Chapter 1

Question 1

what are polypeptides?

Answer 1

the basic component of all proteins

Question 2

where are DNA molecules found?

Answer 2

in eukaryotes: in the chromosomes in the nucleus, but also in the mitochondrion

Question 3

what are the two broad classes of RNA?

w/o functions

Answer 3

1. coding/messenger RNA
2. noncoding RNA

Question 4

what does coding RNA do?

from nucleus/mitochondria?

Answer 4

coding/messenger RNA

> creates polypeptide sequence when decoded

> made in nucleus: needs to be exported to cytoplasm to make proteins

> made in mitochondria: used to make proteins within those organelles

Question 5

what is the function of non coding RNA?

Answer 5

non coding RNA

> do not code for proteins

> often involved in assisting the expression of other genes

> this may involve catalytic RNA molecules (ribozymes)

Question 6

what is the general flow of genetic information?

Answer 6

DNA > RNA > polypeptide

Question 7

what are two processes central in all cellular organisms?

Answer 7

1. transcription

> DNA is used by RNA polymerase as template for synthesizing one of many different types of RNA

2. translation

> mRNA is decoded to make polypeptides

> at ribosomes (large RNA protein complexes found in cytoplasm)

Question 8

how is genetic information encoded/decoded?

Answer 8

genetic information is encoded in the linear sequence of nucleotides in DNA

> and decoded in groups of three nucleotides at a time (triplets)

> this is in turn decoded in groups of three nucleotides (codons)

Question 9

what is the structure of both DNA and RNA?

difference?

Answer 9

large polymers with long linear backbones of alternating residues of a phosphate and a five-carbon sugar

> attached to each sugar is nitrogenous base

> DNA: sugar is deoxyribose

> RNA: sugar is ribose

Question 10

what 4 types of bases are found in DNA/RNA?

Answer 10

DNA:

1. adenine
2. cytosine
3. guanine
4. thymine

RNA:

1. adenine
2. cytosine
3. guanine
4. uracil

Question 11

how to divided bases into two classes?

Answer 11

bases

1. purines (A and G)

> have two interlocked rings

2. pyrimides (C, T, and U)

> have a single ring

Question 12

what is a nucleoside?

Answer 12

carbon attached to the carbon 1 (one prime) of the sugar

Question 13

what is nucleotide?

Answer 13

nucleotide

> a nucleoside with a phosphate group attached at the 5 or 3 prime carbon of the sugar is the basic repeat unit of a DNA strand

Question 14

how are the sugar residues linked in the backbone?

Answer 14

linked by 3,5 phosphodiester bonds

> phosphate links the 3’ carbon atom of one sugar to the 5’ carbon atom of the next sugar

Question 15

what bonds create the DNA helix?

Answer 15

two strands of DNA are held together by hydrogen bonds to form a duplex

Question 16

according to which rule do the base pairs form?

Answer 16

according to the Watson Crick rules

> A pairs with T

> G pairs with C

Question 17

why are the two DNA strands in a duplex described as anti-parallel?

Answer 17

the 5’ -> 3’ direction of the one strand is the opposite to that of its partner

Question 18

why is DNA replication called semi-conservative?

Answer 18

each daughter DNA duplex contains one srand from the parent molecule and one newly synthesized strand

Question 19

what are the two different types of daughter strands?

Answer 19

leading strand

> 5’ -> 3’ growth direction

lagging stand

> 3’ -> 5’ growth direction

Question 20

what is the difference in growth between the leading and lagging strand?

Answer 20

leading always has a free 3’ hydroxyl group

> allows continuous growth in the same direction as replication fork moves

lagging strand in opposite direction of replication fork

> making of DNA segments (Okazaki fragments)

> fragments joint together to form complete DNA strand

>>> DNA synthesis is semi- discontinuous

Question 21

what are “housekeeping genes?

what are other types of genes?

Answer 21

housekeeping genes:

> those genes need to be expressed in essentially all cells

other genes may be tissue specific, or time-specific

> time specific (cell cycle or stage of development)

Question 22

RNA transcription:

> what is the non template strand also called?

> what is the template strand also called?

Answer 22

template strand: antisense strand

> complementary to the RNA strand that is being synthesized

non template strand: sense strand

> is identical to the RNA strand being synthsized, exept for T replacing U

Question 23

how many hydrogen bonds has G-C basepair?

how many hydrogen bonds has A-T basepair?

Answer 23

G-C has 3 hydrogen bonds

A-T has 2 hydrogen bonds

Question 24

transcription factors are called …-acting?

promoters are called …-acting?

why?

Answer 24

transcription factors: trans- acting

promoters: cis- acting

>> transcription factors are produced by remote genes and have to migrate to their sites of actiong

>> promotors are located on the same DNA molecule as the genes that they regulate