Chp 12: Gene Expression And Regulation

Front 1

In the 1940's

Back 1

biologist discovered that most genes contain the information needed to direct the synthesis of a single protein.

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Front 2

Flow of information from

Back 2

DNA to protein.

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Front 3

The DNA of a eukaryotic cell is housed in the

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nucleus.

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Front 4

Protein synthesis occurs on ribosomes in the

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cytoplasm.

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Front 5

A molecule that carries information from DNA in the nucleus to the ribosomes is called

Back 5

ribonucleic acid or RNA.

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Front 6

RNA is

Back 6

1. Singled strand.

2. Sugar ribose instead of deoxyribose in it's backbone.

3.Has the base uracil instead of the base thymine.

Function:

(1). Messenger RNA(mRNA);carries the code foar a protein coding gene from DNA to ribosomes.

(2)Ribosomal RNA(rRNA);combines with proteins to form ribosomes, the structures that link amino acids to form a protein.

(3)Transfer RNA(tRNA);carries amino acids to the ribosomes.

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Front 7

DNA is

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1.Double strand.

2.Sugar deoxyribose.

3.Base thymine instead of uracil.

Function:

(1)Contains genes; the sequence of bases in most genes deteremines the amino acid sequence of a protein.

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Front 8

Scientific Inquiry: One gene, One protein.

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Defects in the metabolism of two amino acids, phenylalanine and tyrosine, can cause albinism or several diseases with symptoms as varied as urine that turns brown when exposed to air(alkaptonuria) or phenylalanine accumulation in the brain, leading to mental retardation (phenylkentonuria).

In the early 1900's, the English physician Archibald Garrod studied the inheritance of these inborn errors of metabolism. He hypothesized that (1)each inborn error of metabolism is caused by a defective version of specific enzyme; (2)each defective enzyme is caused by a defective allele of a single gene; (3)therefore, at least some genes must encode the information needed for the synthesis of enzymes.

In the 1940's geneticist George Beadle and Edward Tatum used the metabolic pathways of a common bread mold, Neurospora crassa, to show that Garrod was correct.

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Front 9

Ribosomes are

Back 9

the structures that carry out translation and are composed of rRNA and many different proteins.

Each consists of two subunits-one small and one large.

Small subunit has binding sites for mRNA, a "start"(methionine) tRNA, and several other proteins that collectively make up the "preinitiation complex," which is essential for assembling the ribosomes and starting protein synthesis.

The large subunit has binding sites for tRNA molecules and a catalytic site for joining the amino acids attached to the tRNA molecules.

Unless the actively are synthesizing proteins, the two subunits remain separate.

During protein synthesis, the subunits come together and clasp an mRNA molecule between them.


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Front 10

Genetic information is transcribed into ______ and then translated into ______.

Back 10

RNA, Protein

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Front 11

In transcription

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the information contained in the DNA of a specific gene is copied into messenger RNA(mRNA), transfer RNA(tRNA), or ribosomal RNA(rRNA).

Thus, a gene is a segment of DNA that can be copied, or transcribed, into RNA.

In eukaryotic cells, transcription occurs in the nucleus.

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Front 12

Translation

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The base sequence of mRNA encodes the amino acid sequence of protein. During protein synthesis, or translation, this mRNA base sequence is decoded. Transfer RNA molecules bring amino acids to the ribosome, where base pairing between mRNA and tRNA converts the base sequence of protein.

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Front 13

The genetic code

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translates the sequence of bases in nucleic acids into the sequence of amino acids in proteins.

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Front 14

Both DNA and RNA contain

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four different bases. A, T(or U in RNA), G, and C.

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Front 15

Proteins are made of

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20 different amino acids.

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Front 16

Physicist George Gamow hypothesized

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that three bases specify a single amino acid.

In 1961, Francis Crick and three coworkers demonstrated that this hypothesis is correct.

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Front 17

Two base codes for amino acid isn't enough to code 20 amino acids.

Back 17

(4x4)=16.

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Front 18

Three base codes for amino acid is enough for 20 amino acids. A three base sequence gives 64 possible combinations.

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(4x4x4)=64

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Front 19

Transcription consists of three steps

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(1)initiation; a promoter region at the beginning of a gene, where transcription is started., (2)elongation; the "body" of the gene where elongation of the RNA strand or occurs., and (3)termination;a termination signal at the end of the gene, where RNA synthesis ceases or terminates.

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Front 20

Translation consists of three steps

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1. Initiation - A ribosome attaches to the mRNA and starts to code at the FMet codon (usualy AUG, sometimes GUG or UUG).

2. Elongation - tRNA brings the corresponding amino acid to each codon as the ribosome moves down the mRNA strand.

3. Termination - Reading of the final mRNA codon (aka the STOP codon), which ends the synthesis of the peptide chain and releases it.

Front 21

RNA polymerase

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is an enzyme that synthesizes RNA.

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Front 22

Near the beginning of every gene is an unstranscribed sequence of DNA called the

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promoter.

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Front 23

In eukaryotic cells, a promoter consists of two main parts:

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(1) a short sequence of bases, often TATAAA, that binds RNA polymerase, and (2) one or more other sequences, often called transcription factor binding sites or response elements.

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Front 24

RNA complementary to DNA is produced via

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transcription

Front 25

RNA lacks the base thymine (which is found in DNA), and DNA lacks the base uracil (which is found in RNA).

Back 25

DNA is composed of four different bases—thymine, adenine, cytosine, and guanine. RNA has all of these except thymine, which is replaced with uracil.

Front 26

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

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translation

Front 27

One way transcription differs from DNA replication is that

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transcription requires only one enzyme whereas DNA replication requires several

Front 28

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

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tRNA

Front 29

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

Back 29

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

Front 30

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

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point mutation

Front 31

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 _____.

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proteins

Front 32

Gene expression can not be regulated in eukaryotic cells by controlling the rate of _____.

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DNA replication

Front 33

The process of RNA synthesis is called

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transcription

Front 34

Information in DNA is carried in

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the order of the nucleotide bases in one DNA strand

Front 35

Which of the following correctly lists the items in order of their relative sizes?

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nucleotide, base pair, codon, promoter, hemoglobin mRNA, hemoglobin gene, ribosome, chromosome

Front 36

Both transcription and translation occur in three steps. What happens during the elongation step of each process?

Back 36

During the elongation step of transcription, the RNA molecule is synthesized. During the elongation step of translation, the protein molecule is synthesized.

Front 37

In translation, tRNA base-pairs with

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mRNA

Front 38

The DNA sequence of a codon in a gene was changed from AAT to AAC. This type of mutation is called a(n) __________.

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neutral mutation

Front 39

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?

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One X chromosome in females is inactivated so that females have only a single X chromosome capable of transcription.

Front 40

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

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During early stages of development, a mutation occurred in the cell that developed into one of the eyes, but not other cells in the embryo.

Front 41

What does mRNA carry from the nucleus?

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information