 9:3:3:1 phenotype ratio

Punnet Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross


intentional breeding in order to determine underlying genotypes

One-trait testcross

When a heterozygous individual is crossed with one that is homozygous recessive, the results are always a 1:1 phenotype ratio;

Two-trait testcross

When an individual is heterozygous for two traits is crossed with one that is recessive for the traits, the offspring have a 1:1:1:1 phenotypic ratio;

the theory of natural selection

genetically based characteristics that enhance an animal's ability to survive, and therefore reproduce, will be passed on to future generations

autosomal chromosomes

The 22 pairs of chromosomes that are responsible for characteristics other than determination of sex.


family trees that show the occurrence of inherited phenotypes in several generations of related individuals


have the gene but don't show the trait

tay-sachs disease

A human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth, followed by death within a few years.

cystic fibrosis

A human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated


Genetic disorder in which the essential digestive enzyme phenylalanine hydroxylase is missing...PKU

sickle cell disease

A hereditary disease that causes normal, round red blood cells to become oblong, or sickle shaped.

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