Chapter 12 - DNA & RNA

Question 1

Who was Frederick Griffith?

Answer 1

A British scientist who was trying to figure out how bacteria make people sick.

Question 2

What did Griffith do to answer his question?

Answer 2

He injected mice with 4 different samples of bacteria. When injected separately, neither the heat killed disease causing bacteria nor the live harmless bacteria killed the mice. But when the 2 were combined, it caused fatal pneumonia.

Question 3

What did Griffith call the process when the heat-killed bacteria had passed its disease causing ability to the harmless strain?

Answer 3

transformation

Question 4

What did Griffith hypothesize from his experiment?

Answer 4

When the live, harmless bacteria and the heat-killed bacteria were mixed, some factor was transferred from the heat-killed cells into the live cells. That factor must contain info that could change the harmless bacteria into disease-causing ones.

Question 5

What did Avery and his group discover?

Answer 5

The nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.

Question 6

What is a bacteriophage?

Answer 6

a kind of virus that infects bacteria (“bacteria eater”)

Question 7

What was Hershey and Chase trying to figure out?

Answer 7

Whether genes were made of protein or DNA. by using bacteriophages

Question 8

What did Hershey and Chase conclude?

Answer 8

the genetic material of the bacteriophage was DNA, not protein

Question 9

What are nucleotides?

Answer 9

units that make up DNA

Question 10

What are genes known to do?

Answer 10

1) carry info from 1 gen. to the next
2) put info to work by determining the heritable characteristics of organisms
3) had to be easily copied

Question 11

What is a nucleotide made of?

Answer 11

a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous (nitrogen-containing) base

Question 12

What are the nitrogenous bases of DNA?

Answer 12

Adenine, Guanine, Cytosine and Thymine

Question 13

Who was Erwin Chargaff?

Answer 13

an American biochemist that discovered that the percentages of guanine and cytosine bases are almost equal and the percentages of adenine and thymine bases are almost equal

Question 14

Who was Rosalind Franklin?

Answer 14

She used X-ray diffraction to get info about the structure of DNA.

Question 15

What did photo 51 show?

Answer 15

Photo 51 showed that the strands of DNA are twisted around each other like coils of spring (helix). The angle of the X suggests that there are 2 strands in the structure. It also suggests that the nitrogenous bases are near the center of the molecule.

Question 16

Who were Watson and Crick?

Answer 16

Made a 3D model of DNA based on Franklin’s Photo 51

Question 17

What is the structure of DNA called? What does it look like?

Answer 17

Double helix; twisted ladder/spiral staircase

Question 18

What is base pairing? What does it state?

Answer 18

Explained Chargaff’s rules; for every adenine molecule, there had to be exactly one thymine molecule. And for each cytosine molecule, there had to be exactly one guanine molecule.

Question 19

Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called what?

Answer 19

chromatin

Question 20

What are histones?

Answer 20

proteins that DNA is wrapped around

Question 21

What is a nucleosome?

Answer 21

beadlike structures of DNA and histone molecules

Question 22

What do nucleosomes do?

Answer 22

fold enormous lengths of DNA into the tiny space available in the cell nucleus

Question 23

What are replication forks?

Answer 23

sites where separation and replication occur

Question 24

What happens in DNA replication?

Answer 24

The DNA molecule separates into 2 strands, and then produces 2 new complementary stands following the rules of base pairing. Each strand of the double helix of DNA serves as a template or model for the new strand

Question 25

What is DNA polymerase?

Answer 25

The principal enzyme involved in DNA replication

Question 26

What does DNA polymerase do?

Answer 26

Joins individual nucleotides to produce a DNA molecule; it proofreads each new DNA strand helping to maximize the odds that each molecule is a perfect copy of the original

Question 27

What are the differences of DNA and RNA?

Answer 27

1) the sugar in RNA is ribose while DNA has deoxyribose 2) RNA is generally single-stranded 3) RNA contains uracil in place of thymine 4) RNA is a disposable copy of a segment of DNA 5) DNA is the blueprint

Question 28

What are messenger RNA (mRNA) ?

Answer 28

RNA molecules that carry copies of protein-making instructions from the DNA to the rest of the cell

Question 29

What is ribosomal RNA (rRNA) ?

Answer 29

RNA found in ribosomes

Question 30

What is transfer RNA (tRNA) ?

Answer 30

transfers each amino acid to the ribosome as it is specified by coded messages in mRNA

Question 31

What enzyme does transcription require?

Answer 31

RNA polymerase

Question 32

What happens during transcription?

Answer 32

RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA

Question 33

What are promoters?

Answer 33

Regions of DNA where RNA polymerase binds to

Question 34

What are introns?

Answer 34

Sequences of nucleotides that are not involved in coding for proteins

Question 35

What are exons?

Answer 35

the DNA sequences that code for proteins; they are "expressed" in protein synthesis

Question 36

What is RNA editing?

Answer 36

RNA molecules edit out the introns out of them before they become functional; exons are spliced together; then a cap and tail are added to form the final RNA molecule

Question 37

What is a codon?

Answer 37

consists of 3 consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide

Question 38

How many possible codons are there?

Answer 38

64 ; some amino acids can be specified by more than one codon

Question 39

What is translation?

Answer 39

the decoding of an mRNA message into a polypeptide chain

Question 40

Where does translation take place?

Answer 40

ribosome

Question 41

What happens during translation?

Answer 41

the cell uses information from mRNA to produce proteins

Question 42

What does tRNA have?

Answer 42

anticodons

Question 43

What does tRNA do in translation?

Answer 43

It brings the amino acid of the specified codon on mRNA as it attaches its anticodon to mRNA

Question 44

What are mutations?

Answer 44

changes in the genetic material

Question 45

What are the 2 types of mutations?

Answer 45

Gene and chromosomal

Question 46

What are gene mutations?

Answer 46

Mutations that produce changes in a single gene

Question 47

What are chromosomal mutations?

Answer 47

Mutations that produce changes in whole chromosomes

Question 48

What are point mutations?

Answer 48

A type of gene mutation that involve changes in one or a few nucleotides

Question 49

What are frameshift mutations?

Answer 49

A type of gene mutation that shift the reading frame of the genetic message (insertion or deletion)

Question 50

What are the 4 types of chromosomal mutations?

Answer 50

deletions, duplications, inversions, and translocations

Question 51

What happens in deletion?

Answer 51

loss of all or part of a chromosome

Question 52

What happens in duplications?

Answer 52

extra copies of parts of a chromosome are made

Question 53

What happens in inversions?

Answer 53

the direction of parts of chromosomes are reversed

Question 54

What happens in translocations?

Answer 54

part of one chromosome breaks off and attaches to another

Question 55

What is polyploidy?

Answer 55

an organism has extra sets of chromosomes (3N or 4N)

Question 56

What is lac operon?

Answer 56

a group of genes that must be expressed in order for the bacterium (E. Coli) to be able to use the sugar lactose as food

Question 57

What is an operator?

Answer 57

region where the lac repressor attaches to

Question 58

How is the lac operon regulated?

Answer 58

A repressor is attached to the operator. RNA polymerase attaches to the promoter. When lactose is present, a lactose molecule attached to the repressor and changes its shape, making it "fall off" the operator. Once the operator is free, RNA polymerase transcribes the lac operon. When lactose is gone, a repressor attaches itself back to the operator and the lac operon is turned off.

Question 59

How are most eukaryotic genes controlled?

Answer 59

individually with regulatory sequences that are much more complex that those of the lac operon

Question 60

Why is gene regulation in eukarytoes more complex than in prokaryotes?

Answer 60

Cell specialization requires genetic specialization but all of the cells in a multicellular organism carry the complete genetic code in their nucleus. Therefore, for proper overall function, only a tiny fraction of the available genes needs to be expressed in the appropriate cells of different tissues. Gene regulation makes this specificity possible

Question 61

Hox genes control what?

Answer 61

Cell specialization