BIO 143 Lecture Notes - Lecture 11: Prestressed Concrete, Helicase, Dna Ligase

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Chapter 11

The Molecule of Heredity

-Heritable information is carried in discrete units called genes

-Genes are parts of structures called chromosomes

-Chromosomes are made of deoxyribonucleic acid and protein

DNA Discovered as Genetic Material

The secrets of DNA function and, therefore, of heredity itself are found in the three-

dimensional structure of the DNA molecule

DNA is composed of four nucleotides

-DNA is made of chains of small subunits called nucleotides

-Each nucleotide has three components

DNA is a double helix of two nucleotide strands

Hydrogen bonds between complementary bases hold two DNA strands together

-DNA is made of two strands of nucleotides

-Within each DNA strand, the phosphate group of one nucleotide bonds to the sugar of the

next nucleotide in the same strand

-The deoxyribose and phosphate portions make up the sugar phasphate backbone

-The nucleotide bases protrude from this backbone

-All the nucleotides within a single DNA strand are oriented in the same direction and thus

have an unbonded sugar at one end and an unbonded phosphate at the other end

-Strands are anti parallel of each other

Hydrogen bonds between complementary bases hold two DNA strands together in a double

helix

The bases protrude inward toward each other from the sugar phosphate backbone like

rungs on a ladder

-The ladder like structure is twisted into a double helix

How Does DNA Replication Ensure Genetic Constancy During Cell Division

Replicatio of DNA is a critical eet i a cell’s life

-All cells come from pre existing cells

-Cells reproduce by dividing in half

-Each of to daughter cells get a eact cop of the paret cell’s geetic iforatio

-Duplication of the parent cell DNA is called DNA replication

DNA replication produces two DNA double helices, each with one original strand and one

new strand

-The fact complementary base pairing suggests a model for how DNA replicates

-The ingredients for DNA replication

-DNA replication begins with enzymes called DNA helicase

-The second strand of new DNA is synthesized along each separated strand by DNA

polymerases

-When replication is complete, each parental strand and the daughter strand that was

copied fromed by base pairing wind together into a new DNA double helix, thus creating

two copies of the original double helix

-DNA ligase

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Document Summary

Heritable information is carried in discrete units called genes. Chromosomes are made of deoxyribonucleic acid and protein. The secrets of dna function and, therefore, of heredity itself are found in the three- dimensional structure of the dna molecule. Dna is made of chains of small subunits called nucleotides. Dna is a double helix of two nucleotide strands. Hydrogen bonds between complementary bases hold two dna strands together. Dna is made of two strands of nucleotides. Within each dna strand, the phosphate group of one nucleotide bonds to the sugar of the next nucleotide in the same strand. The deoxyribose and phosphate portions make up the sugar phasphate backbone. All the nucleotides within a single dna strand are oriented in the same direction and thus have an unbonded sugar at one end and an unbonded phosphate at the other end. Hydrogen bonds between complementary bases hold two dna strands together in a double helix.

Related Questions

Which of the following is False?

A) During base excision repair, a DNA glycosylase produces an apurinic or apyrimidinic site

B) DNA polymerase III proofreads.

C) Photo reactivation repair removes part of the DNA sugar-phosphate backbone

D) Xeroderma pigmentosum patients have a defect in the nucleotide excision repair pathway

In mismatch pair:
A) Either strand serves as template
B) the enzyme identifies the correct template strand because it is modified
C) Both DNA strands are deleted and the homologous chromosomes is used as template

Chromatin modifications:
A) Can be required in eukaryotes for gene expression
B) Can involve histone acetyltransferase enzyme (HAT)
C) Can relax the compact structure of chromatin
D) All of the above

At high concentration of tubulin subunits, translationof tubulin mRNA:
A) Decreases
B) Increases)
C) Remains unchanged

Methylation of DNA ____ Gene expression.
A) Increases
B) Decreases
C) Remains the same

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What step in DNA replication precedes the pairing of complementary bases?

	A.	polymerization of DNA.
	B.	formation of the histone core.
	C.	mitotic division.
	D.	separation of the two strands.
	E.	joining of the two strands.

In eukaryotes, transcription occurs in the

	A.	ribosome.
	B.	mitochondria.
	C.	cell membrane.
	D.	cytoplasm.
	E.	nucleus.

Normal human body cells contain how many chromosomes?

	A.	46
	B.	22
	C.	23
	D.	44
	E.	42

Hershey and Chase performed an experiment in which they used radioactive isotopes to phosphorus and sulfur to label different components of bacterial viruses. Their results clearly showed that

	A.	the viruses did not contain protein.
	B.	genetic material normally contains radioactive isotopes.
	C.	the viruses did not contain DNA.
	D.	protein was entering into the infected bacteria.
	E.	DNA was entering into the infected bacteria.

A package of histones with DNA wrapped around them forms spherical structures called

	A.	nucleosomes.
	B.	lysosomes.
	C.	ribosomes.
	D.	nucleoli.
	E.	chromatin.

DNA replication

	A.	does not require proteins.
	B.	is constantly happening in a cell.
	C.	occurs in G1 of interphase.
	D.	takes place in the nucleus of the cell.
	E.	occurs in the cytoplasm of the cell.

The two subunits of the ribosome join during

	A.	promotion of transcription.
	B.	initiation of translation.
	C.	termination of transcription.
	D.	termination of translation.
	E.	elongation.

DNA replication of a single DNA molecule is referred to as semiconservative because

	A.	each of the two DNA molecules will consist of one parental strand and one newly synthesized strand.
	B.	all the DNA strands in the two DNA molecules will have both parental and newly synthesized DNA.
	C.	it results in two nonidentical DNA molecules.
	D.	of the two DNA molecules, one is made up totally of parental DNA, while the other is entirely newly synthesized DNA.
	E.	one DNA strand is replicated continuously, while the other must be replicated discontinuously.

The bases are bonded to what part of the backbone of the DNA molecule?

	A.	the 4â carbon atom of the sugar molecule.
	B.	the 3â carbon atom of the sugar molecule.
	C.	the 5â carbon atom of the sugar molecule.
	D.	the 1â carbon atom of the sugar molecule.
	E.	the 2â carbon atom of the sugar molecule.

1. Characters that show a continuous range of variation, such as height and eye color, usually are controlled:

a.	by a single gene with two alleles that are codominant.

b.	by many genes with an additive effect.

c.	by epistatic interactions between two genes.

d.	mainly by the environment, with only a small genetic component.

2. In humans, red-green colorblindness is inherited as a sex-linked recessive trait. In order for a woman to be red-green colorblind, which of the following statements must be true.

a.	Her mother must be red-green colorblind.

b.	All of her brothers must be red-green colorblind.

c.	Her father must be red-green colorblind.

d.	All of the above statements must be true if a woman is red-green colorblind.

3. The x-ray crystallography data collected by Rosalind Franklin suggested to Watson and Crick that the:

a.	structure of DNA is a double helix.

b.	two strands of the DNA molecule are joined by hydrogen bonds between the bases.

c.	four bases within DNA pair in a specific way.

d.	two strands of the DNA molecule are joined by covalent bonds between the bases.

4. In the genetic code, _________ one amino acid.

a.	one nucleotide specifies

b.	two nucleotides specify

c.	three nucleotides specify

d.	four nucleotides specify

5. During Meiosis I, a homologous pair of chromosomes may not separate, resulting in daughter cells that have extra chromosomes or are missing chromosomes. This can lead to genetic disorders, including Down Syndrome. This phenomenon is called:

a.	independent assortment.

b.	nondisjunction.

c.	segregation.

d.	crossing over.

6. You are a human geneticist studying the incidence of retinitis pigmentosa in the residents of Tristan de Cunha, a group of small islands in the middle of the southern Atlantic Ocean. The allele for retinitis pigmentosa, which causes a form of blindness, is inherited as an autosomal recessive. You have determined that the frequency of this allele (r) in the population is 0.4 (40%). Using the principles of the Hardy-Weinberg rule, you would estimate the frequency of individuals who are heterozygous for this allele (Rr) in the population to be:

a.	0.16 (16%)

b.	0.24 (24%)

c.	0.36 (36%)

d.	0.48 (48%)

7. Natural selection acts at the level of the:

a.	phenotype.

gene.

c.	population.

d.	nucleotide.

8. You are working with pea plants, trying to recreate the experiments that Mendel performed. You are doing a dihybrid cross with a plant that is heterozygous for both seed shape and seed color, with the genotype RrYy. Which allelic combinations would you expect to find in the gametes produced by this plant?

a.	This plant would produce only RY and ry gametes.

b.	This plant would produce only RrYy gametes.

c.	This plant would produce RY, Ry, rY, and ry gametes.

d.	You cannot determine which gametes this plant can produce without knowing the genotypes of its parents.

9. Biochemist Erwin Chargaff found that in DNA there is a special relationship between the four bases that we now call Chargaff's rule. His observation was that, in an organism's genome the:

a.	percentage of A nucleotides = the percentage of T nucleotides, and the percentage of C nucleotides = the percentage of G nucleotides.

b.	four bases all occur in an equal frequency (25%) within each organism.

c.	percentage of A nucleotides = the percentage of G nucleotides, and the percentage of C nucleotides = the percentage of T nucleotides.

d.	genetic material is composed of proteins, not DNA.

10. During DNA replication:

a.	each strand of the double helix acts as a template for the synthesis of a new strand.

b.	the enzyme DNA polymerase adds nucleotides to the strand being synthesized.

c.	the bases A,C,G and T are required.

d.	All of the above are true of DNA replication.

11. During translation, amino acids are joined by peptide bonds to make polypeptides. The formation of these peptide bonds is catalyzed by:

12. If an allele (R) at a gene with two alleles shows complete dominance, individuals with the genotypes ______ will have the same phenotype.

a.	RR and rr.

RR and Rr

Rr and rr

d.	Each of the three possible genotypes will have a different phenotype.

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BIO 143 Lecture Notes - Lecture 11: Prestressed Concrete, Helicase, Dna Ligase

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