chapter 3 part 3

Question 1

microvilli 1

Answer 1

Extension of plasma membrane that increases surface area; some modified as
sensory receptors.
* Normally many on each cell.

Question 2

genes 1

Answer 2

functional units of heredity.
* Heredity is the transmission of genetic traits from parent to
offspring.
* Each gene is a segment of a DNA molecule that specifies the
structure of an R N A molecule that can function on its own or
produce a protein.

Question 3

gene expression 1

Answer 3

The production of R N A and/or proteins from the information
stored in D N A

Question 4

gene expression steps 1

Answer 4

Gene expression involves two steps:
1. Transcription occurs in the nucleus.
During this process, information stored
in a segment of D N A is used to produce
a complementary R N A molecule called
m R N A.
2. The m R N A moves to the ribosomes in
the cytoplasm where translation
occurs. During this process, the
nucleotide sequence of the m R N A is
used to determine the composition of a
polypeptide chain. t R N A is used to carry specific
amino acids to ribosomes.

Question 5

transcription 1

Answer 5

The strands of D N A are separated.
1. R N A polymerase binds at a
promoter region utilizing
transcription factors.
2. R N A polymerase catalyzes the
formation of a m R N A chain using the
D N A as a template and following the
rules of complimentary base pairing.
* A with U.
* C with G.
* Transcription ends at a terminator
sequence and the R N A is released.
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Question 6

gene complexity 1

Answer 6

• Introns are regions of the gene that are not part of the code for a protein.
• Exons are regions of the gene that are part of the code for a protein.
• The m R N A with the introns is called pre-m R N A.
• Introns are removed from the pre-m R N A by spliceosomes that join the remaining pieces of exons to become functional mR N A.
• In alternative splicing, various combinations of exons are joined into m R N A that allows for different proteins to be made from the same gene.

Question 7

POSTTRANSCRIPTIONAL CHANGE IN MRNA 1

Answer 7

1. Introns within a pre-mRNA are
   removed through the activity of
   spliceosomes.
2. A 7-methylguanosine cap is added
   to one end of mRNA.
3. A series of adenine nucleotides,
   called a poly-A tail, is added to the
   other end. These modifications to
   the ends of the mRNA ensure that
   mRNA travels from the nucleus to
   the cytoplasm and interacts with
   ribosomes during translation.

Question 8

genetic code 1

Answer 8

is the information contained in m R N A and
relates the nucleotide sequence of m R N A to the amino acid
sequence of a protein

Question 9

codons 1

Answer 9

The m R N A is arranged into three nucleotide sequences called codons, each of which specifies an amino acid during translation
Although there are only 20 amino acids, 64 possible codons exist; an amino acid can be designated by more than one codon

Question 10

start codon

Answer 10

A U G codes for methionine and is the start codon

Question 11

stop codons

Answer 11

U A A, U G A, and U A G do not code for any amino acid and are considered stop codons.

Question 12

translation

Answer 12

Process that occurs on ribosomes.
* Turns m R N A into a polypeptide.
* Involves r R N A, t R N A, and m R N A.
* t R N A anticodons are complements of m R N A codons, and the
rRNA catalyzes the formation of a peptide bond between the
amino acids at the opposite end of the t R N A.

Question 13

POSTTRANSLATIONAL PROTEIN PROCESSING

Answer 13

Many proteins have extra amino acids when first produced called proproteins.
* If the proprotein is going to be an enzyme, it is called a
proenzyme.
* Extra amino acids are removed to make a
functional protein or enzyme.
Other posttranslational processing may include adding side chains, or joining separate chains to make one protein.

Question 14

cell cycle steps

Answer 14

Interface
mitosis
prophase
metaphase
anaphase
telophase
cytokinesis

Question 15

interphase

Answer 15

phase between or preparation for cell divisions
replication of DNA
ongoing normal cell activities
Increase in cell size
Replication of organelles
Centrioles duplicated

Question 16

mitosis

Answer 16

A series of events that leads to the production of Two cells by division of a mother cell and two daughter cells
Cells are usually identical
Prophase metaphase anaphase telophase

Question 17

cytokinesis

Answer 17

Division of the cell cytoplasm

Question 18

subphases

Answer 18

part of the interphase:
* G 1 – first gap phase – cells carries out normal activities
* S – synthesis phase – D N A is replicated
* G 2 – second gap phase – preparation for division
* Cells in a resting phase that are not actively dividing or that do
not divide enter a G 0 phase